NC0002468_SARP_Rev0_Appx E_20161201

December 2016 Amec Foster Wheeler Environment & Infrastructure, Inc.
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0
APPENDIX E: ENGINEERING EVALUATIONS AND
ANALYSES - DAN RIVER DECOMMISSIONING PLAN
Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 1 of 9
12/9/2016 (Initial Submittal)

Calculation Title:
Interim Conditions Stormwater Calculation
Summary:
Stormwater channels, culverts, and downdrains have been designed to convey stormwater for a 2
year, 24-hour design storm event considering short-term conditions after decommissioning of the
Primary and Secondary Ash Basin dams.

Notes:
Revision Log:
No. Description Originator Verifier Technical Reviewer
0

Initial Submittal –
12/9/2016

Chris Jordan Stephanie Stanwick Cedric H. Ruhl

Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 2 of 9
12/9/2016 (Initial Submittal)

OBJECTIVE:
The objective of this calculation is to design the stormwater conveyance measures based on
short-term conditions after decommissioning of the Primary and Secondary Ash Basin dams.
METHOD:
Stormwater flow rates will be calculated using SCS method. The hydraulic capacity of existing
and proposed stormwater conveyances will be evaluated using Manning’s equation and
HydroCAD modeling software.
DEFINITION OF VARIABLES:
 = shear;
A = area;
b = bottom width;
CN = curve number;
d = flow depth;
D = channel depth;
i = rainfall depth;
L = length;
n = Manning’s n;
P = wetted perimeter;
Q = flow;
R = hydraulic radius;
S = longitudinal slope;
t = time
T = top width;
Tc = time of concentration;
V = velocity; and
Z = channel side slope.
CALCULATIONS:
1.0 Design conveyances for upstream tributary areas and ash basin
closure channels
Concentrated stormwater flow from upstream tributary areas was assumed to discharge across
the closed ash basin at four locations shown in Figures 1 and 2, and is described in the “Final
Conditions Stormwater Calculation.
1.1 Calculate time of concentration
The time of concentration (Tc) is the time needed for water to flow from the most remote point in
a drainage area to the drainage area outlet. The estimated time of concentration for the drainage
areas is shown in Table 1.

Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 3 of 9
12/9/2016 (Initial Submittal)

The total time of concentration for a catchment generally consists of the following three
components: sheet flow, shallow concentrated flow and channel flow. In the current analysis,
sheet flow was assumed for the first 100 feet of the flow path, after which the flow was generally
classified as shallow concentrated flow. However, if the flow entered a channel within the sub-
catchment, then the flow was classified as channel flow. Several sub-catchments were relatively
small and were hydrologically difficult to generate sheet flow, shallow concentrated flow or
channel flow components for evaluation of time of concentration. A minimum time of concentration
of 6 minutes (as described by TR-55, Ref. 5) was used for such relatively small sub-catchments.
HydroCAD software [Ref. 2] was used to estimate time of concentration based on input
parameters summarized in the following tables:

Drainage
Area ID
Flow Length
{L}
(ft.)
Surface
Description
Manning No.
{n}
Land Slope
(ft/ft)
Time of
Concentration
{Tc,sheet}
(min)
[Ref. 1]
DA-1 Smooth
surface 0.011 0.067 0.7
DA-2 0.150 0.050 6.5
DA-3 0.150 0.018 9.8
DA-4 0.150 0.074 5.6
DA-5A 0.011 0.003 2.5
DA-5B 0.011 0.020 1.2
DA-5C 0.011 0.012 1.4
DA-5D
DA-6A 0.011 0.010 1.5
DA-6B 0.011 0.016 1.3
DA-6C 0.011 0.016 1.3
DA-6D 0.011 0.014 1.3
DA-6E 0.011 0.011 1.5
DA-6F 0.011 0.017 1.2
DA-6G
DA-7A Bare Soil 0.011 0.088 0.6
DA-7B
DA-7C 0.011 0.014 1.3
DA-7D 0.011 0.014 1.3
DA-7E 0.011 0.017 1.2
DA-7F 0.011 0.017 1.2
DA-7G
DA-8A-1A
DA-8A-1B
DA-8A-1C
DA-8A-1D Bare Soil 0.011 0.2 0.5
DA-8A-1E
DA-8A-1F
DA-8A-1G
DA-8A 0.011 0.010 1.5
DA-8B 0.011 0.010 1.5
DA-8C 0.011 0.012 1.4
DA-8D
-NA-
Bare Soil
-NA-
-NA-
-NA-
Bare Soil
Table 1: Time of Concentration from Sheet Flow
-NA-
-NA-
-NA-
Bare Soil
100
Grass:Short
Bare Soil
-NA-
-NA-
-NA-
-NA-

Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 4 of 9
12/9/2016 (Initial Submittal)

Drainage
Area ID
Flow Length
{L}
(ft.)
Surface Description Land Slope
(ft/ft)
Time of
Concentration
{Tc,scf}
(min)
[Ref. 1]
DA-1 2,343 Unpaved 0.039 12.3
DA-2 752 Woodland 0.058 10.4
DA-3 665 Short Grass Pasture 0.051 7.0
DA-4 2,834 Grass Waterway 0.058 13.1
DA-5A 151 0.018 1.2
DA-5B 288 0.014 2.5
DA-5C 218 0.021 1.6
DA-5D
DA-6A 98 0.031 0.6
DA-6B 168 0.027 1.1
DA-6C 168 0.022 1.2
DA-6D 329 0.015 2.8
DA-6E 224 0.020 1.6
DA-6F 148 0.021 1.1
DA-6G
DA-7A 534 Unpaved 0.013 4.8
DA-7B
DA-7C 226 0.024 1.5
DA-7D 277 0.017 2.2
DA-7E 139 0.021 1.0
DA-7F 498 0.008 5.8
DA-7G
DA-8A-1A
DA-8A-1B
DA-8A-1C
DA-8A-1D 576 Unpaved 0.024 3.8
DA-8A-1E
DA-8A-1F
DA-8A-1G
DA-8A 695 0.052 3.2
DA-8B 252 0.020 1.8
DA-8C 320 0.013 2.9
DA-8D
-NA-
-NA-
-NA-
-NA-
Table 2: Time of Concentration from Shallow Concentrated Flow
-NA-
-NA-
-NA-
Unpaved
Unpaved
Unpaved
Unpaved
-NA-
-NA-
-NA-
-NA-

Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 5 of 9
12/9/2016 (Initial Submittal)

Drainage
Area ID
Flow Length
{L}
(ft.)
Channel
Velocity
{V}
(ft/s)
[assumed]
Time of
Concentration
{Tc,channel}
(min)
[Ref. 1]
DA-1 0
DA-2 0
DA-3 0
DA-4 0
DA-5A 973 5.54 2.90
DA-5B 427 3.31 2.20
DA-5C 468 4.24 1.80
DA-5D
DA-6A 212 7.97 0.40
DA-6B 202 8.11 0.40
DA-6C 318 6.10 0.90
DA-6D 269 5.73 0.80
DA-6E 552 3.89 2.40
DA-6F 289 5.40 0.90
DA-6G
DA-7A 245 5.92 0.70
DA-7B
DA-7C 245 4.44 0.90
DA-7D 241 4.44 0.90
DA-7E 289 5.40 0.90
DA-7F 432 4.43 1.60
DA-7G
DA-8A-1A
DA-8A-1B
DA-8A-1C
DA-8A-1D
DA-8A-1E
DA-8A-1F
DA-8A-1G
DA-8A 662 6.28 1.80
DA-8B 564 2.96 3.20
DA-8C 305 5.25 1.00
DA-8D
-NA-
-NA-
Table 3: Time of Concentration from Channel Flow
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-

1.2 Describe land use conditions
Land use conditions for the tributary drainage areas were delineated in the “Final Conditions
Stormwater Calculation”. Land use conditions in drainage areas 5 through 8 were assumed to
change during the ash removal phase and final grading process. Hence, stormwater analysis for
the ash basin was divided in two phases. Under the initial phase of interim conditions, the basin
area was assumed to be a newly graded area with hydric soil class C (Curve Number of 91), with
no vegetative cover. Final long term conditions within the ash basin footprint were assumed to
consist of at least 75% grass cover with hydric soil class C (Curve Number of 74), and are shown
in the “Final Conditions Stormwater Calculation”.

HydroCAD software was used to estimate long-term stormwater flows for drainage areas DA-1
through DA-8 for the 2-year, 24-hour storm event based on the SCS method. The 2 year storm
resulted in 3.4 inch type II 24-hr rainfall [Ref. 1].
Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 6 of 9
12/9/2016 (Initial Submittal)

1.3 Stormwater channel capacity
Stormwater channels in the ash basin area consist of interceptor ditches (INT), toe ditches (TD)
and longitudinal ditches (LD). Interceptor ditches are used within the ash basin footprint to
interrupt drainage lengths and reduce erosion potential. Toe ditches are located along the
southern edge of the ash basin footprint to intercept stormwater and convey flow to the four
defined outlet points which discharge into the Dan River. Longitudinal ditches are located within
the ash basin footprint perpendicular to the slope and convey concentrated flows from upstream
tributary drainage areas to two of the four defined outlet points which discharge into the Dan River.
The proposed stormwater ditch dimensions are presented in the following table:

Channel
ID
Channel
Type
Bottom
Width
{b}
(ft)
MIN.
Depth
{D}
(ft)
Left Side
Slope
{Z1H:V}
Right Side
Slope
{Z 2H:V}
Top Width
{T}
(ft)
Upstream
Invert
(ft)
Downstream
Invert
(ft)
Length
{L}
(ft)
Longitudinal
Slope
{S}
(ft/ft)
5A INT 4 1.5 20 20 514 500 973 0.014
5B INT 0 1.5 20 20 506 504 379 0.005
6A INT 0 1.5 20 20 510 504 212 0.029
6B INT 0 1.5 20 20 510 504 202 0.030
6C INT 0 1.5 20 20 505 500 318 0.017
6D INT 0 1.5 20 20 504 500 269 0.015
7A INT 0 1.5 20 20 510 506 245 0.016
7B INT 0 1.5 20 20 510 509 312 0.006
7C INT 0 1.5 20 20 504 502 245 0.009
7D INT 0 1.5 20 20 504 502 241 0.009
8A INT 6 1.5 20 20 508 500 662 0.012
8B INT 0 1.5 20 20 529 526 381 0.007
DD-1 DIV 2 2 3 3 531 526 304 0.014
DD-2 DIV 2 2 3 3 531 528 48 0.056
DD-3 DIV 2 2 3 3 530 528 80 0.024
DD-4 DIV 2 2 3 3 530 529 94 0.011
DD-5 DIV 2 2 3 3 532 529 40 0.078
DD-6 DIV 2 2 3 3 532 529 40 0.078
5C TD 0 2 5 5 500 498 468 0.005
6E TD 0 2.5 3 3 500 498 552 0.005
6F TD 6 1.5 3 3 500 499 289 0.005
7E TD 6 1.5 3 3 500 499 289 0.005
7F TD 6 2 3 3 500 499 432 0.003
8C TD 6 1.5 3 3 500 499 305 0.005
LD-1A LD 6 6 3 3 508 504 335 0.012
LD-1B LD 6 4 3 3 504 500 312 0.013
LD-1C LD 6 4 3 3 500 498 184 0.010
LD-2A LD 6 4 3 3 510 506 282 0.014
LD-2B LD 6 3 3 3 506 502 306 0.014
LD-2C LD 6 3 3 3 501 498 166 0.018
Table 6: Channel Dimensions
VARIES

The capacity of the proposed stormwater channels was evaluated using Manning’s equation
presented as follows:

𝑉=1.49
𝑛𝑃2/3 𝑃1/2 [Ref. 3]

and
Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 7 of 9
12/9/2016 (Initial Submittal)

𝑃=𝐴𝑉 [Ref. 3]

The flow area “A” and wetted perimeter “P” were calculated using the following relationships
based on the geometry of a trapezoidal channel with a flow depth “d”, bottom width “b”, left side
slope “Z1”, and right side slope “Z2”:

𝐴=𝑏𝑑+0.5𝑍1 𝑑2 +0.5𝑍2 𝑑2
𝑃=𝑏+√[(𝑍1 𝑑)2 +𝑑2 ]+√[(𝑍2 𝑑)2 +𝑑2 ]

The proposed stormwater channel capacities were evaluated assuming a soil channel lining for
the 2-year storm. The trial flow depth and Manning’s n were iteratively modified until the channel
capacity exceeded the peak runoff for the conditions modeled. Short-term straw matting with net
conditions were assumed for the lining conditions of interceptor, toe-ditches, longitudinal ditches
and the diversion ditch. Channel capacity was estimated as shown in the following table:

Channel
ID
Channel
Type Channel Lining
Manning's n
{n}
[Ref. 2]
Trial Flow
Depth
{d}
(ft)
Flow Area
{A}
(ft2)
Wetted
Perimeter
{P}
(ft)
Hydraulic
Radius
{R}
(ft)
Velocity
{V}
(ft/s)
Channel
Capacity
{Q}
(cfs)
Peak Runoff
{Q}
(cfs)
Channel
Capacity >
Peak
Runoff?
Freeboard
(in)
5A INT straw matting with net 0.033 0.51 7.2 24.4 0.3 2.4 17.25 17.16 yes 11.9
5B INT straw matting with net 0.033 0.57 6.5 22.8 0.3 1.4 9.22 8.89 yes 11.2
6A INT straw matting with net 0.033 0.35 2.5 14.0 0.2 2.4 5.85 5.75 yes 13.8
6B INT straw matting with net 0.033 0.47 4.4 18.8 0.2 3.0 13.17 12.71 yes 12.4
6C INT straw matting with net 0.033 0.5 5.0 20.0 0.2 2.3 11.57 11.40 yes 12.0
6D INT straw matting with net 0.033 0.51 5.2 20.4 0.3 2.2 11.68 11.62 yes 11.9
7A INT straw matting with net 0.033 0.62 7.7 24.8 0.3 2.6 20.31 19.49 yes 10.6
7B INT straw matting with net 0.033 0.52 5.4 20.8 0.3 1.4 7.44 7.32 yes 11.8
7C INT straw matting with net 0.033 0.55 6.1 22.0 0.3 1.8 11.14 11.08 yes 11.4
7D INT straw matting with net 0.033 0.56 6.3 22.4 0.3 1.9 11.71 11.68 yes 11.3
8A INT straw matting with net 0.033 0.52 8.5 26.8 0.3 2.3 19.47 19.01 yes 11.8
8B INT straw matting with net 0.033 0.67 9.0 26.8 0.3 1.8 16.14 11.87 yes 10.0
8A-1A DIV straw matting with net 0.033 0.31 0.9 4.0 0.2 2.0 1.83 1.29 yes 20.3
8A-1B DIV straw matting with net 0.033 0.29 0.8 3.8 0.2 3.8 3.20 1.57 yes 20.5
8A-1C DIV straw matting with net 0.033 0.1 0.2 2.6 0.1 1.4 0.31 0.27 yes 22.8
8A-1D DIV straw matting with net 0.033 0.42 1.4 4.7 0.3 2.1 2.83 2.77 yes 19.0
8A-1E DIV straw matting with net 0.033 0.21 0.6 3.3 0.2 3.8 2.10 0.75 yes 21.5
8A-1F DIV straw matting with net 0.033 0.2 0.5 3.3 0.2 3.7 1.92 1.06 yes 21.6
5C TD straw matting with net 0.033 1.08 5.8 11.0 0.5 2.2 12.59 12.27 yes 11.0
6E TD straw matting with net 0.033 1.41 6.0 8.9 0.7 2.3 13.86 13.71 yes 13.1
6F TD straw matting with net 0.033 0.56 4.3 9.5 0.5 1.9 8.23 8.11 yes 11.3
7E TD straw matting with net 0.033 0.55 4.2 9.5 0.4 1.9 7.97 7.47 yes 11.4
7F TD straw matting with net 0.033 0.76 6.3 10.8 0.6 1.9 11.67 11.51 yes 14.9
8C TD straw matting with net 0.033 0.49 3.7 9.1 0.4 1.7 6.32 6.16 yes 12.1
LD-1A LD straw matting with net 0.033 1.29 12.7 14.2 0.9 4.7 59.40 58.94 yes 56.5
LD-1B LD straw matting with net 0.033 1.46 15.2 15.2 1.0 5.1 76.73 75.75 yes 30.5
LD-1C LD straw matting with net 0.033 1.52 16.1 15.6 1.0 4.7 75.61 75.55 yes 29.8
LD-2A LD straw matting with net 0.033 1.36 13.7 14.6 0.9 5.2 70.86 70.67 yes 31.7
LD-2B LD straw matting with net 0.033 1.44 14.9 15.1 1.0 5.3 79.04 78.65 yes 18.7
LD-2C LD straw matting with net 0.033 1.36 13.7 14.6 0.9 5.8 79.78 78.57 yes 19.7
Table 7: Channel Capacity - 2 year Long-Term Straw with matting with Net

Channels designed with straw matting with nets were checked for permissible shear stress, and
actual flow shear as calculated using the following equation:

𝜏=𝛾𝑤𝑎𝑡𝑒𝑟𝑑𝑃 [Ref. 3]

The maximum permissible shear for straw matting with nets is 2 psf [Ref. 3]. The calculated
stability of the ditches was estimated as shown in the following table:

Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 8 of 9
12/9/2016 (Initial Submittal)

Channel
ID
Channel
Type Channel Lining
Unit Weight
of Water
{g water}
(pcf)
Flow Depth
{d}
(ft)
Longitudinal
Slope
{S}
(ft/ft)
Shear
Stress
{}
(psf)
Permissible Shear
{perm}
(psf)
Safe
5A INT straw matting with net 62.4 0.51 0.014 0.45 yes
5B INT straw matting with net 62.4 0.57 0.005 0.19 yes
6A INT straw matting with net 62.4 0.35 0.029 0.62 yes
6B INT straw matting with net 62.4 0.47 0.030 0.88 yes
6C INT straw matting with net 62.4 0.50 0.017 0.52 yes
6D INT straw matting with net 62.4 0.51 0.015 0.49 yes
7A INT straw matting with net 62.4 0.62 0.016 0.63 yes
7B INT straw matting with net 62.4 0.52 0.006 0.18 yes
7C INT straw matting with net 62.4 0.55 0.009 0.32 yes
7D INT straw matting with net 62.4 0.56 0.009 0.33 yes
8A INT straw matting with net 62.4 0.52 0.012 0.38 yes
8B INT straw matting with net 62.4 0.67 0.007 0.29 yes
8A-1A DIV straw matting with net 62.4 0.31 0.014 0.27 yes
8A-1B DIV straw matting with net 62.4 0.29 0.056 1.01 yes
8A-1C DIV straw matting with net 62.4 0.10 0.024 0.15 yes
8A-1D DIV straw matting with net 62.4 0.42 0.011 0.28 yes
8A-1E DIV straw matting with net 62.4 0.21 0.078 1.02 yes
8A-1F DIV straw matting with net 62.4 0.20 0.078 0.97 yes
5C TD straw matting with net 62.4 1.08 0.005 0.36 yes
6E TD straw matting with net 62.4 1.41 0.005 0.40 yes
6F TD straw matting with net 62.4 0.56 0.005 0.18 yes
7E TD straw matting with net 62.4 0.55 0.005 0.18 yes
7F TD straw matting with net 62.4 0.76 0.003 0.16 yes
8C TD straw matting with net 62.4 0.49 0.005 0.15 yes
LD-1A LD straw matting with net 62.4 1.29 0.012 0.99 yes
LD-1B LD straw matting with net 62.4 1.46 0.013 1.15 yes
LD-1C LD straw matting with net 62.4 1.52 0.010 0.99 yes
LD-2A LD straw matting with net 62.4 1.36 0.014 1.21 yes
LD-2B LD straw matting with net 62.4 1.44 0.014 1.27 yes
LD-2C LD straw matting with net 62.4 1.36 0.018 1.53 yes
Table 8: Channel Lining Requirements - Straw Matting
2

DISCUSSION:
The proposed stormwater features have capacity for the 2-year, 24-hour design storm for the
conditions modeled.

FIGURES:
1. Drainage area and time of concentration
2. Land use characteristics

Interim Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 9 of 9
12/9/2016 (Initial Submittal)

REFERENCES:
1. Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.
2. HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.
3. North Carolina Department of Environment and Natural Resources, “Erosion and
Sediment Control Planning and Design Manual”, Revised May 2013.
4. “Standard Specification for Roads and Structures”, North Carolina Department of
Transportation, Raleigh, January 2012.
5. United States Department of Agriculture, “Urban Hydrology for Small W atersheds”,
Technical Release 55, June 1986.
FIGURE 1
Drainage Areas and Flow Paths

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FIGURE 2
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REFERENCE 1

Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.

Precipitation Frequency Data Server
Page 1 of 3
NOAA Atlas 14, Volume 2, Version 3
Location name: Eden, North Carolina, US"
Latitude: 36.4999°, Longitude:-79.7013°
Elevation: 582 ft*
* source: Google Maps "*�,�,,.t
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based
point precipitation frequency estimates with 90% confidence intervals (in inches)'
Average recurrence interval (years)
Duration
���
10
25
50
100
200
500
1000
0.363
0.433
0.512
0.567
0.633
0.676
0.717
0.754
0.796
0.826
5-min
(0.331-0.397)
(0.396-0.473)
(0.467-0.560)
(0.518-0.619)
(0.575-0.688)
(0.612-0.735)
(0.646-0.781)
(0.676-0.822)
(0.708-0.869)
(0.729-0.902)
0.579
0.692
0.820
0.908
1.01
1.08
1.14
1.20
1.26
1.30
10-min
(0 .529-0.634)
(0.633-0.757)
(0.749-0.898)
(0.829-0.991)
(0.917-1.10)
(0.974-1.17)
1 (1.03-1.24)
1 (1.07-1.30)
1 (1.12-1.38)
0.724
0.870
1.04
1.15
1.28
1.36
1.44
1.51
1.59
1.63
15-min
(0.661-0.792)
(0.796-0.951)
(0.947-1.14)
1 (1.05-1.25)
1 (1.16-1.39)
1 (1.23-1.48)
1 (1.30-1.57)
1 (1.35-1.64)
1 (1.41-1.73)
1 (1.44-1.78)
0.993
1.20
1.47
1.66
1.89
2.05
2.21
2.35
2.52
2.64
30-min
(0.906-1.09)
1 (1.10-1.31)
1 (1.35-1.61)
1 (1.52-1.82)
1 (1.72-2.06)
(1.86-2.23)
(1.99-2.40)
(2.11-2.56)
(2.24-2.75)
(2.33-2.89)
1.24
1.51
1.89
2.17
2.52
2.78
3.04
3.29
3.62
3.86
60-min
(1.13-1.35)
(1.38-1.65)
(1.73-2.07)
(1.98-2.36)
(2.29-2.74)
(2.52-3.03)
(2.74-3.31)
(2.95-3.59)
(3.22-3.95)
(3.41-4.22)
1.47
1.79
2.25
2.61
3.08
3.45
3.83
4.20
4.71
5.10
2-hr
(1.35-1.61)
(1.63-1.96)
(2.06-2.46)
(2.38-2.85)
(2.80-3.36)
(3.12-3.75)
(3.44-4.16)
(3.75-4.57)
(4.15-5.12)
(4.45-5.56)
1.59
1.93
2.44
2.82
3.33
3.73
4.13
4.54
5.08
5.50
3-hr
(1.46-1.73)
(1.78-2.11)
(2.24-2.66)
(2.58-3.07)
(3.03-3.62)
(3.38-4.04)
(3.72-4.48)
(4.06-4.92)
( 4.49-5.52)
( 4.81-5.98)
1.96
2.37
2.99
3.48
4.15
4.70
5.28
5.87
6.71
7.38
6-hr
(1.80-2.15)
(2.18-2.61)
(2.74-3.27)
(3.17-3.80)
(3.76-4.53)
(4.22-5.12)
(4.70-5.73)
(5.18-6.37)
(5.82-7.29)
(6.31-8.02)
2.36
2.87
3.63
4.26
5.15
5.89
6.70
7.56
8.81
9.84
12-hr
(2.17-2.59)
(2.63-3.14)
(3.32-3.96)
(3.88-4.62)
(4.65-5.57)
(5.28-6.37)
(5.94-7.21)
(6.62-8.12)
(7.57-9.48)
(8.31-10.6 )
2.81
3.40
4.33
5.10
6.22
7.17
8.20
9.32
11.0
12.4
24-hr
(2.61-3.04)
(3.16-3.68)
(4.02-4.67)
(4.72-5.48)
(5.72-6.68)
(6.55-7.69)
(7.44-8.79)
(8.39-10.0)
(9.74-11.8)
(10.9-13.3)
3.30
3.99
5.04
5.90
7.12
8.13
9.21
10.4
12.0
13.4
2-day
(3.08-3.55)
(3.72-4.30)
(4.70-5.42)
(5.48-6.33)
(6.59-7.63)
(7.48-8.71)
(8.42-9.88)
(9.40-11.1 )
( 10.8-13.0 )
( 11.9-14.5 )
3.49
4.22
5.33
6.23
7.52
8.59
9.72
10.9
12.7
14.2
3-day
(3.26-3.76)
(3.93-4.55)
(4.96-5.73)
(5.79-6.69)
(6.95-8.07)
(7.89-9.21)
(8.88-10.4)
(9.92-11.8)
(11.4-13.7)
( 12.6-15.3)
3.68
4.45
5.61
6.56
7.92
9.04
10.2
11.5
13.4
14.9
4-day
(3.43-3.97)
(4.15-4.80)
(5.23-6.05)
(6.10-7.06)
(7.32-8.51)
(8.31-9.71)
(9.35-11.0)
(10.4-12.4)
(12.0-14.4)
(13.2-16.1)
4.22
5.07
6.29
7.29
8.71
9.88
11.1
12.4
14.3
15.9
7-day
(3.96-4.51)
(4.75-5.42)
(5.89-6.72)
(6.81-7.78)
(8.11-9.28)
(9.14-10.5)
(10.2-11.9)
( 11.4-13.3)
( 12.9-15.3)
( 14.2-17.0)
4.77
5.71
7.01
8.0 6
10.7
12.0
13.3
15.1
16.6
10-day
��69.53
(4.48-5.10 )
(5.37-6.10)
(6.58-7.48 )
(7.55-8.60)
(8.89-10.2 )
(9.96-11.4)
(11.1-12.8)
(12.2-14.2)
(13.8-16.2)
(15.0-17.8)
6.43
7.65
9.20
10.4
12.1
13.4
14.7
16.1
17.9
19.3
20-day
(6.05-6.85)
(7.21-8.16)
(8.66-9.81)
(9.79-11.1)
(11.3-12.9)
(12.5-14.3)
(13.7-15.7)
(14.9-172)
(16.4-19.2)
(17.6-20.8)
30-day
7.95
9.40
11.1
12.3
14.0
15.3
16.5
17.7
19.3
20.5
(7.53-8.41)
(8.91-9.94)
(10.5-11.7)
(11.7-13.0)
(13.2-14.8)
(14.4-16.2)
(15.5-17.5)
(16.6-18.8)
(18.0-20.5)
(19.0-21.9)
45-day
10.0
11.8
13.7
15.2
17.1
18.5
19.8
21.1
22.8
24.0
(9.48-10.6)
(11.2-12.5)
(13.0-14.5)
(14.4-16.0)
(16.1-18.0)
(17.4-19.5)
(18.6-21.0)
(19.8-22.4)
(21.3-24.2)
(22.3-25.6)
12.0
14.0
16.1
17.7
19.7
21.2
22.6
23.9
25.6
26.8
60-day
( 114-12.6) 1
(13.4-14.8) 1
U-15-3-1-7.0) I
(16.8-18.6) 1
U-18-7-2-o.7) 1
(20.0-22.3) 1
U-21-3-2-3.8) 1
(22.5-25.2) J
(24.0-27.1) 11
(25.1-28.4)
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90 % confidence interval. The probability that precipitation frequency estimates (for a
given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5 % . Estimates at upper bounds are not
checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 2 of 3
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Maps & aerials
NOAA Atlas 14, Volume 2, Version 3
created tGMTI: Mon Sep 15 14:27:08 2014
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interval
(years)
— 1
2
— S
10
25
50
100
200
500
1000
Duration
— 5tnln —
2-day
— Ia-Min —
3-4ay
15-mm —
4-day
— 30-min —
7-4ay
— Btr-cnin —
10-day
— 2-11"lr —
2"ay
— 34il —
30-day
— "t —
*15-day
— 12-hr —
60-day
— 24a'rr
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http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 3 of 3
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hvdroloaic Develooment
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions(a)noaa.aov
Disclaimer
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

REFERENCE 2

HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.

1
DA-1
S-01
DA-5A
S-02
DA-5B
S-03
DA-5C
S-04
DA-5D
S-11
DA-6A
S-12
DA-6B
S-13
DA-6D
S-14
DA-6C
S-15
DA-6E
S-16
DA-6F
S-17
DA-6G
R-11
LD-1A
R-12
LD-1B
R-13
LD-1C
R01
Lateral Ditch
1PCB
36" Culvert
6P
Sediment Basin (SB-2)
49P
Sediment Basin 1
Routing Diagram for ST 1
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=22.679 ac 0.00% Impervious Runoff Depth>1.63"Subcatchment 1: DA-1
Flow Length=2,443' Tc=13.0 min CN=83 Runoff=55.79 cfs 3.085 af
Runoff Area=4.000 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-01: DA-5A
Flow Length=1,224' Tc=5.1 min CN=91 Runoff=17.16 cfs 0.763 af
Runoff Area=2.130 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-02: DA-5B
Flow Length=815' Tc=5.9 min CN=91 Runoff=8.89 cfs 0.406 af
Runoff Area=2.830 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-03: DA-5C
Flow Length=786' Tc=4.8 min CN=91 Runoff=12.27 cfs 0.540 af
Runoff Area=2.180 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-04: DA-5D
Tc=5.0 min CN=91 Runoff=9.39 cfs 0.416 af
Runoff Area=1.230 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-11: DA-6A
Flow Length=409' Tc=2.5 min CN=91 Runoff=5.75 cfs 0.235 af
Runoff Area=2.700 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-12: DA-6B
Flow Length=470' Tc=2.4 min CN=91 Runoff=12.67 cfs 0.516 af
Runoff Area=2.700 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-13: DA-6D
Flow Length=699' Tc=5.0 min CN=91 Runoff=11.62 cfs 0.515 af
Runoff Area=2.510 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-14: DA-6C
Flow Length=586' Tc=3.5 min CN=91 Runoff=11.36 cfs 0.479 af
Runoff Area=3.250 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-15: DA-6E
Flow Length=876' Tc=5.6 min CN=91 Runoff=13.71 cfs 0.620 af
Runoff Area=1.780 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-16: DA-6F
Flow Length=537' Tc=3.4 min CN=91 Runoff=8.08 cfs 0.340 af
Runoff Area=2.610 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-17: DA-6G
Tc=5.0 min CN=91 Runoff=11.24 cfs 0.498 af
Avg. Flow Depth=1.33' Max Vel=4.46 fps Inflow=59.30 cfs 3.835 afReach R-11: LD-1A
n=0.035 L=335.0' S=0.0123 '/' Capacity=1,495.75 cfs Outflow=59.09 cfs 3.828 af
Avg. Flow Depth=1.50' Max Vel=4.83 fps Inflow=76.48 cfs 4.823 afReach R-12: LD-1B
n=0.035 L=312.0' S=0.0127 '/' Capacity=599.39 cfs Outflow=75.96 cfs 4.816 af
Avg. Flow Depth=1.57' Max Vel=4.51 fps Inflow=75.96 cfs 4.816 afReach R-13: LD-1C
n=0.035 L=184.0' S=0.0105 '/' Capacity=545.58 cfs Outflow=75.76 cfs 4.811 af
Avg. Flow Depth=0.55' Max Vel=2.36 fps Inflow=26.01 cfs 1.170 afReach R01: Lateral Ditch
n=0.035 L=1,177.0' S=0.0144 '/' Capacity=223.50 cfs Outflow=19.26 cfs 1.160 af
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Peak Elev=514.19' Inflow=55.79 cfs 3.085 afPond 1P: 36" Culvert
36.0" Round Culvert n=0.012 L=157.0' S=0.0127 '/' Outflow=55.79 cfs 3.085 af
Peak Elev=502.22' Storage=4.967 af Inflow=105.30 cfs 6.269 afPond 6P: Sediment Basin (SB-2)
Primary=3.09 cfs 1.451 af Secondary=0.00 cfs 0.000 af Outflow=3.09 cfs 1.451 af
Peak Elev=501.38' Storage=2.115 af Inflow=38.41 cfs 2.116 afPond 49P: Sediment Basin 1
Primary=0.00 cfs 0.000 af Secondary=0.00 cfs 0.000 af Outflow=0.00 cfs 0.000 af
Total Runoff Area = 50.599 ac Runoff Volume = 8.413 af Average Runoff Depth = 2.00"
100.00% Pervious = 50.599 ac 0.00% Impervious = 0.000 ac
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: DA-1
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 55.79 cfs @ 12.05 hrs, Volume= 3.085 af, Depth> 1.63"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
0.322 73 Woods, Fair, HSG C
9.380 96 Gravel surface, HSG C
12.977 74 >75% Grass cover, Good, HSG C
22.679 83 Weighted Average
22.679 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
0.7 100 0.0670 2.30 Sheet Flow, TC for DA1
Smooth surfaces n= 0.011 P2= 3.40"
12.3 2,343 0.0390 3.18 Shallow Concentrated Flow, TC for DA1
Unpaved Kv= 16.1 fps
13.0 2,443 Total
Subcatchment 1: DA-1
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
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60
55
50
45
40
35
30
25
20
15
10
5
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=22.679 ac
Runoff Volume=3.085 af
Runoff Depth>1.63"
Flow Length=2,443'
Tc=13.0 min
CN=83
55.79 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-01: DA-5A
Runoff = 17.16 cfs @ 11.96 hrs, Volume= 0.763 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
4.000 91 Newly graded area, HSG C
4.000 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.0 100 0.0300 1.67 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.2 151 0.0183 2.18 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.9 973 0.0134 5.66 79.20 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.031
5.1 1,224 Total
Subcatchment S-01: DA-5A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=4.000 ac
Runoff Volume=0.763 af
Runoff Depth>2.29"
Flow Length=1,224'
Tc=5.1 min
CN=91
17.16 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-02: DA-5B
Runoff = 8.89 cfs @ 11.97 hrs, Volume= 0.406 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.130 91 Newly graded area, HSG C
2.130 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.2 100 0.0200 1.42 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
2.5 288 0.0140 1.90 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 427 0.0048 3.18 44.53 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.033
5.9 815 Total
Subcatchment S-02: DA-5B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.130 ac
Runoff Volume=0.406 af
Runoff Depth>2.29"
Flow Length=815'
Tc=5.9 min
CN=91
8.89 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-03: DA-5C
Runoff = 12.27 cfs @ 11.96 hrs, Volume= 0.540 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.830 91 Newly graded area, HSG C
2.830 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.4 100 0.0136 1.22 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.6 218 0.0193 2.24 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.8 468 0.0100 4.33 60.60 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
4.8 786 Total
Subcatchment S-03: DA-5C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
12
10
8
6
4
2
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.830 ac
Runoff Volume=0.540 af
Runoff Depth>2.29"
Flow Length=786'
Tc=4.8 min
CN=91
12.27 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-04: DA-5D
Runoff = 9.39 cfs @ 11.96 hrs, Volume= 0.416 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.180 91 Newly graded area, HSG C
2.180 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-04: DA-5D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.180 ac
Runoff Volume=0.416 af
Runoff Depth>2.29"
Tc=5.0 min
CN=91
9.39 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-11: DA-6A
Runoff = 5.75 cfs @ 11.93 hrs, Volume= 0.235 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.230 91 Newly graded area, HSG C
1.230 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.6 100 0.0091 1.03 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
0.6 97 0.0310 2.83 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.3 212 0.0500 11.29 158.09 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
2.5 409 Total
Subcatchment S-11: DA-6A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.230 ac
Runoff Volume=0.235 af
Runoff Depth>2.29"
Flow Length=409'
Tc=2.5 min
CN=91
5.75 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-12: DA-6B
Runoff = 12.67 cfs @ 11.93 hrs, Volume= 0.516 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.700 91 Newly graded area, HSG C
2.700 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.0 100 0.0331 1.73 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.1 168 0.0270 2.65 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.3 202 0.0500 11.29 158.09 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
2.4 470 Total
Subcatchment S-12: DA-6B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
14
12
10
8
6
4
2
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.700 ac
Runoff Volume=0.516 af
Runoff Depth>2.29"
Flow Length=470'
Tc=2.4 min
CN=91
12.67 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-13: DA-6D
Runoff = 11.62 cfs @ 11.96 hrs, Volume= 0.515 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.700 91 Newly graded area, HSG C
2.700 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.3 100 0.0150 1.26 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
2.8 329 0.0150 1.97 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.9 270 0.0090 4.79 67.07 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
5.0 699 Total
Subcatchment S-13: DA-6D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.700 ac
Runoff Volume=0.515 af
Runoff Depth>2.29"
Flow Length=699'
Tc=5.0 min
CN=91
11.62 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-14: DA-6C
Runoff = 11.36 cfs @ 11.94 hrs, Volume= 0.479 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.510 91 Newly graded area, HSG C
2.510 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.3 100 0.0170 1.33 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.2 168 0.0220 2.39 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.0 318 0.0100 5.05 70.70 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
3.5 586 Total
Subcatchment S-14: DA-6C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.510 ac
Runoff Volume=0.479 af
Runoff Depth>2.29"
Flow Length=586'
Tc=3.5 min
CN=91
11.36 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-15: DA-6E
Runoff = 13.71 cfs @ 11.97 hrs, Volume= 0.620 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
3.250 91 Newly graded area, HSG C
3.250 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.4 100 0.0120 1.16 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.6 224 0.0200 2.28 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.6 552 0.0050 3.57 49.99 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
5.6 876 Total
Subcatchment S-15: DA-6E
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
14
12
10
8
6
4
2
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=3.250 ac
Runoff Volume=0.620 af
Runoff Depth>2.29"
Flow Length=876'
Tc=5.6 min
CN=91
13.71 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-16: DA-6F
Runoff = 8.08 cfs @ 11.94 hrs, Volume= 0.340 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.780 91 Newly graded area, HSG C
1.780 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.3 100 0.0170 1.33 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.1 148 0.0210 2.33 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.0 289 0.0090 4.79 67.07 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
3.4 537 Total
Subcatchment S-16: DA-6F
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.780 ac
Runoff Volume=0.340 af
Runoff Depth>2.29"
Flow Length=537'
Tc=3.4 min
CN=91
8.08 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-17: DA-6G
Runoff = 11.24 cfs @ 11.96 hrs, Volume= 0.498 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.610 91 Newly graded area, HSG C
2.610 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-17: DA-6G
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.610 ac
Runoff Volume=0.498 af
Runoff Depth>2.29"
Tc=5.0 min
CN=91
11.24 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-11: LD-1A
Inflow Area = 26.609 ac, 0.00% Impervious, Inflow Depth > 1.73" for 2-Year event
Inflow = 59.30 cfs @ 12.01 hrs, Volume= 3.835 af
Outflow = 59.09 cfs @ 12.04 hrs, Volume= 3.828 af, Atten= 0%, Lag= 1.3 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 4.46 fps, Min. Travel Time= 1.3 min
Avg. Velocity = 1.37 fps, Avg. Travel Time= 4.1 min
Peak Storage= 4,442 cf @ 12.04 hrs
Average Depth at Peak Storage= 1.33'
Bank-Full Depth= 6.00' Flow Area= 144.0 sf, Capacity= 1,495.75 cfs
6.00' x 6.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 42.00'
Length= 335.0' Slope= 0.0123 '/'
Inlet Invert= 508.00', Outlet Invert= 503.88'
Reach R-11: LD-1A
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=26.609 ac
Avg. Flow Depth=1.33'
Max Vel=4.46 fps
n=0.035
L=335.0'
S=0.0123 '/'
Capacity=1,495.75 cfs
59.30 cfs59.09 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-12: LD-1B
Inflow Area = 31.819 ac, 0.00% Impervious, Inflow Depth > 1.82" for 2-Year event
Inflow = 76.48 cfs @ 11.98 hrs, Volume= 4.823 af
Outflow = 75.96 cfs @ 11.99 hrs, Volume= 4.816 af, Atten= 1%, Lag= 0.9 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 4.83 fps, Min. Travel Time= 1.1 min
Avg. Velocity = 1.45 fps, Avg. Travel Time= 3.6 min
Peak Storage= 4,907 cf @ 11.99 hrs
Average Depth at Peak Storage= 1.50'
Bank-Full Depth= 4.00' Flow Area= 72.0 sf, Capacity= 599.39 cfs
6.00' x 4.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 30.00'
Length= 312.0' Slope= 0.0127 '/'
Inlet Invert= 503.88', Outlet Invert= 499.93'
‡
Reach R-12: LD-1B
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
80
70
60
50
40
30
20
10
0
Inflow Area=31.819 ac
Avg. Flow Depth=1.50'
Max Vel=4.83 fps
n=0.035
L=312.0'
S=0.0127 '/'
Capacity=599.39 cfs
76.48 cfs75.96 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-13: LD-1C
Inflow Area = 31.819 ac, 0.00% Impervious, Inflow Depth > 1.82" for 2-Year event
Inflow = 75.96 cfs @ 11.99 hrs, Volume= 4.816 af
Outflow = 75.76 cfs @ 12.00 hrs, Volume= 4.811 af, Atten= 0%, Lag= 0.5 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 4.51 fps, Min. Travel Time= 0.7 min
Avg. Velocity = 1.36 fps, Avg. Travel Time= 2.3 min
Peak Storage= 3,093 cf @ 12.00 hrs
Average Depth at Peak Storage= 1.57'
Bank-Full Depth= 4.00' Flow Area= 72.0 sf, Capacity= 545.58 cfs
6.00' x 4.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 30.00'
Length= 184.0' Slope= 0.0105 '/'
Inlet Invert= 499.93', Outlet Invert= 498.00'
‡
Reach R-13: LD-1C
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
80
70
60
50
40
30
20
10
0
Inflow Area=31.819 ac
Avg. Flow Depth=1.57'
Max Vel=4.51 fps
n=0.035
L=184.0'
S=0.0105 '/'
Capacity=545.58 cfs
75.96 cfs75.76 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R01: Lateral Ditch
Inflow Area = 6.130 ac, 0.00% Impervious, Inflow Depth > 2.29" for 2-Year event
Inflow = 26.01 cfs @ 11.96 hrs, Volume= 1.170 af
Outflow = 19.26 cfs @ 12.02 hrs, Volume= 1.160 af, Atten= 26%, Lag= 3.4 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 2.36 fps, Min. Travel Time= 8.3 min
Avg. Velocity = 0.84 fps, Avg. Travel Time= 23.4 min
Peak Storage= 9,596 cf @ 12.02 hrs
Average Depth at Peak Storage= 0.55'
Bank-Full Depth= 1.50' Flow Area= 51.0 sf, Capacity= 223.50 cfs
4.00' x 1.50' deep channel, n= 0.035
Side Slope Z-value= 20.0 '/' Top Width= 64.00'
Length= 1,177.0' Slope= 0.0144 '/'
Inlet Invert= 514.00', Outlet Invert= 497.00'
‡
Reach R01: Lateral Ditch
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
25
20
15
10
5
0
Inflow Area=6.130 ac
Avg. Flow Depth=0.55'
Max Vel=2.36 fps
n=0.035
L=1,177.0'
S=0.0144 '/'
Capacity=223.50 cfs
26.01 cfs
19.26 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 1P: 36" Culvert
Inflow Area = 22.679 ac, 0.00% Impervious, Inflow Depth > 1.63" for 2-Year event
Inflow = 55.79 cfs @ 12.05 hrs, Volume= 3.085 af
Outflow = 55.79 cfs @ 12.05 hrs, Volume= 3.085 af, Atten= 0%, Lag= 0.0 min
Primary = 55.79 cfs @ 12.05 hrs, Volume= 3.085 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 514.19' @ 12.05 hrs
Flood Elev= 524.00'
Device Routing Invert Outlet Devices
#1 Primary 510.00'36.0" Round 36" RCP Culvert
L= 157.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 510.00' / 508.00' S= 0.0127 '/' Cc= 0.900
n= 0.012, Flow Area= 7.07 sf
Primary OutFlow Max=55.76 cfs @ 12.05 hrs HW=514.18' TW=509.33' (Dynamic Tailwater)
1=36" RCP Culvert (Inlet Controls 55.76 cfs @ 7.89 fps)
Pond 1P: 36" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
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60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=22.679 ac
Peak Elev=514.19'
36.0"
Round Culvert
n=0.012
L=157.0'
S=0.0127 '/'
55.79 cfs55.79 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 6P: Sediment Basin (SB-2)
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 1.91" for 2-Year event
Inflow = 105.30 cfs @ 11.98 hrs, Volume= 6.269 af
Outflow = 3.09 cfs @ 15.68 hrs, Volume= 1.451 af, Atten= 97%, Lag= 222.2 min
Primary = 3.09 cfs @ 15.68 hrs, Volume= 1.451 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 502.22' @ 15.68 hrs Surf.Area= 3.118 ac Storage= 4.967 af
Plug-Flow detention time= 327.3 min calculated for 1.451 af (23% of inflow)
Center-of-Mass det. time= 219.6 min ( 997.4 - 777.8 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 63.755 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.620 0.000 0.000
502.00 2.840 4.325 4.325
504.00 5.420 8.260 12.585
506.00 7.640 13.060 25.645
508.00 9.500 17.140 42.785
510.00 11.470 20.970 63.755
Device Routing Invert Outlet Devices
#1 Primary 499.50'24.0" Round Culvert
L= 103.0' CMP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 498.00' S= 0.0146 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 3.14 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=3.09 cfs @ 15.68 hrs HW=502.22' (Free Discharge)
1=Culvert (Passes 3.09 cfs of 19.81 cfs potential flow)
2=Orifice/Grate (Weir Controls 3.09 cfs @ 1.52 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 22HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 6P: Sediment Basin (SB-2)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=39.459 ac
Peak Elev=502.22'
Storage=4.967 af
105.30 cfs
3.09 cfs3.09 cfs0.00 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 23HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 49P: Sediment Basin 1
Inflow Area = 11.140 ac, 0.00% Impervious, Inflow Depth > 2.28" for 2-Year event
Inflow = 38.41 cfs @ 11.97 hrs, Volume= 2.116 af
Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 501.38' @ 20.00 hrs Surf.Area= 1.712 ac Storage= 2.115 af
Plug-Flow detention time= (not calculated: initial storage exceeds outflow)
Center-of-Mass det. time= (not calculated: no outflow)
Volume Invert Avail.Storage Storage Description
#1 499.50' 41.530 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.540 0.000 0.000
502.00 2.100 3.300 3.300
504.00 3.600 5.700 9.000
506.00 4.990 8.590 17.590
508.00 5.990 10.980 28.570
510.00 6.970 12.960 41.530
Device Routing Invert Outlet Devices
#1 Primary 499.50'12.0" Round Culvert
L= 116.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 497.00' S= 0.0216 '/' Cc= 0.900
n= 0.025, Flow Area= 0.79 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
1=Culvert ( Controls 0.00 cfs)
2=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 24HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 49P: Sediment Basin 1
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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40
35
30
25
20
15
10
5
0
Inflow Area=11.140 ac
Peak Elev=501.38'
Storage=2.115 af
38.41 cfs
0.00 cfs0.00 cfs0.00 cfs
2
DA-2
3
DA4
4
DA-3
9S
DA-8A-1A
10S
DA-8A-1B
12S
DA-8A-1C
13S
DA-8A-1D
14S
DA-8A-1E
15S
DA-8A-1F
38S
DA-8A-1G
S-21
DA-7A
S-22
DA-7B
S-23
DA-7C
S-24
DA-7D
S-25
DA-7E
S-26
DA-7F
S-27
DA-7G
S-41
DA-8A
S-42
DA-8B
S-43
DA-8DS-45
DA-8C
6R
LD-4B
R-21
LD-2A
R-22
LD-2B
R-23
LD-2C
R-41
LD-4A
2PCB
24" Culvert
3P
36" Slope Drain Pipe
4PCB
36" Slope Drain Pipe
8P
Sediment Basin (SB-3)
16PCB
18" Culvert
17PCB
18" Culvert
18PCB
18" Culvert
37P
Sediment Basin (SB-4)
Routing Diagram for ST 2
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=6.060 ac 0.00% Impervious Runoff Depth>1.05"Subcatchment 2: DA-2
Flow Length=852' Tc=17.0 min CN=74 Runoff=8.34 cfs 0.532 af
Runoff Area=74.120 ac 0.00% Impervious Runoff Depth>1.29"Subcatchment 3: DA4
Flow Length=4,921' Tc=22.0 min CN=78 Runoff=109.23 cfs 7.962 af
Runoff Area=2.385 ac 0.00% Impervious Runoff Depth>1.00"Subcatchment 4: DA-3
Flow Length=765' Tc=16.9 min CN=73 Runoff=3.10 cfs 0.199 af
Runoff Area=0.620 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 9S: DA-8A-1A
Tc=6.0 min CN=74 Runoff=1.29 cfs 0.055 af
Runoff Area=0.750 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 10S: DA-8A-1B
Tc=6.0 min CN=74 Runoff=1.57 cfs 0.066 af
Runoff Area=0.130 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 12S: DA-8A-1C
Tc=6.0 min CN=74 Runoff=0.27 cfs 0.011 af
Runoff Area=1.240 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 13S: DA-8A-1D
Flow Length=676' Tc=12.7 min CN=74 Runoff=1.99 cfs 0.109 af
Runoff Area=0.290 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 14S: DA-8A-1E
Tc=0.0 min CN=74 Runoff=0.75 cfs 0.026 af
Runoff Area=0.170 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 15S: DA-8A-1F
Tc=6.0 min CN=74 Runoff=0.35 cfs 0.015 af
Runoff Area=0.350 ac 0.00% Impervious Runoff Depth>1.06"Subcatchment 38S: DA-8A-1G
Tc=6.0 min CN=74 Runoff=0.73 cfs 0.031 af
Runoff Area=4.700 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-21: DA-7A
Flow Length=879' Tc=6.1 min CN=91 Runoff=19.49 cfs 0.897 af
Runoff Area=1.700 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-22: DA-7B
Tc=5.0 min CN=91 Runoff=7.32 cfs 0.324 af
Runoff Area=2.480 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-23: DA-7C
Flow Length=571' Tc=3.9 min CN=91 Runoff=11.08 cfs 0.473 af
Runoff Area=2.650 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-24: DA-7D
Flow Length=618' Tc=4.3 min CN=91 Runoff=11.68 cfs 0.506 af
Runoff Area=1.640 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-25: DA-7E
Flow Length=528' Tc=3.3 min CN=91 Runoff=7.47 cfs 0.313 af
Runoff Area=3.000 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-26: DA-7F
Flow Length=1,030' Tc=8.4 min CN=91 Runoff=11.51 cfs 0.572 af
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Runoff Area=2.260 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-27: DA-7G
Tc=5.0 min CN=91 Runoff=9.73 cfs 0.431 af
Runoff Area=4.740 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-41: DA-8A
Flow Length=1,457' Tc=7.1 min CN=91 Runoff=19.01 cfs 0.904 af
Runoff Area=2.890 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-42: DA-8B
Flow Length=916' Tc=6.4 min CN=91 Runoff=11.87 cfs 0.551 af
Runoff Area=1.770 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-43: DA-8D
Tc=5.0 min CN=91 Runoff=7.62 cfs 0.338 af
Runoff Area=1.480 ac 0.00% Impervious Runoff Depth>2.29"Subcatchment S-45: DA-8C
Flow Length=725' Tc=6.0 min CN=91 Runoff=6.16 cfs 0.282 af
Inflow=26.98 cfs 1.948 afReach 6R: LD-4B
Outflow=26.98 cfs 1.948 af
Avg. Flow Depth=1.36' Max Vel=5.15 fps Inflow=71.30 cfs 9.706 afReach R-21: LD-2A
n=0.033 L=282.0' S=0.0143 '/' Capacity=674.58 cfs Outflow=70.67 cfs 9.696 af
Avg. Flow Depth=1.44' Max Vel=5.30 fps Inflow=79.03 cfs 10.675 afReach R-22: LD-2B
n=0.033 L=306.0' S=0.0142 '/' Capacity=357.35 cfs Outflow=78.65 cfs 10.663 af
Avg. Flow Depth=1.28' Max Vel=6.21 fps Inflow=78.65 cfs 10.663 afReach R-23: LD-2C
n=0.033 L=165.0' S=0.0221 '/' Capacity=445.67 cfs Outflow=78.57 cfs 10.658 af
Avg. Flow Depth=0.53' Max Vel=2.06 fps Inflow=26.90 cfs 1.416 afReach R-41: LD-4A
n=0.035 L=1,410.0' S=0.0106 '/' Capacity=77.78 cfs Outflow=18.21 cfs 1.397 af
Peak Elev=513.30' Inflow=8.34 cfs 0.532 afPond 2P: 24" Culvert
24.0" Round Culvert n=0.012 L=167.0' S=0.0240 '/' Outflow=8.34 cfs 0.532 af
Peak Elev=536.50' Storage=59,457 cf Inflow=109.23 cfs 7.962 afPond 3P: 36" Slope Drain Pipe
Outflow=58.01 cfs 7.953 af
Peak Elev=529.59' Inflow=3.10 cfs 0.199 afPond 4P: 36" Slope Drain Pipe
36.0" Round Culvert n=0.013 L=150.0' S=0.1263 '/' Outflow=3.10 cfs 0.199 af
Peak Elev=502.72' Storage=7.175 af Inflow=103.10 cfs 11.974 afPond 8P: Sediment Basin (SB-3)
Primary=21.79 cfs 6.427 af Secondary=0.00 cfs 0.000 af Outflow=21.79 cfs 6.427 af
Peak Elev=526.20' Inflow=2.86 cfs 0.121 afPond 16P: 18" Culvert
Outflow=2.86 cfs 0.121 af
Peak Elev=528.16' Inflow=2.16 cfs 0.121 afPond 17P: 18" Culvert
Outflow=2.16 cfs 0.121 af
Peak Elev=528.10' Inflow=0.98 cfs 0.041 afPond 18P: 18" Culvert
Outflow=0.98 cfs 0.041 af
Peak Elev=502.03' Storage=2.466 af Inflow=39.32 cfs 2.568 afPond 37P: Sediment Basin (SB-4)
Primary=0.72 cfs 0.102 af Secondary=0.00 cfs 0.000 af Outflow=0.72 cfs 0.102 af
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Total Runoff Area = 115.425 ac Runoff Volume = 14.598 af Average Runoff Depth = 1.52"
100.00% Pervious = 115.425 ac 0.00% Impervious = 0.000 ac
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: DA-2
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 8.34 cfs @ 12.11 hrs, Volume= 0.532 af, Depth> 1.05"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.555 73 Woods, Fair, HSG C
0.140 96 Gravel surface, HSG C
4.365 74 >75% Grass cover, Good, HSG C
6.060 74 Weighted Average
6.060 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.6 100 0.0500 0.25 Sheet Flow, TC for DA2
Grass: Short n= 0.150 P2= 3.40"
10.4 752 0.0580 1.20 Shallow Concentrated Flow, TC for DA2
Woodland Kv= 5.0 fps
17.0 852 Total
Subcatchment 2: DA-2
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=6.060 ac
Runoff Volume=0.532 af
Runoff Depth>1.05"
Flow Length=852'
Tc=17.0 min
CN=74
8.34 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 3: DA4
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 109.23 cfs @ 12.15 hrs, Volume= 7.962 af, Depth> 1.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
9.930 73 Woods, Fair, HSG C
15.051 96 Gravel surface, HSG C
49.139 74 >75% Grass cover, Good, HSG C
74.120 78 Weighted Average
74.120 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.6 100 0.0740 0.30 Sheet Flow, TC for DA4
Grass: Short n= 0.150 P2= 3.40"
13.1 2,834 0.0580 3.61 Shallow Concentrated Flow, TC for DA4
Grassed Waterway Kv= 15.0 fps
3.3 1,987 10.00 Direct Entry, TC for DA4
22.0 4,921 Total
Subcatchment 3: DA4
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
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120
110
100
90
80
70
60
50
40
30
20
10
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=74.120 ac
Runoff Volume=7.962 af
Runoff Depth>1.29"
Flow Length=4,921'
Tc=22.0 min
CN=78
109.23 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 4: DA-3
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 3.10 cfs @ 12.11 hrs, Volume= 0.199 af, Depth> 1.00"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.260 73 Woods, Fair, HSG C
0.000 96 Gravel surface, HSG C
1.125 74 >75% Grass cover, Good, HSG C
2.385 73 Weighted Average
2.385 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
9.9 100 0.0180 0.17 Sheet Flow, TC for DA3
Grass: Short n= 0.150 P2= 3.40"
7.0 665 0.0511 1.58 Shallow Concentrated Flow, TC for DA3
Short Grass Pasture Kv= 7.0 fps
16.9 765 Total
Subcatchment 4: DA-3
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
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3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.385 ac
Runoff Volume=0.199 af
Runoff Depth>1.00"
Flow Length=765'
Tc=16.9 min
CN=73
3.10 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 9S: DA-8A-1A
Runoff = 1.29 cfs @ 11.98 hrs, Volume= 0.055 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 0.620 74
0.620 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 9S: DA-8A-1A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
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1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=0.620 ac
Runoff Volume=0.055 af
Runoff Depth>1.06"
Tc=6.0 min
CN=74
1.29 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 10S: DA-8A-1B
Runoff = 1.57 cfs @ 11.98 hrs, Volume= 0.066 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 0.750 74
0.750 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 10S: DA-8A-1B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=0.750 ac
Runoff Volume=0.066 af
Runoff Depth>1.06"
Tc=6.0 min
CN=74
1.57 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 12S: DA-8A-1C
Runoff = 0.27 cfs @ 11.98 hrs, Volume= 0.011 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 0.130 74
0.130 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 12S: DA-8A-1C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
0.3
0.25
0.2
0.15
0.1
0.05
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=0.130 ac
Runoff Volume=0.011 af
Runoff Depth>1.06"
Tc=6.0 min
CN=74
0.27 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 13S: DA-8A-1D
Runoff = 1.99 cfs @ 12.06 hrs, Volume= 0.109 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 1.240 74
1.240 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.8 100 0.2000 0.44 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
8.9 576 0.0240 1.08 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
12.7 676 Total
Subcatchment 13S: DA-8A-1D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.240 ac
Runoff Volume=0.109 af
Runoff Depth>1.06"
Flow Length=676'
Tc=12.7 min
CN=74
1.99 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 14S: DA-8A-1E
Runoff = 0.75 cfs @ 11.90 hrs, Volume= 0.026 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 0.290 74
0.290 100.00% Pervious Area
Subcatchment 14S: DA-8A-1E
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=0.290 ac
Runoff Volume=0.026 af
Runoff Depth>1.06"
Tc=0.0 min
CN=74
0.75 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 15S: DA-8A-1F
Runoff = 0.35 cfs @ 11.98 hrs, Volume= 0.015 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 0.170 74
0.170 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 15S: DA-8A-1F
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=0.170 ac
Runoff Volume=0.015 af
Runoff Depth>1.06"
Tc=6.0 min
CN=74
0.35 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 38S: DA-8A-1G
Runoff = 0.73 cfs @ 11.98 hrs, Volume= 0.031 af, Depth> 1.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
* 0.350 74
0.350 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 38S: DA-8A-1G
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=0.350 ac
Runoff Volume=0.031 af
Runoff Depth>1.06"
Tc=6.0 min
CN=74
0.73 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-21: DA-7A
Runoff = 19.49 cfs @ 11.97 hrs, Volume= 0.897 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
4.700 91 Newly graded area, HSG C
4.700 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
0.6 100 0.0880 2.56 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
4.8 534 0.0130 1.84 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.7 245 0.0186 5.90 82.65 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
6.1 879 Total
Subcatchment S-21: DA-7A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=4.700 ac
Runoff Volume=0.897 af
Runoff Depth>2.29"
Flow Length=879'
Tc=6.1 min
CN=91
19.49 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-22: DA-7B
Runoff = 7.32 cfs @ 11.96 hrs, Volume= 0.324 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.700 91 Newly graded area, HSG C
1.700 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-22: DA-7B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.700 ac
Runoff Volume=0.324 af
Runoff Depth>2.29"
Tc=5.0 min
CN=91
7.32 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-23: DA-7C
Runoff = 11.08 cfs @ 11.95 hrs, Volume= 0.473 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.480 91 Newly graded area, HSG C
2.480 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.4 100 0.0140 1.23 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.5 226 0.0242 2.50 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.0 245 0.0090 4.11 57.49 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
3.9 571 Total
Subcatchment S-23: DA-7C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.480 ac
Runoff Volume=0.473 af
Runoff Depth>2.29"
Flow Length=571'
Tc=3.9 min
CN=91
11.08 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-24: DA-7D
Runoff = 11.68 cfs @ 11.95 hrs, Volume= 0.506 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.650 91 Newly graded area, HSG C
2.650 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.4 100 0.0140 1.23 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
2.2 277 0.0170 2.10 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.7 241 0.0167 5.59 78.31 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
4.3 618 Total
Subcatchment S-24: DA-7D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.650 ac
Runoff Volume=0.506 af
Runoff Depth>2.29"
Flow Length=618'
Tc=4.3 min
CN=91
11.68 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-25: DA-7E
Runoff = 7.47 cfs @ 11.94 hrs, Volume= 0.313 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.640 91 Newly graded area, HSG C
1.640 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.2 100 0.0181 1.36 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.0 139 0.0213 2.35 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.1 289 0.0070 4.23 59.15 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
3.3 528 Total
Subcatchment S-25: DA-7E
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.640 ac
Runoff Volume=0.313 af
Runoff Depth>2.29"
Flow Length=528'
Tc=3.3 min
CN=91
7.47 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-26: DA-7F
Runoff = 11.51 cfs @ 12.00 hrs, Volume= 0.572 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
3.000 91 Newly graded area, HSG C
3.000 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.3 100 0.0166 1.32 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
5.8 498 0.0080 1.44 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.3 432 0.0122 5.58 78.09 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.030
8.4 1,030 Total
Subcatchment S-26: DA-7F
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=3.000 ac
Runoff Volume=0.572 af
Runoff Depth>2.29"
Flow Length=1,030'
Tc=8.4 min
CN=91
11.51 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-27: DA-7G
Runoff = 9.73 cfs @ 11.96 hrs, Volume= 0.431 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.260 91 Newly graded area, HSG C
2.260 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-27: DA-7G
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.260 ac
Runoff Volume=0.431 af
Runoff Depth>2.29"
Tc=5.0 min
CN=91
9.73 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 22HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-41: DA-8A
Runoff = 19.01 cfs @ 11.98 hrs, Volume= 0.904 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
4.740 91 Newly graded area, HSG C
4.740 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.6 100 0.0100 1.07 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
3.2 695 0.0520 3.67 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.3 662 0.0118 4.70 65.83 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
7.1 1,457 Total
Subcatchment S-41: DA-8A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=4.740 ac
Runoff Volume=0.904 af
Runoff Depth>2.29"
Flow Length=1,457'
Tc=7.1 min
CN=91
19.01 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 23HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-42: DA-8B
Runoff = 11.87 cfs @ 11.97 hrs, Volume= 0.551 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
2.890 91 Newly graded area, HSG C
2.890 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.5 100 0.0104 1.09 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
1.8 252 0.0204 2.30 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
3.1 564 0.0050 3.06 42.85 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
6.4 916 Total
Subcatchment S-42: DA-8B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=2.890 ac
Runoff Volume=0.551 af
Runoff Depth>2.29"
Flow Length=916'
Tc=6.4 min
CN=91
11.87 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 24HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-43: DA-8D
Runoff = 7.62 cfs @ 11.96 hrs, Volume= 0.338 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.770 91 Newly graded area, HSG C
1.770 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-43: DA-8D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.770 ac
Runoff Volume=0.338 af
Runoff Depth>2.29"
Tc=5.0 min
CN=91
7.62 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 25HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-45: DA-8C
Runoff = 6.16 cfs @ 11.97 hrs, Volume= 0.282 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 2-Year Rainfall=3.40"
Area (ac) CN Description
1.480 91 Newly graded area, HSG C
1.480 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
1.4 100 0.0120 1.16 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.40"
2.9 320 0.0130 1.84 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
1.7 305 0.0050 3.06 42.85 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
6.0 725 Total
Subcatchment S-45: DA-8C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.40"
Runoff Area=1.480 ac
Runoff Volume=0.282 af
Runoff Depth>2.29"
Flow Length=725'
Tc=6.0 min
CN=91
6.16 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 26HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach 6R: LD-4B
Inflow Area = 13.565 ac, 0.00% Impervious, Inflow Depth > 1.72" for 2-Year event
Inflow = 26.98 cfs @ 12.01 hrs, Volume= 1.948 af
Outflow = 26.98 cfs @ 12.01 hrs, Volume= 1.948 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Reach 6R: LD-4B
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
30
25
20
15
10
5
0
Inflow Area=13.565 ac
26.98 cfs26.98 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 27HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-21: LD-2A
Inflow Area = 86.580 ac, 0.00% Impervious, Inflow Depth > 1.35" for 2-Year event
Inflow = 71.30 cfs @ 12.08 hrs, Volume= 9.706 af
Outflow = 70.67 cfs @ 12.09 hrs, Volume= 9.696 af, Atten= 1%, Lag= 0.7 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 5.15 fps, Min. Travel Time= 0.9 min
Avg. Velocity = 1.92 fps, Avg. Travel Time= 2.5 min
Peak Storage= 3,866 cf @ 12.09 hrs
Average Depth at Peak Storage= 1.36'
Bank-Full Depth= 4.00' Flow Area= 72.0 sf, Capacity= 674.58 cfs
6.00' x 4.00' deep channel, n= 0.033
Side Slope Z-value= 3.0 '/' Top Width= 30.00'
Length= 282.0' Slope= 0.0143 '/'
Inlet Invert= 510.00', Outlet Invert= 505.98'
‡
Reach R-21: LD-2A
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
70
60
50
40
30
20
10
0
Inflow Area=86.580 ac
Avg. Flow Depth=1.36'
Max Vel=5.15 fps
n=0.033
L=282.0'
S=0.0143 '/'
Capacity=674.58 cfs
71.30 cfs70.67 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 28HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-22: LD-2B
Inflow Area = 91.710 ac, 0.00% Impervious, Inflow Depth > 1.40" for 2-Year event
Inflow = 79.03 cfs @ 11.99 hrs, Volume= 10.675 af
Outflow = 78.65 cfs @ 12.00 hrs, Volume= 10.663 af, Atten= 0%, Lag= 0.8 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 5.30 fps, Min. Travel Time= 1.0 min
Avg. Velocity = 1.99 fps, Avg. Travel Time= 2.6 min
Peak Storage= 4,540 cf @ 12.00 hrs
Average Depth at Peak Storage= 1.44'
Bank-Full Depth= 3.00' Flow Area= 45.0 sf, Capacity= 357.35 cfs
6.00' x 3.00' deep channel, n= 0.033
Side Slope Z-value= 3.0 '/' Top Width= 24.00'
Length= 306.0' Slope= 0.0142 '/'
Inlet Invert= 505.98', Outlet Invert= 501.64'
‡
Reach R-22: LD-2B
Inflow
Outflow
Hydrograph
Time (hours)
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80
70
60
50
40
30
20
10
0
Inflow Area=91.710 ac
Avg. Flow Depth=1.44'
Max Vel=5.30 fps
n=0.033
L=306.0'
S=0.0142 '/'
Capacity=357.35 cfs
79.03 cfs78.65 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 29HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-23: LD-2C
Inflow Area = 91.710 ac, 0.00% Impervious, Inflow Depth > 1.40" for 2-Year event
Inflow = 78.65 cfs @ 12.00 hrs, Volume= 10.663 af
Outflow = 78.57 cfs @ 12.01 hrs, Volume= 10.658 af, Atten= 0%, Lag= 0.3 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 6.21 fps, Min. Travel Time= 0.4 min
Avg. Velocity = 2.31 fps, Avg. Travel Time= 1.2 min
Peak Storage= 2,086 cf @ 12.01 hrs
Average Depth at Peak Storage= 1.28'
Bank-Full Depth= 3.00' Flow Area= 45.0 sf, Capacity= 445.67 cfs
6.00' x 3.00' deep channel, n= 0.033
Side Slope Z-value= 3.0 '/' Top Width= 24.00'
Length= 165.0' Slope= 0.0221 '/'
Inlet Invert= 501.64', Outlet Invert= 498.00'
‡
Reach R-23: LD-2C
Inflow
Outflow
Hydrograph
Time (hours)
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80
70
60
50
40
30
20
10
0
Inflow Area=91.710 ac
Avg. Flow Depth=1.28'
Max Vel=6.21 fps
n=0.033
L=165.0'
S=0.0221 '/'
Capacity=445.67 cfs
78.65 cfs78.57 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 30HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-41: LD-4A
Inflow Area = 10.675 ac, 0.00% Impervious, Inflow Depth > 1.59" for 2-Year event
Inflow = 26.90 cfs @ 11.99 hrs, Volume= 1.416 af
Outflow = 18.21 cfs @ 12.07 hrs, Volume= 1.397 af, Atten= 32%, Lag= 4.8 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 2.06 fps, Min. Travel Time= 11.4 min
Avg. Velocity = 0.73 fps, Avg. Travel Time= 32.0 min
Peak Storage= 12,440 cf @ 12.07 hrs
Average Depth at Peak Storage= 0.53'
Bank-Full Depth= 1.00' Flow Area= 26.0 sf, Capacity= 77.78 cfs
6.00' x 1.00' deep channel, n= 0.035
Side Slope Z-value= 20.0 '/' Top Width= 46.00'
Length= 1,410.0' Slope= 0.0106 '/'
Inlet Invert= 512.00', Outlet Invert= 497.00'
‡
Reach R-41: LD-4A
Inflow
Outflow
Hydrograph
Time (hours)
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30
25
20
15
10
5
0
Inflow Area=10.675 ac
Avg. Flow Depth=0.53'
Max Vel=2.06 fps
n=0.035
L=1,410.0'
S=0.0106 '/'
Capacity=77.78 cfs
26.90 cfs
18.21 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 31HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 2P: 24" Culvert
Inflow Area = 6.060 ac, 0.00% Impervious, Inflow Depth > 1.05" for 2-Year event
Inflow = 8.34 cfs @ 12.11 hrs, Volume= 0.532 af
Outflow = 8.34 cfs @ 12.11 hrs, Volume= 0.532 af, Atten= 0%, Lag= 0.0 min
Primary = 8.34 cfs @ 12.11 hrs, Volume= 0.532 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 513.30' @ 12.11 hrs
Flood Elev= 528.00'
Device Routing Invert Outlet Devices
#1 Primary 512.00'24.0" Round Culvert
L= 167.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 512.00' / 508.00' S= 0.0240 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
Primary OutFlow Max=8.33 cfs @ 12.11 hrs HW=513.29' TW=511.36' (Dynamic Tailwater)
1=Culvert (Inlet Controls 8.33 cfs @ 3.87 fps)
Pond 2P: 24" Culvert
Inflow
Primary
Hydrograph
Time (hours)
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9
8
7
6
5
4
3
2
1
0
Inflow Area=6.060 ac
Peak Elev=513.30'
24.0"
Round Culvert
n=0.012
L=167.0'
S=0.0240 '/'
8.34 cfs8.34 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 32HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 3P: 36" Slope Drain Pipe
Inflow Area = 74.120 ac, 0.00% Impervious, Inflow Depth > 1.29" for 2-Year event
Inflow = 109.23 cfs @ 12.15 hrs, Volume= 7.962 af
Outflow = 58.01 cfs @ 12.37 hrs, Volume= 7.953 af, Atten= 47%, Lag= 13.4 min
Primary = 58.01 cfs @ 12.37 hrs, Volume= 7.953 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 536.50' @ 12.37 hrs Surf.Area= 64,287 sf Storage= 59,457 cf
Plug-Flow detention time= 8.0 min calculated for 7.953 af (100% of inflow)
Center-of-Mass det. time= 7.5 min ( 816.6 - 809.1 )
Volume Invert Avail.Storage Storage Description
#1 535.00' 2,237,064 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
535.00 0 0 0
536.00 58,048 29,024 29,024
541.00 120,747 446,988 476,012
546.00 174,399 737,865 1,213,877
551.00 234,876 1,023,188 2,237,064
Device Routing Invert Outlet Devices
#1 Primary 528.50'36.0" Round Culvert
L= 207.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 528.50' / 510.00' S= 0.0894 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 7.07 sf
#2 Device 1 530.00'36.0" Round Culvert
L= 530.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 530.00' / 528.50' S= 0.0028 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#3 Device 2 535.00'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=58.01 cfs @ 12.37 hrs HW=536.50' TW=511.29' (Dynamic Tailwater)
1=Culvert (Passes 58.01 cfs of 86.76 cfs potential flow)
2=Culvert (Barrel Controls 58.01 cfs @ 8.21 fps)
3=Orifice/Grate (Passes 58.01 cfs of 119.83 cfs potential flow)
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 33HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 3P: 36" Slope Drain Pipe
Inflow
Primary
Hydrograph
Time (hours)
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120
110
100
90
80
70
60
50
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30
20
10
0
Inflow Area=74.120 ac
Peak Elev=536.50'
Storage=59,457 cf
109.23 cfs
58.01 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 34HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 4P: 36" Slope Drain Pipe
Inflow Area = 2.385 ac, 0.00% Impervious, Inflow Depth > 1.00" for 2-Year event
Inflow = 3.10 cfs @ 12.11 hrs, Volume= 0.199 af
Outflow = 3.10 cfs @ 12.11 hrs, Volume= 0.199 af, Atten= 0%, Lag= 0.0 min
Primary = 3.10 cfs @ 12.11 hrs, Volume= 0.199 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 529.59' @ 12.11 hrs
Flood Elev= 532.00'
Device Routing Invert Outlet Devices
#1 Primary 528.94'36.0" Round Culvert
L= 150.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 528.94' / 510.00' S= 0.1263 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 7.07 sf
Primary OutFlow Max=3.10 cfs @ 12.11 hrs HW=529.59' TW=512.52' (Dynamic Tailwater)
1=Culvert (Inlet Controls 3.10 cfs @ 2.75 fps)
Pond 4P: 36" Slope Drain Pipe
Inflow
Primary
Hydrograph
Time (hours)
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3
2
1
0
Inflow Area=2.385 ac
Peak Elev=529.59'
36.0"
Round Culvert
n=0.013
L=150.0'
S=0.1263 '/'
3.10 cfs3.10 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 35HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 8P: Sediment Basin (SB-3)
Inflow Area = 98.610 ac, 0.00% Impervious, Inflow Depth > 1.46" for 2-Year event
Inflow = 103.10 cfs @ 11.99 hrs, Volume= 11.974 af
Outflow = 21.79 cfs @ 13.14 hrs, Volume= 6.427 af, Atten= 79%, Lag= 69.2 min
Primary = 21.79 cfs @ 13.14 hrs, Volume= 6.427 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 502.72' @ 13.14 hrs Surf.Area= 3.796 ac Storage= 7.175 af
Plug-Flow detention time= 196.6 min calculated for 6.424 af (54% of inflow)
Center-of-Mass det. time= 115.7 min ( 918.0 - 802.3 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 61.472 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.870 0.000 0.000
502.00 2.940 4.762 4.762
504.00 5.330 8.270 13.032
506.00 7.160 12.490 25.522
508.00 8.940 16.100 41.622
510.00 10.910 19.850 61.472
Device Routing Invert Outlet Devices
#1 Primary 499.50'30.0" Round Culvert
L= 91.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 496.00' S= 0.0385 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 4.91 sf
#2 Device 1 502.00'42.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=21.79 cfs @ 13.14 hrs HW=502.72' (Free Discharge)
1=Culvert (Passes 21.79 cfs of 33.14 cfs potential flow)
2=Orifice/Grate (Weir Controls 21.79 cfs @ 2.77 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 36HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 8P: Sediment Basin (SB-3)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
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110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=98.610 ac
Peak Elev=502.72'
Storage=7.175 af
103.10 cfs
21.79 cfs21.79 cfs
0.00 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 37HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 16P: 18" Culvert
Inflow Area = 1.370 ac, 0.00% Impervious, Inflow Depth > 1.06" for 2-Year event
Inflow = 2.86 cfs @ 11.98 hrs, Volume= 0.121 af
Outflow = 2.86 cfs @ 11.98 hrs, Volume= 0.121 af, Atten= 0%, Lag= 0.0 min
Primary = 2.86 cfs @ 11.98 hrs, Volume= 0.121 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 526.20' @ 11.98 hrs
Flood Elev= 528.00'
Device Routing Invert Outlet Devices
#1 Primary 524.00'18.0" Round Culvert
L= 100.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 524.00' / 510.00' S= 0.1400 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf
#2 Device 1 526.00'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Device 2 526.00'1.2" x 16.5" Horiz. Orifice/Grate X 2.00 columns X 8 rows C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=2.86 cfs @ 11.98 hrs HW=526.20' TW=512.47' (Dynamic Tailwater)
1=Culvert (Passes 2.86 cfs of 10.23 cfs potential flow)
2=Orifice/Grate (Weir Controls 2.86 cfs @ 1.45 fps)
3=Orifice/Grate (Passes 2.86 cfs of 4.70 cfs potential flow)
Pond 16P: 18" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
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3
2
1
0
Inflow Area=1.370 ac
Peak Elev=526.20'
2.86 cfs2.86 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 38HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 17P: 18" Culvert
Inflow Area = 1.370 ac, 0.00% Impervious, Inflow Depth > 1.06" for 2-Year event
Inflow = 2.16 cfs @ 12.04 hrs, Volume= 0.121 af
Outflow = 2.16 cfs @ 12.04 hrs, Volume= 0.121 af, Atten= 0%, Lag= 0.0 min
Primary = 2.16 cfs @ 12.04 hrs, Volume= 0.121 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 528.16' @ 12.04 hrs
Flood Elev= 530.00'
Device Routing Invert Outlet Devices
#1 Device 2 528.00'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#2 Primary 526.00'18.0" Round Culvert
L= 70.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 526.00' / 512.00' S= 0.2000 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf
#3 Device 1 528.00'1.2" x 16.5" Horiz. Orifice/Grate X 2.00 columns X 8 rows C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=2.16 cfs @ 12.04 hrs HW=528.16' TW=512.53' (Dynamic Tailwater)
2=Culvert (Passes 2.16 cfs of 10.11 cfs potential flow)
1=Orifice/Grate (Weir Controls 2.16 cfs @ 1.32 fps)
3=Orifice/Grate (Passes 2.16 cfs of 4.28 cfs potential flow)
Pond 17P: 18" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
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2
1
0
Inflow Area=1.370 ac
Peak Elev=528.16'
2.16 cfs2.16 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 39HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 18P: 18" Culvert
Inflow Area = 0.460 ac, 0.00% Impervious, Inflow Depth > 1.06" for 2-Year event
Inflow = 0.98 cfs @ 11.90 hrs, Volume= 0.041 af
Outflow = 0.98 cfs @ 11.90 hrs, Volume= 0.041 af, Atten= 0%, Lag= 0.0 min
Primary = 0.98 cfs @ 11.90 hrs, Volume= 0.041 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 528.10' @ 11.90 hrs
Flood Elev= 530.00'
Device Routing Invert Outlet Devices
#1 Device 2 528.00'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#2 Primary 526.00'18.0" Round Culvert
L= 70.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 526.00' / 510.00' S= 0.2286 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf
#3 Device 1 528.00'1.2" x 16.5" Horiz. Orifice/Grate X 2.00 columns X 8 rows C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.97 cfs @ 11.90 hrs HW=528.10' TW=512.36' (Dynamic Tailwater)
2=Culvert (Passes 0.97 cfs of 9.87 cfs potential flow)
1=Orifice/Grate (Weir Controls 0.97 cfs @ 1.01 fps)
3=Orifice/Grate (Passes 0.97 cfs of 3.28 cfs potential flow)
Pond 18P: 18" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
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1
0
Inflow Area=0.460 ac
Peak Elev=528.10'
0.98 cfs0.98 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 40HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 37P: Sediment Basin (SB-4)
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 1.83" for 2-Year event
Inflow = 39.32 cfs @ 11.99 hrs, Volume= 2.568 af
Outflow = 0.72 cfs @ 19.56 hrs, Volume= 0.102 af, Atten= 98%, Lag= 454.2 min
Primary = 0.72 cfs @ 19.56 hrs, Volume= 0.102 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 502.03' @ 19.56 hrs Surf.Area= 1.584 ac Storage= 2.466 af
Plug-Flow detention time= 621.4 min calculated for 0.102 af (4% of inflow)
Center-of-Mass det. time= 367.0 min ( 1,145.9 - 778.9 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 37.962 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.370 0.000 0.000
502.00 1.560 2.413 2.413
504.00 2.950 4.510 6.923
506.00 4.390 7.340 14.262
508.00 6.010 10.400 24.662
510.00 7.290 13.300 37.962
Device Routing Invert Outlet Devices
#1 Primary 498.00'36.0" Round Culvert
L= 150.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 498.00' / 495.00' S= 0.0200 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#2 Device 1 502.00'104.0" x 104.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=0.72 cfs @ 19.56 hrs HW=502.03' (Free Discharge)
1=Culvert (Passes 0.72 cfs of 54.18 cfs potential flow)
2=Orifice/Grate (Weir Controls 0.72 cfs @ 0.61 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 41HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 37P: Sediment Basin (SB-4)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
40
35
30
25
20
15
10
5
0
Inflow Area=16.815 ac
Peak Elev=502.03'
Storage=2.466 af
39.32 cfs
0.72 cfs0.72 cfs0.00 cfs
REFERENCE 3

North Carolina Department of Environment and Natural Resources, “Erosion and Sediment
Control Planning and Design Manual”, Revised May 2013.

Appendices
This section addresses the design of stable conveyance channels and
diversions using flexible linings. A stable channel is defined as a channel
which is nonsilting and nonscouring. To minimize silting in the channel, flow
velocities should remain constant or increase slightly throughout the channel
length. This is especially important in designing diversion channels and can
be accomplished by adjusting channel grade. Procedures presented in this
section address the problems of erosion and scour. More advanced procedures
for permanent, unlined channels may be found elsewhere. (References: Garde
and Ranga Raju, 1980)
Diversions are channels usually with a supporting ridge on the lower side.
They are generally located to divert flows across a slope and are designed
following the same procedures as other channels. Design tables for vegetated
diversions and waterways are included at the end of this section.
Flexible channel linings are generally preferred to rigid linings from an
erosion control standpoint because they conform to changes in channel shape
without failure and are less susceptible to damage from frost heaving, soil
swelling and shrinking, and excessive soil pore water pressure from lack of
drainage. Flexible linings also are generally less expensive to construct, and
when vegetated, are more natural in appearance. On the other hand, flexible
linings generally have higher roughness and require a larger cross section for
the same discharge.
EROSION CONtROL CRItERIa
The minimum design criteria for conveyance channels require that two
primary conditions be satisfied: the channel system must have capacity for
the peak flow expected from the 10-year storm and the channel lining must be
resistant to erosion for the design velocity. In some cases, out-of-bank flow
may be considered a functional part of the channel system. In these cases,
flow capacities and design velocities should be considered separately for out-
of-bank flows and channel flows.
Both the capacity of the channel and the velocity of flow are functions of the
channel lining, cross-sectional area and slope. The channel system must carry
the design flow, fit site conditions, and be stable.
Sta BLE CHaNNEL DESIGN mEtHODS
Two accepted procedures for designing stable channels with flexible linings
are: (1) the permissible velocity approach; and (2) the tractive force approach.
Under the permissible velocity approach, the channel is considered stable if the
design, mean velocity is lower than the maximum permissible velocity. Under
the tractive force approach, erosive stress evaluated at the boundary between
flowing water and lining materials must be less than the minimum unit tractive
force that will cause serious erosion of material from a level channel bed.
8.05 DESIGN Of Sta BLE CHaNNELS aND DIVERSIONS
8.05.1
8
8.05.2
The permissible velocity procedure is recommended for the design of vegetative
channels because of common usage and the availability of reliable design
tables. The tractive force approach is recommended for design of channels
with temporary synthetic liners or riprap liners. The tractive force procedure
is described in full in the U.S. Department of Transportation, Federal Highway
Administration Bulletin, Design of Roadside Channels with Flexible Linings.
Permissible Velocity
Procedure
The permissible velocity procedure uses two equations to calculate flow:
Manning’s equation,
V = 1.49 R2/3 S1/2 n
where:
V = average velocity in the channel in ft/sec.
n = Manning’s roughness coefficient, based upon the lining of the
channel
R = hydraulic radius, wetted cross-sectional area/wetted perimeter
in ft
S = slope of the channel in ft/ft
and the continuity equation,
Q = AV
where:
Q = flow in the channel in cfs
A = cross-sectional area of flow within the channel in ft2
V = average velocity in the channel in ft/sec.
Manning’s equation and the continuity equation are used together to determine
channel capacity and flow velocity. A nomograph for solving Manning’s
equation is given in Figure 8.05a.
Selecting Permanent
Channel Lining
Channel lining materials include such flexible materials as grass, riprap and
gabions, as well as rigid materials such as paving blocks, flag stone, gunite,
asphalt, and concrete. The design of concrete and similar rigid linings
is generally not restricted by flow velocities. However, flexible channel
linings do have maximum permissible flow velocities beyond which they are
susceptible to erosion. The designer should select the type of liner that best
fits site conditions.
Table 8.05a lists maximum permissible velocities for established grass linings
and soil conditions. Before grass is established, permissible velocity is
determined by the choice of temporary liner. Permissible velocities for riprap
linings are higher than for grass and depend on the stone size selected.
Appendices
8.05.3
8
8.05.4
Table 8.05a
Maximum Allowable Design Velocities1
for Vegetated Channels
Typical
Channel Slope
Application
Soil
Characteristics2
Grass Lining Permissible Velocity3
for Established Grass
Lining (ft/sec)
0-5%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
5.0
4.5
4.5
4.5
3.5
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
6.0
5.5
5.5
5.5
4.5
5-10%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
4.5
4.0
4.0
4.0
3.0
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
5.5
5.0
5.0
5.0
3.5
>10%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
3.5
2.5
2.5
2.5
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
4.5
3.5
3.5
3.5
Source: USDA-SCS Modified
NOTE:1Permissible Velocity based on 10-year storm peak runoff
2Soil erodibility based on resistance to soil movement from concentrated flowing water.
3Before grass is established, permissible velocity is determined by the type of temporary liner used.
Selecting Channel
Cross-Section
Geometry
To calculate the required size of an open channel, assume the design flow is
uniform and does not vary with time. Since actual flow conditions change
throughout the length of a channel, subdivide the channel into design reaches,
and design each reach to carry the appropriate capacity.
The three most commonly used channel cross-sections are “V”-shaped,
parabolic, and trapezoidal. Figure 8.05b gives mathematical formulas for the
area, hydraulic radius and top width of each of these shapes.
Appendices
8.05.5
8
8.05.6 Rev. 12/93
Design Procedure-
Permissible Velocity
The following is a step-by-step procedure for designing a runoff conveyance
channel using Manning’s equation and the continuity equation:
Step 1. Determine the required flow capacity, Q, by estimating peak runoff
rate for the design storm (Appendix 8.03).
Step 2. Determine the slope and select channel geometry and lining.
Step 3. Determine the permissible velocity for the lining selected, or the
desired velocity, if paved. (see Table 8.05a, page 8.05.4)
Step 4. Make an initial estimate of channel size—divide the required Q by the
permissible velocity to reach a “first try” estimate of channel flow area. Then
select a geometry, depth, and top width to fit site conditions.
Step 5. Calculate the hydraulic radius, R, from channel geometry (Figure
8.05b, page 8.05.5).
Step 6. Determine roughness coefficient n.
Structural Linings—see Table 8.05b, page 8.05.6.
Grass Lining:
a. Determine retardance class for vegetation from Table 8.05c, page
8.05.8. To meet stability requirement, use retardance for newly
mowed condition (generally C or D). To determine channel capacity,
use at least one retardance class higher.
b. Determine n from Figure 8.05c, page 8.05.7.
Step 7. Calculate the actual channel velocity, V, using Manning’s equation
(Figure 8.05a, pg. 8.05.3), and calculate channel capacity, Q, using the
continuity equation.
Step 8. Check results against permissible velocity and required design
capacity to determine if design is acceptable.
Step 9. If design is not acceptable, alter channel dimensions as appropriate.
For trapezoidal channels, this adjustment is usually made by changing the
bottom width.
Table 8.05b
Manning’s n for Structural
Channel Linings
Channel Lining
Recommended
n values
Asphaltic concrete, machine placed
Asphalt, exposed prefabricated
Concrete
Metal, corrugated
Plastic
Shotcrete
Gabion
Earth
0.014
0.015
0.015
0.024
0.013
0.017
0.030
0.020
Source: American Society of Civil Engineers (modified)
Appendices
Rev. 12/93 8.05.7
Step 10. For grass-lined channels once the appropriate channel dimensions
have been selected for low retardance conditions, repeat steps 6 through 8
using a higher retardance class, corresponding to tall grass. Adjust capacity of
the channel by varying depth where site conditions permit.
NOTE 1: If design velocity is greater than 2.0 ft/sec., a temporary lining
may be required to stabilize the channel until vegetation is established.
The temporary liner may be designed for peak flow from the 2-year storm.
If a channel requires a temporary lining, the designer should analyze
shear stresses in the channel to select the liner that provides protection
and promotes establishment of vegetation. For the design of temporary
liners, use tractive force procedure.
NOTE 2: Design Tables—Vegetated Channels and Diversions at the end
of this section may be used to design grass-lined channels with parabolic
cross-sections.
Step 11. Check outlet for carrying capacity and stability. If discharge
velocities exceed allowable velocities for the receiving stream, an outlet
protection structure will be required (Table 8.05d, page 8.05.9).
Sample Problem 8.05a illustrates the design of a grass-lined channel.
8
8.05.8
Table 8.05c
Retardance Classification for Vegetal Covers
Retardance Cover Condition
A Reed canarygrass
Weeping lovegrass
Excellent stand, tall (average 36”)
Excellent stand, tall (average 30”)
B Tall fescue
Bermudagrass
Grass-legume mixture
(tall fescue,red
fescue, sericea
lespedeza)
Grass mixture
(timothy, smooth
bromegrass or
orchardgrass)
Sericea lespedeza
Reed canarygrass
Alfalfa
Good stand, uncut, (average 18”)
Good stand, tall (average 12”)
Good stand, uncut
Good stand, uncut (average 20”)
Good stand, not woody, tall (average 19”)
Good stand, cut, (average 12-15”)
Good stand, uncut (average 11”)
C Tall fescue
Bermudagrass
Bahiagrass
Grass-legume mixture--
summer (orchardgrass,
redtop and annual
lespedeza)
Centipedegrass
Kentucky bluegrass
Redtop
Good stand (8-12”)
Good stand, cut (average 6”)
Good stand, uncut (6-8”)
Good stand, uncut (6-8”)
Very dense cover (average 6”)
Good stand, headed (6-12”)
Good stand, uncut (15-20”)
D Tall fescue
Bermudagrass
Bahiagrass
Grass-legume mixture--
fall-spring (orchardgrass,
redtop, and
annual lespedeza)
Red fescue
Centipedegrass
Kentucky bluegrass
Good stand, cut (3-4”)
Good stand, cut (2.5”)
Good stand, cut (3-4”)
Good stand, uncut (4-5”)
Good stand, uncut (12-18”)
Good stand, cut (3-4”)
Good stand, cut (3-4”)
E Bermudagrass
Bermudagrass
Good stand, cut (1.5”)
Burned stubble
Modified from: USDA-SCS, 1969. Engineering Field Manual.
Appendices
8.05.9
Table 8.05d
Maximum Permissible
Velocities for Unprotected
Soils in Existing Channels.
Materials
Maximum Permissible
Velocities (fps)
Fine Sand (noncolloidal)
Sand Loam (noncolloidal)
Silt Loam (noncolloidal)
Ordinary Firm Loam
Fine Gravel
Stiff Clay (very colloidal)
Graded, Loam to Cobbles (noncolloidal)
Graded, Silt to Cobbles (colloidal)
Alluvial Silts (noncolloidal)
Alluvial Silts (colloidal)
Coarse Gravel (noncolloidal)
Cobbles and Shingles
2.5
2.5
3.0
3.5
5.0
5.0
5.0
5.5
3.5
5.0
6.0
5.5
Sample Problem 8.05a
Design of a
Grass-lined Channel.
Given:
Design Q10 = 16.6 cfs
Proposed channel grade = 2%
Proposed vegetation: Tall fescue
Soil: Creedmoor (easily erodible)
Permissible velocity, Vp = 4.5 ft/s (Table 8.05a)
Retardance class: “B” uncut, “D” cut (Table 8.05c).
Trapezoidal channel dimensions:
designing for low retardance condition (retardance class D)
design to meet Vp.
Find:
Channel dimensions
Solution:
Make an initial estimate of channel size
A = Q/V, 16.6 cfs/4.5 ft/sec = 3.69 ft2
Try bottom width = 3.0 ft w/side slopes of 3:1
Z = 3
A = bd + Zd2
P = b + 2d Z2 + 1
R = AP
An iterative solution using Figure 8.05a to relate flow depth to Manning’s n
proceeds as follows: Manning’s equation is used to check velocities.
*From Fig. 8.05c, pg. 8.05.7, Retardance Class d (VR=4.5x0.54=2.43)
d (ft) A (ft
2) R (ft) *n Vt (fps) Q (cfs) Comments
0.8 4.32 0.54 0.043 3.25 14.0 V<Vp OK,
Q<Q10
(too small, try deeper channel)
0.9 5.13 0.59 0.042 3.53 18.10 V<Vp, OK,
Q>Q10, OK
Now design for high retardance (class B):
For the ease of construction and maintenance assume and
try d = 1.5 ft and trial velocity Vt = 3.0 ft/sec
d (ft) A (ft
2) R (ft)Vt (fps)n V (fps) Q (cfs) Comments
1.5 11.25 0.90 3.0
2.0
1.6
**1.5
0.08
0.11
0.12
0.13
2.5
1.8
1.6
1.5
28
20
18
17
reduce Vtreduce Vt
Q>Q10 OK
** These assumptions = actual V (fps.) (chart continued on next page)
8
8.05.10 Rev. 12/93
(continued)
Sample Problem 8.05a
Design of a
Grass-lined Channel.
Channel summary:
Trapezoidal shape, Z = 3, b = 3 ft, d = 1.5 ft, grade = 2%
Note: In Sample Problem 8.05a the “n-value” is first chosen based on a
permissible velocity and not a design velocity criteria. Therefore, the use of
Table 8.05c may not be as accurate as individual retardance class charts when
a design velocity is the determining factor.
Tractive Force
Procedure
The design of riprap-lined channels and temporary channel linings is based on
analysis of tractive force.
NOTE: This procedure is for uniform flow in channels and is not to be
used for design of deenergizing devices and may not be valid for larger
channels.
To calculate the required size of an open channel, assume the design flow is
uniform and does not vary with time. Since actual flow conditions change
through the length of a channel, subdivide the channel into design reaches as
appropriate.
PERMISSIBLE SHEAR STRESS
The permissible shear stress, Td, is the force required to initiate movement of
the lining material. Permissible shear stress for the liner is not related to the
erodibility of the underlying soil. However, if the lining is eroded or broken,
the bed material will be exposed to the erosive force of the flow.
COMPUTING NORMAL DEPTH
The first step in selecting an appropriate lining is to compute the design
flow depth (the normal depth) and determine the shear stress.
Normal depths can be calculated by Manning’s equation as shown for
trapezoidal channels in Figure 8.05d. Values of the Manning’s roughness
coefficient for different ranges of depth are provided in Table 8.05e for
temporary linings and Table 8.05f for riprap. The coefficient of roughness
generally decreases with increasing flow depth.
n value for Depth Ranges*
Table 8.05e
Manning’s Roughness
Coefficients for Temporary
Lining Materials
0-0.5 ft 0.5-2.0 ft >2.0 ft
Lining Type
Woven Paper Net
Jute Net
Fiberglass Roving
Straw with Net
Curled Wood Mat
Synthetic Mat
0.016
0.028
0.028
0.065
0.066
0.036
0.015
0.022
0.021
0.033
0.035
0.025
0.015
0.019
0.019
0.025
0.028
0.021
* Adapted from: FHWA-HEC 15, Pg. 37 - April 1988
Appendices
Rev. 12/93 8.05.11
8
8.05.12 Rev. 12/93
Table 8.05f Manning’s Roughness Coefficient
n - value
n value for Depth Ranges
Lining Category Lining Type 0-0.5 ft
(0-15 cm)
0.5-2.0 ft
(15-60 cm)
2.0 ft
(>60 cm)
Rigid Concrete
Grouted Riprap
Stone Masonry
Soil Cement
Asphalt
0.015
0.040
0.042
0.025
0.018
0.013
0.030
0.032
0.022
0.016
0.013
0.028
0.030
0.020
0.016
Unlined Bare Soil
Rock Cut
0.023
0.045
0.020
0.035
0.020
0.025
Gravel Riprap 1-inch (2.5-cm) D502-inch (5-cm) D50
0.044
0.066
0.033
0.041
0.030
0.034
Rock Riprap 6-inch (15-cm) D5012-inch (30-cm) D50
0.104
--
0.069
0.078
0.035
0.040
Note: Values listed are representative values for the respective depth ranges. Manning’s roughness coefficients, n, vary with the flow depth.
DETERMINING SHEAR STRESS
Shear stress, T, at normal depth is computed for the lining by the following
equation:
T = yds
Td = Permissible shear stress
where:
T = shear stress in lb/ft2
y = unit weight of water, 62.4 lb/ft3
d = flow depth in ft
s = channel gradient in ft/ft
If the permissible shear stress, Td, given in Table 8.05g is greater than the
computed shear stress, the riprap or temporary lining is considered acceptable.
If a lining is unacceptable, select a lining with a higher permissible shear stress
and repeat the calculations for normal depth and shear stress. In some cases it
may be necessary to alter channel dimensions to reduce the shear stress.
Computing tractive force around a channel bend requires special considerations
because the change in flow direction imposes higher shear stress on the channel
bottom and banks. The maximum shear stress in a bend, Tb, is given by the
following equation:
Tb = KbT
where:
Tb = bend shear stress in lb/ft2
kb = bend factor
T = computed stress for straight channel in lb/ft2
The value of kb is related to the radius of curvature of the channel at its center
line, Rc, and the bottom width of the channel, B, Figure 8.05e. The length of
channel requiring protection downstream from a bend, Lp, is a function of the
roughness of the lining material and the hydraulic radius as shown in Figure
8.05f.
Appendices
Rev. 12/93 8.05.13
Table 8.05g
Permissible Shear Stresses
for Riprap and Temporary
Liners
Permissible Unit Shear Stress, Td
Lining Category Lining Type (lb/ft2)
Temporary Woven Paper Net
Jute Net
Fiberglass Roving:
Single
Double
Straw with Net
Curled Wood mat
Synthetic Mat
0.15
0.45
0.60
0.85
1.45
1.55
2.00
d50 Stone Size (inches)
Gravel Riprap 1
2
0.33
0.67
Rock Riprap 6
9
12
15
18
21
24
2.00
3.00
4.00
5.00
6.00
7.80
8.00
Adapted From: FHWA, HEC-15, April 1983, pgs. 17 & 37.
Design Procedure-
Temporary Liners
The following is a step-by-step procedure for designing a temporary liner for
a channel. Because temporary liners have a short period of service, the design
Q may be reduced. For liners that are needed for six months or less, the 2-year
frequency storm is recommended.
Step 1. Select a liner material suitable for site conditions and application.
Determine roughness coefficient from manufacturer’s specifications or Table
8.05e, page 8.05.10.
Step 2. Calculate the normal flow depth using Manning’s equation (Figure
8.05d). Check to see that depth is consistent with that assumed for selection of
Manning’s n in Figure 8.05d, page 8.05.11. For smaller runoffs Figure 8.05d
is not as clearly defined. Recommended solutions can be determined by using
the Manning equation.
Step 3. Calculate shear stress at normal depth.
Step 4. Compare computed shear stress with the permissible shear stress for
the liner.
Step 5. If computed shear is greater than permissible shear, adjust channel
dimensions to reduce shear, or select a more resistant lining and repeat steps
1 through 4.
Design of a channel with temporary lining is illustrated in Sample Problem
8.05b, page 8.05.14.
8
8.05.14 Rev. 12/93
Sample Problem 8.05b
Design of a Temporary Liner
for a Vegetated Channel
Given:
Q2 = 16.6 cfs
Bottom width = 3.0 ft
Z = 3
n = 0.02 (Use basic n value for channels cut in earth (Table 8.05b)
Vp = 2.0 ft/sec maximum allowable velocity for bare soil (pg. 6.30.1)
Channel gradient = 2%
Find:
Suitable temporary liner material
Solution:
Using Manning’s equation:
b(ft) d(ft) A(ft
2) R(ft) V(fps) Q(cfs) Comments
3.0 0.59 2.82 0.42 5.88 16.60 V>Vp,
(needs protection)
Q Q2, OK
Velocity >2.0 fps channel requires temporary liner:*
Calculate channel design with straw with net as temporary liner.
n = 0.033 (Table 8.05e). Td = 1.45 (Table 8.05g, pg. 8.05.13)
b(ft) d(ft) A(ft
2) R(ft) V(fps) Q(cfs) Comments
3.0 0.76 4.05 1.94 4.10 16.60 V<Td, OK
Calculate shear stress for Q2 conditions:
T = yds where: y = unit weight of water (62.4 lb/ft3)
d = flow depth in ft
s = channel gradient in ft/ft
T = (62.4)(0.76)(0.02) = 0.95 T<Td, OK
Temporary liner: straw with net.
*In some cases the solution is not as clearly defined; the use of a more conservative material is
recommended.
DESIGN OF RIPRAP LINING-MILD GRADIENT
The mild gradient channel procedure is applicable for channel grades less than
10%. The method assumes that the channel cross section has been designed
properly, including undercut and that the remaining problem is to provide a
stable riprap lining.
Side slope stability. As the angle of the side slope approaches the angle of
repose of the channel lining, the lining material becomes less stable. The
stability of a side slope is given by the tractive force ratio, K2, a function of the
side slope and the angle of repose of the rock lining material.
The rock size to be used for the channel lining can be determined by comparing
the tractive force ratio, an indicator of side slope stability, to the shear stress
on the sides and shear stress on the bottom of the channel. The angle of
repose for different rock shapes and sized is shown in Figure 8.05g. The
required rock size (mean diameter of the gradation, d50) for the side slopes is
determined from the following equation:
d50 (sides) = K1 d50 (bottom) K2where:
K1 = ratio of shear stress on the sides, Ts, and bottom, T, of a
trapezoidal channel (Figure 8.05h),
K2 = tractive force ratio (Figure 8.05i).
Appendices
Rev. 12/93 8.05.15
8
8.05.16 Rev. 12/93
Appendices
Rev. 12/93 8.05.17
Selection of riprap gradation and thickness. Riprap gradation should
have a smooth size distribution curve. The largest stone size in the
gradation should not exceed 1.5 times the d50 size. The most important
criterion is that interstices formed by larger stones be filled with smaller sizes
in an interlocking fashion, preventing the formation of open pockets. These
gradation requirements apply regardless of the type of filter design used.
In general, riprap constructed with angular stone performs best. Round stones
are acceptable as riprap provided they are not placed on side slopes steeper than
3:1. Flat, slab-like stones should be avoided since they are easily dislodged by
the flow. An approximate guide to stone shape is that neither the breadth nor
the thickness of a single stone be less than one-third its length.
The thickness of a riprap lining should equal 1.5 times the diameter of the
largest rock size in the gradation.
Filter design: When rock riprap is used, an appropriate underlying filter
material must be selected. The filter material may be either a granular, gravel
or sand filter blanket, or a geotextile fabric.
8
8.05.18 Rev. 12/93
For a granular filter blanket, the following criteria must be met:
d15 filter
d85 base < 5
5 <d15 filter
d15 base < 40
d50 filter
d50 base < 40
Where “filter” refers to the overlying riprap or gravel and “base” refers to
the underlying soil, sand or gravel. The relationship must hold between the
filter blanket and base material and between the riprap and filter blanket.
The minimum thickness for a filter blanket should not be less than 6
inches.
In selecting a filter fabric, the fabric should have a permeability at least
equal to the soil and a pore structure that will hold back the base soil. The
following properties are essential to assure performance under riprap:
• For filter fabric covering a base with granular particles containing 50
percent or less (by weight) of fine particles (less than U.S. Standard
Sieve No. 200):
a. d85 base (mm)/EOS* filter cloth (mm) > 1.
b. Total open area of filter is less than 36%.
• Filter fabric covering other soils:
a. EOS less than U.S. Standard Sieve No. 70.
b. Total open area of filter less than 10%.
*EOS - Equivalent Opening Size to a U.S. Standard Sieve Size
Design Procedure-
Riprap Lining, Mild
Gradient
The following is a step-by-step procedure for designing a riprap channel
lining with mild gradients. This procedure is designed for smaller channels
that are generally used as erosion control measures, and is not intended for
conveyance channels.
Additional design information for lined channels may be obtained from the
National Technical Information Services (NTIS) by obtaining a copy of the
National Cooperative Highway Research Program Report No. 108, titled
“Tentative Design Procedure for Riprap - Lined Channels”.
Step 1. Select a riprap size, and look up the Manning’s n value (Table 8.05f)
and permissible shear stress, Td (Table 8.05g).
Step 2. Calculate the normal flow depth in the channel, using Manning’s
equation (Figure 8.05d). Check that the n value for the calculated normal
depth is consistent with that determined in step 1.
Step 3. Calculate shear stress at normal depth.
REFERENCE 4

“Standard Specification for Roads and Structures”, North Carolina Department of
Transportation, Raleigh, January 2012.

Section 1043

10-62
All stone shall meet the approval of the Engineer. While no specific gradation is required, 1
there shall be equal distribution of the various sizes of the stone within the required size 2
range. The size of an individual stone particle will be determined by measuring its long 3
dimension. 4
Stone or broken concrete for rip rap shall meet Table 1042-1 for the class and size 5
distribution. 6
TABLE 1042-1
ACCEPTANCE CRITERIA FOR RIP RAP AND STONE FOR EROSION CONTROL
Required Stone Sizes, inches Class Minimum Midrange Maximum
A 2 4 6
B 5 8 12
1 5 10 17
2 9 14 23
No more than 5.0% of the material furnished can be less than the minimum size specified nor 7
no more than 10.0% of the material can exceed the maximum size specified. 8
SECTION 1043 9
AGGREGATE FROM CRUSHED CONCRETE 10
1043-1 GENERAL 11
Aggregate from crushed concrete is a recycled product made by crushing concrete obtained 12
from concrete truck clean out, demolition of existing concrete structures or pavement, or 13
similar sources and transported from a crushing facility. It does not include concrete 14
pavements that are rubblelized, broken or otherwise crushed in place on the roadway. 15
The crushed material must meet all sources approval requirements described in Sections 1005 16
and 1006 with the exception of the sodium sulfate test requirement. Deleterious materials 17
shall not be more than 3%. 18
Sampling and acceptance for the determination of gradaction, LL and PI will be performed as 19
described in the Aggregate QC/QA Program Manual and the Aggregate Sampling Manual. 20
1043-2 AGGREGATE BASE COURSE 21
The material shall meet the ABC gradation. The LL of the material shall be raised 5 points to 22
no more than 35. 23
1043-3 AGGREGATE SHOULDER BORROW 24
The material shall meet Section 1019. 25
1043-4 CLEAN COARSE AGGREGATE FOR ASPHALT 26
The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 27
shall be approved by the Engineer, and the mix shall meet all requirements. 28
1043-5 CLEAN COARSE AGGREGATE FOR CONCRETE 29
The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 30
is restricted to Class B concrete mixes only. Use of the material shall be approved by the 31
Engineer, and the concrete shall meet all requirements. 32
SECTION 1044 33
SUBSURFACE DRAINAGE MATERIALS 34
1044-1 SUBDRAIN FINE AGGREGATE 35
Subdrain fine aggregate shall meet No. 2S or 2MS in Table 1005-2. 36
NCDOT 2012 Standard Specifications
REFERENCE 5

United States Department of Agriculture, “Urban Hydrology for Small Watersheds”, Technical
Release 55, June 1986.

Technical Release 55
Urban Hydrology for Small Watersheds
Time of Concentration and Travel TimeChapter 3
3–4 (210-VI-TR-55, Second Ed., June 1986)
Manning’s equation is:
V rs
n
=149
2
3
1
2.[eq. 3-4]
where:
V = average velocity (ft/s)
r = hydraulic radius (ft) and is equal to a/pw
a = cross sectional flow area (ft
2)
pw = wetted perimeter (ft)
s = slope of the hydraulic grade line (channel
slope, ft/ft)
n = Manning’s roughness coefficient for open
channel flow.
Manning’s n values for open channel flow can be
obtained from standard textbooks such as Chow
(1959) or Linsley et al. (1982). After average velocity is
computed using equation 3-4, Tt for the channel seg-
ment can be estimated using equation 3-1.
Reservoirs or lakes
Sometimes it is necessary to estimate the velocity of
flow through a reservoir or lake at the outlet of a
watershed. This travel time is normally very small and
can be assumed as zero.
Limitations
•Manning’s kinematic solution should not be used
for sheet flow longer than 300 feet. Equation 3-3
was developed for use with the four standard
rainfall intensity-duration relationships.
•In watersheds with storm sewers, carefully identify
the appropriate hydraulic flow path to estimate Tc.
Storm sewers generally handle only a small portion
of a large event. The rest of the peak flow travels
by streets, lawns, and so on, to the outlet. Consult a
standard hydraulics textbook to determine average
velocity in pipes for either pressure or nonpressure
flow.
•The minimum Tc used in TR-55 is 0.1 hour.
•A culvert or bridge can act as a reservoir outlet if
there is significant storage behind it. The proce-
dures in TR-55 can be used to determine the peak
flow upstream of the culvert. Detailed storage
routing procedures should be used to determine
the outflow through the culvert.
Example 3-1
The sketch below shows a watershed in Dyer County,
northwestern Tennessee. The problem is to compute
Tc at the outlet of the watershed (point D). The 2-year
24-hour rainfall depth is 3.6 inches. All three types of
flow occur from the hydraulically most distant point
(A) to the point of interest (D). To compute Tc, first
determine Tt for each segment from the following
information:
Segment AB: Sheet flow; dense grass; slope (s) = 0.01
ft/ft; and length (L) = 100 ft. Segment BC: Shallow
concentrated flow; unpaved; s = 0.01 ft/ft; and
L = 1,400 ft. Segment CD: Channel flow; Manning’s
n = .05; flow area (a) = 27 ft2; wetted perimeter
(pw) = 28.2 ft; s = 0.005 ft/ft; and L = 7,300 ft.
See figure 3-2 for the computations made on
worksheet 3.
A B C D
7,300 ft1,400 ft100 ft
(Not to scale)
Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 1 of 13
12/9/2016 (Initial Submittal)

Calculation Title:
Final Conditions Stormwater Calculation
Summary:
Stormwater channels, culverts, and downdrains were designed to convey stormwater for a 100 year,
24-hour design storm event considering long-term conditions after decommissioning of the Primary and
Secondary Ash Basin dams.

Notes:
Revision Log:
No. Description Originator Verifier Technical Reviewer
0

Initial Submittal –
12/9/2016

Chris Jordan Stephanie Stanwick Cedric H. Ruhl

Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 2 of 13
12/9/2016 (Initial Submittal)

OBJECTIVE:
The objective of this calculation is to design the stormwater conveyance measures based on long-
term conditions after decommissioning of the Primary and Secondary Ash Basin dams.
METHOD:
Stormwater flow rates will be calculated using the SCS method. The hydraulic capacity of existing
and proposed stormwater conveyances will be evaluated using Manning’s equation and
HydroCAD modeling software.
DEFINITION OF VARIABLES:
 = shear;
A = area;
b = bottom width;
CN = curve number;
d = flow depth;
D = channel depth;
i = rainfall depth;
L = length;
n = Manning’s n;
P = wetted perimeter;
Q = flow;
R = hydraulic radius;
S = longitudinal slope;
t = time
T = top width;
Tc = time of concentration;
V = velocity; and
Z = channel side slope.
CALCULATIONS:
1.0 Design conveyances for upstream tributary areas and ash basin
closure channels
Concentrated stormwater flow from upstream tributary areas was assumed to discharge across
the closed ash basin at five locations shown in Figures 1 and 2, and are described below.

Drainage area DA-1 is the area draining to the inlet of the existing 48-inch diameter corrugated
metal pipe (CMP) west of Edgewood Road. The 48-inch CMP historically conveyed stormwater
flow underneath the primary ash basin and into the Dan River. The CMP has been grouted, and
water from this area is currently discharged by pumping. A proposed channel will convey
additional stormwater flow from additional tributary areas west of the 48-inch CMP pipe inlet.
Upon completion of basin closure activities, a new pipe will restore flow from the area of the inlet
at the existing grouted 48-inch diameter CMP to the ash basin closure area. The new pipe will
Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 3 of 13
12/9/2016 (Initial Submittal)

discharge into a channel that will convey stormwater flow across the closed ash basin area and
into the Dan River.

Drainage area DA-2 is the area flowing into the inlet of the existing 54-inch diameter RCP. The
54-inch pipe connects to a drop inlet which conveys water through a 36-inch diameter RCP and
outlets into the secondary ash basin in the vicinity of the intermediate dike. The upstream end of
the 54-inch diameter RCP pipe has been temporarily sealed with a grout plug. Upon completion
of basin closure activities, the grout plug will be removed and a new section of pipe will restore
flow to the ash basin closure area. The new pipe will discharge into a channel that will convey
stormwater flow across the closed ash basin area and into the Dan River.

Drainage area DA-3 has a 36-inch culvert which conveys stormwater underneath the railroad
tracks and discharges into the secondary ash basin. Upon completion of basin closure activities,
a slope drain will convey flow from the culvert to the ash basin closure area. The slope drain will
discharge into a channel that will convey flow across the closed ash basin area and into the Dan
River.

Drainage area DA-4 is the area flowing into the outlet pipe for the dredge area between Ash Fills
1 and 2, which currently discharges into the secondary ash basin. Upon completion of basin
closure activities, a slope drain will convey flow from the outlet pipe to the ash basin closure area.
The slope drain will discharge into a channel that will convey stormwater flow into a channel that
will convey flow across the closed ash basin area and into the Dan River.

Drainage area DA-8A-1A is the area in between the 36-inch culvert and the ash basin. Upon
completion of basin closure activities, a diversion ditch will be installed between the rail line and
ash basin perimeter road, with multiple slope drains that discharge into the ash basin footprint.

The existing ash basin area was divided in four main drainage areas based on post-closure
stormwater discharge locations into the Dan River. The main drainage areas are numbered west
to east as DA-5, DA-6, DA-7 and DA-8. The drainage areas were sub-divided to analyze
stormwater flows to collector channels. These drainage areas within the footprint are assumed
to be bare soil initially, and vegetated in the final conditions. The water flow path in the ash basin
footprint was assumed to follow an inter-connected network of interceptor ditches, toe ditches and
longitudinal ditches, which finally discharge the water to the Dan River.
1.1 Estimate drainage areas
Drainage areas were delineated to drain stormwater for long-term conditions after construction of
the proposed Dan River Landfill and closure of the existing ash units (Ash Fills 1 and 2, Primary
and Secondary Ash Basins). The drainage areas are defined in Figure 1 and are summarized in
the following table:

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Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 4 of 13
12/9/2016 (Initial Submittal)

Drainage
Area ID
Drainage Area
{A}
(ac)
Curve Number
(CN)
Drainage
Area ID
Drainage Area
{A}
(ac)
Curve Number
(CN)
DA-1 22.70 83 DA-7C 2.48 74
DA-2 6.10 74 DA-7D 2.65 74
DA-3 2.39 74 DA-7E 1.64 74
DA-4 74.10 78 DA-7F 3.00 74
DA-5A 4.03 74 DA-7G 2.26 74
DA-5B 2.13 74 DA-8A-1A 0.62 74
DA-5C 2.83 74 DA-8A-1B 0.75 74
DA-5D 2.18 74 DA-8A-1C 0.13 74
DA-6A 1.23 74 DA-8A-1D 1.24 74
DA-6B 2.78 74 DA-8A-1E 0.29 74
DA-6C 2.51 74 DA-8A-1F 0.17 74
DA-6D 2.70 74 DA-8A-1G 0.35 74
DA-6E 3.25 74 DA-8A 4.89 74
DA-6F 1.78 74 DA-8B 2.88 74
DA-6G 2.61 74 DA-8C 1.48 74
DA-7A 4.69 74 DA-8D 1.77 74
DA-7B 1.71 74
Table 1: Summary of Drainage Areas

1.2 Calculate time of concentration
The time of concentration (Tc) is the time needed for water to flow from the most remote point in
a drainage area to the drainage area outlet. The estimated time of concentration for the drainage
areas is shown in Figure 1.

The total time of concentration for a catchment generally consists of the following three
components: sheet flow, shallow concentrated flow and channel flow. In the current analysis,
sheet flow was assumed for the first 100 feet of the flow path, after which the flow was generally
classified as shallow concentrated flow. However, if the flow entered a channel within the sub-
catchment, then the flow was classified as channel flow. Several sub-catchments were relatively
small and were hydrologically difficult to generate sheet flow, shallow concentrated flow or
channel flow components for evaluation of time of concentration. A minimum time of concentration
of 6 minutes (as described by TR-55, Ref. 5) was used for such relatively small sub-catchments.
HydroCAD software [Ref. 2] was used to estimate time of concentration based on input
parameters summarized in the following tables:

Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 5 of 13
12/9/2016 (Initial Submittal)

Drainage
Area ID
Flow Length
{L}
(ft.)
Surface
Description
Manning No.
{n}
Land Slope
(ft/ft)
Time of
Concentration
{Tc,sheet}
(min)
DA-1 Smooth
surface 0.011 0.067 0.7
DA-2 0.150 0.050 6.5
DA-3 0.150 0.074 5.6
DA-4 0.150 0.043 6.9
DA-5A 0.150 0.073 5.6
DA-5B 0.150 0.025 8.6
DA-5C 0.150 0.014 10.9
DA-5D
DA-6A 0.150 0.010 12.8
DA-6B 0.150 0.033 7.7
DA-6C 0.150 0.017 10.0
DA-6D 0.150 0.015 10.5
DA-6E 0.150 0.012 11.5
DA-6F 0.150 0.017 10
DA-6G
DA-7A Grass: Short 0.150 0.072 5.6
DA-7B
DA-7C 0.150 0.016 10.4
DA-7D 0.150 0.011 12.1
DA-7E 0.150 0.018 9.8
DA-7F 0.150 0.017 10.1
DA-7G
DA-8A-1A
DA-8A-1B
DA-8A-1C
DA-8A-1D Grass: Short 0.150 0.200 3.8
DA-8A-1E
DA-8A-1F
DA-8A-1G
DA-8A 0.150 0.100 4.9
DA-8B 0.150 0.010 12.2
DA-8C 0.150 0.014 10.7
DA-8D
Table 2: Time of Concentration from Sheet Flow
Grass: Short
-NA-
-NA-
-NA-
Grass: Short
100
Grass: Short
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
Grass: Short

Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 6 of 13
12/9/2016 (Initial Submittal)

Drainage
Area ID
Flow Length
{L}
(ft.)
Surface Description Land Slope
(ft/ft)
Time of
Concentration
{Tc,scf}
(min)
DA-1 2,343 Unpaved 0.039 12.3
DA-2 752 Woodland 0.058 10.5
DA-3 665 Short Grass Pasture 0.051 7.0
DA-4 2,834 Grass Waterway 0.058 13.1
DA-5A 0 0.0 0.000 0.0
DA-5B 288 0.014 5.8
DA-5C 218 0.021 3.6
DA-5D
DA-6A 98 0.031 1.3
DA-6B 168 0.027 2.4
DA-6C 168 0.022 2.7
DA-6D 329 0.015 6.4
DA-6E 224 0.020 3.8
DA-6F 148 0.021 2.4
DA-6G
DA-7A 534 Short Grass Pasture 0.013 11.2
DA-7B
DA-7C 226 0.024 3.5
DA-7D 277 0.017 5.1
DA-7E 139 0.021 2.3
DA-7F 498 0.008 13.3
DA-7G
DA-8A-1A
DA-8A-1B
DA-8A-1C
DA-8A-1D 576 Short Grass Pasture 0.024 8.9
DA-8A-1E
DA-8A-1F
DA-81-1G
DA-8A 695 0.052 7.3
DA-8B 252 0.020 4.2
DA-8C 320 0.013 6.7
DA-8D
-NA-
-NA-
Table 3: Time of Concentration from Shallow Concentrated Flow
-NA-
-NA-
-NA-
Short Grass Pasture
Short Grass Pasture
Short Grass Pasture
Short Grass Pasture
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-

Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 7 of 13
12/9/2016 (Initial Submittal)

Drainage
Area ID
Flow Length
{L}
(ft.)
Channel
Velocity
{V}
(ft/s)
Time of
Concentration
{Tc,channel}
(min)
DA-1 0
DA-2 0
DA-3 0
DA-4 0
DA-5A 973 3.16 5.10
DA-5B 428 1.89 3.80
DA-5C 468 2.42 3.20
DA-5D
DA-6A 212 4.55 0.80
DA-6B 202 4.63 0.70
DA-6C 318 3.49 1.50
DA-6D 269 3.28 1.40
DA-6E 552 2.23 4.10
DA-6F 289 3.09 1.60
DA-6G
DA-7A 245 3.38 1.20
DA-7B
DA-7C 245 2.54 1.60
DA-7D 241 2.54 1.60
DA-7E 289 3.09 1.60
DA-7F 432 2.53 2.80
DA-7G
DA-8A-1A
DA-8A-1B
DA-8A-1C
DA-8A-1D
DA-8A-1E
DA-8A-1F
DA-8A-1G
DA-8A 662 3.59 3.10
DA-8B 564 1.69 5.60
DA-8C 305 3.00 1.70
DA-8D
-NA-
-NA-
-NA-
-NA-
Table 4: Time of Concentration from Channel Flow
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-

Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 8 of 13
12/9/2016 (Initial Submittal)

Drainage
Area ID
Time of
Concentration
{Tc,sheet}
(min)
Time of
Concentration
{Tc,scf}
(min)
Time of
Concentration
{Tc,channel}
(min)
Total Time of
Concentration
{Tc,total}
(min)
DA-1 0.7 12.3 0.0 13.0
DA-2 6.5 10.5 0.0 17.0
DA-3 5.6 7.0 0.0 12.6
DA-4 6.9 13.1 0.0 20.0
DA-5A 5.6 0.0 5.1 10.7
DA-5B 8.6 5.8 3.8 18.2
DA-5C 10.9 3.6 3.2 17.7
DA-5D 6.0
DA-6A 12.8 1.3 0.8 14.9
DA-6B 7.7 2.4 0.7 10.8
DA-6C 10.0 2.7 1.5 14.2
DA-6D 10.5 6.4 1.4 18.3
DA-6E 11.5 3.8 4.1 19.4
DA-6F 10.0 2.4 1.6 14.0
DA-6G 6.0
DA-7A 5.6 11.2 1.2 18.0
DA-7B 6.0
DA-7C 10.4 3.5 1.6 15.5
DA-7D 12.1 5.1 1.6 18.8
DA-7E 9.8 2.3 1.6 13.7
DA-7F 10.1 13.3 2.8 26.2
DA-7G 6.0
DA-8A-1A 6.0
DA-8A-1B 6.0
DA-8A-1C 6.0
DA-8A-1D 3.8 8.9 0.0 12.7
DA-8A-1E 6.0
DA-8A-1F 6.0
DA-8A-1G 6.0
DA-8A 4.9 7.3 3.1 15.3
DA-8B 12.2 4.2 5.6 22.0
DA-8C 10.7 6.7 1.7 19.1
DA-8D 6.0-NA-
Table 5: Total Time of Concentration
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-
-NA-

1.3 Describe land use conditions
Land use conditions were estimated based on anticipated long-term conditions as shown in Figure
2. For the purpose of this calculation, it was assumed that the post-closure use of the Ash Fill 2
area will consist of a gravel lay-down area consistent with the current land use. Site soils were
assumed to consist of hydric soil class C. Land use conditions and associated curve numbers for
tributary areas numbered DA-1 through DA-8A-1G are summarized in the following table:

Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 9 of 13
12/9/2016 (Initial Submittal)

Curve Number
{CN}
[Ref. 2]
Area
{A}
(ac)
Curve Number
{CN}
[Ref. 2]
Area
{A}
(ac)
Curve Number
{CN}
[Ref. 2]
Area
{A}
(ac)
Curve Number
{CN}
[Ref. 2]
Area
{A}
(ac)
DA-1 74 12.69 73 0.32 96 9.76 0 0.00 83 22.77
DA-2 74 4.35 73 1.53 96 0.14 0 0.00 74 6.03
DA-3 74 1.26 73 1.12 96 0.00 0 0.00 74 2.39
DA-4 74 49.19 73 9.94 96 14.96 0 0.00 78 74.10
DA-8A-1A 74 0.62 73 0 96 0 0 0.00 74 0.62
DA-8A-1B 74 0.75 73 0 96 0 0 0.00 74 0.75
DA-8A-1C 74 0.13 73 0 96 0 0 0.00 74 0.13
DA-8A-1D 74 1.24 73 0 96 0 0 0.00 74 1.24
DA-8A-1E 74 0.29 73 0 96 0 0 0.00 74 0.29
DA-8A-1F 74 0.17 73 0 96 0 0 0.00 74 0.17
DA-8A-1G 74 0.35 73 0 96 0 0 0.00 74 0.35
Table 6: Land use conditions for tributary areas
Total Area
{A}
(ac)
Drainage
Area ID
Land Use = Grass Land Use = Woods Land Use = Gravel Land Use = Impervious Composite
Curve Number
{CN}

Land use conditions in drainage areas 5 through 8 were assumed to change during the ash
removal phase and final grading process. Hence, stormwater analysis for the ash basin was
divided in two phases. Under the initial phase of interim conditions, the basin area was assumed
to be newly graded area with hydric soil class C (Curve Number of 91), and with no vegetative
cover and are calculated in the “Interim Conditions Stormwater Calculation”. Final long term
conditions within the ash basin footprint were assumed to consist of at least 75% grass cover with
hydric soil class C (Curve Number of 74).

HydroCAD software was used to estimate long-term stormwater flows for drainage areas DA-1
through DA-8 for the 100-year, 24-hour storm event based on the SCS method. The 100 year
storm resulted in 8.4 inch type II 24-hr rainfall [Ref. 1].
1.4 Stormwater channel capacity
Stormwater channels in the ash basin area consist of interceptor ditches (INT), toe ditches (TD)
and longitudinal ditches (LD). Interceptor ditches are used within the ash basin footprint to
interrupt drainage lengths and reduce erosion potential. Toe ditches are located along the
southern edge of the ash basin footprint to intercept stormwater and convey flow to the four
defined outlet points which discharge into the Dan River. Longitudinal ditches are located within
the ash basin footprint perpendicular to the slope and convey concentrated flows from upstream
tributary drainage areas to two of the four defined outlet points which discharge into the Dan River.
The proposed stormwater ditch dimensions are presented in the following table:

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Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 10 of 13
12/9/2016 (Initial Submittal)

Channel
ID
Channel
Type
Bottom
Width
{b}
(ft)
MIN.
Depth
{D}
(ft)
Left Side
Slope
{Z1H:V}
Right Side
Slope
{Z2H:V}
Top Width
{T}
(ft)
Upstream
Invert
(ft)
Downstream
Invert
(ft)
Length
{L}
(ft)
Longitudinal
Slope
{S}
(ft/ft)
5A INT 4 1.5 20 20 514 500 973 0.014
5B INT 0 1.5 20 20 506 504 379 0.005
6A INT 0 1.5 20 20 510 504 212 0.029
6B INT 0 1.5 20 20 510 504 202 0.030
6C INT 0 1.5 20 20 505 500 318 0.017
6D INT 0 1.5 20 20 504 500 269 0.015
7A INT 0 1.5 20 20 510 506 245 0.016
7B INT 0 1.5 20 20 510 509 312 0.006
7C INT 0 1.5 20 20 504 502 245 0.009
7D INT 0 1.5 20 20 504 502 241 0.009
8A INT 6 1.5 20 20 508 500 662 0.012
8B INT 0 1.5 20 20 504 502 564 0.004
DD-1 DIV 2 2 3 3 529 526 381 0.007
DD-2 DIV 2 2 3 3 531 526 304 0.014
DD-3 DIV 2 2 3 3 531 528 48 0.056
DD-4 DIV 2 2 3 3 530 528 80 0.024
DD-5 DIV 2 2 3 3 530 529 94 0.011
DD-6 DIV 2 2 3 3 532 529 40 0.078
5C TD 0 2 5 5 2.50 0 468 0.005
6E TD 0 2.5 3 3 2.68 0 552 0.005
6F TD 6 1.5 3 3 1.36 0 289 0.005
7E TD 6 1.5 3 3 1.40 0 289 0.005
7F TD 6 2 3 3 1.40 0 432 0.003
8C TD 6 1.5 3 3 1.39 0 305 0.005
LD-1A LD 6 6 3 3 508 504 335 0.012
LD-1B LD 6 4 3 3 504 500 312 0.013
LD-1C LD 6 4 3 3 500 498 184 0.010
LD-1D LD 6 4 3 3 498 497 107 0.009
LD-2A LD 6 4 3 3 510 506 282 0.014
LD-2B LD 6 3 3 3 506 502 306 0.014
LD-2C LD 6 3 3 3 501 498 166 0.018
LD-2D LD 6 3 3 3 498 496 107 0.019
Table 7: Channel Dimensions
VARIES

The capacity of the proposed stormwater channels was evaluated using Manning’s equation
presented as follows:

𝑉=1.49
𝑛𝑃2/3 𝑃1/2 [Ref. 3]

and

𝑃=𝐴𝑉 [Ref. 3]

The flow area “A” and wetted perimeter “P” were calculated using the following relationships
based on the geometry of a trapezoidal channel with a flow depth “d”, bottom width “b”, left side
slope “Z1”, and right side slope “Z2”:

𝐴=𝑏𝑑+0.5𝑍1 𝑑2 +0.5𝑍2 𝑑2
𝑃=𝑏+√[(𝑍1 𝑑)2 +𝑑2 ]+√[(𝑍2 𝑑)2 +𝑑2 ]

Final Conditions Stormwater Calculation Dam Decommissioning Plan
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Amec Foster Wheeler Project No. 7810-14-0065 11 of 13
12/9/2016 (Initial Submittal)

The proposed stormwater channel capacities were evaluated assuming a soil channel lining for
the 100-year storm. The trial flow depth and Manning’s n were iteratively modified until the
channel capacity exceeded the peak runoff for the conditions modeled. The proposed stormwater
channels are anticipated to be stable when vegetated for the conditions modeled. A vegetative
class “C” was assumed for the long-term grass channel lining conditions of interceptor and toe-
ditches. However, longitudinal ditches were assumed to be lined with rock rip-rap (d50 = 9 inch)
as designed in a subsequent section of this calculation. Channel capacity was estimated as
shown in the following table:

Channel
ID
Channel
Type
Channel
Lining
Manning's n
{n}
Trial Flow
Depth
{d}
(ft)
Flow Area
{A}
(ft2)
Wetted
Perimeter
{P}
(ft)
Hydraulic
Radius
{R}
(ft)
Velocity
{V}
(ft/s)
Channel
Capacity
{Q}
(cfs)
Peak
Runoff
{Q}
(cfs)
Channel
Capacity >
Peak
Runoff?
Freeboard
(in)
5A INT grass 0.132 1.04 25.8 45.7 0.6 0.9 23.60 23.07 yes 5.5
5B INT grass 0.24 1.36 37.0 54.5 0.7 0.3 12.89 12.69 yes 1.7
6A INT grass 0.212 0.8 12.8 32.0 0.4 0.6 8.25 8.06 yes 8.4
6B INT grass 0.108 0.87 15.1 34.8 0.4 1.4 20.78 20.34 yes 7.6
6C INT grass 0.125 0.96 18.4 38.4 0.5 0.9 17.40 16.91 yes 6.5
6D INT grass 0.13 0.97 18.8 38.8 0.5 0.9 16.46 15.99 yes 6.4
7A INT grass 0.112 1.1 24.2 44.1 0.5 1.1 27.60 26.01 yes 4.8
7B INT grass 0.201 1.33 35.4 53.3 0.7 0.4 14.95 14.90 yes 2.0
7C INT grass 0.16 1.15 26.5 46.1 0.6 0.6 16.43 16.03 yes 4.2
7D INT grass 0.2 1.23 30.3 49.3 0.6 0.5 15.75 15.43 yes 3.2
8A INT grass 0.102 1.13 32.3 51.3 0.6 1.2 37.68 30.78 yes 4.4
8B INT grass 0.205 1.47 43.2 58.9 0.7 0.4 15.64 15.49 yes 0.4
DD-1 DIV grass 0.125 1.21 6.8 9.7 0.7 0.8 5.32 5.54 no 9.5
DD-2 DIV grass 0.092 1 5.0 8.3 0.6 1.4 6.87 6.70 yes 12.0
DD-3 DIV grass 0.23 0.48 1.7 5.0 0.3 0.7 1.20 1.16 yes 18.2
DD-4 DIV grass 0.079 0.93 4.5 7.9 0.6 2.0 8.84 8.79 yes 12.8
DD-5 DIV grass 0.151 0.94 4.5 7.9 0.6 0.7 3.18 3.14 yes 12.7
DD-6 DIV grass 0.1 0.33 1.0 4.1 0.2 1.6 1.59 1.52 yes 20.0
5C TD grass 0.082 1.73 15.0 17.6 0.8 1.2 17.80 17.37 yes 3.2
6E TD grass 0.071 2.08 13.0 13.2 1.0 1.4 18.80 18.62 yes 5.0
6F TD grass 0.101 1.3 12.9 14.2 0.9 0.9 12.20 12.05 yes 2.4
7E TD grass 0.102 1.25 12.2 13.9 0.9 0.9 11.33 11.21 yes 3.0
7F TD grass 0.096 1.69 18.7 16.7 1.1 1.0 17.81 14.40 yes 3.7
8C TD grass 0.104 1.12 10.5 13.1 0.8 0.8 8.74 8.56 yes 4.6
LD-1A LD rock rip-rap 0.0375 2.59 35.7 22.4 1.6 6.0 214.40 213.37 yes 40.9
LD-1B LD rock rip-rap 0.0375 2.74 39.0 23.3 1.7 6.3 245.20 244.15 yes 15.1
LD-1C LD rock rip-rap 0.0375 2.86 41.7 24.1 1.7 5.9 244.64 243.77 yes 13.7
LD-1D LD rock rip-rap 0.0375 3.14 48.4 25.9 1.9 5.8 282.54 208.99 yes 10.3
LD-2A LD rock rip-rap 0.0375 2 24.0 18.6 1.3 5.6 134.71 133.14 yes 24.0
LD-2B LD rock rip-rap 0.0375 2.21 27.9 20.0 1.4 5.9 165.07 163.73 yes 9.5
LD-2C LD rock rip-rap 0.0375 2.09 25.6 19.2 1.3 6.5 166.02 163.69 yes 10.9
LD-2D LD rock rip-rap 0.0375 2.22 28.1 20.0 1.4 6.8 191.29 190.27 yes 9.4
Table 8: Channel Capacity - 100 year Long-Term Grassed Conditions

The permissible velocity for a channel with grass lining (tall fescue), slope of 0% to 5%, and easily
erodible soils is 4.5 feet per second [Ref. 3], which is greater than the calculated channel velocities
for the conditions modeled. Hence, interceptor ditches, toe ditches and the diversion ditch have
adequate lining stability for the conditions modeled.

Longitudinal channels designed with rock rip-rap were checked for permissible shear stress, and
actual flow shear as calculated using the following equation:

𝜏=𝛾𝑤𝑎𝑡𝑒𝑟𝑑𝑃 [Ref. 3]
Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 12 of 13
12/9/2016 (Initial Submittal)

The maximum permissible shear for rock rip-rap (d50 = 9 inch) is 3 psf [Ref. 3]. The calculated
stability of the longitudinal ditches was estimated as shown in the following table:

Channel
ID
Channel
Type Channel Lining
Unit Weight
of Water
{gwater}
(pcf)
Flow Depth
{d}
(ft)
Longitudinal
Slope
{S}
(ft/ft)
Shear
Stress
{}
(psf)
Permissible
Shear
{perm}
(psf)
Safe
LD-1A LD rock rip rap 62.4 2.59 0.0123 1.99 3 Yes
LD-1B LD rock rip rap 62.4 2.74 0.0127 2.16 3 Yes
LD-1C LD rock rip rap 62.4 2.86 0.0105 1.87 3 Yes
LD-1D LD rock rip rap 62.4 3.14 0.0093 1.83 3 Yes
LD-2A LD rock rip rap 62.4 2.00 0.0143 1.78 3 Yes
LD-2B LD rock rip rap 62.4 2.21 0.0142 1.96 3 Yes
LD-2C LD rock rip rap 62.4 2.09 0.0181 2.36 3 Yes
LD-2D LD rock rip rap 62.4 2.22 0.0187 2.59 3 Yes
Table 9: Channel Lining Requirements - Rock Rip-Rap (d 50 = 9 inch)

The maximum particle size for the rock rip-rap lining should be greater than 1.5 times d50, i.e.,
13.5 inch [Ref. 3]. Hence, NC-DOT Class 1 rock rip-rap (d50 = 10 inches, dmax = 17 inches) is
proposed for the longitudinal channel lining [Ref. 4], and will be underlain with a filter fabric.
1.5 Design stormwater culverts and slope drains
Culverts and slope drains will convey stormwater flows from the tributary drainage areas to the
ash basin closure area. Drainage area DA-1 discharges to an existing grouted 48-inch diameter
CMP which will be removed and replaced with a 48-inch diameter HDPE pipe to convey flow to a
longitudinal ditch.

Drainage area DA-2 discharges to an existing 54-inch RCP with a grout plug at the inlet. The 54-
inch RCP connects to a drop inlet and a 36-inch diameter RCP. The existing drop inlet and 36-
inch RCP will be removed and replaced with a 54-inch diameter HDPE culvert/downdrain to
convey flow to a longitudinal ditch. The grout plug at the inlet of the existing 54-inch RCP will be
removed to restore flow.

Drainage area DA-3 discharges to an existing 36-inch diameter RCP which conveys flow into the
secondary ash basin. A 36-inch diameter HDPE slope drain will be mechanically fastened to the
existing 36-inch RCP to convey flow to an energy dissipater.

Drainage area DA-4 discharges to an existing 36-inch diameter RCP which conveys flow into the
secondary ash basin. A portion of the existing 36-inch diameter RCP will be removed. A 36-inch
diameter HDPE slope drain will be mechanically fastened to the remaining portion of the existing
36-inch diameter RCP to convey flow to longitudinal ditch.

Drainage area DA-8A-1 will discharge to a diversion ditch that runs along the outside perimeter
road. The diversion ditch will have drop inlets placed along the bottom that discharge to slope
drains which convey flow from DA-8A-1 to the ash basin. The drop inlets that will be placed in the
diversion ditch will be 3’x2’x2’ deep precast concrete boxes covered by a metal grate with 2 rows
of openings.
Final Conditions Stormwater Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 13 of 13
12/9/2016 (Initial Submittal)

The culverts and slope drains were designed using HydroCAD software as summarized in the
following table:

Slope
Drain ID
Drainage
Area
ID
Culvert
Diameter
(inch)
New Pipe
Material
Slope
(ft/ft)
Length
(ft)
Manning's n
(-)
Runoff - 100
year long term
(cfs)
Water Surface
Elevation
(ft)
Flood
Elevation
(ft)
Freeboard
(ft)
SD-1 DA-1 48 HDPE 0.02 157 0.013 186.5 522 524 2.5
SD-2 DA-2 54 HDPE 0.02 200 0.013 37.5 515 528 13.0
SD-3 DA-4 36 HDPE 0.01 577 0.013 81.3 541 558 17.0
SD-4 DA-8A-1AB 18 HDPE 0.14 100 0.013 12.24 527 528 0.7
SD-5 DA-3 36 HDPE 0.01 577 0.013 16.6 530 532 2.0
SD-6 DA-8A-1CD 18 HDPE 0.20 70 0.013 9.57 529 530 1.2
SD-7 DA-8A-1EF 18 HDPE 0.23 70 0.013 4.24 528 530 1.6
Table 11: Storm Water Culverts

DISCUSSION:
The proposed stormwater features have capacity for the 100-year, 24-hour design storm for the
conditions modeled.

FIGURES:
1. Drainage area and time of concentration
2. Land use characteristics

REFERENCES:
1. Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.
2. HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.
3. North Carolina Department of Environment and Natural Resources, “Erosion and
Sediment Control Planning and Design Manual”, Revised May 2013.
4. “Standard Specification for Roads and Structures”, North Carolina Department of
Transportation, Raleigh, January 2012.
5. United States Department of Agriculture, “Urban Hydrology for Small W atersheds”,
Technical Release 55, June 1986.
FIGURE 1
Drainage Areas and Flow Paths

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FIGURE 2
Land Use

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REFERENCE 1

Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.

Precipitation Frequency Data Server
Page 1 of 3
NOAA Atlas 14, Volume 2, Version 3
Location name: Eden, North Carolina, US"
Latitude: 36.4999°, Longitude:-79.7013°
Elevation: 582 ft*
* source: Google Maps "*�,�,,.t
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based
point precipitation frequency estimates with 90% confidence intervals (in inches)'
Average recurrence interval (years)
Duration
���
10
25
50
100
200
500
1000
0.363
0.433
0.512
0.567
0.633
0.676
0.717
0.754
0.796
0.826
5-min
(0.331-0.397)
(0.396-0.473)
(0.467-0.560)
(0.518-0.619)
(0.575-0.688)
(0.612-0.735)
(0.646-0.781)
(0.676-0.822)
(0.708-0.869)
(0.729-0.902)
0.579
0.692
0.820
0.908
1.01
1.08
1.14
1.20
1.26
1.30
10-min
(0 .529-0.634)
(0.633-0.757)
(0.749-0.898)
(0.829-0.991)
(0.917-1.10)
(0.974-1.17)
1 (1.03-1.24)
1 (1.07-1.30)
1 (1.12-1.38)
0.724
0.870
1.04
1.15
1.28
1.36
1.44
1.51
1.59
1.63
15-min
(0.661-0.792)
(0.796-0.951)
(0.947-1.14)
1 (1.05-1.25)
1 (1.16-1.39)
1 (1.23-1.48)
1 (1.30-1.57)
1 (1.35-1.64)
1 (1.41-1.73)
1 (1.44-1.78)
0.993
1.20
1.47
1.66
1.89
2.05
2.21
2.35
2.52
2.64
30-min
(0.906-1.09)
1 (1.10-1.31)
1 (1.35-1.61)
1 (1.52-1.82)
1 (1.72-2.06)
(1.86-2.23)
(1.99-2.40)
(2.11-2.56)
(2.24-2.75)
(2.33-2.89)
1.24
1.51
1.89
2.17
2.52
2.78
3.04
3.29
3.62
3.86
60-min
(1.13-1.35)
(1.38-1.65)
(1.73-2.07)
(1.98-2.36)
(2.29-2.74)
(2.52-3.03)
(2.74-3.31)
(2.95-3.59)
(3.22-3.95)
(3.41-4.22)
1.47
1.79
2.25
2.61
3.08
3.45
3.83
4.20
4.71
5.10
2-hr
(1.35-1.61)
(1.63-1.96)
(2.06-2.46)
(2.38-2.85)
(2.80-3.36)
(3.12-3.75)
(3.44-4.16)
(3.75-4.57)
(4.15-5.12)
(4.45-5.56)
1.59
1.93
2.44
2.82
3.33
3.73
4.13
4.54
5.08
5.50
3-hr
(1.46-1.73)
(1.78-2.11)
(2.24-2.66)
(2.58-3.07)
(3.03-3.62)
(3.38-4.04)
(3.72-4.48)
(4.06-4.92)
( 4.49-5.52)
( 4.81-5.98)
1.96
2.37
2.99
3.48
4.15
4.70
5.28
5.87
6.71
7.38
6-hr
(1.80-2.15)
(2.18-2.61)
(2.74-3.27)
(3.17-3.80)
(3.76-4.53)
(4.22-5.12)
(4.70-5.73)
(5.18-6.37)
(5.82-7.29)
(6.31-8.02)
2.36
2.87
3.63
4.26
5.15
5.89
6.70
7.56
8.81
9.84
12-hr
(2.17-2.59)
(2.63-3.14)
(3.32-3.96)
(3.88-4.62)
(4.65-5.57)
(5.28-6.37)
(5.94-7.21)
(6.62-8.12)
(7.57-9.48)
(8.31-10.6 )
2.81
3.40
4.33
5.10
6.22
7.17
8.20
9.32
11.0
12.4
24-hr
(2.61-3.04)
(3.16-3.68)
(4.02-4.67)
(4.72-5.48)
(5.72-6.68)
(6.55-7.69)
(7.44-8.79)
(8.39-10.0)
(9.74-11.8)
(10.9-13.3)
3.30
3.99
5.04
5.90
7.12
8.13
9.21
10.4
12.0
13.4
2-day
(3.08-3.55)
(3.72-4.30)
(4.70-5.42)
(5.48-6.33)
(6.59-7.63)
(7.48-8.71)
(8.42-9.88)
(9.40-11.1 )
( 10.8-13.0 )
( 11.9-14.5 )
3.49
4.22
5.33
6.23
7.52
8.59
9.72
10.9
12.7
14.2
3-day
(3.26-3.76)
(3.93-4.55)
(4.96-5.73)
(5.79-6.69)
(6.95-8.07)
(7.89-9.21)
(8.88-10.4)
(9.92-11.8)
(11.4-13.7)
( 12.6-15.3)
3.68
4.45
5.61
6.56
7.92
9.04
10.2
11.5
13.4
14.9
4-day
(3.43-3.97)
(4.15-4.80)
(5.23-6.05)
(6.10-7.06)
(7.32-8.51)
(8.31-9.71)
(9.35-11.0)
(10.4-12.4)
(12.0-14.4)
(13.2-16.1)
4.22
5.07
6.29
7.29
8.71
9.88
11.1
12.4
14.3
15.9
7-day
(3.96-4.51)
(4.75-5.42)
(5.89-6.72)
(6.81-7.78)
(8.11-9.28)
(9.14-10.5)
(10.2-11.9)
( 11.4-13.3)
( 12.9-15.3)
( 14.2-17.0)
4.77
5.71
7.01
8.0 6
10.7
12.0
13.3
15.1
16.6
10-day
��69.53
(4.48-5.10 )
(5.37-6.10)
(6.58-7.48 )
(7.55-8.60)
(8.89-10.2 )
(9.96-11.4)
(11.1-12.8)
(12.2-14.2)
(13.8-16.2)
(15.0-17.8)
6.43
7.65
9.20
10.4
12.1
13.4
14.7
16.1
17.9
19.3
20-day
(6.05-6.85)
(7.21-8.16)
(8.66-9.81)
(9.79-11.1)
(11.3-12.9)
(12.5-14.3)
(13.7-15.7)
(14.9-172)
(16.4-19.2)
(17.6-20.8)
30-day
7.95
9.40
11.1
12.3
14.0
15.3
16.5
17.7
19.3
20.5
(7.53-8.41)
(8.91-9.94)
(10.5-11.7)
(11.7-13.0)
(13.2-14.8)
(14.4-16.2)
(15.5-17.5)
(16.6-18.8)
(18.0-20.5)
(19.0-21.9)
45-day
10.0
11.8
13.7
15.2
17.1
18.5
19.8
21.1
22.8
24.0
(9.48-10.6)
(11.2-12.5)
(13.0-14.5)
(14.4-16.0)
(16.1-18.0)
(17.4-19.5)
(18.6-21.0)
(19.8-22.4)
(21.3-24.2)
(22.3-25.6)
12.0
14.0
16.1
17.7
19.7
21.2
22.6
23.9
25.6
26.8
60-day
( 114-12.6) 1
(13.4-14.8) 1
U-15-3-1-7.0) I
(16.8-18.6) 1
U-18-7-2-o.7) 1
(20.0-22.3) 1
U-21-3-2-3.8) 1
(22.5-25.2) J
(24.0-27.1) 11
(25.1-28.4)
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90 % confidence interval. The probability that precipitation frequency estimates (for a
given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5 % . Estimates at upper bounds are not
checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 2 of 3
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created tGMTI: Mon Sep 15 14:27:08 2014
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— 5tnln —
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http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 3 of 3
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hvdroloaic Develooment
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions(a)noaa.aov
Disclaimer
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

REFERENCE 2

HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.

1
DA-1
S-01
DA-5A
S-02
DA-5B
S-03
DA-5C
S-04
DA-5D
S-11
DA-6A
S-12
DA-6B
S-13
DA-6D
S-14
DA-6C
S-15
DA-6E
S-16
DA-6F
S-17
DA-6G
R-11
LD-1A
R-12
LD-1B
R-13
LD-1C
R-15
Outlet-2
R01
Lateral Ditch
R02
Outlet-1
1PCB
48" Culvert
Routing Diagram for LT_1
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=22.679 ac 0.00% Impervious Runoff Depth>5.77"Subcatchment 1: DA-1
Flow Length=2,443' Tc=13.0 min CN=83 Runoff=186.52 cfs 10.909 af
Runoff Area=3.330 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-01: DA-5A
Flow Length=1,171' Tc=13.4 min CN=74 Runoff=23.07 cfs 1.313 af
Runoff Area=2.130 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-02: DA-5B
Flow Length=816' Tc=18.3 min CN=74 Runoff=12.69 cfs 0.839 af
Runoff Area=2.830 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-03: DA-5C
Flow Length=786' Tc=17.3 min CN=74 Runoff=17.37 cfs 1.115 af
Runoff Area=2.180 ac 0.00% Impervious Runoff Depth>4.75"Subcatchment S-04: DA-5D
Tc=5.0 min CN=74 Runoff=20.17 cfs 0.862 af
Runoff Area=1.230 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-11: DA-6A
Flow Length=410' Tc=15.1 min CN=74 Runoff=8.06 cfs 0.485 af
Runoff Area=2.700 ac 0.00% Impervious Runoff Depth>4.74"Subcatchment S-12: DA-6B
Flow Length=440' Tc=10.9 min CN=74 Runoff=20.34 cfs 1.066 af
Runoff Area=2.700 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-13: DA-6D
Flow Length=698' Slope=0.0150 '/' Tc=18.5 min CN=74 Runoff=15.99 cfs 1.063 af
Runoff Area=2.510 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-14: DA-6C
Flow Length=586' Tc=14.3 min CN=74 Runoff=16.91 cfs 0.990 af
Runoff Area=3.250 ac 0.00% Impervious Runoff Depth>4.72"Subcatchment S-15: DA-6E
Flow Length=876' Tc=19.6 min CN=74 Runoff=18.62 cfs 1.279 af
Runoff Area=1.780 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-16: DA-6F
Flow Length=537' Tc=14.1 min CN=74 Runoff=12.05 cfs 0.702 af
Runoff Area=2.610 ac 0.00% Impervious Runoff Depth>4.75"Subcatchment S-17: DA-6G
Tc=5.0 min CN=74 Runoff=24.15 cfs 1.032 af
Avg. Flow Depth=2.50' Max Vel=6.30 fps Inflow=214.35 cfs 12.460 afReach R-11: LD-1A
n=0.035 L=335.0' S=0.0123 '/' Capacity=1,495.75 cfs Outflow=213.37 cfs 12.447 af
Avg. Flow Depth=2.65' Max Vel=6.60 fps Inflow=245.08 cfs 14.500 afReach R-12: LD-1B
n=0.035 L=312.0' S=0.0127 '/' Capacity=599.39 cfs Outflow=244.15 cfs 14.487 af
Avg. Flow Depth=2.77' Max Vel=6.16 fps Inflow=244.15 cfs 14.487 afReach R-13: LD-1C
n=0.035 L=184.0' S=0.0105 '/' Capacity=545.58 cfs Outflow=243.77 cfs 14.479 af
Inflow=280.99 cfs 17.492 afReach R-15: Outlet-2
Outflow=280.99 cfs 17.492 af
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Avg. Flow Depth=0.65' Max Vel=2.63 fps Inflow=35.01 cfs 2.152 afReach R01: Lateral Ditch
n=0.035 L=1,177.0' S=0.0144 '/' Capacity=223.50 cfs Outflow=29.28 cfs 2.136 af
Inflow=49.75 cfs 4.113 afReach R02: Outlet-1
Outflow=49.75 cfs 4.113 af
Peak Elev=521.50' Inflow=186.52 cfs 10.909 afPond 1P: 48" Culvert
48.0" Round Culvert n=0.012 L=157.0' S=0.0127 '/' Outflow=186.52 cfs 10.909 af
Total Runoff Area = 49.929 ac Runoff Volume = 21.656 af Average Runoff Depth = 5.20"
100.00% Pervious = 49.929 ac 0.00% Impervious = 0.000 ac
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: DA-1
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 186.52 cfs @ 12.04 hrs, Volume= 10.909 af, Depth> 5.77"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
0.322 73 Woods, Fair, HSG C
9.380 96 Gravel surface, HSG C
12.977 74 >75% Grass cover, Good, HSG C
22.679 83 Weighted Average
22.679 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
0.7 100 0.0670 2.30 Sheet Flow, TC for DA1
Smooth surfaces n= 0.011 P2= 3.40"
12.3 2,343 0.0390 3.18 Shallow Concentrated Flow, TC for DA1
Unpaved Kv= 16.1 fps
13.0 2,443 Total
Subcatchment 1: DA-1
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
200
180
160
140
120
100
80
60
40
20
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=22.679 ac
Runoff Volume=10.909 af
Runoff Depth>5.77"
Flow Length=2,443'
Tc=13.0 min
CN=83
186.52 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-01: DA-5A
Runoff = 23.07 cfs @ 12.05 hrs, Volume= 1.313 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
3.330 74 >75% Grass cover, Good, HSG C
3.330 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.7 100 0.0730 0.29 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
2.7 151 0.0183 0.95 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
5.0 920 0.0134 3.10 61.92 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50'
n= 0.035 Earth, dense weeds
13.4 1,171 Total
Subcatchment S-01: DA-5A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=3.330 ac
Runoff Volume=1.313 af
Runoff Depth>4.73"
Flow Length=1,171'
Tc=13.4 min
CN=74
23.07 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-02: DA-5B
Runoff = 12.69 cfs @ 12.10 hrs, Volume= 0.839 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.130 74 >75% Grass cover, Good, HSG C
2.130 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
8.7 100 0.0250 0.19 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
5.8 288 0.0140 0.83 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
3.8 428 0.0050 1.89 37.83 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50'
n= 0.035 Earth, dense weeds
18.3 816 Total
Subcatchment S-02: DA-5B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.130 ac
Runoff Volume=0.839 af
Runoff Depth>4.73"
Flow Length=816'
Tc=18.3 min
CN=74
12.69 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-03: DA-5C
Runoff = 17.37 cfs @ 12.09 hrs, Volume= 1.115 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.830 74 >75% Grass cover, Good, HSG C
2.830 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.1 100 0.0136 0.15 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
3.6 218 0.0210 1.01 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
2.6 468 0.0050 3.03 47.54 Channel Flow,
Area= 15.7 sf Perim= 15.5' r= 1.01'
n= 0.035 Earth, dense weeds
17.3 786 Total
Subcatchment S-03: DA-5C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.830 ac
Runoff Volume=1.115 af
Runoff Depth>4.73"
Flow Length=786'
Tc=17.3 min
CN=74
17.37 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-04: DA-5D
Runoff = 20.17 cfs @ 11.96 hrs, Volume= 0.862 af, Depth> 4.75"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.180 74 >75% Grass cover, Good, HSG C
2.180 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-04: DA-5D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.180 ac
Runoff Volume=0.862 af
Runoff Depth>4.75"
Tc=5.0 min
CN=74
20.17 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-11: DA-6A
Runoff = 8.06 cfs @ 12.07 hrs, Volume= 0.485 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.230 74 >75% Grass cover, Good, HSG C
1.230 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
13.0 100 0.0091 0.13 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
1.3 98 0.0310 1.23 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
0.8 212 0.0290 4.55 91.09 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50'
n= 0.035 Earth, dense weeds
15.1 410 Total
Subcatchment S-11: DA-6A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.230 ac
Runoff Volume=0.485 af
Runoff Depth>4.73"
Flow Length=410'
Tc=15.1 min
CN=74
8.06 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-12: DA-6B
Runoff = 20.34 cfs @ 12.03 hrs, Volume= 1.066 af, Depth> 4.74"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.700 74 >75% Grass cover, Good, HSG C
2.700 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0331 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
2.4 168 0.0270 1.15 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
0.7 172 0.0090 4.11 57.49 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
10.9 440 Total
Subcatchment S-12: DA-6B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.700 ac
Runoff Volume=1.066 af
Runoff Depth>4.74"
Flow Length=440'
Tc=10.9 min
CN=74
20.34 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-13: DA-6D
Runoff = 15.99 cfs @ 12.11 hrs, Volume= 1.063 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.700 74 >75% Grass cover, Good, HSG C
2.700 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.7 100 0.0150 0.16 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
6.4 329 0.0150 0.86 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.4 269 0.0150 3.28 65.51 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
18.5 698 Total
Subcatchment S-13: DA-6D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.700 ac
Runoff Volume=1.063 af
Runoff Depth>4.73"
Flow Length=698'
Slope=0.0150 '/'
Tc=18.5 min
CN=74
15.99 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-14: DA-6C
Runoff = 16.91 cfs @ 12.06 hrs, Volume= 0.990 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.510 74 >75% Grass cover, Good, HSG C
2.510 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.1 100 0.0170 0.16 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
2.7 168 0.0226 1.05 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.5 318 0.0170 3.49 69.75 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
14.3 586 Total
Subcatchment S-14: DA-6C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.510 ac
Runoff Volume=0.990 af
Runoff Depth>4.73"
Flow Length=586'
Tc=14.3 min
CN=74
16.91 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-15: DA-6E
Runoff = 18.62 cfs @ 12.12 hrs, Volume= 1.279 af, Depth> 4.72"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
3.250 74 >75% Grass cover, Good, HSG C
3.250 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.7 100 0.0120 0.14 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
3.8 224 0.0200 0.99 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
4.1 552 0.0027 2.23 34.93 Channel Flow,
Area= 15.7 sf Perim= 15.5' r= 1.01' n= 0.035
19.6 876 Total
Subcatchment S-15: DA-6E
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=3.250 ac
Runoff Volume=1.279 af
Runoff Depth>4.72"
Flow Length=876'
Tc=19.6 min
CN=74
18.62 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-16: DA-6F
Runoff = 12.05 cfs @ 12.06 hrs, Volume= 0.702 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.780 74 >75% Grass cover, Good, HSG C
1.780 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.1 100 0.0170 0.16 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
2.4 148 0.0210 1.01 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.6 289 0.0050 3.06 42.85 Channel Flow,
Area= 14.0 sf Perim= 13.6' r= 1.03' n= 0.035
14.1 537 Total
Subcatchment S-16: DA-6F
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.780 ac
Runoff Volume=0.702 af
Runoff Depth>4.73"
Flow Length=537'
Tc=14.1 min
CN=74
12.05 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-17: DA-6G
Runoff = 24.15 cfs @ 11.96 hrs, Volume= 1.032 af, Depth> 4.75"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.610 74 >75% Grass cover, Good, HSG C
2.610 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-17: DA-6G
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
25
20
15
10
5
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.610 ac
Runoff Volume=1.032 af
Runoff Depth>4.75"
Tc=5.0 min
CN=74
24.15 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-11: LD-1A
Inflow Area = 26.609 ac, 0.00% Impervious, Inflow Depth > 5.62" for 100-Year event
Inflow = 214.35 cfs @ 12.04 hrs, Volume= 12.460 af
Outflow = 213.37 cfs @ 12.05 hrs, Volume= 12.447 af, Atten= 0%, Lag= 0.7 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 6.30 fps, Min. Travel Time= 0.9 min
Avg. Velocity = 2.01 fps, Avg. Travel Time= 2.8 min
Peak Storage= 11,336 cf @ 12.05 hrs
Average Depth at Peak Storage= 2.50'
Bank-Full Depth= 6.00' Flow Area= 144.0 sf, Capacity= 1,495.75 cfs
6.00' x 6.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 42.00'
Length= 335.0' Slope= 0.0123 '/'
Inlet Invert= 508.00', Outlet Invert= 503.88'
Reach R-11: LD-1A
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
240
220
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=26.609 ac
Avg. Flow Depth=2.50'
Max Vel=6.30 fps
n=0.035
L=335.0'
S=0.0123 '/'
Capacity=1,495.75 cfs
214.35 cfs213.37 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-12: LD-1B
Inflow Area = 31.819 ac, 0.00% Impervious, Inflow Depth > 5.47" for 100-Year event
Inflow = 245.08 cfs @ 12.06 hrs, Volume= 14.500 af
Outflow = 244.15 cfs @ 12.07 hrs, Volume= 14.487 af, Atten= 0%, Lag= 0.6 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 6.60 fps, Min. Travel Time= 0.8 min
Avg. Velocity = 2.11 fps, Avg. Travel Time= 2.5 min
Peak Storage= 11,538 cf @ 12.07 hrs
Average Depth at Peak Storage= 2.65'
Bank-Full Depth= 4.00' Flow Area= 72.0 sf, Capacity= 599.39 cfs
6.00' x 4.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 30.00'
Length= 312.0' Slope= 0.0127 '/'
Inlet Invert= 503.88', Outlet Invert= 499.93'
‡
Reach R-12: LD-1B
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
250
200
150
100
50
0
Inflow Area=31.819 ac
Avg. Flow Depth=2.65'
Max Vel=6.60 fps
n=0.035
L=312.0'
S=0.0127 '/'
Capacity=599.39 cfs
245.08 cfs244.15 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-13: LD-1C
Inflow Area = 31.819 ac, 0.00% Impervious, Inflow Depth > 5.46" for 100-Year event
Inflow = 244.15 cfs @ 12.07 hrs, Volume= 14.487 af
Outflow = 243.77 cfs @ 12.07 hrs, Volume= 14.479 af, Atten= 0%, Lag= 0.4 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 6.16 fps, Min. Travel Time= 0.5 min
Avg. Velocity = 1.98 fps, Avg. Travel Time= 1.5 min
Peak Storage= 7,286 cf @ 12.07 hrs
Average Depth at Peak Storage= 2.77'
Bank-Full Depth= 4.00' Flow Area= 72.0 sf, Capacity= 545.58 cfs
6.00' x 4.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 30.00'
Length= 184.0' Slope= 0.0105 '/'
Inlet Invert= 499.93', Outlet Invert= 498.00'
‡
Reach R-13: LD-1C
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
250
200
150
100
50
0
Inflow Area=31.819 ac
Avg. Flow Depth=2.77'
Max Vel=6.16 fps
n=0.035
L=184.0'
S=0.0105 '/'
Capacity=545.58 cfs
244.15 cfs243.77 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-15: Outlet-2
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 5.32" for 100-Year event
Inflow = 280.99 cfs @ 12.07 hrs, Volume= 17.492 af
Outflow = 280.99 cfs @ 12.07 hrs, Volume= 17.492 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Reach R-15: Outlet-2
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
300
250
200
150
100
50
0
Inflow Area=39.459 ac
280.99 cfs280.99 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R01: Lateral Ditch
Inflow Area = 5.460 ac, 0.00% Impervious, Inflow Depth > 4.73" for 100-Year event
Inflow = 35.01 cfs @ 12.07 hrs, Volume= 2.152 af
Outflow = 29.28 cfs @ 12.14 hrs, Volume= 2.136 af, Atten= 16%, Lag= 4.5 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Max. Velocity= 2.63 fps, Min. Travel Time= 7.5 min
Avg. Velocity = 1.03 fps, Avg. Travel Time= 19.0 min
Peak Storage= 13,114 cf @ 12.14 hrs
Average Depth at Peak Storage= 0.65'
Bank-Full Depth= 1.50' Flow Area= 51.0 sf, Capacity= 223.50 cfs
4.00' x 1.50' deep channel, n= 0.035
Side Slope Z-value= 20.0 '/' Top Width= 64.00'
Length= 1,177.0' Slope= 0.0144 '/'
Inlet Invert= 514.00', Outlet Invert= 497.00'
‡
Reach R01: Lateral Ditch
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
35
30
25
20
15
10
5
0
Inflow Area=5.460 ac
Avg. Flow Depth=0.65'
Max Vel=2.63 fps
n=0.035
L=1,177.0'
S=0.0144 '/'
Capacity=223.50 cfs
35.01 cfs
29.28 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R02: Outlet-1
Inflow Area = 10.470 ac, 0.00% Impervious, Inflow Depth > 4.71" for 100-Year event
Inflow = 49.75 cfs @ 12.11 hrs, Volume= 4.113 af
Outflow = 49.75 cfs @ 12.11 hrs, Volume= 4.113 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Reach R02: Outlet-1
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=10.470 ac
49.75 cfs49.75 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 22HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 1P: 48" Culvert
Inflow Area = 22.679 ac, 0.00% Impervious, Inflow Depth > 5.77" for 100-Year event
Inflow = 186.52 cfs @ 12.04 hrs, Volume= 10.909 af
Outflow = 186.52 cfs @ 12.04 hrs, Volume= 10.909 af, Atten= 0%, Lag= 0.0 min
Primary = 186.52 cfs @ 12.04 hrs, Volume= 10.909 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 521.50' @ 12.04 hrs
Flood Elev= 524.00'
Device Routing Invert Outlet Devices
#1 Primary 510.00'48.0" Round 48" RCP Culvert
L= 157.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 510.00' / 508.00' S= 0.0127 '/' Cc= 0.900
n= 0.012, Flow Area= 12.57 sf
Primary OutFlow Max=186.37 cfs @ 12.04 hrs HW=521.49' TW=510.50' (Dynamic Tailwater)
1=48" RCP Culvert (Inlet Controls 186.37 cfs @ 14.83 fps)
Pond 1P: 48" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=22.679 ac
Peak Elev=521.50'
48.0"
Round Culvert
n=0.012
L=157.0'
S=0.0127 '/'
186.52 cfs186.52 cfs
2
DA-2
3
DA4
4
DA-3
9S
DA-8A-1A
10S
DA-8A-1B
12S
DA-8A-1C
13S
DA-8A-1D
14S
DA-8A-1E
15S
DA-8A-1F
38S
DA-8A-1G
S-21
DA-7A
S-22
DA-7B
S-23
DA-7C
S-24
DA-7D
S-25
DA-7E
S-26
DA-7F
S-27
DA-7G
S-41
DA-8A
S-42
DA-8B
S-43
DA-8DS-45
DA-8C
6R
LD-4B
R-21
LD-2A
R-22
LD-2B
R-23
LD-2C
R-25
Outlet-3
R-41
LD-4A
R-42
Outlet-4
2PCB
54" Slope Drain
3P
36" Slope Drain Pipe
4PCB
36" Slope Drain Pipe
16PCB
18" Culvert
17PCB
18" Culvert
18PCB
18" Culvert
Routing Diagram for LT_2
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 2
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=6.060 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment 2: DA-2
Flow Length=852' Tc=17.0 min CN=74 Runoff=37.45 cfs 2.387 af
Runoff Area=71.320 ac 0.00% Impervious Runoff Depth>5.29"Subcatchment 3: DA4
Flow Length=4,921' Tc=23.4 min CN=79 Runoff=407.62 cfs 31.447 af
Runoff Area=2.385 ac 0.00% Impervious Runoff Depth>4.62"Subcatchment 4: DA-3
Flow Length=765' Tc=12.6 min CN=73 Runoff=16.60 cfs 0.918 af
Runoff Area=0.620 ac 0.00% Impervious Runoff Depth>4.74"Subcatchment 9S: DA-8A-1A
Tc=6.0 min CN=74 Runoff=5.54 cfs 0.245 af
Runoff Area=0.750 ac 0.00% Impervious Runoff Depth>4.74"Subcatchment 10S: DA-8A-1B
Tc=6.0 min CN=74 Runoff=6.70 cfs 0.297 af
Runoff Area=0.130 ac 0.00% Impervious Runoff Depth>4.74"Subcatchment 12S: DA-8A-1C
Tc=6.0 min CN=74 Runoff=1.16 cfs 0.051 af
Runoff Area=1.240 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment 13S: DA-8A-1D
Flow Length=676' Tc=12.7 min CN=74 Runoff=8.79 cfs 0.489 af
Runoff Area=0.290 ac 0.00% Impervious Runoff Depth>4.75"Subcatchment 14S: DA-8A-1E
Tc=0.0 min CN=74 Runoff=3.14 cfs 0.115 af
Runoff Area=0.170 ac 0.00% Impervious Runoff Depth>4.74"Subcatchment 15S: DA-8A-1F
Tc=6.0 min CN=74 Runoff=1.52 cfs 0.067 af
Runoff Area=0.350 ac 0.00% Impervious Runoff Depth>4.74"Subcatchment 38S: DA-8A-1G
Tc=6.0 min CN=74 Runoff=3.13 cfs 0.138 af
Runoff Area=4.350 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-21: DA-7A
Flow Length=879' Tc=18.1 min CN=74 Runoff=26.01 cfs 1.713 af
Runoff Area=1.610 ac 0.00% Impervious Runoff Depth>4.75"Subcatchment S-22: DA-7B
Tc=5.0 min CN=74 Runoff=14.90 cfs 0.637 af
Runoff Area=2.480 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-23: DA-7C
Flow Length=571' Tc=15.6 min CN=74 Runoff=16.03 cfs 0.978 af
Runoff Area=2.650 ac 0.00% Impervious Runoff Depth>4.72"Subcatchment S-24: DA-7D
Flow Length=618' Tc=19.0 min CN=74 Runoff=15.43 cfs 1.043 af
Runoff Area=1.640 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-25: DA-7E
Flow Length=528' Tc=13.8 min CN=74 Runoff=11.21 cfs 0.647 af
Runoff Area=3.000 ac 0.00% Impervious Runoff Depth>4.71"Subcatchment S-26: DA-7F
Flow Length=1,030' Tc=26.4 min CN=74 Runoff=14.40 cfs 1.178 af
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Runoff Area=2.260 ac 0.00% Impervious Runoff Depth>4.75"Subcatchment S-27: DA-7G
Tc=5.0 min CN=74 Runoff=20.91 cfs 0.894 af
Runoff Area=4.740 ac 0.00% Impervious Runoff Depth>4.73"Subcatchment S-41: DA-8A
Flow Length=1,457' Tc=15.4 min CN=74 Runoff=30.78 cfs 1.868 af
Runoff Area=2.890 ac 0.00% Impervious Runoff Depth>4.72"Subcatchment S-42: DA-8B
Flow Length=916' Tc=22.1 min CN=74 Runoff=15.49 cfs 1.137 af
Runoff Area=1.770 ac 0.00% Impervious Runoff Depth>4.75"Subcatchment S-43: DA-8D
Tc=5.0 min CN=74 Runoff=16.38 cfs 0.700 af
Runoff Area=1.480 ac 0.00% Impervious Runoff Depth>4.72"Subcatchment S-45: DA-8C
Flow Length=725' Tc=19.3 min CN=74 Runoff=8.56 cfs 0.583 af
Inflow=70.33 cfs 5.289 afReach 6R: LD-4B
Outflow=70.33 cfs 5.289 af
Avg. Flow Depth=1.92' Max Vel=5.87 fps Inflow=133.30 cfs 36.146 afReach R-21: LD-2A
n=0.035 L=282.0' S=0.0143 '/' Capacity=636.03 cfs Outflow=133.14 cfs 36.124 af
Avg. Flow Depth=2.13' Max Vel=6.20 fps Inflow=163.94 cfs 38.145 afReach R-22: LD-2B
n=0.035 L=306.0' S=0.0142 '/' Capacity=336.93 cfs Outflow=163.73 cfs 38.120 af
Avg. Flow Depth=1.91' Max Vel=7.28 fps Inflow=163.73 cfs 38.120 afReach R-23: LD-2C
n=0.035 L=165.0' S=0.0221 '/' Capacity=420.20 cfs Outflow=163.69 cfs 38.109 af
Inflow=190.27 cfs 40.828 afReach R-25: Outlet-3
Outflow=190.27 cfs 40.828 af
Avg. Flow Depth=0.86' Max Vel=2.74 fps Inflow=67.72 cfs 4.189 afReach R-41: LD-4A
n=0.035 L=1,410.0' S=0.0106 '/' Capacity=77.78 cfs Outflow=55.22 cfs 4.152 af
Inflow=81.99 cfs 6.571 afReach R-42: Outlet-4
Outflow=81.99 cfs 6.571 af
Peak Elev=514.15' Inflow=37.45 cfs 2.387 afPond 2P: 54" Slope Drain
54.0" Round Culvert n=0.012 L=90.0' S=0.0222 '/' Outflow=37.45 cfs 2.387 af
Peak Elev=541.31' Storage=513,893 cf Inflow=407.62 cfs 31.447 afPond 3P: 36" Slope Drain Pipe
Outflow=81.28 cfs 31.408 af
Peak Elev=530.54' Inflow=16.60 cfs 0.918 afPond 4P: 36" Slope Drain Pipe
36.0" Round Culvert n=0.013 L=150.0' S=0.1263 '/' Outflow=16.60 cfs 0.918 af
Peak Elev=527.34' Inflow=12.24 cfs 0.542 afPond 16P: 18" Culvert
Outflow=12.24 cfs 0.542 af
Peak Elev=528.82' Inflow=9.57 cfs 0.541 afPond 17P: 18" Culvert
Outflow=9.57 cfs 0.541 af
Peak Elev=528.26' Inflow=4.24 cfs 0.182 afPond 18P: 18" Culvert
Outflow=4.24 cfs 0.182 af
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Total Runoff Area = 112.185 ac Runoff Volume = 47.533 af Average Runoff Depth = 5.08"
100.00% Pervious = 112.185 ac 0.00% Impervious = 0.000 ac
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: DA-2
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 37.45 cfs @ 12.09 hrs, Volume= 2.387 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.555 73 Woods, Fair, HSG C
0.140 96 Gravel surface, HSG C
4.365 74 >75% Grass cover, Good, HSG C
6.060 74 Weighted Average
6.060 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.6 100 0.0500 0.25 Sheet Flow, TC for DA2
Grass: Short n= 0.150 P2= 3.40"
10.4 752 0.0580 1.20 Shallow Concentrated Flow, TC for DA2
Woodland Kv= 5.0 fps
17.0 852 Total
Subcatchment 2: DA-2
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
40
35
30
25
20
15
10
5
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=6.060 ac
Runoff Volume=2.387 af
Runoff Depth>4.73"
Flow Length=852'
Tc=17.0 min
CN=74
37.45 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 3: DA4
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 407.62 cfs @ 12.16 hrs, Volume= 31.447 af, Depth> 5.29"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
9.930 73 Woods, Fair, HSG C
15.051 96 Gravel surface, HSG C
46.339 74 >75% Grass cover, Good, HSG C
71.320 79 Weighted Average
71.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.0 100 0.0430 0.24 Sheet Flow, TC for DA4
Grass: Short n= 0.150 P2= 3.40"
13.1 2,834 0.0580 3.61 Shallow Concentrated Flow, TC for DA4
Grassed Waterway Kv= 15.0 fps
3.3 1,987 10.00 Direct Entry, TC for DA4
23.4 4,921 Total
Subcatchment 3: DA4
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
450
400
350
300
250
200
150
100
50
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=71.320 ac
Runoff Volume=31.447 af
Runoff Depth>5.29"
Flow Length=4,921'
Tc=23.4 min
CN=79
407.62 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 4: DA-3
I am not going to consider channel flow in this scenerio to more closely reflect insitu circumstances.
Runoff = 16.60 cfs @ 12.04 hrs, Volume= 0.918 af, Depth> 4.62"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.260 73 Woods, Fair, HSG C
0.000 96 Gravel surface, HSG C
1.125 74 >75% Grass cover, Good, HSG C
2.385 73 Weighted Average
2.385 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.6 100 0.0740 0.30 Sheet Flow, TC for DA3
Grass: Short n= 0.150 P2= 3.40"
7.0 665 0.0511 1.58 Shallow Concentrated Flow, TC for DA3
Short Grass Pasture Kv= 7.0 fps
12.6 765 Total
Subcatchment 4: DA-3
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.385 ac
Runoff Volume=0.918 af
Runoff Depth>4.62"
Flow Length=765'
Tc=12.6 min
CN=73
16.60 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 9S: DA-8A-1A
Runoff = 5.54 cfs @ 11.97 hrs, Volume= 0.245 af, Depth> 4.74"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 0.620 74
0.620 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 9S: DA-8A-1A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=0.620 ac
Runoff Volume=0.245 af
Runoff Depth>4.74"
Tc=6.0 min
CN=74
5.54 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 10S: DA-8A-1B
Runoff = 6.70 cfs @ 11.97 hrs, Volume= 0.297 af, Depth> 4.74"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 0.750 74
0.750 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 10S: DA-8A-1B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
7
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=0.750 ac
Runoff Volume=0.297 af
Runoff Depth>4.74"
Tc=6.0 min
CN=74
6.70 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 12S: DA-8A-1C
Runoff = 1.16 cfs @ 11.97 hrs, Volume= 0.051 af, Depth> 4.74"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 0.130 74
0.130 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 12S: DA-8A-1C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=0.130 ac
Runoff Volume=0.051 af
Runoff Depth>4.74"
Tc=6.0 min
CN=74
1.16 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 13S: DA-8A-1D
Runoff = 8.79 cfs @ 12.04 hrs, Volume= 0.489 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 1.240 74
1.240 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.8 100 0.2000 0.44 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
8.9 576 0.0240 1.08 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
12.7 676 Total
Subcatchment 13S: DA-8A-1D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.240 ac
Runoff Volume=0.489 af
Runoff Depth>4.73"
Flow Length=676'
Tc=12.7 min
CN=74
8.79 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 14S: DA-8A-1E
Runoff = 3.14 cfs @ 11.90 hrs, Volume= 0.115 af, Depth> 4.75"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 0.290 74
0.290 100.00% Pervious Area
Subcatchment 14S: DA-8A-1E
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=0.290 ac
Runoff Volume=0.115 af
Runoff Depth>4.75"
Tc=0.0 min
CN=74
3.14 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 15S: DA-8A-1F
Runoff = 1.52 cfs @ 11.97 hrs, Volume= 0.067 af, Depth> 4.74"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 0.170 74
0.170 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 15S: DA-8A-1F
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=0.170 ac
Runoff Volume=0.067 af
Runoff Depth>4.74"
Tc=6.0 min
CN=74
1.52 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment 38S: DA-8A-1G
Runoff = 3.13 cfs @ 11.97 hrs, Volume= 0.138 af, Depth> 4.74"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
* 0.350 74
0.350 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
6.0 Direct Entry,
Subcatchment 38S: DA-8A-1G
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=0.350 ac
Runoff Volume=0.138 af
Runoff Depth>4.74"
Tc=6.0 min
CN=74
3.13 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-21: DA-7A
Runoff = 26.01 cfs @ 12.10 hrs, Volume= 1.713 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
4.350 74 >75% Grass cover, Good, HSG C
4.350 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.7 100 0.0720 0.29 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
11.2 534 0.0130 0.80 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.2 245 0.0160 3.38 67.66 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
18.1 879 Total
Subcatchment S-21: DA-7A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
25
20
15
10
5
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=4.350 ac
Runoff Volume=1.713 af
Runoff Depth>4.73"
Flow Length=879'
Tc=18.1 min
CN=74
26.01 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-22: DA-7B
Runoff = 14.90 cfs @ 11.96 hrs, Volume= 0.637 af, Depth> 4.75"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.610 74 >75% Grass cover, Good, HSG C
1.610 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-22: DA-7B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.610 ac
Runoff Volume=0.637 af
Runoff Depth>4.75"
Tc=5.0 min
CN=74
14.90 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-23: DA-7C
Runoff = 16.03 cfs @ 12.08 hrs, Volume= 0.978 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.480 74 >75% Grass cover, Good, HSG C
2.480 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.5 100 0.0155 0.16 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
3.5 226 0.0242 1.09 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.6 245 0.0090 2.54 50.75 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
15.6 571 Total
Subcatchment S-23: DA-7C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.480 ac
Runoff Volume=0.978 af
Runoff Depth>4.73"
Flow Length=571'
Tc=15.6 min
CN=74
16.03 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-24: DA-7D
Runoff = 15.43 cfs @ 12.11 hrs, Volume= 1.043 af, Depth> 4.72"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.650 74 >75% Grass cover, Good, HSG C
2.650 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
12.3 100 0.0106 0.14 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
5.1 277 0.0170 0.91 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.6 241 0.0090 2.54 50.75 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
19.0 618 Total
Subcatchment S-24: DA-7D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.650 ac
Runoff Volume=1.043 af
Runoff Depth>4.72"
Flow Length=618'
Tc=19.0 min
CN=74
15.43 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-25: DA-7E
Runoff = 11.21 cfs @ 12.06 hrs, Volume= 0.647 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.640 74 >75% Grass cover, Good, HSG C
1.640 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
9.9 100 0.0181 0.17 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
2.3 139 0.0213 1.02 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.6 289 0.0050 3.03 47.54 Channel Flow,
Area= 15.7 sf Perim= 15.5' r= 1.01' n= 0.035
13.8 528 Total
Subcatchment S-25: DA-7E
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
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(
c
f
s
)
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.640 ac
Runoff Volume=0.647 af
Runoff Depth>4.73"
Flow Length=528'
Tc=13.8 min
CN=74
11.21 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-26: DA-7F
Runoff = 14.40 cfs @ 12.20 hrs, Volume= 1.178 af, Depth> 4.71"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
3.000 74 >75% Grass cover, Good, HSG C
3.000 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.2 100 0.0166 0.16 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
13.3 498 0.0080 0.63 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
2.9 432 0.0035 2.51 39.44 Channel Flow,
Area= 15.7 sf Perim= 15.7' r= 1.00' n= 0.035
26.4 1,030 Total
Subcatchment S-26: DA-7F
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=3.000 ac
Runoff Volume=1.178 af
Runoff Depth>4.71"
Flow Length=1,030'
Tc=26.4 min
CN=74
14.40 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-27: DA-7G
Runoff = 20.91 cfs @ 11.96 hrs, Volume= 0.894 af, Depth> 4.75"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.260 74 >75% Grass cover, Good, HSG C
2.260 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-27: DA-7G
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.260 ac
Runoff Volume=0.894 af
Runoff Depth>4.75"
Tc=5.0 min
CN=74
20.91 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 22HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-41: DA-8A
Runoff = 30.78 cfs @ 12.07 hrs, Volume= 1.868 af, Depth> 4.73"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
4.740 74 >75% Grass cover, Good, HSG C
4.740 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 100 0.1000 0.33 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
7.3 695 0.0520 1.60 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
3.1 662 0.0180 3.59 71.77 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
15.4 1,457 Total
Subcatchment S-41: DA-8A
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
30
25
20
15
10
5
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=4.740 ac
Runoff Volume=1.868 af
Runoff Depth>4.73"
Flow Length=1,457'
Tc=15.4 min
CN=74
30.78 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 23HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-42: DA-8B
Runoff = 15.49 cfs @ 12.15 hrs, Volume= 1.137 af, Depth> 4.72"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
2.890 74 >75% Grass cover, Good, HSG C
2.890 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
12.3 100 0.0104 0.13 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
4.2 252 0.0204 1.00 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
5.6 564 0.0040 1.69 33.83 Channel Flow,
Area= 20.0 sf Perim= 40.0' r= 0.50' n= 0.035
22.1 916 Total
Subcatchment S-42: DA-8B
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=2.890 ac
Runoff Volume=1.137 af
Runoff Depth>4.72"
Flow Length=916'
Tc=22.1 min
CN=74
15.49 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 24HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-43: DA-8D
Runoff = 16.38 cfs @ 11.96 hrs, Volume= 0.700 af, Depth> 4.75"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.770 74 >75% Grass cover, Good, HSG C
1.770 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment S-43: DA-8D
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.770 ac
Runoff Volume=0.700 af
Runoff Depth>4.75"
Tc=5.0 min
CN=74
16.38 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 25HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Subcatchment S-45: DA-8C
Runoff = 8.56 cfs @ 12.12 hrs, Volume= 0.583 af, Depth> 4.72"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Type II 24-hr 100-Year Rainfall=8.20"
Area (ac) CN Description
1.480 74 >75% Grass cover, Good, HSG C
1.480 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.9 100 0.0143 0.15 Sheet Flow,
Grass: Short n= 0.150 P2= 3.40"
6.7 320 0.0130 0.80 Shallow Concentrated Flow,
Short Grass Pasture Kv= 7.0 fps
1.7 305 0.0050 3.03 47.54 Channel Flow,
Area= 15.7 sf Perim= 15.5' r= 1.01' n= 0.035
19.3 725 Total
Subcatchment S-45: DA-8C
Runoff
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
100-Year Rainfall=8.20"
Runoff Area=1.480 ac
Runoff Volume=0.583 af
Runoff Depth>4.72"
Flow Length=725'
Tc=19.3 min
CN=74
8.56 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 26HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach 6R: LD-4B
Inflow Area = 13.565 ac, 0.00% Impervious, Inflow Depth > 4.68" for 100-Year event
Inflow = 70.33 cfs @ 12.12 hrs, Volume= 5.289 af
Outflow = 70.33 cfs @ 12.12 hrs, Volume= 5.289 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Reach 6R: LD-4B
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
70
60
50
40
30
20
10
0
Inflow Area=13.565 ac
70.33 cfs70.33 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 27HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-21: LD-2A
Inflow Area = 83.340 ac, 0.00% Impervious, Inflow Depth > 5.20" for 100-Year event
Inflow = 133.30 cfs @ 12.11 hrs, Volume= 36.146 af
Outflow = 133.14 cfs @ 12.12 hrs, Volume= 36.124 af, Atten= 0%, Lag= 0.5 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Max. Velocity= 5.87 fps, Min. Travel Time= 0.8 min
Avg. Velocity = 3.19 fps, Avg. Travel Time= 1.5 min
Peak Storage= 6,392 cf @ 12.12 hrs
Average Depth at Peak Storage= 1.92'
Bank-Full Depth= 4.00' Flow Area= 72.0 sf, Capacity= 636.03 cfs
6.00' x 4.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 30.00'
Length= 282.0' Slope= 0.0143 '/'
Inlet Invert= 510.00', Outlet Invert= 505.98'
‡
Reach R-21: LD-2A
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
140
120
100
80
60
40
20
0
Inflow Area=83.340 ac
Avg. Flow Depth=1.92'
Max Vel=5.87 fps
n=0.035
L=282.0'
S=0.0143 '/'
Capacity=636.03 cfs
133.30 cfs133.14 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 28HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-22: LD-2B
Inflow Area = 88.470 ac, 0.00% Impervious, Inflow Depth > 5.17" for 100-Year event
Inflow = 163.94 cfs @ 12.11 hrs, Volume= 38.145 af
Outflow = 163.73 cfs @ 12.12 hrs, Volume= 38.120 af, Atten= 0%, Lag= 0.6 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Max. Velocity= 6.20 fps, Min. Travel Time= 0.8 min
Avg. Velocity = 3.23 fps, Avg. Travel Time= 1.6 min
Peak Storage= 8,087 cf @ 12.12 hrs
Average Depth at Peak Storage= 2.13'
Bank-Full Depth= 3.00' Flow Area= 45.0 sf, Capacity= 336.93 cfs
6.00' x 3.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 24.00'
Length= 306.0' Slope= 0.0142 '/'
Inlet Invert= 505.98', Outlet Invert= 501.64'
‡
Reach R-22: LD-2B
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
180
160
140
120
100
80
60
40
20
0
Inflow Area=88.470 ac
Avg. Flow Depth=2.13'
Max Vel=6.20 fps
n=0.035
L=306.0'
S=0.0142 '/'
Capacity=336.93 cfs
163.94 cfs163.73 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 29HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-23: LD-2C
Inflow Area = 88.470 ac, 0.00% Impervious, Inflow Depth > 5.17" for 100-Year event
Inflow = 163.73 cfs @ 12.12 hrs, Volume= 38.120 af
Outflow = 163.69 cfs @ 12.12 hrs, Volume= 38.109 af, Atten= 0%, Lag= 0.3 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Max. Velocity= 7.28 fps, Min. Travel Time= 0.4 min
Avg. Velocity = 3.77 fps, Avg. Travel Time= 0.7 min
Peak Storage= 3,708 cf @ 12.12 hrs
Average Depth at Peak Storage= 1.91'
Bank-Full Depth= 3.00' Flow Area= 45.0 sf, Capacity= 420.20 cfs
6.00' x 3.00' deep channel, n= 0.035
Side Slope Z-value= 3.0 '/' Top Width= 24.00'
Length= 165.0' Slope= 0.0221 '/'
Inlet Invert= 501.64', Outlet Invert= 498.00'
‡
Reach R-23: LD-2C
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
180
160
140
120
100
80
60
40
20
0
Inflow Area=88.470 ac
Avg. Flow Depth=1.91'
Max Vel=7.28 fps
n=0.035
L=165.0'
S=0.0221 '/'
Capacity=420.20 cfs
163.73 cfs163.69 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 30HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-25: Outlet-3
Inflow Area = 95.370 ac, 0.00% Impervious, Inflow Depth > 5.14" for 100-Year event
Inflow = 190.27 cfs @ 12.11 hrs, Volume= 40.828 af
Outflow = 190.27 cfs @ 12.11 hrs, Volume= 40.828 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Reach R-25: Outlet-3
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=95.370 ac
190.27 cfs190.27 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 31HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-41: LD-4A
Inflow Area = 10.675 ac, 0.00% Impervious, Inflow Depth > 4.71" for 100-Year event
Inflow = 67.72 cfs @ 12.03 hrs, Volume= 4.189 af
Outflow = 55.22 cfs @ 12.11 hrs, Volume= 4.152 af, Atten= 18%, Lag= 5.1 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Max. Velocity= 2.74 fps, Min. Travel Time= 8.6 min
Avg. Velocity = 1.07 fps, Avg. Travel Time= 22.0 min
Peak Storage= 28,390 cf @ 12.11 hrs
Average Depth at Peak Storage= 0.86'
Bank-Full Depth= 1.00' Flow Area= 26.0 sf, Capacity= 77.78 cfs
6.00' x 1.00' deep channel, n= 0.035
Side Slope Z-value= 20.0 '/' Top Width= 46.00'
Length= 1,410.0' Slope= 0.0106 '/'
Inlet Invert= 512.00', Outlet Invert= 497.00'
‡
Reach R-41: LD-4A
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
70
60
50
40
30
20
10
0
Inflow Area=10.675 ac
Avg. Flow Depth=0.86'
Max Vel=2.74 fps
n=0.035
L=1,410.0'
S=0.0106 '/'
Capacity=77.78 cfs
67.72 cfs
55.22 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 32HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-42: Outlet-4
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 4.69" for 100-Year event
Inflow = 81.99 cfs @ 12.11 hrs, Volume= 6.571 af
Outflow = 81.99 cfs @ 12.11 hrs, Volume= 6.571 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Reach R-42: Outlet-4
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
90
80
70
60
50
40
30
20
10
0
Inflow Area=16.815 ac
81.99 cfs81.99 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 33HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 2P: 54" Slope Drain
Inflow Area = 6.060 ac, 0.00% Impervious, Inflow Depth > 4.73" for 100-Year event
Inflow = 37.45 cfs @ 12.09 hrs, Volume= 2.387 af
Outflow = 37.45 cfs @ 12.09 hrs, Volume= 2.387 af, Atten= 0%, Lag= 0.0 min
Primary = 37.45 cfs @ 12.09 hrs, Volume= 2.387 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 514.15' @ 12.09 hrs
Flood Elev= 528.00'
Device Routing Invert Outlet Devices
#1 Primary 512.00'54.0" Round Culvert
L= 90.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 512.00' / 510.00' S= 0.0222 '/' Cc= 0.900
n= 0.012, Flow Area= 15.90 sf
Primary OutFlow Max=37.44 cfs @ 12.09 hrs HW=514.15' TW=511.92' (Dynamic Tailwater)
1=Culvert (Inlet Controls 37.44 cfs @ 4.99 fps)
Pond 2P: 54" Slope Drain
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
40
35
30
25
20
15
10
5
0
Inflow Area=6.060 ac
Peak Elev=514.15'
54.0"
Round Culvert
n=0.012
L=90.0'
S=0.0222 '/'
37.45 cfs37.45 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 34HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 3P: 36" Slope Drain Pipe
Inflow Area = 71.320 ac, 0.00% Impervious, Inflow Depth > 5.29" for 100-Year event
Inflow = 407.62 cfs @ 12.16 hrs, Volume= 31.447 af
Outflow = 81.28 cfs @ 12.70 hrs, Volume= 31.408 af, Atten= 80%, Lag= 32.7 min
Primary = 81.28 cfs @ 12.70 hrs, Volume= 31.408 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 541.31' @ 12.70 hrs Surf.Area= 124,068 sf Storage= 513,893 cf
Plug-Flow detention time= 51.3 min calculated for 31.393 af (100% of inflow)
Center-of-Mass det. time= 50.7 min ( 829.2 - 778.5 )
Volume Invert Avail.Storage Storage Description
#1 535.00' 2,237,064 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
535.00 0 0 0
536.00 58,048 29,024 29,024
541.00 120,747 446,988 476,012
546.00 174,399 737,865 1,213,877
551.00 234,876 1,023,188 2,237,064
Device Routing Invert Outlet Devices
#1 Primary 528.50'36.0" Round Culvert
L= 207.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 528.50' / 510.00' S= 0.0894 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 7.07 sf
#2 Device 1 530.00'36.0" Round Culvert
L= 530.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 530.00' / 528.50' S= 0.0028 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#3 Device 2 535.00'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=81.28 cfs @ 12.70 hrs HW=541.31' TW=511.59' (Dynamic Tailwater)
1=Culvert (Passes 81.28 cfs of 114.46 cfs potential flow)
2=Culvert (Barrel Controls 81.28 cfs @ 11.50 fps)
3=Orifice/Grate (Passes 81.28 cfs of 302.36 cfs potential flow)
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 35HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 3P: 36" Slope Drain Pipe
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
450
400
350
300
250
200
150
100
50
0
Inflow Area=71.320 ac
Peak Elev=541.31'
Storage=513,893 cf
407.62 cfs
81.28 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 36HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 4P: 36" Slope Drain Pipe
Inflow Area = 2.385 ac, 0.00% Impervious, Inflow Depth > 4.62" for 100-Year event
Inflow = 16.60 cfs @ 12.04 hrs, Volume= 0.918 af
Outflow = 16.60 cfs @ 12.04 hrs, Volume= 0.918 af, Atten= 0%, Lag= 0.0 min
Primary = 16.60 cfs @ 12.04 hrs, Volume= 0.918 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 530.54' @ 12.04 hrs
Flood Elev= 532.00'
Device Routing Invert Outlet Devices
#1 Primary 528.94'36.0" Round Culvert
L= 150.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 528.94' / 510.00' S= 0.1263 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 7.07 sf
Primary OutFlow Max=16.59 cfs @ 12.04 hrs HW=530.54' TW=512.83' (Dynamic Tailwater)
1=Culvert (Inlet Controls 16.59 cfs @ 4.31 fps)
Pond 4P: 36" Slope Drain Pipe
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
18
16
14
12
10
8
6
4
2
0
Inflow Area=2.385 ac
Peak Elev=530.54'
36.0"
Round Culvert
n=0.013
L=150.0'
S=0.1263 '/'
16.60 cfs16.60 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 37HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 16P: 18" Culvert
Inflow Area = 1.370 ac, 0.00% Impervious, Inflow Depth > 4.74" for 100-Year event
Inflow = 12.24 cfs @ 11.97 hrs, Volume= 0.542 af
Outflow = 12.24 cfs @ 11.97 hrs, Volume= 0.542 af, Atten= 0%, Lag= 0.0 min
Primary = 12.24 cfs @ 11.97 hrs, Volume= 0.542 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 527.34' @ 11.97 hrs
Flood Elev= 528.00'
Device Routing Invert Outlet Devices
#1 Primary 524.00'18.0" Round Culvert
L= 100.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 524.00' / 510.00' S= 0.1400 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf
#2 Device 1 526.00'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Device 2 526.00'1.2" x 16.5" Horiz. Orifice/Grate X 2.00 columns X 8 rows C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=12.23 cfs @ 11.97 hrs HW=527.33' TW=512.71' (Dynamic Tailwater)
1=Culvert (Passes 12.23 cfs of 13.67 cfs potential flow)
2=Orifice/Grate (Passes 12.23 cfs of 33.34 cfs potential flow)
3=Orifice/Grate (Orifice Controls 12.23 cfs @ 5.56 fps)
Pond 16P: 18" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
12
10
8
6
4
2
0
Inflow Area=1.370 ac
Peak Elev=527.34'
12.24 cfs12.24 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 38HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 17P: 18" Culvert
Inflow Area = 1.370 ac, 0.00% Impervious, Inflow Depth > 4.74" for 100-Year event
Inflow = 9.57 cfs @ 12.03 hrs, Volume= 0.541 af
Outflow = 9.57 cfs @ 12.03 hrs, Volume= 0.541 af, Atten= 0%, Lag= 0.0 min
Primary = 9.57 cfs @ 12.03 hrs, Volume= 0.541 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 528.82' @ 12.03 hrs
Flood Elev= 530.00'
Device Routing Invert Outlet Devices
#1 Device 2 528.00'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#2 Primary 526.00'18.0" Round Culvert
L= 70.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 526.00' / 512.00' S= 0.2000 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf
#3 Device 1 528.00'1.2" x 16.5" Horiz. Orifice/Grate X 2.00 columns X 8 rows C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=9.56 cfs @ 12.03 hrs HW=528.81' TW=512.82' (Dynamic Tailwater)
2=Culvert (Passes 9.56 cfs of 12.23 cfs potential flow)
1=Orifice/Grate (Passes 9.56 cfs of 24.04 cfs potential flow)
3=Orifice/Grate (Orifice Controls 9.56 cfs @ 4.35 fps)
Pond 17P: 18" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=1.370 ac
Peak Elev=528.82'
9.57 cfs9.57 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 39HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 18P: 18" Culvert
Inflow Area = 0.460 ac, 0.00% Impervious, Inflow Depth > 4.75" for 100-Year event
Inflow = 4.24 cfs @ 11.90 hrs, Volume= 0.182 af
Outflow = 4.24 cfs @ 11.90 hrs, Volume= 0.182 af, Atten= 0%, Lag= 0.0 min
Primary = 4.24 cfs @ 11.90 hrs, Volume= 0.182 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 528.26' @ 11.90 hrs
Flood Elev= 530.00'
Device Routing Invert Outlet Devices
#1 Device 2 528.00'24.0" x 36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#2 Primary 526.00'18.0" Round Culvert
L= 70.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 526.00' / 510.00' S= 0.2286 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf
#3 Device 1 528.00'1.2" x 16.5" Horiz. Orifice/Grate X 2.00 columns X 8 rows C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=4.23 cfs @ 11.90 hrs HW=528.26' TW=512.58' (Dynamic Tailwater)
2=Culvert (Passes 4.23 cfs of 10.44 cfs potential flow)
1=Orifice/Grate (Weir Controls 4.23 cfs @ 1.65 fps)
3=Orifice/Grate (Passes 4.23 cfs of 5.36 cfs potential flow)
Pond 18P: 18" Culvert
Inflow
Primary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
4
3
2
1
0
Inflow Area=0.460 ac
Peak Elev=528.26'
4.24 cfs4.24 cfs
REFERENCE 3

North Carolina Department of Environment and Natural Resources, “Erosion and Sediment
Control Planning and Design Manual”, Revised May 2013.

Appendices
This section addresses the design of stable conveyance channels and
diversions using flexible linings. A stable channel is defined as a channel
which is nonsilting and nonscouring. To minimize silting in the channel, flow
velocities should remain constant or increase slightly throughout the channel
length. This is especially important in designing diversion channels and can
be accomplished by adjusting channel grade. Procedures presented in this
section address the problems of erosion and scour. More advanced procedures
for permanent, unlined channels may be found elsewhere. (References: Garde
and Ranga Raju, 1980)
Diversions are channels usually with a supporting ridge on the lower side.
They are generally located to divert flows across a slope and are designed
following the same procedures as other channels. Design tables for vegetated
diversions and waterways are included at the end of this section.
Flexible channel linings are generally preferred to rigid linings from an
erosion control standpoint because they conform to changes in channel shape
without failure and are less susceptible to damage from frost heaving, soil
swelling and shrinking, and excessive soil pore water pressure from lack of
drainage. Flexible linings also are generally less expensive to construct, and
when vegetated, are more natural in appearance. On the other hand, flexible
linings generally have higher roughness and require a larger cross section for
the same discharge.
EROSION CONtROL CRItERIa
The minimum design criteria for conveyance channels require that two
primary conditions be satisfied: the channel system must have capacity for
the peak flow expected from the 10-year storm and the channel lining must be
resistant to erosion for the design velocity. In some cases, out-of-bank flow
may be considered a functional part of the channel system. In these cases,
flow capacities and design velocities should be considered separately for out-
of-bank flows and channel flows.
Both the capacity of the channel and the velocity of flow are functions of the
channel lining, cross-sectional area and slope. The channel system must carry
the design flow, fit site conditions, and be stable.
Sta BLE CHaNNEL DESIGN mEtHODS
Two accepted procedures for designing stable channels with flexible linings
are: (1) the permissible velocity approach; and (2) the tractive force approach.
Under the permissible velocity approach, the channel is considered stable if the
design, mean velocity is lower than the maximum permissible velocity. Under
the tractive force approach, erosive stress evaluated at the boundary between
flowing water and lining materials must be less than the minimum unit tractive
force that will cause serious erosion of material from a level channel bed.
8.05 DESIGN Of Sta BLE CHaNNELS aND DIVERSIONS
8.05.1
8
8.05.2
The permissible velocity procedure is recommended for the design of vegetative
channels because of common usage and the availability of reliable design
tables. The tractive force approach is recommended for design of channels
with temporary synthetic liners or riprap liners. The tractive force procedure
is described in full in the U.S. Department of Transportation, Federal Highway
Administration Bulletin, Design of Roadside Channels with Flexible Linings.
Permissible Velocity
Procedure
The permissible velocity procedure uses two equations to calculate flow:
Manning’s equation,
V = 1.49 R2/3 S1/2 n
where:
V = average velocity in the channel in ft/sec.
n = Manning’s roughness coefficient, based upon the lining of the
channel
R = hydraulic radius, wetted cross-sectional area/wetted perimeter
in ft
S = slope of the channel in ft/ft
and the continuity equation,
Q = AV
where:
Q = flow in the channel in cfs
A = cross-sectional area of flow within the channel in ft2
V = average velocity in the channel in ft/sec.
Manning’s equation and the continuity equation are used together to determine
channel capacity and flow velocity. A nomograph for solving Manning’s
equation is given in Figure 8.05a.
Selecting Permanent
Channel Lining
Channel lining materials include such flexible materials as grass, riprap and
gabions, as well as rigid materials such as paving blocks, flag stone, gunite,
asphalt, and concrete. The design of concrete and similar rigid linings
is generally not restricted by flow velocities. However, flexible channel
linings do have maximum permissible flow velocities beyond which they are
susceptible to erosion. The designer should select the type of liner that best
fits site conditions.
Table 8.05a lists maximum permissible velocities for established grass linings
and soil conditions. Before grass is established, permissible velocity is
determined by the choice of temporary liner. Permissible velocities for riprap
linings are higher than for grass and depend on the stone size selected.
Appendices
8.05.3
8
8.05.4
Table 8.05a
Maximum Allowable Design Velocities1
for Vegetated Channels
Typical
Channel Slope
Application
Soil
Characteristics2
Grass Lining Permissible Velocity3
for Established Grass
Lining (ft/sec)
0-5%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
5.0
4.5
4.5
4.5
3.5
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
6.0
5.5
5.5
5.5
4.5
5-10%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
4.5
4.0
4.0
4.0
3.0
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
5.5
5.0
5.0
5.0
3.5
>10%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
3.5
2.5
2.5
2.5
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
4.5
3.5
3.5
3.5
Source: USDA-SCS Modified
NOTE:1Permissible Velocity based on 10-year storm peak runoff
2Soil erodibility based on resistance to soil movement from concentrated flowing water.
3Before grass is established, permissible velocity is determined by the type of temporary liner used.
Selecting Channel
Cross-Section
Geometry
To calculate the required size of an open channel, assume the design flow is
uniform and does not vary with time. Since actual flow conditions change
throughout the length of a channel, subdivide the channel into design reaches,
and design each reach to carry the appropriate capacity.
The three most commonly used channel cross-sections are “V”-shaped,
parabolic, and trapezoidal. Figure 8.05b gives mathematical formulas for the
area, hydraulic radius and top width of each of these shapes.
Appendices
8.05.5
8
8.05.6 Rev. 12/93
Design Procedure-
Permissible Velocity
The following is a step-by-step procedure for designing a runoff conveyance
channel using Manning’s equation and the continuity equation:
Step 1. Determine the required flow capacity, Q, by estimating peak runoff
rate for the design storm (Appendix 8.03).
Step 2. Determine the slope and select channel geometry and lining.
Step 3. Determine the permissible velocity for the lining selected, or the
desired velocity, if paved. (see Table 8.05a, page 8.05.4)
Step 4. Make an initial estimate of channel size—divide the required Q by the
permissible velocity to reach a “first try” estimate of channel flow area. Then
select a geometry, depth, and top width to fit site conditions.
Step 5. Calculate the hydraulic radius, R, from channel geometry (Figure
8.05b, page 8.05.5).
Step 6. Determine roughness coefficient n.
Structural Linings—see Table 8.05b, page 8.05.6.
Grass Lining:
a. Determine retardance class for vegetation from Table 8.05c, page
8.05.8. To meet stability requirement, use retardance for newly
mowed condition (generally C or D). To determine channel capacity,
use at least one retardance class higher.
b. Determine n from Figure 8.05c, page 8.05.7.
Step 7. Calculate the actual channel velocity, V, using Manning’s equation
(Figure 8.05a, pg. 8.05.3), and calculate channel capacity, Q, using the
continuity equation.
Step 8. Check results against permissible velocity and required design
capacity to determine if design is acceptable.
Step 9. If design is not acceptable, alter channel dimensions as appropriate.
For trapezoidal channels, this adjustment is usually made by changing the
bottom width.
Table 8.05b
Manning’s n for Structural
Channel Linings
Channel Lining
Recommended
n values
Asphaltic concrete, machine placed
Asphalt, exposed prefabricated
Concrete
Metal, corrugated
Plastic
Shotcrete
Gabion
Earth
0.014
0.015
0.015
0.024
0.013
0.017
0.030
0.020
Source: American Society of Civil Engineers (modified)
Appendices
Rev. 12/93 8.05.7
Step 10. For grass-lined channels once the appropriate channel dimensions
have been selected for low retardance conditions, repeat steps 6 through 8
using a higher retardance class, corresponding to tall grass. Adjust capacity of
the channel by varying depth where site conditions permit.
NOTE 1: If design velocity is greater than 2.0 ft/sec., a temporary lining
may be required to stabilize the channel until vegetation is established.
The temporary liner may be designed for peak flow from the 2-year storm.
If a channel requires a temporary lining, the designer should analyze
shear stresses in the channel to select the liner that provides protection
and promotes establishment of vegetation. For the design of temporary
liners, use tractive force procedure.
NOTE 2: Design Tables—Vegetated Channels and Diversions at the end
of this section may be used to design grass-lined channels with parabolic
cross-sections.
Step 11. Check outlet for carrying capacity and stability. If discharge
velocities exceed allowable velocities for the receiving stream, an outlet
protection structure will be required (Table 8.05d, page 8.05.9).
Sample Problem 8.05a illustrates the design of a grass-lined channel.
8
8.05.8
Table 8.05c
Retardance Classification for Vegetal Covers
Retardance Cover Condition
A Reed canarygrass
Weeping lovegrass
Excellent stand, tall (average 36”)
Excellent stand, tall (average 30”)
B Tall fescue
Bermudagrass
Grass-legume mixture
(tall fescue,red
fescue, sericea
lespedeza)
Grass mixture
(timothy, smooth
bromegrass or
orchardgrass)
Sericea lespedeza
Reed canarygrass
Alfalfa
Good stand, uncut, (average 18”)
Good stand, tall (average 12”)
Good stand, uncut
Good stand, uncut (average 20”)
Good stand, not woody, tall (average 19”)
Good stand, cut, (average 12-15”)
Good stand, uncut (average 11”)
C Tall fescue
Bermudagrass
Bahiagrass
Grass-legume mixture--
summer (orchardgrass,
redtop and annual
lespedeza)
Centipedegrass
Kentucky bluegrass
Redtop
Good stand (8-12”)
Good stand, cut (average 6”)
Good stand, uncut (6-8”)
Good stand, uncut (6-8”)
Very dense cover (average 6”)
Good stand, headed (6-12”)
Good stand, uncut (15-20”)
D Tall fescue
Bermudagrass
Bahiagrass
Grass-legume mixture--
fall-spring (orchardgrass,
redtop, and
annual lespedeza)
Red fescue
Centipedegrass
Kentucky bluegrass
Good stand, cut (3-4”)
Good stand, cut (2.5”)
Good stand, cut (3-4”)
Good stand, uncut (4-5”)
Good stand, uncut (12-18”)
Good stand, cut (3-4”)
Good stand, cut (3-4”)
E Bermudagrass
Bermudagrass
Good stand, cut (1.5”)
Burned stubble
Modified from: USDA-SCS, 1969. Engineering Field Manual.
Appendices
8.05.9
Table 8.05d
Maximum Permissible
Velocities for Unprotected
Soils in Existing Channels.
Materials
Maximum Permissible
Velocities (fps)
Fine Sand (noncolloidal)
Sand Loam (noncolloidal)
Silt Loam (noncolloidal)
Ordinary Firm Loam
Fine Gravel
Stiff Clay (very colloidal)
Graded, Loam to Cobbles (noncolloidal)
Graded, Silt to Cobbles (colloidal)
Alluvial Silts (noncolloidal)
Alluvial Silts (colloidal)
Coarse Gravel (noncolloidal)
Cobbles and Shingles
2.5
2.5
3.0
3.5
5.0
5.0
5.0
5.5
3.5
5.0
6.0
5.5
Sample Problem 8.05a
Design of a
Grass-lined Channel.
Given:
Design Q10 = 16.6 cfs
Proposed channel grade = 2%
Proposed vegetation: Tall fescue
Soil: Creedmoor (easily erodible)
Permissible velocity, Vp = 4.5 ft/s (Table 8.05a)
Retardance class: “B” uncut, “D” cut (Table 8.05c).
Trapezoidal channel dimensions:
designing for low retardance condition (retardance class D)
design to meet Vp.
Find:
Channel dimensions
Solution:
Make an initial estimate of channel size
A = Q/V, 16.6 cfs/4.5 ft/sec = 3.69 ft2
Try bottom width = 3.0 ft w/side slopes of 3:1
Z = 3
A = bd + Zd2
P = b + 2d Z2 + 1
R = AP
An iterative solution using Figure 8.05a to relate flow depth to Manning’s n
proceeds as follows: Manning’s equation is used to check velocities.
*From Fig. 8.05c, pg. 8.05.7, Retardance Class d (VR=4.5x0.54=2.43)
d (ft) A (ft
2) R (ft) *n Vt (fps) Q (cfs) Comments
0.8 4.32 0.54 0.043 3.25 14.0 V<Vp OK,
Q<Q10
(too small, try deeper channel)
0.9 5.13 0.59 0.042 3.53 18.10 V<Vp, OK,
Q>Q10, OK
Now design for high retardance (class B):
For the ease of construction and maintenance assume and
try d = 1.5 ft and trial velocity Vt = 3.0 ft/sec
d (ft) A (ft
2) R (ft)Vt (fps)n V (fps) Q (cfs) Comments
1.5 11.25 0.90 3.0
2.0
1.6
**1.5
0.08
0.11
0.12
0.13
2.5
1.8
1.6
1.5
28
20
18
17
reduce Vtreduce Vt
Q>Q10 OK
** These assumptions = actual V (fps.) (chart continued on next page)
8
8.05.10 Rev. 12/93
(continued)
Sample Problem 8.05a
Design of a
Grass-lined Channel.
Channel summary:
Trapezoidal shape, Z = 3, b = 3 ft, d = 1.5 ft, grade = 2%
Note: In Sample Problem 8.05a the “n-value” is first chosen based on a
permissible velocity and not a design velocity criteria. Therefore, the use of
Table 8.05c may not be as accurate as individual retardance class charts when
a design velocity is the determining factor.
Tractive Force
Procedure
The design of riprap-lined channels and temporary channel linings is based on
analysis of tractive force.
NOTE: This procedure is for uniform flow in channels and is not to be
used for design of deenergizing devices and may not be valid for larger
channels.
To calculate the required size of an open channel, assume the design flow is
uniform and does not vary with time. Since actual flow conditions change
through the length of a channel, subdivide the channel into design reaches as
appropriate.
PERMISSIBLE SHEAR STRESS
The permissible shear stress, Td, is the force required to initiate movement of
the lining material. Permissible shear stress for the liner is not related to the
erodibility of the underlying soil. However, if the lining is eroded or broken,
the bed material will be exposed to the erosive force of the flow.
COMPUTING NORMAL DEPTH
The first step in selecting an appropriate lining is to compute the design
flow depth (the normal depth) and determine the shear stress.
Normal depths can be calculated by Manning’s equation as shown for
trapezoidal channels in Figure 8.05d. Values of the Manning’s roughness
coefficient for different ranges of depth are provided in Table 8.05e for
temporary linings and Table 8.05f for riprap. The coefficient of roughness
generally decreases with increasing flow depth.
n value for Depth Ranges*
Table 8.05e
Manning’s Roughness
Coefficients for Temporary
Lining Materials
0-0.5 ft 0.5-2.0 ft >2.0 ft
Lining Type
Woven Paper Net
Jute Net
Fiberglass Roving
Straw with Net
Curled Wood Mat
Synthetic Mat
0.016
0.028
0.028
0.065
0.066
0.036
0.015
0.022
0.021
0.033
0.035
0.025
0.015
0.019
0.019
0.025
0.028
0.021
* Adapted from: FHWA-HEC 15, Pg. 37 - April 1988
8
8.05.12 Rev. 12/93
Table 8.05f Manning’s Roughness Coefficient
n - value
n value for Depth Ranges
Lining Category Lining Type 0-0.5 ft
(0-15 cm)
0.5-2.0 ft
(15-60 cm)
2.0 ft
(>60 cm)
Rigid Concrete
Grouted Riprap
Stone Masonry
Soil Cement
Asphalt
0.015
0.040
0.042
0.025
0.018
0.013
0.030
0.032
0.022
0.016
0.013
0.028
0.030
0.020
0.016
Unlined Bare Soil
Rock Cut
0.023
0.045
0.020
0.035
0.020
0.025
Gravel Riprap 1-inch (2.5-cm) D502-inch (5-cm) D50
0.044
0.066
0.033
0.041
0.030
0.034
Rock Riprap 6-inch (15-cm) D5012-inch (30-cm) D50
0.104
--
0.069
0.078
0.035
0.040
Note: Values listed are representative values for the respective depth ranges. Manning’s roughness coefficients, n, vary with the flow depth.
DETERMINING SHEAR STRESS
Shear stress, T, at normal depth is computed for the lining by the following
equation:
T = yds
Td = Permissible shear stress
where:
T = shear stress in lb/ft2
y = unit weight of water, 62.4 lb/ft3
d = flow depth in ft
s = channel gradient in ft/ft
If the permissible shear stress, Td, given in Table 8.05g is greater than the
computed shear stress, the riprap or temporary lining is considered acceptable.
If a lining is unacceptable, select a lining with a higher permissible shear stress
and repeat the calculations for normal depth and shear stress. In some cases it
may be necessary to alter channel dimensions to reduce the shear stress.
Computing tractive force around a channel bend requires special considerations
because the change in flow direction imposes higher shear stress on the channel
bottom and banks. The maximum shear stress in a bend, Tb, is given by the
following equation:
Tb = KbT
where:
Tb = bend shear stress in lb/ft2
kb = bend factor
T = computed stress for straight channel in lb/ft2
The value of kb is related to the radius of curvature of the channel at its center
line, Rc, and the bottom width of the channel, B, Figure 8.05e. The length of
channel requiring protection downstream from a bend, Lp, is a function of the
roughness of the lining material and the hydraulic radius as shown in Figure
8.05f.
Appendices
Rev. 12/93 8.05.13
Table 8.05g
Permissible Shear Stresses
for Riprap and Temporary
Liners
Permissible Unit Shear Stress, Td
Lining Category Lining Type (lb/ft2)
Temporary Woven Paper Net
Jute Net
Fiberglass Roving:
Single
Double
Straw with Net
Curled Wood mat
Synthetic Mat
0.15
0.45
0.60
0.85
1.45
1.55
2.00
d50 Stone Size (inches)
Gravel Riprap 1
2
0.33
0.67
Rock Riprap 6
9
12
15
18
21
24
2.00
3.00
4.00
5.00
6.00
7.80
8.00
Adapted From: FHWA, HEC-15, April 1983, pgs. 17 & 37.
Design Procedure-
Temporary Liners
The following is a step-by-step procedure for designing a temporary liner for
a channel. Because temporary liners have a short period of service, the design
Q may be reduced. For liners that are needed for six months or less, the 2-year
frequency storm is recommended.
Step 1. Select a liner material suitable for site conditions and application.
Determine roughness coefficient from manufacturer’s specifications or Table
8.05e, page 8.05.10.
Step 2. Calculate the normal flow depth using Manning’s equation (Figure
8.05d). Check to see that depth is consistent with that assumed for selection of
Manning’s n in Figure 8.05d, page 8.05.11. For smaller runoffs Figure 8.05d
is not as clearly defined. Recommended solutions can be determined by using
the Manning equation.
Step 3. Calculate shear stress at normal depth.
Step 4. Compare computed shear stress with the permissible shear stress for
the liner.
Step 5. If computed shear is greater than permissible shear, adjust channel
dimensions to reduce shear, or select a more resistant lining and repeat steps
1 through 4.
Design of a channel with temporary lining is illustrated in Sample Problem
8.05b, page 8.05.14.
REFERENCE 4

“Standard Specification for Roads and Structures”, North Carolina Department of
Transportation, Raleigh, January 2012.

Section 1043

10-62
All stone shall meet the approval of the Engineer. While no specific gradation is required, 1
there shall be equal distribution of the various sizes of the stone within the required size 2
range. The size of an individual stone particle will be determined by measuring its long 3
dimension. 4
Stone or broken concrete for rip rap shall meet Table 1042-1 for the class and size 5
distribution. 6
TABLE 1042-1
ACCEPTANCE CRITERIA FOR RIP RAP AND STONE FOR EROSION CONTROL
Required Stone Sizes, inches Class Minimum Midrange Maximum
A 2 4 6
B 5 8 12
1 5 10 17
2 9 14 23
No more than 5.0% of the material furnished can be less than the minimum size specified nor 7
no more than 10.0% of the material can exceed the maximum size specified. 8
SECTION 1043 9
AGGREGATE FROM CRUSHED CONCRETE 10
1043-1 GENERAL 11
Aggregate from crushed concrete is a recycled product made by crushing concrete obtained 12
from concrete truck clean out, demolition of existing concrete structures or pavement, or 13
similar sources and transported from a crushing facility. It does not include concrete 14
pavements that are rubblelized, broken or otherwise crushed in place on the roadway. 15
The crushed material must meet all sources approval requirements described in Sections 1005 16
and 1006 with the exception of the sodium sulfate test requirement. Deleterious materials 17
shall not be more than 3%. 18
Sampling and acceptance for the determination of gradaction, LL and PI will be performed as 19
described in the Aggregate QC/QA Program Manual and the Aggregate Sampling Manual. 20
1043-2 AGGREGATE BASE COURSE 21
The material shall meet the ABC gradation. The LL of the material shall be raised 5 points to 22
no more than 35. 23
1043-3 AGGREGATE SHOULDER BORROW 24
The material shall meet Section 1019. 25
1043-4 CLEAN COARSE AGGREGATE FOR ASPHALT 26
The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 27
shall be approved by the Engineer, and the mix shall meet all requirements. 28
1043-5 CLEAN COARSE AGGREGATE FOR CONCRETE 29
The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 30
is restricted to Class B concrete mixes only. Use of the material shall be approved by the 31
Engineer, and the concrete shall meet all requirements. 32
SECTION 1044 33
SUBSURFACE DRAINAGE MATERIALS 34
1044-1 SUBDRAIN FINE AGGREGATE 35
Subdrain fine aggregate shall meet No. 2S or 2MS in Table 1005-2. 36
NCDOT 2012 Standard Specifications
REFERENCE 5

United States Department of Agriculture, “Urban Hydrology for Small Watersheds”, Technical
Release 55, June 1986.

Technical Release 55
Urban Hydrology for Small Watersheds
Time of Concentration and Travel TimeChapter 3
3–4 (210-VI-TR-55, Second Ed., June 1986)
Manning’s equation is:
V rs
n
=149
2
3
1
2.[eq. 3-4]
where:
V = average velocity (ft/s)
r = hydraulic radius (ft) and is equal to a/pw
a = cross sectional flow area (ft
2)
pw = wetted perimeter (ft)
s = slope of the hydraulic grade line (channel
slope, ft/ft)
n = Manning’s roughness coefficient for open
channel flow.
Manning’s n values for open channel flow can be
obtained from standard textbooks such as Chow
(1959) or Linsley et al. (1982). After average velocity is
computed using equation 3-4, Tt for the channel seg-
ment can be estimated using equation 3-1.
Reservoirs or lakes
Sometimes it is necessary to estimate the velocity of
flow through a reservoir or lake at the outlet of a
watershed. This travel time is normally very small and
can be assumed as zero.
Limitations
•Manning’s kinematic solution should not be used
for sheet flow longer than 300 feet. Equation 3-3
was developed for use with the four standard
rainfall intensity-duration relationships.
•In watersheds with storm sewers, carefully identify
the appropriate hydraulic flow path to estimate Tc.
Storm sewers generally handle only a small portion
of a large event. The rest of the peak flow travels
by streets, lawns, and so on, to the outlet. Consult a
standard hydraulics textbook to determine average
velocity in pipes for either pressure or nonpressure
flow.
•The minimum Tc used in TR-55 is 0.1 hour.
•A culvert or bridge can act as a reservoir outlet if
there is significant storage behind it. The proce-
dures in TR-55 can be used to determine the peak
flow upstream of the culvert. Detailed storage
routing procedures should be used to determine
the outflow through the culvert.
Example 3-1
The sketch below shows a watershed in Dyer County,
northwestern Tennessee. The problem is to compute
Tc at the outlet of the watershed (point D). The 2-year
24-hour rainfall depth is 3.6 inches. All three types of
flow occur from the hydraulically most distant point
(A) to the point of interest (D). To compute Tc, first
determine Tt for each segment from the following
information:
Segment AB: Sheet flow; dense grass; slope (s) = 0.01
ft/ft; and length (L) = 100 ft. Segment BC: Shallow
concentrated flow; unpaved; s = 0.01 ft/ft; and
L = 1,400 ft. Segment CD: Channel flow; Manning’s
n = .05; flow area (a) = 27 ft2; wetted perimeter
(pw) = 28.2 ft; s = 0.005 ft/ft; and L = 7,300 ft.
See figure 3-2 for the computations made on
worksheet 3.
A B C D
7,300 ft1,400 ft100 ft
(Not to scale)
Outlet Channel Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 1 of 4
12/9/2016 (Initial Submittal)

Calculation Title:
Outlet Channel Calculation
Summary:
The outlet channels for the Dan River dam decommissioning were designed for stability and capacity for
a Type II 100-year, 24-hour design storm event of 8.20 inches while maintaining channel lining stability.

Notes:

Revision Log:
No. Description Originator Verifier Technical Reviewer
0

Initial Submittal –
12/9/2016

Chris Jordan Stephanie Stanwick Cedric H Ruhl

Outlet Channel Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 2 of 4
12/9/2016 (Initial Submittal)

OBJECTIVE:
The objective of this calculation is to design the outlet channels from the final closure conditions
of the Primary and Secondary ash basins. The four outlet channels convey flow from the footprint
of the decommissioned impoundment to gabion outlets into the Dan River.
METHOD:
The outlet channels were evaluated using Manning’s equation for the 100-year, 24 hour design
storm event.
DEFINITION OF VARIABLES:
A = drainage area;
AC = cross-section area of flow through channel;
b = bottom width of flow through channel;
d = depth of flow through channel;
CN = curve number;
D = channel depth;
i = rainfall depth;
n = Manning’s roughness co-efficient for flow through channel;
P = wetted perimeter of flow through channel;
Q = discharge flow;
R = hydraulic radius of flow through channel;
S = longitudinal slope of the channel flow;
T = top width of flow through channel;
V = velocity of flow through channel; and
Z = channel side slope.
CALCULATIONS:
1.0 Outlet Channels
Four stormwater outlet channels will be constructed to convey flow from the footprint of the
decommissioned impoundment to gabion outlets into the Dan River. Design criteria for the
channels was first evaluated by estimating the peak flow to the channels using the SCS method,
and then evaluating the channel capacity using Manning’s equation [Ref. 3]. The channels were
designed for capacity for the 100-year design storm.

1.1 Channel peak flow rates
The times of concentration from contributing drainage areas to the outlet channels are delineated
and shown in the “Final Conditions Stormwater Calculation” package. Peak flow rates to the outlet
channels have been calculated in HydroCAD for a 100-year, 24 hour design storm event and are
shown in the following table:
Outlet Channel Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 3 of 4
12/9/2016 (Initial Submittal)

Channel
ID Tributary Drainage Area
Design
Storm
Event
(years)
Rainfall for 24-Hour Storm
{i}
(in)
(Ref. 1)
Design
Flow
{Q100}
(cfs)
OC-1 DA-5A - 5D 100 8.2 49.8
OC-2 DA-1, DA-6A - 6G 100 8.2 281.0
OC-3 DA-2, DA-4, DA-7A - 7G 100 8.2 190.3
OC-4 DA-3, DA-8A-1, DA-8A - 8D 100 8.2 82.0
Table 1: Peak Flow Rates

1.2 Channel capacity
The stormwater outlet channels were assumed to be trapezoidal channels with dimensions as
presented in the following table:
Channel
ID
Channel
Type
Bottom
Width
{b}
(ft)
MIN.
Depth
{D}
(ft)
Left Side
Slope
{Z1H:V}
Right Side
Slope
{Z2H:V}
Top Width
{T}
(ft)
Upstream
Invert
(ft)
Downstream
Invert
(ft)
Length
{L}
(ft)
Longitudinal
Slope
{S}
(ft/ft)
OC-1 Outlet 3 2 3 3 499.5 497 116 0.022
OC-2 Outlet 9 2 3 3 499.5 496 103 0.034
OC-3 Outlet 9 2 3 3 499.5 497 91 0.027
OC-4 Outlet 3 2 3 3 498.0 495 150 0.020
Table 2: Channel Dimensions
VARIES

The capacity of each stormwater channel was evaluated using Manning’s equation [Ref. 3] as
presented in the following equation:
𝑉=1.49
𝑛𝑃2/3 𝑃1/2
Where n is Manning’s coefficient, R is hydraulic radius and S is the longitudinal slope of
the stormwater flow.
The total discharge was given by:
𝑃=𝐴𝐶𝑉
The flow cross-section area “AC” and wetted perimeter “P” were calculated based on the geometry
of a trapezoidal channel with a flow depth “d”, bottom width “b”, left side slope “Z1”, and right side
slope “Z2”, using the following relationships:

𝐴𝐶=𝑏𝑑+0.5𝑍1 𝑑2 +0.5𝑍2 𝑑2
𝑃=𝑏+√[(𝑍1 𝑑)2 +𝑑2 ]+√[(𝑍2 𝑑)2 +𝑑2 ]
Each channel was assumed to have rip-rap lining and was evaluated for capacity for the 100-
year, 24-hour design storm event. The trial flow depth and Manning’s n were iteratively modified
until the channel capacity exceeded the predicted peak runoff for the conditions modeled.
Channel capacity estimated for the minimum channel grade is shown in the following table:

Outlet Channel Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 4 of 4
12/9/2016 (Initial Submittal)

Channel
ID
Channel
Type
Channel
Lining
Manning's n
{n}
[Ref. 2]
Trial Flow
Depth
{d}
(ft)
Flow Area
{A}
(ft2)
Wetted
Perimeter
{P}
(ft)
Hydraulic
Radius
{R}
(ft)
Velocity
{V}
(ft/s)
Channel
Capacity
{Q}
(cfs)
Peak
Runoff
{Q}
(cfs)
Channel
Capacity >
Peak Runoff?
Freeboard
(in)
OC-1 Outlet riprap 0.03 1.24 8.3 10.8 0.8 6.1 50.98 49.75 yes 9.1
OC-2 Outlet riprap 0.03 1.82 26.3 20.5 1.3 10.8 284.51 280.99 yes 2.2
OC-3 Outlet riprap 0.03 1.56 21.3 18.9 1.1 8.9 190.72 190.27 yes 5.3
OC-4 Outlet riprap 0.03 1.58 12.2 13.0 0.9 6.7 82.50 81.99 yes 5.0
Table 3: Channel Capacity - 100 years Long-Term Conditions

The hydraulic analyses indicate that the outlet channels have capacity to pass the 100-year, 24-
hour design storm.

DISCUSSION:
The outlet channels for the Dan River dam decommissioning were designed for stability and
capacity for a Type II 100-year, 24-hour design storm event of 8.20 inches while maintaining
channel lining stability.
REFERENCES:
1. Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.
2. HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.
3. North Carolina Department of Environment and Natural Resources, “Erosion and
Sediment Control Planning and Design Manual”, Revised May 2013.

REFERENCE 1

Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation
Frequency Estimates”, NOAA National Weather Service, obtained September 15, 2014.

Precipitation Frequency Data Server
Page 1 of 3
NOAA Atlas 14, Volume 2, Version 3
Location name: Eden, North Carolina, US"
Latitude: 36.4999°, Longitude:-79.7013°
Elevation: 582 ft*
* source: Google Maps "*�,�,,.t
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based
point precipitation frequency estimates with 90% confidence intervals (in inches)'
Average recurrence interval (years)
Duration
���
10
25
50
100
200
500
1000
0.363
0.433
0.512
0.567
0.633
0.676
0.717
0.754
0.796
0.826
5-min
(0.331-0.397)
(0.396-0.473)
(0.467-0.560)
(0.518-0.619)
(0.575-0.688)
(0.612-0.735)
(0.646-0.781)
(0.676-0.822)
(0.708-0.869)
(0.729-0.902)
0.579
0.692
0.820
0.908
1.01
1.08
1.14
1.20
1.26
1.30
10-min
(0 .529-0.634)
(0.633-0.757)
(0.749-0.898)
(0.829-0.991)
(0.917-1.10)
(0.974-1.17)
1 (1.03-1.24)
1 (1.07-1.30)
1 (1.12-1.38)
0.724
0.870
1.04
1.15
1.28
1.36
1.44
1.51
1.59
1.63
15-min
(0.661-0.792)
(0.796-0.951)
(0.947-1.14)
1 (1.05-1.25)
1 (1.16-1.39)
1 (1.23-1.48)
1 (1.30-1.57)
1 (1.35-1.64)
1 (1.41-1.73)
1 (1.44-1.78)
0.993
1.20
1.47
1.66
1.89
2.05
2.21
2.35
2.52
2.64
30-min
(0.906-1.09)
1 (1.10-1.31)
1 (1.35-1.61)
1 (1.52-1.82)
1 (1.72-2.06)
(1.86-2.23)
(1.99-2.40)
(2.11-2.56)
(2.24-2.75)
(2.33-2.89)
1.24
1.51
1.89
2.17
2.52
2.78
3.04
3.29
3.62
3.86
60-min
(1.13-1.35)
(1.38-1.65)
(1.73-2.07)
(1.98-2.36)
(2.29-2.74)
(2.52-3.03)
(2.74-3.31)
(2.95-3.59)
(3.22-3.95)
(3.41-4.22)
1.47
1.79
2.25
2.61
3.08
3.45
3.83
4.20
4.71
5.10
2-hr
(1.35-1.61)
(1.63-1.96)
(2.06-2.46)
(2.38-2.85)
(2.80-3.36)
(3.12-3.75)
(3.44-4.16)
(3.75-4.57)
(4.15-5.12)
(4.45-5.56)
1.59
1.93
2.44
2.82
3.33
3.73
4.13
4.54
5.08
5.50
3-hr
(1.46-1.73)
(1.78-2.11)
(2.24-2.66)
(2.58-3.07)
(3.03-3.62)
(3.38-4.04)
(3.72-4.48)
(4.06-4.92)
( 4.49-5.52)
( 4.81-5.98)
1.96
2.37
2.99
3.48
4.15
4.70
5.28
5.87
6.71
7.38
6-hr
(1.80-2.15)
(2.18-2.61)
(2.74-3.27)
(3.17-3.80)
(3.76-4.53)
(4.22-5.12)
(4.70-5.73)
(5.18-6.37)
(5.82-7.29)
(6.31-8.02)
2.36
2.87
3.63
4.26
5.15
5.89
6.70
7.56
8.81
9.84
12-hr
(2.17-2.59)
(2.63-3.14)
(3.32-3.96)
(3.88-4.62)
(4.65-5.57)
(5.28-6.37)
(5.94-7.21)
(6.62-8.12)
(7.57-9.48)
(8.31-10.6 )
2.81
3.40
4.33
5.10
6.22
7.17
8.20
9.32
11.0
12.4
24-hr
(2.61-3.04)
(3.16-3.68)
(4.02-4.67)
(4.72-5.48)
(5.72-6.68)
(6.55-7.69)
(7.44-8.79)
(8.39-10.0)
(9.74-11.8)
(10.9-13.3)
3.30
3.99
5.04
5.90
7.12
8.13
9.21
10.4
12.0
13.4
2-day
(3.08-3.55)
(3.72-4.30)
(4.70-5.42)
(5.48-6.33)
(6.59-7.63)
(7.48-8.71)
(8.42-9.88)
(9.40-11.1 )
( 10.8-13.0 )
( 11.9-14.5 )
3.49
4.22
5.33
6.23
7.52
8.59
9.72
10.9
12.7
14.2
3-day
(3.26-3.76)
(3.93-4.55)
(4.96-5.73)
(5.79-6.69)
(6.95-8.07)
(7.89-9.21)
(8.88-10.4)
(9.92-11.8)
(11.4-13.7)
( 12.6-15.3)
3.68
4.45
5.61
6.56
7.92
9.04
10.2
11.5
13.4
14.9
4-day
(3.43-3.97)
(4.15-4.80)
(5.23-6.05)
(6.10-7.06)
(7.32-8.51)
(8.31-9.71)
(9.35-11.0)
(10.4-12.4)
(12.0-14.4)
(13.2-16.1)
4.22
5.07
6.29
7.29
8.71
9.88
11.1
12.4
14.3
15.9
7-day
(3.96-4.51)
(4.75-5.42)
(5.89-6.72)
(6.81-7.78)
(8.11-9.28)
(9.14-10.5)
(10.2-11.9)
( 11.4-13.3)
( 12.9-15.3)
( 14.2-17.0)
4.77
5.71
7.01
8.0 6
10.7
12.0
13.3
15.1
16.6
10-day
��69.53
(4.48-5.10 )
(5.37-6.10)
(6.58-7.48 )
(7.55-8.60)
(8.89-10.2 )
(9.96-11.4)
(11.1-12.8)
(12.2-14.2)
(13.8-16.2)
(15.0-17.8)
6.43
7.65
9.20
10.4
12.1
13.4
14.7
16.1
17.9
19.3
20-day
(6.05-6.85)
(7.21-8.16)
(8.66-9.81)
(9.79-11.1)
(11.3-12.9)
(12.5-14.3)
(13.7-15.7)
(14.9-172)
(16.4-19.2)
(17.6-20.8)
30-day
7.95
9.40
11.1
12.3
14.0
15.3
16.5
17.7
19.3
20.5
(7.53-8.41)
(8.91-9.94)
(10.5-11.7)
(11.7-13.0)
(13.2-14.8)
(14.4-16.2)
(15.5-17.5)
(16.6-18.8)
(18.0-20.5)
(19.0-21.9)
45-day
10.0
11.8
13.7
15.2
17.1
18.5
19.8
21.1
22.8
24.0
(9.48-10.6)
(11.2-12.5)
(13.0-14.5)
(14.4-16.0)
(16.1-18.0)
(17.4-19.5)
(18.6-21.0)
(19.8-22.4)
(21.3-24.2)
(22.3-25.6)
12.0
14.0
16.1
17.7
19.7
21.2
22.6
23.9
25.6
26.8
60-day
( 114-12.6) 1
(13.4-14.8) 1
U-15-3-1-7.0) I
(16.8-18.6) 1
U-18-7-2-o.7) 1
(20.0-22.3) 1
U-21-3-2-3.8) 1
(22.5-25.2) J
(24.0-27.1) 11
(25.1-28.4)
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90 % confidence interval. The probability that precipitation frequency estimates (for a
given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5 % . Estimates at upper bounds are not
checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 2 of 3
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created tGMTI: Mon Sep 15 14:27:08 2014
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— 5tnln —
2-day
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10-day
— 2-11"lr —
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— 34il —
30-day
— "t —
*15-day
— 12-hr —
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http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 3 of 3
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hvdroloaic Develooment
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions(a)noaa.aov
Disclaimer
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

REFRENCE 2

HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.

R-15
Outlet-2
R02
Outlet-1
Routing Diagram for LT_1
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Inflow=280.99 cfs 17.492 afReach R-15: Outlet-2
Outflow=280.99 cfs 17.492 af
Inflow=49.75 cfs 4.113 afReach R02: Outlet-1
Outflow=49.75 cfs 4.113 af
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-15: Outlet-2
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 5.32" for 100-Year event
Inflow = 280.99 cfs @ 12.07 hrs, Volume= 17.492 af
Outflow = 280.99 cfs @ 12.07 hrs, Volume= 17.492 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Reach R-15: Outlet-2
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
300
250
200
150
100
50
0
Inflow Area=39.459 ac
280.99 cfs280.99 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_1
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R02: Outlet-1
Inflow Area = 10.470 ac, 0.00% Impervious, Inflow Depth > 4.71" for 100-Year event
Inflow = 49.75 cfs @ 12.11 hrs, Volume= 4.113 af
Outflow = 49.75 cfs @ 12.11 hrs, Volume= 4.113 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Reach R02: Outlet-1
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=10.470 ac
49.75 cfs49.75 cfs
R-25
Outlet-3
R-42
Outlet-4
Routing Diagram for LT_2
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 2
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Inflow=190.27 cfs 40.828 afReach R-25: Outlet-3
Outflow=190.27 cfs 40.828 af
Inflow=81.99 cfs 6.571 afReach R-42: Outlet-4
Outflow=81.99 cfs 6.571 af
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-25: Outlet-3
Inflow Area = 95.370 ac, 0.00% Impervious, Inflow Depth > 5.14" for 100-Year event
Inflow = 190.27 cfs @ 12.11 hrs, Volume= 40.828 af
Outflow = 190.27 cfs @ 12.11 hrs, Volume= 40.828 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Reach R-25: Outlet-3
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=95.370 ac
190.27 cfs190.27 cfs
Type II 24-hr 100-Year Rainfall=8.20"LT_2
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Reach R-42: Outlet-4
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 4.69" for 100-Year event
Inflow = 81.99 cfs @ 12.11 hrs, Volume= 6.571 af
Outflow = 81.99 cfs @ 12.11 hrs, Volume= 6.571 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 2
Reach R-42: Outlet-4
Inflow
Outflow
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
90
80
70
60
50
40
30
20
10
0
Inflow Area=16.815 ac
81.99 cfs81.99 cfs
REFERENCE 3

North Carolina Department of Environment and Natural Resources, “Erosion and
Sediment Control Planning and Design Manual”, Revised May 2013.

Appendices
This section addresses the design of stable conveyance channels and
diversions using flexible linings. A stable channel is defined as a channel
which is nonsilting and nonscouring. To minimize silting in the channel, flow
velocities should remain constant or increase slightly throughout the channel
length. This is especially important in designing diversion channels and can
be accomplished by adjusting channel grade. Procedures presented in this
section address the problems of erosion and scour. More advanced procedures
for permanent, unlined channels may be found elsewhere. (References: Garde
and Ranga Raju, 1980)
Diversions are channels usually with a supporting ridge on the lower side.
They are generally located to divert flows across a slope and are designed
following the same procedures as other channels. Design tables for vegetated
diversions and waterways are included at the end of this section.
Flexible channel linings are generally preferred to rigid linings from an
erosion control standpoint because they conform to changes in channel shape
without failure and are less susceptible to damage from frost heaving, soil
swelling and shrinking, and excessive soil pore water pressure from lack of
drainage. Flexible linings also are generally less expensive to construct, and
when vegetated, are more natural in appearance. On the other hand, flexible
linings generally have higher roughness and require a larger cross section for
the same discharge.
EROSION CONtROL CRItERIa
The minimum design criteria for conveyance channels require that two
primary conditions be satisfied: the channel system must have capacity for
the peak flow expected from the 10-year storm and the channel lining must be
resistant to erosion for the design velocity. In some cases, out-of-bank flow
may be considered a functional part of the channel system. In these cases,
flow capacities and design velocities should be considered separately for out-
of-bank flows and channel flows.
Both the capacity of the channel and the velocity of flow are functions of the
channel lining, cross-sectional area and slope. The channel system must carry
the design flow, fit site conditions, and be stable.
Sta BLE CHaNNEL DESIGN mEtHODS
Two accepted procedures for designing stable channels with flexible linings
are: (1) the permissible velocity approach; and (2) the tractive force approach.
Under the permissible velocity approach, the channel is considered stable if the
design, mean velocity is lower than the maximum permissible velocity. Under
the tractive force approach, erosive stress evaluated at the boundary between
flowing water and lining materials must be less than the minimum unit tractive
force that will cause serious erosion of material from a level channel bed.
8.05 DESIGN Of Sta BLE CHaNNELS aND DIVERSIONS
8.05.1
8
8.05.2
The permissible velocity procedure is recommended for the design of vegetative
channels because of common usage and the availability of reliable design
tables. The tractive force approach is recommended for design of channels
with temporary synthetic liners or riprap liners. The tractive force procedure
is described in full in the U.S. Department of Transportation, Federal Highway
Administration Bulletin, Design of Roadside Channels with Flexible Linings.
Permissible Velocity
Procedure
The permissible velocity procedure uses two equations to calculate flow:
Manning’s equation,
V = 1.49 R2/3 S1/2 n
where:
V = average velocity in the channel in ft/sec.
n = Manning’s roughness coefficient, based upon the lining of the
channel
R = hydraulic radius, wetted cross-sectional area/wetted perimeter
in ft
S = slope of the channel in ft/ft
and the continuity equation,
Q = AV
where:
Q = flow in the channel in cfs
A = cross-sectional area of flow within the channel in ft2
V = average velocity in the channel in ft/sec.
Manning’s equation and the continuity equation are used together to determine
channel capacity and flow velocity. A nomograph for solving Manning’s
equation is given in Figure 8.05a.
Selecting Permanent
Channel Lining
Channel lining materials include such flexible materials as grass, riprap and
gabions, as well as rigid materials such as paving blocks, flag stone, gunite,
asphalt, and concrete. The design of concrete and similar rigid linings
is generally not restricted by flow velocities. However, flexible channel
linings do have maximum permissible flow velocities beyond which they are
susceptible to erosion. The designer should select the type of liner that best
fits site conditions.
Table 8.05a lists maximum permissible velocities for established grass linings
and soil conditions. Before grass is established, permissible velocity is
determined by the choice of temporary liner. Permissible velocities for riprap
linings are higher than for grass and depend on the stone size selected.
Appendices
8.05.3
8
8.05.4
Table 8.05a
Maximum Allowable Design Velocities1
for Vegetated Channels
Typical
Channel Slope
Application
Soil
Characteristics2
Grass Lining Permissible Velocity3
for Established Grass
Lining (ft/sec)
0-5%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
5.0
4.5
4.5
4.5
3.5
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
6.0
5.5
5.5
5.5
4.5
5-10%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
4.5
4.0
4.0
4.0
3.0
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
Grass-legume mixture
5.5
5.0
5.0
5.0
3.5
>10%Easily Erodible
Non-plastic
(Sands & Silts)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
3.5
2.5
2.5
2.5
Erosion Resistant
Plastic
(Clay mixes)
Bermudagrass
Tall fescue
Bahiagrass
Kentucky bluegrass
4.5
3.5
3.5
3.5
Source: USDA-SCS Modified
NOTE:1Permissible Velocity based on 10-year storm peak runoff
2Soil erodibility based on resistance to soil movement from concentrated flowing water.
3Before grass is established, permissible velocity is determined by the type of temporary liner used.
Selecting Channel
Cross-Section
Geometry
To calculate the required size of an open channel, assume the design flow is
uniform and does not vary with time. Since actual flow conditions change
throughout the length of a channel, subdivide the channel into design reaches,
and design each reach to carry the appropriate capacity.
The three most commonly used channel cross-sections are “V”-shaped,
parabolic, and trapezoidal. Figure 8.05b gives mathematical formulas for the
area, hydraulic radius and top width of each of these shapes.
Appendices
8.05.5
8
8.05.6 Rev. 12/93
Design Procedure-
Permissible Velocity
The following is a step-by-step procedure for designing a runoff conveyance
channel using Manning’s equation and the continuity equation:
Step 1. Determine the required flow capacity, Q, by estimating peak runoff
rate for the design storm (Appendix 8.03).
Step 2. Determine the slope and select channel geometry and lining.
Step 3. Determine the permissible velocity for the lining selected, or the
desired velocity, if paved. (see Table 8.05a, page 8.05.4)
Step 4. Make an initial estimate of channel size—divide the required Q by the
permissible velocity to reach a “first try” estimate of channel flow area. Then
select a geometry, depth, and top width to fit site conditions.
Step 5. Calculate the hydraulic radius, R, from channel geometry (Figure
8.05b, page 8.05.5).
Step 6. Determine roughness coefficient n.
Structural Linings—see Table 8.05b, page 8.05.6.
Grass Lining:
a. Determine retardance class for vegetation from Table 8.05c, page
8.05.8. To meet stability requirement, use retardance for newly
mowed condition (generally C or D). To determine channel capacity,
use at least one retardance class higher.
b. Determine n from Figure 8.05c, page 8.05.7.
Step 7. Calculate the actual channel velocity, V, using Manning’s equation
(Figure 8.05a, pg. 8.05.3), and calculate channel capacity, Q, using the
continuity equation.
Step 8. Check results against permissible velocity and required design
capacity to determine if design is acceptable.
Step 9. If design is not acceptable, alter channel dimensions as appropriate.
For trapezoidal channels, this adjustment is usually made by changing the
bottom width.
Table 8.05b
Manning’s n for Structural
Channel Linings
Channel Lining
Recommended
n values
Asphaltic concrete, machine placed
Asphalt, exposed prefabricated
Concrete
Metal, corrugated
Plastic
Shotcrete
Gabion
Earth
0.014
0.015
0.015
0.024
0.013
0.017
0.030
0.020
Source: American Society of Civil Engineers (modified)
Appendices
Rev. 12/93 8.05.7
Step 10. For grass-lined channels once the appropriate channel dimensions
have been selected for low retardance conditions, repeat steps 6 through 8
using a higher retardance class, corresponding to tall grass. Adjust capacity of
the channel by varying depth where site conditions permit.
NOTE 1: If design velocity is greater than 2.0 ft/sec., a temporary lining
may be required to stabilize the channel until vegetation is established.
The temporary liner may be designed for peak flow from the 2-year storm.
If a channel requires a temporary lining, the designer should analyze
shear stresses in the channel to select the liner that provides protection
and promotes establishment of vegetation. For the design of temporary
liners, use tractive force procedure.
NOTE 2: Design Tables—Vegetated Channels and Diversions at the end
of this section may be used to design grass-lined channels with parabolic
cross-sections.
Step 11. Check outlet for carrying capacity and stability. If discharge
velocities exceed allowable velocities for the receiving stream, an outlet
protection structure will be required (Table 8.05d, page 8.05.9).
Sample Problem 8.05a illustrates the design of a grass-lined channel.
8
8.05.8
Table 8.05c
Retardance Classification for Vegetal Covers
Retardance Cover Condition
A Reed canarygrass
Weeping lovegrass
Excellent stand, tall (average 36”)
Excellent stand, tall (average 30”)
B Tall fescue
Bermudagrass
Grass-legume mixture
(tall fescue,red
fescue, sericea
lespedeza)
Grass mixture
(timothy, smooth
bromegrass or
orchardgrass)
Sericea lespedeza
Reed canarygrass
Alfalfa
Good stand, uncut, (average 18”)
Good stand, tall (average 12”)
Good stand, uncut
Good stand, uncut (average 20”)
Good stand, not woody, tall (average 19”)
Good stand, cut, (average 12-15”)
Good stand, uncut (average 11”)
C Tall fescue
Bermudagrass
Bahiagrass
Grass-legume mixture--
summer (orchardgrass,
redtop and annual
lespedeza)
Centipedegrass
Kentucky bluegrass
Redtop
Good stand (8-12”)
Good stand, cut (average 6”)
Good stand, uncut (6-8”)
Good stand, uncut (6-8”)
Very dense cover (average 6”)
Good stand, headed (6-12”)
Good stand, uncut (15-20”)
D Tall fescue
Bermudagrass
Bahiagrass
Grass-legume mixture--
fall-spring (orchardgrass,
redtop, and
annual lespedeza)
Red fescue
Centipedegrass
Kentucky bluegrass
Good stand, cut (3-4”)
Good stand, cut (2.5”)
Good stand, cut (3-4”)
Good stand, uncut (4-5”)
Good stand, uncut (12-18”)
Good stand, cut (3-4”)
Good stand, cut (3-4”)
E Bermudagrass
Bermudagrass
Good stand, cut (1.5”)
Burned stubble
Modified from: USDA-SCS, 1969. Engineering Field Manual.
Appendices
8.05.9
Table 8.05d
Maximum Permissible
Velocities for Unprotected
Soils in Existing Channels.
Materials
Maximum Permissible
Velocities (fps)
Fine Sand (noncolloidal)
Sand Loam (noncolloidal)
Silt Loam (noncolloidal)
Ordinary Firm Loam
Fine Gravel
Stiff Clay (very colloidal)
Graded, Loam to Cobbles (noncolloidal)
Graded, Silt to Cobbles (colloidal)
Alluvial Silts (noncolloidal)
Alluvial Silts (colloidal)
Coarse Gravel (noncolloidal)
Cobbles and Shingles
2.5
2.5
3.0
3.5
5.0
5.0
5.0
5.5
3.5
5.0
6.0
5.5
Sample Problem 8.05a
Design of a
Grass-lined Channel.
Given:
Design Q10 = 16.6 cfs
Proposed channel grade = 2%
Proposed vegetation: Tall fescue
Soil: Creedmoor (easily erodible)
Permissible velocity, Vp = 4.5 ft/s (Table 8.05a)
Retardance class: “B” uncut, “D” cut (Table 8.05c).
Trapezoidal channel dimensions:
designing for low retardance condition (retardance class D)
design to meet Vp.
Find:
Channel dimensions
Solution:
Make an initial estimate of channel size
A = Q/V, 16.6 cfs/4.5 ft/sec = 3.69 ft2
Try bottom width = 3.0 ft w/side slopes of 3:1
Z = 3
A = bd + Zd2
P = b + 2d Z2 + 1
R = AP
An iterative solution using Figure 8.05a to relate flow depth to Manning’s n
proceeds as follows: Manning’s equation is used to check velocities.
*From Fig. 8.05c, pg. 8.05.7, Retardance Class d (VR=4.5x0.54=2.43)
d (ft) A (ft
2) R (ft) *n Vt (fps) Q (cfs) Comments
0.8 4.32 0.54 0.043 3.25 14.0 V<Vp OK,
Q<Q10
(too small, try deeper channel)
0.9 5.13 0.59 0.042 3.53 18.10 V<Vp, OK,
Q>Q10, OK
Now design for high retardance (class B):
For the ease of construction and maintenance assume and
try d = 1.5 ft and trial velocity Vt = 3.0 ft/sec
d (ft) A (ft
2) R (ft)Vt (fps)n V (fps) Q (cfs) Comments
1.5 11.25 0.90 3.0
2.0
1.6
**1.5
0.08
0.11
0.12
0.13
2.5
1.8
1.6
1.5
28
20
18
17
reduce Vtreduce Vt
Q>Q10 OK
** These assumptions = actual V (fps.) (chart continued on next page)
8
8.05.10 Rev. 12/93
(continued)
Sample Problem 8.05a
Design of a
Grass-lined Channel.
Channel summary:
Trapezoidal shape, Z = 3, b = 3 ft, d = 1.5 ft, grade = 2%
Note: In Sample Problem 8.05a the “n-value” is first chosen based on a
permissible velocity and not a design velocity criteria. Therefore, the use of
Table 8.05c may not be as accurate as individual retardance class charts when
a design velocity is the determining factor.
Tractive Force
Procedure
The design of riprap-lined channels and temporary channel linings is based on
analysis of tractive force.
NOTE: This procedure is for uniform flow in channels and is not to be
used for design of deenergizing devices and may not be valid for larger
channels.
To calculate the required size of an open channel, assume the design flow is
uniform and does not vary with time. Since actual flow conditions change
through the length of a channel, subdivide the channel into design reaches as
appropriate.
PERMISSIBLE SHEAR STRESS
The permissible shear stress, Td, is the force required to initiate movement of
the lining material. Permissible shear stress for the liner is not related to the
erodibility of the underlying soil. However, if the lining is eroded or broken,
the bed material will be exposed to the erosive force of the flow.
COMPUTING NORMAL DEPTH
The first step in selecting an appropriate lining is to compute the design
flow depth (the normal depth) and determine the shear stress.
Normal depths can be calculated by Manning’s equation as shown for
trapezoidal channels in Figure 8.05d. Values of the Manning’s roughness
coefficient for different ranges of depth are provided in Table 8.05e for
temporary linings and Table 8.05f for riprap. The coefficient of roughness
generally decreases with increasing flow depth.
n value for Depth Ranges*
Table 8.05e
Manning’s Roughness
Coefficients for Temporary
Lining Materials
0-0.5 ft 0.5-2.0 ft >2.0 ft
Lining Type
Woven Paper Net
Jute Net
Fiberglass Roving
Straw with Net
Curled Wood Mat
Synthetic Mat
0.016
0.028
0.028
0.065
0.066
0.036
0.015
0.022
0.021
0.033
0.035
0.025
0.015
0.019
0.019
0.025
0.028
0.021
* Adapted from: FHWA-HEC 15, Pg. 37 - April 1988
8
8.05.12 Rev. 12/93
Table 8.05f Manning’s Roughness Coefficient
n - value
n value for Depth Ranges
Lining Category Lining Type 0-0.5 ft
(0-15 cm)
0.5-2.0 ft
(15-60 cm)
2.0 ft
(>60 cm)
Rigid Concrete
Grouted Riprap
Stone Masonry
Soil Cement
Asphalt
0.015
0.040
0.042
0.025
0.018
0.013
0.030
0.032
0.022
0.016
0.013
0.028
0.030
0.020
0.016
Unlined Bare Soil
Rock Cut
0.023
0.045
0.020
0.035
0.020
0.025
Gravel Riprap 1-inch (2.5-cm) D502-inch (5-cm) D50
0.044
0.066
0.033
0.041
0.030
0.034
Rock Riprap 6-inch (15-cm) D5012-inch (30-cm) D50
0.104
--
0.069
0.078
0.035
0.040
Note: Values listed are representative values for the respective depth ranges. Manning’s roughness coefficients, n, vary with the flow depth.
DETERMINING SHEAR STRESS
Shear stress, T, at normal depth is computed for the lining by the following
equation:
T = yds
Td = Permissible shear stress
where:
T = shear stress in lb/ft2
y = unit weight of water, 62.4 lb/ft3
d = flow depth in ft
s = channel gradient in ft/ft
If the permissible shear stress, Td, given in Table 8.05g is greater than the
computed shear stress, the riprap or temporary lining is considered acceptable.
If a lining is unacceptable, select a lining with a higher permissible shear stress
and repeat the calculations for normal depth and shear stress. In some cases it
may be necessary to alter channel dimensions to reduce the shear stress.
Computing tractive force around a channel bend requires special considerations
because the change in flow direction imposes higher shear stress on the channel
bottom and banks. The maximum shear stress in a bend, Tb, is given by the
following equation:
Tb = KbT
where:
Tb = bend shear stress in lb/ft2
kb = bend factor
T = computed stress for straight channel in lb/ft2
The value of kb is related to the radius of curvature of the channel at its center
line, Rc, and the bottom width of the channel, B, Figure 8.05e. The length of
channel requiring protection downstream from a bend, Lp, is a function of the
roughness of the lining material and the hydraulic radius as shown in Figure
8.05f.
Appendices
Rev. 12/93 8.05.13
Table 8.05g
Permissible Shear Stresses
for Riprap and Temporary
Liners
Permissible Unit Shear Stress, Td
Lining Category Lining Type (lb/ft2)
Temporary Woven Paper Net
Jute Net
Fiberglass Roving:
Single
Double
Straw with Net
Curled Wood mat
Synthetic Mat
0.15
0.45
0.60
0.85
1.45
1.55
2.00
d50 Stone Size (inches)
Gravel Riprap 1
2
0.33
0.67
Rock Riprap 6
9
12
15
18
21
24
2.00
3.00
4.00
5.00
6.00
7.80
8.00
Adapted From: FHWA, HEC-15, April 1983, pgs. 17 & 37.
Design Procedure-
Temporary Liners
The following is a step-by-step procedure for designing a temporary liner for
a channel. Because temporary liners have a short period of service, the design
Q may be reduced. For liners that are needed for six months or less, the 2-year
frequency storm is recommended.
Step 1. Select a liner material suitable for site conditions and application.
Determine roughness coefficient from manufacturer’s specifications or Table
8.05e, page 8.05.10.
Step 2. Calculate the normal flow depth using Manning’s equation (Figure
8.05d). Check to see that depth is consistent with that assumed for selection of
Manning’s n in Figure 8.05d, page 8.05.11. For smaller runoffs Figure 8.05d
is not as clearly defined. Recommended solutions can be determined by using
the Manning equation.
Step 3. Calculate shear stress at normal depth.
Step 4. Compare computed shear stress with the permissible shear stress for
the liner.
Step 5. If computed shear is greater than permissible shear, adjust channel
dimensions to reduce shear, or select a more resistant lining and repeat steps
1 through 4.
Design of a channel with temporary lining is illustrated in Sample Problem
8.05b, page 8.05.14.
Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 1 of 7
12/9/2016 (Initial Submittal)

Calculation Title:
Temporary Sediment Basins Calculation
Summary:
The temporary sediment basins were designed in accordance with the North Carolina Department of
Environment and Natural Resources (NCDENR) “Erosion and Sediment Control Planning and Design
Manual”.

Notes:

Revision Log:
No. Description Originator Verifier Technical Reviewer
0

Initial Submittal –
12/9/2016

Chris Jordan Stephanie Stanwick Cedric H. Ruhl

Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 2 of 7
12/9/2016 (Initial Submittal)

OBJECTIVE:
The objective of this calculation is to design the temporary sediment basins for the interim closure
conditions of the Primary and Secondary ash basins
METHOD:
The temporary sediment basins were designed in accordance with the North Carolina Department
of Environment and Natural Resources (NCDENR) “Erosion and Sediment Control Planning and
Design Manual” [Ref. 1]. The 100-year storm event was also evaluated.
DEFINITION OF VARIABLES:
A = area;
CN = curve number;
d = flow depth;
i = rainfall depth;
L = length;
n = Manning’s n;
Q = flow;
S = longitudinal slope;
Tc = time of concentration; and
V = velocity
CALCULATIONS:
1.0 Design of temporary sediment basin
The sediment basins will be installed prior to the full removal of the southern dike. Basins will be
used as containment until final construction and stabilization of stormwater conveyance devices
has been completed. Sediment basin outlets will be located at the final discharge point for the
final, stabilized conditions. Land use and time of concentration for short term, interim conditions
has been calculated in the “Interim Conditions Stormwater Calculation”.
1.1 Sediment Basin Configuration
The sediment basin stage-storage curves are presented in the following table:

Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 3 of 7
12/9/2016 (Initial Submittal)

Sediment Basin ID Elevation
(ft)
Surface Area
(ft2)
Incremental
Storage
Volume
(ft3)
Total Storage
Volume
(ft3)
Notes
499.5 23,638 0 0 Bottom of Basin
502 91,335 143,716 143,716 Riser Invert
504 157,004 248,339 392,055
506 217,187 374,191 766,246
508 261,101 478,288 1,244,534 Emergency Spillway Invert
510 303,774 564,875 1,809,409 Crest of Basin
499.5 27,133 0 0 Bottom of Basin
502 123,530 188,329 188,329 Riser Invert
504 235,949 359,479 547,808
506 332,784 568,733 1,116,541
508 414,029 746,813 1,863,354 Emergency Spillway Invert
510 499,518 913,547 2,776,901 Crest of Basin
499.5 37,965 0 0 Bottom of Basin
502 127,980 207,431 207,431 Riser Invert
504 232,275 360,255 567,686
506 311,809 544,084 1,111,770
508 389,284 701,093 1,812,863 Emergency Spillway Invert
510 475,061 864,345 2,677,208 Crest of Basin
498.0 16,092 0 0 Bottom of Basin
502 67,831 167,846 167,846 Riser Invert
504 128,509 196,340 364,186
506 191,174 319,683 683,869
508 261,872 453,046 1,136,915 Emergency Spillway Invert
510 317,714 579,586 1,716,501 Crest of Basin
SB-1
SB-2
SB-3
SB-4
Table 1: Sediment Basin Stage-Storage Information

Sediment Basins 1 through 3 will consist of a 36 inch diameter vertical corrugated metal pipe
(CMP) riser pipe that discharges through a culvert to the Dan River. Sediment Basin 4 discharges
through an existing NPDES permitted outfall to the Dan River.
The emergency spillway for each basin will consist of a trapezoidal shaped spillway with an invert
elevation of 508, height of 2 feet, bottom width of 10 feet and side slopes of 10H:1V.
1.2 Sediment Basin Hydraulic Performance
The sediment basin hydraulic performance was evaluated for the 2-year, 10-year, 25-year, and
100-year, 24-hour storm events based on NOAA Atlas 14 rainfall data [Ref. 5]. The sediment
basin hydraulic performance was evaluated using HydroCAD software, the results of which are
presented in Reference 3 and summarized in the following table:
Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 4 of 7
12/9/2016 (Initial Submittal)

Sediment Basin ID Elevation
(ft)Notes
499.50 Bottom of Basin
501.38 Water Surface Elevation from 2-Year Storm Event
502.00 Riser Invert
502.07 Water Surface Elevation from 10-Year Storm Event
502.31 Water Surface Elevation from 25-Year Storm Event
502.58 Water Surface Elevation from 100-Year Storm Event
508.00 Emergency Spillway Invert
510.00 Crest of Basin
499.50 Bottom of Basin
502 Riser Invert
502.22 Water Surface Elevation from 2-Year Storm Event
502.8 Water Surface Elevation from 10-Year Storm Event
503.66 Water Surface Elevation from 25-Year Storm Event
504.05 Water Surface Elevation from 100-Year Storm Event
508 Emergency Spillway Invert
510 Crest of Basin
499.50 Bottom of Basin
502 Riser Invert
502.8 Water Surface Elevation from 2-Year Storm Event
503.79 Water Surface Elevation from 10-Year Storm Event
504.48 Water Surface Elevation from 25-Year Storm Event
505.63 Water Surface Elevation from 100-Year Storm Event
508 Emergency Spillway Invert
510 Crest of Basin
499.50 Bottom of Basin
502 Riser Invert
502.04 Water Surface Elevation from 2-Year Storm Event
502.22 Water Surface Elevation from 10-Year Storm Event
502.4 Water Surface Elevation from 25-Year Storm Event
502.73 Water Surface Elevation from 100-Year Storm Event
508 Emergency Spillway Invert
510 Crest of Basin
Table 2: Sediment Basin Hydraulic Performance
SB-1
SB-2
SB-3
SB-4

Each sediment basin has enough capacity to store the 100-year storm event without activating
the emergency spillway. Sediment basin SB-1 can store a 2-year storm event without activating
the riser pipe spillway.
1.3 Skimmer Design
The skimmer will discharge at a constant rate depending on the orifice size as shown in the
following table:
Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 5 of 7
12/9/2016 (Initial Submittal)

Sediment Basin ID Volume to De-Water
(ft3)
Orifice Size
(in)
[Ref. 4]
Discharge
Rate
(ft3/hr)
Dewatering Time
(hours)
[Ref. 4]
Dewatering Time
(days)
[Ref. 4]
1.5 72 1,996 83.2
2.0 137 1,051 43.8
2.5 260 553 23.1
3.0 407 353 14.7
4.0 838 172 7.1
5.0 1,368 105 4.4
6.0 2,160 67 2.8
8.0 4,082 35 1.5
1.5 72 2,616 109.0
2.0 137 1,377 57.4
2.5 260 725 30.2
3.0 407 462 19.3
4.0 838 225 9.4
5.0 1,368 138 5.7
6.0 2,160 87 3.6
8.0 4,082 46 1.9
1.5 72 2,881 120.0
2.0 137 1,516 63.2
2.5 260 799 33.3
3.0 407 509 21.2
4.0 838 248 10.3
5.0 1,368 152 6.3
6.0 2,160 96 4.0
8.0 4,082 51 2.1
1.5 72 2,331 97.1
2.0 137 1,227 51.1
2.5 260 646 26.9
3.0 407 412 17.2
4.0 838 200 8.3
5.0 1,368 123 5.1
6.0 2,160 78 3.2
8.0 4,082 41 1.7
SB-4
Table 3: Skimmer Design
SB-1 143,716
SB-2
SB-3
188,329
207,431
167,846

All four sediment basins were selected to use a skimmer with a 6-inch orifice for dewatering times
in excess of 48 hours.
1.4 Sediment Basin Design Summary
The sediment basin was designed to meet the requirements of the NCDENR “Erosion and
Sediment Control Planning and Design Manual” [Ref. 1] as summarized in the following table:

Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 6 of 7
12/9/2016 (Initial Submittal)

Sediment Basin ID Minimum Design Requirement Actual Design Requirement
Maximum drainage area = 100 acres 11.14
Maximum design life = 3 years Less than 3 Years
Minimum Design Storm = 10-year 100-year
Volume = 1,800 ft3/ac = 20,160 ft3 143,716
Surface Area = 435 ft2/cfs = 20,114 ft3 91,335
Minimum dewatering time = 48 hours 67.00
Maximum drainage area = 100 acres 39.46
Maximum design life = 3 years Less than 3 Years
Minimum Design Storm = 10-year 100-year
Volume = 1,800 ft3/ac = 36,012 ft4 188,329
Surface Area = 435 ft2/cfs =75,864 ft4 123,530
Minimum dewatering time = 48 hours 87.00
Maximum drainage area = 100 acres 98.61
Maximum design life = 3 years Less than 3 Years
Minimum Design Storm = 10-year 100-year
Volume = 1,800 ft3/ac = 33,120 ft5 207,431
Surface Area = 435 ft2/cfs = 64,262 ft5 127,980
Minimum dewatering time = 48 hours 96.00
Maximum drainage area = 100 acres 16.81
Maximum design life = 3 years Less than 3 Years
Minimum Design Storm = 10-year 100-year
Volume = 1,800 ft3/ac = 26,640 ft6 167,846
Surface Area = 435 ft2/cfs = 24,917 ft6 67,831
Minimum dewatering time = 48 hours 78.00
SB-2
SB-3
SB-4
Table 4: Sediment Basin Design Summary
SB-1

The proposed sediment basins meet the design requirements.
1.5 Anti-Flotation Block
Sediment basin risers will be anchored to the ground using antiflotation devices. Sediment Basin
4 will use a pre-existing concrete antiflotation device while Sediment Basins 1, 2 and 3 will use a
5 ft x 5 ft x 1.5 ft concrete block. The design of the antiflotation block is summarized in the following
table:
Sediment Basin ID
Riser
Diameter
(ft)
Riser
Height
(ft)
Mass of Water
Displaced by
Riser
(lbs)
Block Length
(ft)
Block
Width
(ft)
Block
Height
(ft)
Buoyant
Unit
Weight of
Block
(pcf)
Mass of
Block
(Rectangle)
(lbs)
Safety Factor
Against
Flotation
(Rectangle)
SB-1 3.0 2.5 1,103 5.0 5.0 1.5 87.6 3,285 2.98
SB-2 3.0 2.5 1,103 5.0 5.0 1.5 87.6 3,285 2.98
SB-3 3.0 2.5 1,103 5.0 5.0 1.5 87.6 3,285 2.98
Table 5: Rectangular Anti-Flotation Block Design Summary

The safety factor against flotation is 2.98, which is greater than the minimum required safety factor
of 1.1 [Ref. 1].
DISCUSSION:
The temporary sediment basins were designed in accordance with the North Carolina
Department of Environment and Natural Resources (NCDENR) “Erosion and Sediment Control
Planning and Design Manual”.
Temporary Sediment Basins Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 7 of 7
12/9/2016 (Initial Submittal)

REFERENCES:
1. North Carolina Department of Environment and Natural Resources, “Erosion and Sediment
Control Planning and Design Manual”, Revised May 2013.
2. United States Department of Agriculture, “Urban Hydrology for Small Watersheds”, Technical
Release 44, June 1986.
3. HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.
4. J.W. Faircloth & Son, Inc. “Determining the Skimmer Size and the Required Orifice for the
Faircloth Skimmer Surface Drain” Revised November 2007.
5. Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.

REFERENCE 1

North Carolina Department of Environment and Natural Resources, “Erosion and Sediment
Control Planning and Design Manual”, Revised May 2013.
Appendices
Rev. 6/06 8.03.17
table 8.03e Runoff curve numbers of urban areas1
---------------------------------------Cover Description-------------------------
Curve number for
---------hydrologic soil group--------
Cover type and hydrologic condition Average percent
impervious area2 ABCD
Fully developed urban areas (vegetation established)
Open space (lawns, parks, golf courses, cemeteries, etc.) 3:
Poor condition (grass cover < 50%) .............................68 79 86 89
Fair condition (grass cover 50% to 75%) .....................49 69 79 84
Good condition (grass cover > 75%) ............................39 61 74 80
Impervious areas:
Paved parking lots, roofs, driveways, etc.
(excluding right-of-way) ...............................................98 98 98 98
Streets and roads:
Paved; curbs and storm sewers (excluding
right-of-way) ..................................................................98 98 98 98
Paved; open ditches (including right-of-way) ................83 89 92 93
Gravel (including right-of-way) ......................................76 85 89 91
Dirt (including right-of-way) ...........................................72 82 87 89
Urban districts:
Commercial and business ................................................. 85 89 92 94 95
Industrial ...........................................................................72 81 88 91 93
Residential districts by average lot size:
1/8 acre or less (town houses) ......................................... 65 77 85 90 92
1/4 acre ............................................................................ 38 61 75 83 87
1/3 acre .............................................................................30 57 72 81 86
1/2 acre .............................................................................25 54 70 80 85
1 acre ...............................................................................20 51 68 79 84
2 acres ..............................................................................12 46 65 77 82
Developing urban areas
Newly graded areas
(pervious areas only, no vegetation) 4 ..............................77 86 91 94
Idle lands (CN’s are determined using cover types
similar to those in table 2-2c).
1. Average runoff condition, and Ia = 0.2S.
2. The average percent impervious area shown was used to develop the composite CN’s. Other assumptions are as follows: impervious
areas are directly connected to the drainage system, impervious areas have a CN of 98, and pervious areas are considered equivalent
to open space in good hydrologic condition. CN’s for other combinations of conditions may be computed using Figure 8.03c or 8.03d.
3. CN’s shown are equivalent to those of pasture. Composite CN’s may be computed for other combinations of open space cover type.
4. Composite CN’s to use for the design of temporary measures during grading and construction should be computed using Figure 8.03c
or 8.03d based on the degree of development (impervious area percentage) and the CN’s for the newly graded pervious areas.
Practice Standards and Specifications

6.61
Definition An earthen embankment suitably located to capture sediment with a primary
spillway system consisting of a riser and barrel pipe.

Purpose To retain sediment on the construction site, and prevent sedimentation in off-site
streams, lakes, and drainageways.

Conditions Where Special limitation – This practice applies only to the design and installation of
Practice Applies sediment basins where failure of the structure would not result in the loss of life,
damage to homes or buildings, or interrupt the use of public roads or utilities.
All high hazard potential dams and structures taller than 25 feet, and that also
have a maximum storage capacity of 50 acre-feet or more are subject to the
N.C. Dam Safety . Law of 1967
Sediment basins are needed where drainage areas exceed design criteria of other
measures. Specific criteria for installation of a sediment basin are as follows:
• Keep the drainage area less than 100 acres;
• Ensure that basin location provides a convenient concentration point for
sediment-laden flows from the area served;
• Ensure that basin location allows access for sediment removal and
proper disposal under all weather conditions; and
• Keep the basin life limited to 3 years, unless it is designed as a
permanent structure;
Do not locate sediment basins in intermittent or perennial streams.

Planning Select key locations for sediment basins during initial site evaluation. Install
Considerations basins before any land-disturbance takes place within the drainage area.
Select basin sites to capture sediment from all areas that are not treated
adequately by other sediment controls. Always consider access for cleanout and
disposal of the trapped sediment. Locations where a pond can be formed by
constructing a low dam across a natural swale are generally preferred to sites that
require excavation. Where practical, divert sediment-free runoff away from the
basin.
Sediment trapping efficiency is primarily a function of sediment particle size and
the ratio of basin surface area to inflow rate. Therefore, design the basin to have
a large surface area for its volume. Figure 6.61a shows the relationship between
the ratio of surface area to peak inflow rate and trap efficiency observed by
Barfield and Clar (1986).
Sediment basins with an expected life greater than 3 years should be designed as
permanent structures. Often sediment basins are converted to stormwater ponds.
In these cases, the structure should be designed by a qualified professional
engineer experienced in the design of dams. Permanent ponds and artificial lakes
are beyond the scope of this practice standard. USDA Soil Conservation
Services Practice Standard Ponds Code No. 378 provides criteria for design of
permanent ponds.
SEDIMENT BASIN
Rev. 5/13 6.61.1
Practice Standards and Specifications

Figure 6.61a Relationship between the ratio of surface area to peak inflow rate and trap efficiency.

Design Criteria Summary:
Primary Spillway: Riser/Barrel Pipe
Temporary Sediment Basin:
Maximum Drainage Area: 100 acres
Minimum Sediment Storage Volume: 1800 cubic feet per acre of disturbed area
Minimum Surface Area: 435 square feet per cfs of Q 10
Minimum L/W Ratio: 2:1
peak inflow
Maximum L/W Ratio: 6:1
Minimum Depth: 2 feet
Dewatering Mechanism: Skimmer(s) attached at bottom of riser
pipe or flashboard riser
Minimum Dewatering Time: 48 hours
Baffles Required: 3 baffles* (*Note: Basins less than 20 feet in length may use 2 baffles.)

Drainage areas- Limit drainage areas to 100 acres.
Design basin life- Ensure a design basin life of 3 years or less.
Dam height- Limit dam height to 15 feet. Height of a dam is measured from the
top of the dam to the lowest point at the downstream toe. Volume is measured
from the top of the dam when determining if the dam impounds enough water to
be regulated by the Dam Safety Law.

Rev. 5/136.61.2
Practice Standards and Specifications

Basin locations- Select areas that:
• Provide capacity for sediment storage from as much of the planned
disturbed area as practical;
• Exclude runoff from undisturbed areas where practical;
• Provide access for sediment removal throughout the life of the project and;
• Interfere minimally with construction activities.
Basin shape- Ensure that the flow length to basin width ratio is at least 2:1 to
improve trapping efficiency. This basin shape may be attained by site selection
or excavation. Length is measured at the elevation of the principal spillway.
Storage volume- Ensure that the sediment storage volume of the basin, as
measured to the elevation of the crest of the principal spillway, is at least 1,800
ft3/acre for the disturbed area draining into the basin (1,800 ft3
Remove sediment from the basin when approximately one-half of the storage
volume has been filled.
is equivalent to a
½ inch of sediment per acre of basin drainage area).
Spillway capacity- The spillway system must carry the peak runoff from the 10-
year storm with a minimum 1 foot freeboard in the emergency spillway.
Base runoff computations on the disturbed soil cover conditions expected
during the effective life of the structure.
Principal spillway- Construct the principal spillway with a vertical riser
connected to a horizontal barrel that extends through the embankment and outlets
beyond the downstream toe of the dam, or an equivalent design.
• Capacity- The primary spillway system must carry the peak runoff from
the 2-year storm, with the water surface at the emergency spillway crest
elevation.
Sediment cleanout elevation- Show the distance from the top of the riser to the
pool level when the basin is 50 percent full. This elevation should also be
marked in the field with a permanent stake set at this ground elevation (not the
top of the stake).
Crest elevation- Keep the crest elevation of the riser a minimum of 1 foot below
the crest elevation of the emergency spillway.
Riser and Barrel- Keep the minimum barrel size at 15 inches for corrugated
metal pipe or 12 inches for smooth wall pipe to facilitate installation and reduce
potential for failure from blockage. Ensure that the pipe is capable of
withstanding the maximum external loading without yielding, buckling or
cracking. To improve the efficiency of the principal spillway system, make the
cross-sectional area of the riser at least 1.5 times that of the barrel. The riser
should be sized to minimize the range of stages when orifice flow will occur.
Pipe Connections- Ensure that all conduit connections are watertight. Rod and
lug type connector bands with gaskets are preferred for corrugated metal pipe to
assure watertightness under maximum loading and internal pressure. Do not use
dimple (universal) connectors under any circumstances.
• Trash guard- It is important that a suitable trash guard be installed to
prevent the riser and barrel pipes from becoming clogged. Install a trash
guard on the top of the riser to prevent trash and other debris from
Rev. 5/13 6.61.3
Practice Standards and Specifications

clogging the conduit. A combination anti-vortex device and trash guard
improves the efficiency of the principal spillway and protects against
trash intake.
• Protection against piping- Install at least one watertight anti-seep collar
with a minimum projection of 1.5 feet around the barrel of principal
spillway conduits, 8 inches or larger in diameter. Locate the anti-seep
collar slightly downstream from the dam center line. A properly
designed drainage diaphragm installed around the barrel may be used
instead of an anti-seep collar when it is appropriate.
• Protection against flotation- Secure the riser by an anchor with buoyant
weight greater than 1.1 times the water displaced by the riser.
• Outlet- Protect the outlet of barrel against erosion.
Discharge velocities must be within allowable limits for the receiving stream
(References: Outlet Protection).
Basin dewatering- The basin should be provided with a mechanism to dewater
the basin from the water surface. Previously sediment basins were dewatered
with a perforated riser. These were designed to dewater relatively quickly and
draw water from the entire water column. Dewatering from the surface provides
greater trapping efficiency. Two common methods are a skimmer and flashboard
riser.
• Skimmer- A floating skimmer should be attached to the base of the riser.
The orifice in the skimmer will control the rate of dewatering. The
skimmer should be sized to dewater the basin in 2-5 days. A chart to
determine the appropriate skimmer and orifice size is included on page
6.64.3. See Practice 6.64, Skimmer Basins for details on the installation
of skimmers.

Figure 6.61b Sediment basin with skimmer attached to riser for dewatering.
Photo Credit: Town of Apex
Rev. 5/136.61.4
Practice Standards and Specifications

• Flashboard Riser- A different approach is to use a flashboard riser, which
forces the basin to fill to a given level before the water tops the riser. In
this way it is similar to a solid riser, but with the option of being able to
lower the water level in the basin when accumulated sediment must be
removed. Flashboard risers are usually fabricated as a box or as a riser
pipe cut in half. The open face has slots on each side into which boards
or “stop logs” are placed, forcing the water up and over them. This
device should be sized the same way as a typical riser.

Forcing the water to exit the sediment basin from the top of the water
column has the same advantages in sediment capture as the skimmer. A
flashboard riser basin will have an adjustable, permanent pool which also
improves basin efficiency. This method is a disadvantage when the
sediment needs to be removed because the operator may need to remove
the boards down to the sediment level to drain the basin. Flashboard
risers are a good option for stilling basins for pump discharges, or when
sandy soil conditions will allow dewatering of the basin through
infiltration. They should not be selected when the basin will have to be
cleaned frequently, or when located in clay soils.

Figure 6.61c Flashboard Riser installation example.
Photo credit: NC State University

Rev. 5/13 6.61.5
Practice Standards and Specifications

Emergency spillway- Construct the entire flow area of the emergency
spillway in undisturbed soil (not fill). Make the cross section trapezoidal
with side slopes of 3:1 or flatter. Make the control section of the spillway
straight and at least 20 feet long. The inlet portion of the spillway may be
curved to improve alignment, but ensure that the outlet section is straight due
to supercritical flow in this portion.
• Capacity- The minimum design capacity of the emergency spillway must
be the peak rate of runoff from the 10-year storm, less any reduction due
to flow in the principal spillway. In no case should freeboard of the
emergency spillway be less than 1 foot above the design depth of flow.
• Velocity- Ensure that the velocity of flow discharged from the basin is
non-erosive for the existing conditions. When velocities exceed that
allowable for the receiving areas, provide outlet protection (References:
Outlet Protection).
Embankment-
• Cut-off trench- Excavate a trench at the center line of the embankment.
Ensure that the trench is in undisturbed soil and extends through the
length of the embankment to the elevation of the riser crest at each end.
A minimum of depth of 2 feet is recommended.
• Top width- The minimum top width of the dam is shown in Table 6.61a.
• Freeboard- Ensure that the minimum difference between the design
water elevation in the emergency spillway and the top of the settled
embankment is 1 foot.
• Side slopes- Make the side slopes of the impoundment structure 2.5:1 or
flatter (Figure 6.61d).
• Allowance for settlement- Increase the constructed height of the fill at
least 10 percent above the design height to allow for settlement.
• Erosion protection- Stabilize all areas disturbed by construction (except
the lower ½ of the sediment pool) by suitable means immediately after
completing the basin (References: Surface Stabilization).
Design information included in the Appendices may be used to develop final
plans for sediment basins (References: Appendices).
Trap efficiency- Improve sediment basin trapping efficiency by employing the
following considerations in the basin design:
• Surface area- In the design of the settling pond, allow the largest surface
area possible. Studies of Barfield and Clar (1986) indicate that surface
area (in acres) should be larger than 0.01 times the peak inflow rate in
cfs, or 435 sq. ft. per cfs of peak flow.
• Length- The length to width ratio should be between 2:1 to 6:1.

Fill Height Minimum Top Width
less than 10 ft 8.0 ft
10 ft to 15 ft 10.0 ft
Table 6.61a
Acceptable Dimensions for
Basin Embankment
Rev. 5/136.61.6
Practice Standards and Specifications

• Baffles- Provides a minimum of three porous baffles to evenly distribute
flow across the basin and reduces turbulence. Basins less than 20 feet in
length may use 2 baffles .
• Inlets- Locate the sediment inlets to the basin the greatest distance from
the principal spillway.

• Inflow rate- Reduce the inflow velocity and divert all sediment-free
runoff.

Construction 1. Site preparations- Clear, grub, and strip topsoil from areas under the
Specifications embankment to remove trees, vegetation, roots, and other objectionable material.
Delay clearing the pool area until the dam is complete and then remove brush,
trees, and other objectionable materials to facilitate sediment cleanout. Stockpile
all topsoil or soil containing organic matter for use on the outer shell of the
embankment to facilitate vegetative establishment. Place temporary sediment
control measures below the basin as needed.
2. Cut-off trench- Excavate a cut-off trench along the center line of the earth fill
embankment. Cut the trench to stable soil material, but in no case make it less
than 2 feet deep. The cut-off trench must extend into both abutments to at least
the elevation of the riser crest. Make the minimum bottom width wide enough to
permit operation of excavation and compaction equipment, but in no case less
than 2 feet. Make side slopes of the trench no steeper than 1:1. Compaction
requirements are the same as those for the embankment. Keep the trench dry
during backfilling and compaction operations.
3. Embankment- Take fill material from the approved areas shown on the plans.
It should be clean mineral soil, free of roots, woody vegetation, rocks, and other
objectionable material. Scarify areas on which fill is to be placed before placing fill.
The fill material must contain sufficient moisture so it can be formed by hand
into a ball without crumbling. If water can be squeezed out of the ball, it is too
wet for proper compaction. Place fill material in 6 to 8 inch continuous layers
over the entire length of the fill area and compact it. Compaction may be
obtained by routing the construction hauling equipment over the fill so that the
entire surface of each layer is traversed by at least one wheel or tread track of
heavy equipment, or a compactor may be used. Construct the embankment to an
elevation 10 percent higher than the design height to allow for settling.
4. Conduit spillways- Securely attach the riser to the barrel or barrel stub to
make a watertight structural connection. Secure all connections between barrel
sections by approved watertight assemblies. Place the barrel and riser on a firm,
smooth foundation of impervious soil. Do not use pervious material such as
sand, gravel, or crushed stone as backfill around the pipe or anti-seep collars.
Place the fill material around the pipe spillway in 4-inch layers, and compact it
under and around the pipe to at least the same density as the adjacent
embankment. Care must be taken not to raise the pipe from firm contact
with its foundation when compacting under the pipe haunches.
• Dewatering- Allow the maximum reasonable detention period before the
basin is completely dewatered-at least 48 hours.
Rev. 5/13 6.61.7
Practice Standards and Specifications

Place a minimum depth of 2 feet of compacted backfill over the pipe spillway
before crossing it with construction equipment. Anchor the riser in place by
concrete or other satisfactory means to prevent flotation. In no case should the
pipe conduit be installed by cutting a trench through the dam after the
embankment is complete.

5. Emergency spillway- Install the emergency spillway in undisturbed soil. The
achievement of planned elevations, grade, design width, and entrance and exit
channel slopes are critical to the successful operation of the emergency spillway.

6. Inlets- Discharge water into the basin in a manner to prevent erosion. Use
diversions with outlet protection to divert sediment-laden water to the upper end
of the pool area to improve basin trap efficiency (References: Runoff Control
Measures and Outlet Protection).

7. Erosion control- Construct the structure so that the disturbed area is
minimized. Divert surface water away from bare areas. Complete the
embankment before the area is cleared. Stabilize the emergency spillway
embankment and all other disturbed areas above the crest of the principal
spillway immediately after construction (References: Surface Stabilization).

8. Install porous baffles as specified in Practice 6.65, Porous Baffles.

9. Safety- Sediment basins may attract children and can be dangerous. Avoid
steep side slopes, and fence and mark basins with warning signs if trespassing is
likely. Follow all state and local requirements.

Maintenance Inspect temporary sediment basins at least weekly and after each significant (1/2
inch or greater) rainfall event and repair immediately. Remove sediment and
restore the basin to its original dimensions when it accumulates to one-half the
design depth. Place removed sediment in an area with sediment controls.
Check the embankment, spillways, and outlet for erosion damage, and inspect the
embankment for piping and settlement. Make all necessary repairs immediately.
Remove all trash and other debris from the riser and pool area.

Rev. 5/136.61.8
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Rev. 5/13 6.61.9
Practice Standards and Specifications

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Practice Standards and Specifications

References Surface Stabilization
6.10, Temporary Seeding
6.11, Permanent Seeding
6.12, Sodding
6.13, Trees, Shrubs, Vines, and Ground Covers
Runoff Control Measures
6.20, Temporary Diversions
6.21, Permanent Diversions
6.22, Perimeter Dike
Outlet Protection
6.40, Level Spreader
6.41, Outlet Stabilization Structure
Sediment Traps and Barriers
6.64, Skimmer Sediment Basin
6.65, Porous Baffles
Appendices
8.01, Soil Information
8.02, Vegetation Tables
8.03, Estimating Runoff
8.04, Estimating Roughness Coefficients
8.05, Design of Stable Channels and Diversions
8.06, Design of Riprap Outlet Protection
8.07, Sediment Basin Design
8.08, The Sediment Control Law
Barfield, B.J. and M.L. Clar. Erosion and Sediment Control Practices.
Report to the Sediment and Stormwater Division – Maryland Water
Resources Administration, 1986.

Rev. 5/136.61.10
REFERENCE 2

United States Department of Agriculture, “Urban Hydrology for Small Watersheds”, Technical
Release 44, June 1986.
Technical Release 55
Urban Hydrology for Small Watersheds
Time of Concentration and Travel TimeChapter 3
3–4 (210-VI-TR-55, Second Ed., June 1986)
Manning’s equation is:
V rs
n
=149
2
3
1
2.[eq. 3-4]
where:
V = average velocity (ft/s)
r = hydraulic radius (ft) and is equal to a/pw
a = cross sectional flow area (ft
2)
pw = wetted perimeter (ft)
s = slope of the hydraulic grade line (channel
slope, ft/ft)
n = Manning’s roughness coefficient for open
channel flow.
Manning’s n values for open channel flow can be
obtained from standard textbooks such as Chow
(1959) or Linsley et al. (1982). After average velocity is
computed using equation 3-4, Tt for the channel seg-
ment can be estimated using equation 3-1.
Reservoirs or lakes
Sometimes it is necessary to estimate the velocity of
flow through a reservoir or lake at the outlet of a
watershed. This travel time is normally very small and
can be assumed as zero.
Limitations
•Manning’s kinematic solution should not be used
for sheet flow longer than 300 feet. Equation 3-3
was developed for use with the four standard
rainfall intensity-duration relationships.
•In watersheds with storm sewers, carefully identify
the appropriate hydraulic flow path to estimate Tc.
Storm sewers generally handle only a small portion
of a large event. The rest of the peak flow travels
by streets, lawns, and so on, to the outlet. Consult a
standard hydraulics textbook to determine average
velocity in pipes for either pressure or nonpressure
flow.
•The minimum Tc used in TR-55 is 0.1 hour.
•A culvert or bridge can act as a reservoir outlet if
there is significant storage behind it. The proce-
dures in TR-55 can be used to determine the peak
flow upstream of the culvert. Detailed storage
routing procedures should be used to determine
the outflow through the culvert.
Example 3-1
The sketch below shows a watershed in Dyer County,
northwestern Tennessee. The problem is to compute
Tc at the outlet of the watershed (point D). The 2-year
24-hour rainfall depth is 3.6 inches. All three types of
flow occur from the hydraulically most distant point
(A) to the point of interest (D). To compute Tc, first
determine Tt for each segment from the following
information:
Segment AB: Sheet flow; dense grass; slope (s) = 0.01
ft/ft; and length (L) = 100 ft. Segment BC: Shallow
concentrated flow; unpaved; s = 0.01 ft/ft; and
L = 1,400 ft. Segment CD: Channel flow; Manning’s
n = .05; flow area (a) = 27 ft2; wetted perimeter
(pw) = 28.2 ft; s = 0.005 ft/ft; and L = 7,300 ft.
See figure 3-2 for the computations made on
worksheet 3.
A B C D
7,300 ft1,400 ft100 ft
(Not to scale)
REFERENCE 3

HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013.

6P
Sediment Basin (SB-2)
49P
Sediment Basin 1
Routing Diagram for ST 1
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=502.22' Storage=4.967 af Inflow=105.30 cfs 6.269 afPond 6P: Sediment Basin (SB-2)
Primary=3.09 cfs 1.451 af Secondary=0.00 cfs 0.000 af Outflow=3.09 cfs 1.451 af
Peak Elev=501.38' Storage=2.115 af Inflow=38.41 cfs 2.116 afPond 49P: Sediment Basin 1
Primary=0.00 cfs 0.000 af Secondary=0.00 cfs 0.000 af Outflow=0.00 cfs 0.000 af
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 6P: Sediment Basin (SB-2)
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 1.91" for 2-Year event
Inflow = 105.30 cfs @ 11.98 hrs, Volume= 6.269 af
Outflow = 3.09 cfs @ 15.68 hrs, Volume= 1.451 af, Atten= 97%, Lag= 222.2 min
Primary = 3.09 cfs @ 15.68 hrs, Volume= 1.451 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 502.22' @ 15.68 hrs Surf.Area= 3.118 ac Storage= 4.967 af
Plug-Flow detention time= 327.3 min calculated for 1.451 af (23% of inflow)
Center-of-Mass det. time= 219.6 min ( 997.4 - 777.8 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 63.755 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.620 0.000 0.000
502.00 2.840 4.325 4.325
504.00 5.420 8.260 12.585
506.00 7.640 13.060 25.645
508.00 9.500 17.140 42.785
510.00 11.470 20.970 63.755
Device Routing Invert Outlet Devices
#1 Primary 499.50'24.0" Round Culvert
L= 103.0' CMP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 498.00' S= 0.0146 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 3.14 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=3.09 cfs @ 15.68 hrs HW=502.22' (Free Discharge)
1=Culvert (Passes 3.09 cfs of 19.81 cfs potential flow)
2=Orifice/Grate (Weir Controls 3.09 cfs @ 1.52 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 6P: Sediment Basin (SB-2)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=39.459 ac
Peak Elev=502.22'
Storage=4.967 af
105.30 cfs
3.09 cfs3.09 cfs0.00 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 49P: Sediment Basin 1
Inflow Area = 11.140 ac, 0.00% Impervious, Inflow Depth > 2.28" for 2-Year event
Inflow = 38.41 cfs @ 11.97 hrs, Volume= 2.116 af
Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 501.38' @ 20.00 hrs Surf.Area= 1.712 ac Storage= 2.115 af
Plug-Flow detention time= (not calculated: initial storage exceeds outflow)
Center-of-Mass det. time= (not calculated: no outflow)
Volume Invert Avail.Storage Storage Description
#1 499.50' 41.530 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.540 0.000 0.000
502.00 2.100 3.300 3.300
504.00 3.600 5.700 9.000
506.00 4.990 8.590 17.590
508.00 5.990 10.980 28.570
510.00 6.970 12.960 41.530
Device Routing Invert Outlet Devices
#1 Primary 499.50'12.0" Round Culvert
L= 116.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 497.00' S= 0.0216 '/' Cc= 0.900
n= 0.025, Flow Area= 0.79 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
1=Culvert ( Controls 0.00 cfs)
2=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 1
Printed 10/19/2015Prepared by AMEC
Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 49P: Sediment Basin 1
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
40
35
30
25
20
15
10
5
0
Inflow Area=11.140 ac
Peak Elev=501.38'
Storage=2.115 af
38.41 cfs
0.00 cfs0.00 cfs0.00 cfs
Type II 24-hr 10-Year Rainfall=5.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=502.80' Storage=7.012 af Inflow=186.29 cfs 11.362 afPond 6P: Sediment Basin (SB-2)
Primary=22.07 cfs 6.330 af Secondary=0.00 cfs 0.000 af Outflow=22.07 cfs 6.330 af
Peak Elev=502.08' Storage=3.480 af Inflow=65.41 cfs 3.634 afPond 49P: Sediment Basin 1
Primary=0.76 cfs 0.154 af Secondary=0.00 cfs 0.000 af Outflow=0.76 cfs 0.154 af
Type II 24-hr 10-Year Rainfall=5.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 6P: Sediment Basin (SB-2)
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 3.46" for 10-Year event
Inflow = 186.29 cfs @ 11.98 hrs, Volume= 11.362 af
Outflow = 22.07 cfs @ 12.56 hrs, Volume= 6.330 af, Atten= 88%, Lag= 34.9 min
Primary = 22.07 cfs @ 12.56 hrs, Volume= 6.330 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 502.80' @ 12.56 hrs Surf.Area= 3.873 ac Storage= 7.012 af
Plug-Flow detention time= 198.2 min calculated for 6.330 af (56% of inflow)
Center-of-Mass det. time= 121.5 min ( 886.2 - 764.7 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 63.755 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.620 0.000 0.000
502.00 2.840 4.325 4.325
504.00 5.420 8.260 12.585
506.00 7.640 13.060 25.645
508.00 9.500 17.140 42.785
510.00 11.470 20.970 63.755
Device Routing Invert Outlet Devices
#1 Primary 499.50'24.0" Round Culvert
L= 103.0' CMP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 498.00' S= 0.0146 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 3.14 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=22.07 cfs @ 12.56 hrs HW=502.80' (Free Discharge)
1=Culvert (Passes 22.07 cfs of 22.94 cfs potential flow)
2=Orifice/Grate (Weir Controls 22.07 cfs @ 2.93 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 10-Year Rainfall=5.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 6P: Sediment Basin (SB-2)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=39.459 ac
Peak Elev=502.80'
Storage=7.012 af
186.29 cfs
22.07 cfs22.07 cfs
0.00 cfs
Type II 24-hr 10-Year Rainfall=5.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 49P: Sediment Basin 1
Inflow Area = 11.140 ac, 0.00% Impervious, Inflow Depth > 3.91" for 10-Year event
Inflow = 65.41 cfs @ 11.97 hrs, Volume= 3.634 af
Outflow = 0.76 cfs @ 20.00 hrs, Volume= 0.154 af, Atten= 99%, Lag= 481.6 min
Primary = 0.76 cfs @ 20.00 hrs, Volume= 0.154 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 502.08' @ 20.00 hrs Surf.Area= 2.163 ac Storage= 3.480 af
Plug-Flow detention time= 684.9 min calculated for 0.154 af (4% of inflow)
Center-of-Mass det. time= 364.2 min ( 1,117.4 - 753.2 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 41.530 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.540 0.000 0.000
502.00 2.100 3.300 3.300
504.00 3.600 5.700 9.000
506.00 4.990 8.590 17.590
508.00 5.990 10.980 28.570
510.00 6.970 12.960 41.530
Device Routing Invert Outlet Devices
#1 Primary 499.50'12.0" Round Culvert
L= 116.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 497.00' S= 0.0216 '/' Cc= 0.900
n= 0.025, Flow Area= 0.79 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=0.76 cfs @ 20.00 hrs HW=502.08' (Free Discharge)
1=Culvert (Passes 0.76 cfs of 3.29 cfs potential flow)
2=Orifice/Grate (Weir Controls 0.76 cfs @ 0.95 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 10-Year Rainfall=5.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 49P: Sediment Basin 1
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
w

(
c
f
s
)
70
60
50
40
30
20
10
0
Inflow Area=11.140 ac
Peak Elev=502.08'
Storage=3.480 af
65.41 cfs
0.76 cfs0.76 cfs0.00 cfs
Type II 24-hr 25-Year Rainfall=5.70"ST 1
Printed 10/19/2015Prepared by AMEC
Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=503.01' Storage=7.861 af Inflow=209.05 cfs 12.823 afPond 6P: Sediment Basin (SB-2)
Primary=23.98 cfs 7.739 af Secondary=0.00 cfs 0.000 af Outflow=23.98 cfs 7.739 af
Peak Elev=502.12' Storage=3.559 af Inflow=72.94 cfs 4.062 afPond 49P: Sediment Basin 1
Primary=1.30 cfs 0.536 af Secondary=0.00 cfs 0.000 af Outflow=1.30 cfs 0.536 af
Type II 24-hr 25-Year Rainfall=5.70"ST 1
Printed 10/19/2015Prepared by AMEC
Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 6P: Sediment Basin (SB-2)
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 3.90" for 25-Year event
Inflow = 209.05 cfs @ 11.98 hrs, Volume= 12.823 af
Outflow = 23.98 cfs @ 12.57 hrs, Volume= 7.739 af, Atten= 89%, Lag= 35.6 min
Primary = 23.98 cfs @ 12.57 hrs, Volume= 7.739 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 503.01' @ 12.57 hrs Surf.Area= 4.146 ac Storage= 7.861 af
Plug-Flow detention time= 192.5 min calculated for 7.739 af (60% of inflow)
Center-of-Mass det. time= 119.1 min ( 881.1 - 762.0 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 63.755 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.620 0.000 0.000
502.00 2.840 4.325 4.325
504.00 5.420 8.260 12.585
506.00 7.640 13.060 25.645
508.00 9.500 17.140 42.785
510.00 11.470 20.970 63.755
Device Routing Invert Outlet Devices
#1 Primary 499.50'24.0" Round Culvert
L= 103.0' CMP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 498.00' S= 0.0146 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 3.14 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=23.98 cfs @ 12.57 hrs HW=503.01' (Free Discharge)
1=Culvert (Inlet Controls 23.98 cfs @ 7.63 fps)
2=Orifice/Grate (Passes 23.98 cfs of 31.40 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 25-Year Rainfall=5.70"ST 1
Printed 10/19/2015Prepared by AMEC
Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 6P: Sediment Basin (SB-2)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
220
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=39.459 ac
Peak Elev=503.01'
Storage=7.861 af
209.05 cfs
23.98 cfs23.98 cfs
0.00 cfs
Type II 24-hr 25-Year Rainfall=5.70"ST 1
Printed 10/19/2015Prepared by AMEC
Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 49P: Sediment Basin 1
Inflow Area = 11.140 ac, 0.00% Impervious, Inflow Depth > 4.38" for 25-Year event
Inflow = 72.94 cfs @ 11.97 hrs, Volume= 4.062 af
Outflow = 1.30 cfs @ 17.09 hrs, Volume= 0.536 af, Atten= 98%, Lag= 306.9 min
Primary = 1.30 cfs @ 17.09 hrs, Volume= 0.536 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 502.12' @ 17.09 hrs Surf.Area= 2.191 ac Storage= 3.559 af
Plug-Flow detention time= 491.7 min calculated for 0.536 af (13% of inflow)
Center-of-Mass det. time= 286.8 min ( 1,037.2 - 750.4 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 41.530 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.540 0.000 0.000
502.00 2.100 3.300 3.300
504.00 3.600 5.700 9.000
506.00 4.990 8.590 17.590
508.00 5.990 10.980 28.570
510.00 6.970 12.960 41.530
Device Routing Invert Outlet Devices
#1 Primary 499.50'12.0" Round Culvert
L= 116.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 497.00' S= 0.0216 '/' Cc= 0.900
n= 0.025, Flow Area= 0.79 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=1.30 cfs @ 17.09 hrs HW=502.12' (Free Discharge)
1=Culvert (Passes 1.30 cfs of 3.31 cfs potential flow)
2=Orifice/Grate (Weir Controls 1.30 cfs @ 1.14 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 25-Year Rainfall=5.70"ST 1
Printed 10/19/2015Prepared by AMEC
Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 49P: Sediment Basin 1
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
80
70
60
50
40
30
20
10
0
Inflow Area=11.140 ac
Peak Elev=502.12'
Storage=3.559 af
72.94 cfs
1.30 cfs1.30 cfs0.00 cfs
Type II 24-hr 100-Year Rainfall=8.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=504.06' Storage=12.886 af Inflow=323.07 cfs 20.282 afPond 6P: Sediment Basin (SB-2)
Primary=28.52 cfs 14.779 af Secondary=0.00 cfs 0.000 af Outflow=28.52 cfs 14.779 af
Peak Elev=502.58' Storage=4.647 af Inflow=110.59 cfs 6.224 afPond 49P: Sediment Basin 1
Primary=3.49 cfs 2.260 af Secondary=0.00 cfs 0.000 af Outflow=3.49 cfs 2.260 af
Type II 24-hr 100-Year Rainfall=8.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 6P: Sediment Basin (SB-2)
Inflow Area = 39.459 ac, 0.00% Impervious, Inflow Depth > 6.17" for 100-Year event
Inflow = 323.07 cfs @ 11.98 hrs, Volume= 20.282 af
Outflow = 28.52 cfs @ 12.70 hrs, Volume= 14.779 af, Atten= 91%, Lag= 43.7 min
Primary = 28.52 cfs @ 12.70 hrs, Volume= 14.779 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 504.06' @ 12.70 hrs Surf.Area= 5.481 ac Storage= 12.886 af
Plug-Flow detention time= 227.8 min calculated for 14.772 af (73% of inflow)
Center-of-Mass det. time= 164.7 min ( 916.2 - 751.5 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 63.755 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.620 0.000 0.000
502.00 2.840 4.325 4.325
504.00 5.420 8.260 12.585
506.00 7.640 13.060 25.645
508.00 9.500 17.140 42.785
510.00 11.470 20.970 63.755
Device Routing Invert Outlet Devices
#1 Primary 499.50'24.0" Round Culvert
L= 103.0' CMP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 498.00' S= 0.0146 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 3.14 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=28.52 cfs @ 12.70 hrs HW=504.06' (Free Discharge)
1=Culvert (Inlet Controls 28.52 cfs @ 9.08 fps)
2=Orifice/Grate (Passes 28.52 cfs of 48.79 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 100-Year Rainfall=8.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 6P: Sediment Basin (SB-2)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
350
300
250
200
150
100
50
0
Inflow Area=39.459 ac
Peak Elev=504.06'
Storage=12.886 af
323.07 cfs
28.52 cfs28.52 cfs
0.00 cfs
Type II 24-hr 100-Year Rainfall=8.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 49P: Sediment Basin 1
Inflow Area = 11.140 ac, 0.00% Impervious, Inflow Depth > 6.70" for 100-Year event
Inflow = 110.59 cfs @ 11.97 hrs, Volume= 6.224 af
Outflow = 3.49 cfs @ 14.12 hrs, Volume= 2.260 af, Atten= 97%, Lag= 128.8 min
Primary = 3.49 cfs @ 14.12 hrs, Volume= 2.260 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs
Peak Elev= 502.58' @ 14.12 hrs Surf.Area= 2.536 ac Storage= 4.647 af
Plug-Flow detention time= 335.4 min calculated for 2.259 af (36% of inflow)
Center-of-Mass det. time= 221.6 min ( 961.6 - 740.1 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 41.530 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.540 0.000 0.000
502.00 2.100 3.300 3.300
504.00 3.600 5.700 9.000
506.00 4.990 8.590 17.590
508.00 5.990 10.980 28.570
510.00 6.970 12.960 41.530
Device Routing Invert Outlet Devices
#1 Primary 499.50'12.0" Round Culvert
L= 116.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 497.00' S= 0.0216 '/' Cc= 0.900
n= 0.025, Flow Area= 0.79 sf
#2 Device 1 502.00'36.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=3.49 cfs @ 14.12 hrs HW=502.58' (Free Discharge)
1=Culvert (Barrel Controls 3.49 cfs @ 4.44 fps)
2=Orifice/Grate (Passes 3.49 cfs of 13.65 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 100-Year Rainfall=8.20"ST 1
Printed 10/19/2015Prepared by AMEC
Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 49P: Sediment Basin 1
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
120
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=11.140 ac
Peak Elev=502.58'
Storage=4.647 af
110.59 cfs
3.49 cfs3.49 cfs0.00 cfs
8P
Sediment Basin (SB-3)
37P
Sediment Basin (SB-4)
Routing Diagram for ST 2
Prepared by AMEC, Printed 10/19/2015
HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=502.72' Storage=7.175 af Inflow=103.10 cfs 11.974 afPond 8P: Sediment Basin (SB-3)
Primary=21.79 cfs 6.427 af Secondary=0.00 cfs 0.000 af Outflow=21.79 cfs 6.427 af
Peak Elev=502.03' Storage=2.466 af Inflow=39.32 cfs 2.568 afPond 37P: Sediment Basin (SB-4)
Primary=0.72 cfs 0.102 af Secondary=0.00 cfs 0.000 af Outflow=0.72 cfs 0.102 af
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 8P: Sediment Basin (SB-3)
Inflow Area = 98.610 ac, 0.00% Impervious, Inflow Depth > 1.46" for 2-Year event
Inflow = 103.10 cfs @ 11.99 hrs, Volume= 11.974 af
Outflow = 21.79 cfs @ 13.14 hrs, Volume= 6.427 af, Atten= 79%, Lag= 69.2 min
Primary = 21.79 cfs @ 13.14 hrs, Volume= 6.427 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 502.72' @ 13.14 hrs Surf.Area= 3.796 ac Storage= 7.175 af
Plug-Flow detention time= 196.6 min calculated for 6.424 af (54% of inflow)
Center-of-Mass det. time= 115.7 min ( 918.0 - 802.3 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 61.472 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.870 0.000 0.000
502.00 2.940 4.762 4.762
504.00 5.330 8.270 13.032
506.00 7.160 12.490 25.522
508.00 8.940 16.100 41.622
510.00 10.910 19.850 61.472
Device Routing Invert Outlet Devices
#1 Primary 499.50'30.0" Round Culvert
L= 91.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 496.00' S= 0.0385 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 4.91 sf
#2 Device 1 502.00'42.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=21.79 cfs @ 13.14 hrs HW=502.72' (Free Discharge)
1=Culvert (Passes 21.79 cfs of 33.14 cfs potential flow)
2=Orifice/Grate (Weir Controls 21.79 cfs @ 2.77 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 8P: Sediment Basin (SB-3)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=98.610 ac
Peak Elev=502.72'
Storage=7.175 af
103.10 cfs
21.79 cfs21.79 cfs
0.00 cfs
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 37P: Sediment Basin (SB-4)
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 1.83" for 2-Year event
Inflow = 39.32 cfs @ 11.99 hrs, Volume= 2.568 af
Outflow = 0.72 cfs @ 19.56 hrs, Volume= 0.102 af, Atten= 98%, Lag= 454.2 min
Primary = 0.72 cfs @ 19.56 hrs, Volume= 0.102 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 502.03' @ 19.56 hrs Surf.Area= 1.584 ac Storage= 2.466 af
Plug-Flow detention time= 621.4 min calculated for 0.102 af (4% of inflow)
Center-of-Mass det. time= 367.0 min ( 1,145.9 - 778.9 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 37.962 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.370 0.000 0.000
502.00 1.560 2.413 2.413
504.00 2.950 4.510 6.923
506.00 4.390 7.340 14.262
508.00 6.010 10.400 24.662
510.00 7.290 13.300 37.962
Device Routing Invert Outlet Devices
#1 Primary 498.00'36.0" Round Culvert
L= 150.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 498.00' / 495.00' S= 0.0200 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#2 Device 1 502.00'104.0" x 104.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=0.72 cfs @ 19.56 hrs HW=502.03' (Free Discharge)
1=Culvert (Passes 0.72 cfs of 54.18 cfs potential flow)
2=Orifice/Grate (Weir Controls 0.72 cfs @ 0.61 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.40"ST 2
Printed 10/19/2015Prepared by AMEC
Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 37P: Sediment Basin (SB-4)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
40
35
30
25
20
15
10
5
0
Inflow Area=16.815 ac
Peak Elev=502.03'
Storage=2.466 af
39.32 cfs
0.72 cfs0.72 cfs0.00 cfs
Type II 24-hr 10-Year Rainfall=5.10"ST 2
Printed 10/19/2015Prepared by AMEC
Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=503.79' Storage=11.927 af Inflow=182.08 cfs 22.836 afPond 8P: Sediment Basin (SB-3)
Primary=41.19 cfs 16.919 af Secondary=0.00 cfs 0.000 af Outflow=41.19 cfs 16.919 af
Peak Elev=502.22' Storage=2.766 af Inflow=69.27 cfs 4.543 afPond 37P: Sediment Basin (SB-4)
Primary=11.39 cfs 2.055 af Secondary=0.00 cfs 0.000 af Outflow=11.39 cfs 2.055 af
Type II 24-hr 10-Year Rainfall=5.10"ST 2
Printed 10/19/2015Prepared by AMEC
Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 8P: Sediment Basin (SB-3)
Inflow Area = 98.610 ac, 0.00% Impervious, Inflow Depth > 2.78" for 10-Year event
Inflow = 182.08 cfs @ 11.98 hrs, Volume= 22.836 af
Outflow = 41.19 cfs @ 13.98 hrs, Volume= 16.919 af, Atten= 77%, Lag= 120.1 min
Primary = 41.19 cfs @ 13.98 hrs, Volume= 16.919 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 503.79' @ 13.98 hrs Surf.Area= 5.076 ac Storage= 11.927 af
Plug-Flow detention time= 164.7 min calculated for 16.919 af (74% of inflow)
Center-of-Mass det. time= 106.3 min ( 906.2 - 799.9 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 61.472 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.870 0.000 0.000
502.00 2.940 4.762 4.762
504.00 5.330 8.270 13.032
506.00 7.160 12.490 25.522
508.00 8.940 16.100 41.622
510.00 10.910 19.850 61.472
Device Routing Invert Outlet Devices
#1 Primary 499.50'30.0" Round Culvert
L= 91.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 496.00' S= 0.0385 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 4.91 sf
#2 Device 1 502.00'42.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=41.19 cfs @ 13.98 hrs HW=503.79' (Free Discharge)
1=Culvert (Inlet Controls 41.19 cfs @ 8.39 fps)
2=Orifice/Grate (Passes 41.19 cfs of 61.94 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 10-Year Rainfall=5.10"ST 2
Printed 10/19/2015Prepared by AMEC
Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 8P: Sediment Basin (SB-3)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=98.610 ac
Peak Elev=503.79'
Storage=11.927 af
182.08 cfs
41.19 cfs41.19 cfs
0.00 cfs
Type II 24-hr 10-Year Rainfall=5.10"ST 2
Printed 10/19/2015Prepared by AMEC
Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 37P: Sediment Basin (SB-4)
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 3.24" for 10-Year event
Inflow = 69.27 cfs @ 11.99 hrs, Volume= 4.543 af
Outflow = 11.39 cfs @ 12.55 hrs, Volume= 2.055 af, Atten= 84%, Lag= 33.9 min
Primary = 11.39 cfs @ 12.55 hrs, Volume= 2.055 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 502.22' @ 12.55 hrs Surf.Area= 1.710 ac Storage= 2.766 af
Plug-Flow detention time= 200.8 min calculated for 2.055 af (45% of inflow)
Center-of-Mass det. time= 111.9 min ( 879.0 - 767.1 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 37.962 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.370 0.000 0.000
502.00 1.560 2.413 2.413
504.00 2.950 4.510 6.923
506.00 4.390 7.340 14.262
508.00 6.010 10.400 24.662
510.00 7.290 13.300 37.962
Device Routing Invert Outlet Devices
#1 Primary 498.00'36.0" Round Culvert
L= 150.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 498.00' / 495.00' S= 0.0200 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#2 Device 1 502.00'104.0" x 104.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=11.39 cfs @ 12.55 hrs HW=502.22' (Free Discharge)
1=Culvert (Passes 11.39 cfs of 56.09 cfs potential flow)
2=Orifice/Grate (Weir Controls 11.39 cfs @ 1.52 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 10-Year Rainfall=5.10"ST 2
Printed 10/19/2015Prepared by AMEC
Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 37P: Sediment Basin (SB-4)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
70
60
50
40
30
20
10
0
Inflow Area=16.815 ac
Peak Elev=502.22'
Storage=2.766 af
69.27 cfs
11.39 cfs11.39 cfs
0.00 cfs
Type II 24-hr 25-Year Rainfall=6.22"ST 2
Printed 10/19/2015Prepared by AMEC
Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=504.48' Storage=15.691 af Inflow=220.19 cfs 30.504 afPond 8P: Sediment Basin (SB-3)
Primary=45.64 cfs 24.118 af Secondary=0.00 cfs 0.000 af Outflow=45.64 cfs 24.118 af
Peak Elev=502.40' Storage=3.095 af Inflow=89.78 cfs 5.905 afPond 37P: Sediment Basin (SB-4)
Primary=28.82 cfs 3.405 af Secondary=0.00 cfs 0.000 af Outflow=28.82 cfs 3.405 af
Type II 24-hr 25-Year Rainfall=6.22"ST 2
Printed 10/19/2015Prepared by AMEC
Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 8P: Sediment Basin (SB-3)
Inflow Area = 98.610 ac, 0.00% Impervious, Inflow Depth > 3.71" for 25-Year event
Inflow = 220.19 cfs @ 11.97 hrs, Volume= 30.504 af
Outflow = 45.64 cfs @ 14.68 hrs, Volume= 24.118 af, Atten= 79%, Lag= 162.3 min
Primary = 45.64 cfs @ 14.68 hrs, Volume= 24.118 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 504.48' @ 14.68 hrs Surf.Area= 5.768 ac Storage= 15.691 af
Plug-Flow detention time= 181.1 min calculated for 24.106 af (79% of inflow)
Center-of-Mass det. time= 130.6 min ( 932.5 - 801.9 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 61.472 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.870 0.000 0.000
502.00 2.940 4.762 4.762
504.00 5.330 8.270 13.032
506.00 7.160 12.490 25.522
508.00 8.940 16.100 41.622
510.00 10.910 19.850 61.472
Device Routing Invert Outlet Devices
#1 Primary 499.50'30.0" Round Culvert
L= 91.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 496.00' S= 0.0385 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 4.91 sf
#2 Device 1 502.00'42.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=45.64 cfs @ 14.68 hrs HW=504.48' (Free Discharge)
1=Culvert (Inlet Controls 45.64 cfs @ 9.30 fps)
2=Orifice/Grate (Passes 45.64 cfs of 72.94 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 25-Year Rainfall=6.22"ST 2
Printed 10/19/2015Prepared by AMEC
Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 8P: Sediment Basin (SB-3)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
Fl
o
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(
c
f
s
)
240
220
200
180
160
140
120
100
80
60
40
20
0
Inflow Area=98.610 ac
Peak Elev=504.48'
Storage=15.691 af
220.19 cfs
45.64 cfs45.64 cfs
0.00 cfs
Type II 24-hr 25-Year Rainfall=6.22"ST 2
Printed 10/19/2015Prepared by AMEC
Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 37P: Sediment Basin (SB-4)
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 4.21" for 25-Year event
Inflow = 89.78 cfs @ 11.99 hrs, Volume= 5.905 af
Outflow = 28.82 cfs @ 12.29 hrs, Volume= 3.405 af, Atten= 68%, Lag= 18.2 min
Primary = 28.82 cfs @ 12.29 hrs, Volume= 3.405 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 502.40' @ 12.29 hrs Surf.Area= 1.839 ac Storage= 3.095 af
Plug-Flow detention time= 160.9 min calculated for 3.404 af (58% of inflow)
Center-of-Mass det. time= 83.1 min ( 844.7 - 761.6 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 37.962 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.370 0.000 0.000
502.00 1.560 2.413 2.413
504.00 2.950 4.510 6.923
506.00 4.390 7.340 14.262
508.00 6.010 10.400 24.662
510.00 7.290 13.300 37.962
Device Routing Invert Outlet Devices
#1 Primary 498.00'36.0" Round Culvert
L= 150.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 498.00' / 495.00' S= 0.0200 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#2 Device 1 502.00'104.0" x 104.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=28.82 cfs @ 12.29 hrs HW=502.40' (Free Discharge)
1=Culvert (Passes 28.82 cfs of 57.97 cfs potential flow)
2=Orifice/Grate (Weir Controls 28.82 cfs @ 2.07 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 25-Year Rainfall=6.22"ST 2
Printed 10/19/2015Prepared by AMEC
Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 37P: Sediment Basin (SB-4)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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(
c
f
s
)
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=16.815 ac
Peak Elev=502.40'
Storage=3.095 af
89.78 cfs
28.82 cfs28.82 cfs
0.00 cfs
Type II 24-hr 100-Year Rainfall=8.20"ST 2
Printed 10/19/2015Prepared by AMEC
Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Time span=0.00-20.00 hrs, dt=0.01 hrs, 2001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Peak Elev=505.63' Storage=22.942 af Inflow=283.94 cfs 44.603 afPond 8P: Sediment Basin (SB-3)
Primary=52.22 cfs 32.389 af Secondary=0.00 cfs 0.000 af Outflow=52.22 cfs 32.389 af
Peak Elev=502.73' Storage=3.734 af Inflow=126.84 cfs 8.377 afPond 37P: Sediment Basin (SB-4)
Primary=61.16 cfs 5.859 af Secondary=0.00 cfs 0.000 af Outflow=61.16 cfs 5.859 af
Type II 24-hr 100-Year Rainfall=8.20"ST 2
Printed 10/19/2015Prepared by AMEC
Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 8P: Sediment Basin (SB-3)
Inflow Area = 98.610 ac, 0.00% Impervious, Inflow Depth > 5.43" for 100-Year event
Inflow = 283.94 cfs @ 11.97 hrs, Volume= 44.603 af
Outflow = 52.22 cfs @ 15.93 hrs, Volume= 32.389 af, Atten= 82%, Lag= 237.4 min
Primary = 52.22 cfs @ 15.93 hrs, Volume= 32.389 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Starting Elev= 497.00' Surf.Area= 0.000 ac Storage= 0.000 af
Peak Elev= 505.63' @ 15.93 hrs Surf.Area= 6.822 ac Storage= 22.942 af
Plug-Flow detention time= 208.8 min calculated for 32.389 af (73% of inflow)
Center-of-Mass det. time= 145.0 min ( 953.5 - 808.5 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 61.472 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.870 0.000 0.000
502.00 2.940 4.762 4.762
504.00 5.330 8.270 13.032
506.00 7.160 12.490 25.522
508.00 8.940 16.100 41.622
510.00 10.910 19.850 61.472
Device Routing Invert Outlet Devices
#1 Primary 499.50'30.0" Round Culvert
L= 91.0' CPP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 499.50' / 496.00' S= 0.0385 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior, Flow Area= 4.91 sf
#2 Device 1 502.00'42.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=52.22 cfs @ 15.93 hrs HW=505.63' (Free Discharge)
1=Culvert (Inlet Controls 52.22 cfs @ 10.64 fps)
2=Orifice/Grate (Passes 52.22 cfs of 88.27 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 100-Year Rainfall=8.20"ST 2
Printed 10/19/2015Prepared by AMEC
Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 8P: Sediment Basin (SB-3)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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o
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(
c
f
s
)
300
250
200
150
100
50
0
Inflow Area=98.610 ac
Peak Elev=505.63'
Storage=22.942 af
283.94 cfs
52.22 cfs52.22 cfs
0.00 cfs
Type II 24-hr 100-Year Rainfall=8.20"ST 2
Printed 10/19/2015Prepared by AMEC
Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Summary for Pond 37P: Sediment Basin (SB-4)
Inflow Area = 16.815 ac, 0.00% Impervious, Inflow Depth > 5.98" for 100-Year event
Inflow = 126.84 cfs @ 11.99 hrs, Volume= 8.377 af
Outflow = 61.16 cfs @ 12.17 hrs, Volume= 5.859 af, Atten= 52%, Lag= 10.9 min
Primary = 61.16 cfs @ 12.17 hrs, Volume= 5.859 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 502.73' @ 12.17 hrs Surf.Area= 2.066 ac Storage= 3.734 af
Plug-Flow detention time= 132.7 min calculated for 5.859 af (70% of inflow)
Center-of-Mass det. time= 65.6 min ( 819.7 - 754.2 )
Volume Invert Avail.Storage Storage Description
#1 499.50' 37.962 af Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
499.50 0.370 0.000 0.000
502.00 1.560 2.413 2.413
504.00 2.950 4.510 6.923
506.00 4.390 7.340 14.262
508.00 6.010 10.400 24.662
510.00 7.290 13.300 37.962
Device Routing Invert Outlet Devices
#1 Primary 498.00'36.0" Round Culvert
L= 150.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 498.00' / 495.00' S= 0.0200 '/' Cc= 0.900
n= 0.012 Concrete pipe, finished, Flow Area= 7.07 sf
#2 Device 1 502.00'104.0" x 104.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#3 Secondary 508.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28)
Head (feet) 0.00 2.00
Width (feet) 10.00 50.00
Primary OutFlow Max=61.16 cfs @ 12.17 hrs HW=502.73' (Free Discharge)
1=Culvert (Inlet Controls 61.16 cfs @ 8.65 fps)
2=Orifice/Grate (Passes 61.16 cfs of 70.50 cfs potential flow)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=499.50' (Free Discharge)
3=Custom Weir/Orifice ( Controls 0.00 cfs)
Type II 24-hr 100-Year Rainfall=8.20"ST 2
Printed 10/19/2015Prepared by AMEC
Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC
Pond 37P: Sediment Basin (SB-4)
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
20191817161514131211109876543210
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o
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(
c
f
s
)
140
120
100
80
60
40
20
0
Inflow Area=16.815 ac
Peak Elev=502.73'
Storage=3.734 af
126.84 cfs
61.16 cfs61.16 cfs
0.00 cfs
REFERENCE 4

J.W. Faircloth & Son, Inc. “Determining the Skimmer Size and the Required Orifice for the
Faircloth Skimmer Surface Drain” Revised November 2007.

November 6, 2007 1
Determining the Skimmer Size
and the Required Orifice
for the
Faircloth Skimmer® Surface Drain
November 2007

Important note: The orifice sizing chart in the Pennsylvania Erosion
Control Manual and reproduced in the North Carolina Design Manual
DOES NOT APPLY to our skimmers. It will give the wrong size orifice
and not specify which size skimmer is required. Please use the
information below to choose the size skimmer required for the basin
volume provided and determine the orifice size required for the drawdown
time, typically 4-7 days in Pennsylvania and 3 days in North Carolina.

The size of a Faircloth Skimmer®, for example a 4” skimmer, refers to the maximum diameter of
the skimmer inlet. The inlet on each of the 8 sizes offered can be reduced to adjust the flow rate
by cutting a hole or orifice in a plug using an adjustable cutter (both supplied).

Determining the skimmer size needed and the orifice for that skimmer required to drain the
sediment basin’s volume in the required time involves two steps: First, determining the size
skimmer required based on the volume to be drained and the number of days to drain it; and
Second, calculate the orifice size to adjust the flow rate and “customize” the skimmer for the
basin’s volume. The second step is not always necessary if the flow rate for the skimmer with
the inlet wide open equals or is close to the flow rate required for the basin volume and the
drawdown time.

Both the skimmer size and the required orifice radius for the skimmer should be shown for each
basin on the erosion and sediment control plan. Make it clear that the dimension is either the
radius or the diameter. It is also helpful to give the basin volume in case there are questions.
During the skimmer installation the required orifice can be cut in the plastic plug using the
supplied adjustable cutter and installed in the skimmer using the instructions provided.

The plan review and enforcement authority may require the calculations showing that the
skimmer used can drain the basin in the required time.

Determining the Skimmer Size

Step 1. Below are approximate skimmer maximum flow capacities based on typical draw
down requirements, which can vary between States and jurisdictions and watersheds. If one 6”
skimmer does not provide enough capacity, multiple skimmers can be used to drain the basin.
For drawdown times not shown, multiply the 24-hour figure by the number of days required.

Example: A basin’s volume is 29,600 cubic feet and it must be drained in 3 days. A 3” skimmer
with the inlet wide open will work perfectly. (Actually, the chart below gives 29,322 cubic feet but
this is well within the accuracy of the calculations and the basin’s constructed volume.)
Example: A basin’s volume is 39,000 cubic feet and it must be drained in 3 days. The 3”
skimmer is too small; a 4” skimmer has enough capacity but it is too large, so the inlet will need
to be reduced using step 2 to adjust the flow rate for the basin’s volume. (It needs a 3.2”
diameter orifice.)

1½” skimmer: 1,728 cubic feet in 24 hours 6,912 cubic feet in 4 days
with a 1½” head 3,456 cubic feet in 2 days 12,096 cubic feet in 7 days
5,184 cubic feet in 3 days

2” skimmer: 3,283 cubic feet in 24 hours 13,132 cubic feet in 4 days
with a 2” head 6,566 cubic feet in 2 days 22,982 cubic feet in 7 days
9,849 cubic feet in 3 days

2½” skimmer: 6,234 cubic feet in 24 hours 24,936 cubic feet in 4 days
with a 2.5” head 12,468 cubic feet in 2 days 43,638 cubic feet in 7 days
Revised 11-6-07 18,702 cubic feet in 3 days

3” skimmer: 9,774 cubic feet in 24 hours 39,096 cubic feet in 4 days
with a 3” head 19,547 cubic feet in 2 days 68,415 cubic feet in 7 days
29,322 cubic feet in 3 days

4” skimmer: 20,109 cubic feet in 24 hours 80,436 cubic feet in 4 days
with a 4” head 40,218 cubic feet in 2 days 140,763 cubic feet in 7 days
Revised 11-6-07 60,327 cubic feet in 3 days

5” skimmer: 32,832 cubic feet in 24 hours 131,328 cubic feet in 4 days
with a 4” head 65,664 cubic feet in 2 days 229,824 cubic feet in 7 days
98,496 cubic feet in 3 days

6” skimmer: 51,840 cubic feet in 24 hours 207,360 cubic feet in 4 days
with a 5” head 103,680 cubic feet in 2 days 362,880 cubic feet in 7 days
155,520 cubic feet in 3 days

8” skimmer: 97,978 cubic feet in 24 hours 391,912 cubic feet in 4 days
with a 6” head 195,956 cubic feet in 2 days 685,846 cubic feet in 7 days
CUSTOM 293,934 cubic feet in 3 days
MADE BY ORDER CALL!

Determining the Orifice

Step 2. To determine the orifice required to reduce the flow rate for the basin’s volume and the
number of days to drain the basin, simply use the formula volume ÷ factor (from the chart
below) for the same size skimmer chosen in the first step and the same number of days. This
calculation will give the area of the required orifice. Then calculate the orifice radius using Area
= π r2 and solving for r, )14.3/(Arear=.The supplied cutter can be adjusted to this radius to
cut the orifice in the plug. The instructions with the plug and cutter has a ruler divided into tenths
of inches. Again, this step is not always necessary as explained above.

An alternative method is to use the orifice equation with the head for a particular skimmer
shown on the previous page and determine the orifice needed to give the required flow for the
volume and draw down time. C = 0.59 is used in this chart.

Example: A 4” skimmer is the smallest skimmer that will drain 39,000 cubic feet in 3 days but a
4” inlet will drain the basin too fast (in 1.9 days) To determine the orifice required use the factor
of 4,803 from the chart below for a 4” skimmer and a drawdown time of 3 days. 39,000 cubic

November 6, 2007 2
feet ÷ 4,803 = 8.12 square inches of orifice required. Calculate the orifice radius using Area = π
r2 and solving for r, )14.3/12.8(=r and r = 1.61”. As a practical matter 1.6” is about as close
as the cutter can be adjusted and the orifice cut..

Factors (in cubic feet of flow per square inch of opening through a round orifice with the head
for that skimmer and for the drawdown times shown) for determining the orifice radius for a
basin’s volume to be drained. This quick method works because the orifice is centered and has
a constant head (given above in Step 1).

1½” skimmer: 960 to drain in 24 hours 3,840 to drain in 4 days
1,920 to drain in 2 days 6,720 to drain in 7 days
2,880 to drain in 3 days

2” skimmer: 1,123 to drain in 24 hours 4,492 to drain in 4 days
2,246 to drain in 2 days 7,861 to drain in 7 days
3,369 to drain in 3 days

2½” skimmer: 1,270 to drain in 24 hours 5,080 to drain in 4 days
Revised 11-6-07 2,540 to drain in 2 days 8,890 to drain in 7 days
3,810 to drain in 3 days

3” skimmer: 1,382 to drain in 24 hours 5,528 to drain in 4 days
2,765 to drain in 2 days 9,677 to drain in 7 days
4,146 to drain in 3 days

4” skimmer: 1,601 to drain in 24 hours 6,404 to drain in 4 days
Revised 11-6-07 3,202 to drain in 2 days 11,207 to drain in 7 days
4,803 to drain in 3 days

5” skimmer: 1,642 to drain in 24 hours 6,568 to drain in 4 days
3,283 to drain in 2 days 11,491 to drain in 7 days
4,926 to drain in 3 days

6” skimmer: 1,814 to drain in 24 hours 7,256 to drain in 4 days
3,628 to drain in 2 days 12,701 to drain in 7 days
5,442 to drain in 3 days

8” skimmer: 1,987 to drain in 24 hours 7,948 to drain in 4 days
3,974 to drain in 2 days 13,909 to drain in 7 days
5,961 to drain in 3 days

J. W. Faircloth & Son, Inc.
Post Office Box 757
412-A Buttonwood Drive
Hillsborough, North Carolina 27278
Telephone [phone] FAX [phone]
FairclothSkimmer.com [e-mail]

Orifice sizing Revised 2-2-01; 3-3-05; 2-1-07; 11-6-07

November 6, 2007 3
REFERENCE 5

Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency
Estimates”, NOAA National Weather Service, obtained September 15, 2014.

Precipitation Frequency Data Server
Page 1 of 3
NOAA Atlas 14, Volume 2, Version 3
Location name: Eden, North Carolina, US"
Latitude: 36.4999°, Longitude:-79.7013°
Elevation: 582 ft*
* source: Google Maps "*�,�,,.t
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based
point precipitation frequency estimates with 90% confidence intervals (in inches)'
Average recurrence interval (years)
Duration
���
10
25
50
100
200
500
1000
0.363
0.433
0.512
0.567
0.633
0.676
0.717
0.754
0.796
0.826
5-min
(0.331-0.397)
(0.396-0.473)
(0.467-0.560)
(0.518-0.619)
(0.575-0.688)
(0.612-0.735)
(0.646-0.781)
(0.676-0.822)
(0.708-0.869)
(0.729-0.902)
0.579
0.692
0.820
0.908
1.01
1.08
1.14
1.20
1.26
1.30
10-min
(0 .529-0.634)
(0.633-0.757)
(0.749-0.898)
(0.829-0.991)
(0.917-1.10)
(0.974-1.17)
1 (1.03-1.24)
1 (1.07-1.30)
1 (1.12-1.38)
0.724
0.870
1.04
1.15
1.28
1.36
1.44
1.51
1.59
1.63
15-min
(0.661-0.792)
(0.796-0.951)
(0.947-1.14)
1 (1.05-1.25)
1 (1.16-1.39)
1 (1.23-1.48)
1 (1.30-1.57)
1 (1.35-1.64)
1 (1.41-1.73)
1 (1.44-1.78)
0.993
1.20
1.47
1.66
1.89
2.05
2.21
2.35
2.52
2.64
30-min
(0.906-1.09)
1 (1.10-1.31)
1 (1.35-1.61)
1 (1.52-1.82)
1 (1.72-2.06)
(1.86-2.23)
(1.99-2.40)
(2.11-2.56)
(2.24-2.75)
(2.33-2.89)
1.24
1.51
1.89
2.17
2.52
2.78
3.04
3.29
3.62
3.86
60-min
(1.13-1.35)
(1.38-1.65)
(1.73-2.07)
(1.98-2.36)
(2.29-2.74)
(2.52-3.03)
(2.74-3.31)
(2.95-3.59)
(3.22-3.95)
(3.41-4.22)
1.47
1.79
2.25
2.61
3.08
3.45
3.83
4.20
4.71
5.10
2-hr
(1.35-1.61)
(1.63-1.96)
(2.06-2.46)
(2.38-2.85)
(2.80-3.36)
(3.12-3.75)
(3.44-4.16)
(3.75-4.57)
(4.15-5.12)
(4.45-5.56)
1.59
1.93
2.44
2.82
3.33
3.73
4.13
4.54
5.08
5.50
3-hr
(1.46-1.73)
(1.78-2.11)
(2.24-2.66)
(2.58-3.07)
(3.03-3.62)
(3.38-4.04)
(3.72-4.48)
(4.06-4.92)
( 4.49-5.52)
( 4.81-5.98)
1.96
2.37
2.99
3.48
4.15
4.70
5.28
5.87
6.71
7.38
6-hr
(1.80-2.15)
(2.18-2.61)
(2.74-3.27)
(3.17-3.80)
(3.76-4.53)
(4.22-5.12)
(4.70-5.73)
(5.18-6.37)
(5.82-7.29)
(6.31-8.02)
2.36
2.87
3.63
4.26
5.15
5.89
6.70
7.56
8.81
9.84
12-hr
(2.17-2.59)
(2.63-3.14)
(3.32-3.96)
(3.88-4.62)
(4.65-5.57)
(5.28-6.37)
(5.94-7.21)
(6.62-8.12)
(7.57-9.48)
(8.31-10.6 )
2.81
3.40
4.33
5.10
6.22
7.17
8.20
9.32
11.0
12.4
24-hr
(2.61-3.04)
(3.16-3.68)
(4.02-4.67)
(4.72-5.48)
(5.72-6.68)
(6.55-7.69)
(7.44-8.79)
(8.39-10.0)
(9.74-11.8)
(10.9-13.3)
3.30
3.99
5.04
5.90
7.12
8.13
9.21
10.4
12.0
13.4
2-day
(3.08-3.55)
(3.72-4.30)
(4.70-5.42)
(5.48-6.33)
(6.59-7.63)
(7.48-8.71)
(8.42-9.88)
(9.40-11.1 )
( 10.8-13.0 )
( 11.9-14.5 )
3.49
4.22
5.33
6.23
7.52
8.59
9.72
10.9
12.7
14.2
3-day
(3.26-3.76)
(3.93-4.55)
(4.96-5.73)
(5.79-6.69)
(6.95-8.07)
(7.89-9.21)
(8.88-10.4)
(9.92-11.8)
(11.4-13.7)
( 12.6-15.3)
3.68
4.45
5.61
6.56
7.92
9.04
10.2
11.5
13.4
14.9
4-day
(3.43-3.97)
(4.15-4.80)
(5.23-6.05)
(6.10-7.06)
(7.32-8.51)
(8.31-9.71)
(9.35-11.0)
(10.4-12.4)
(12.0-14.4)
(13.2-16.1)
4.22
5.07
6.29
7.29
8.71
9.88
11.1
12.4
14.3
15.9
7-day
(3.96-4.51)
(4.75-5.42)
(5.89-6.72)
(6.81-7.78)
(8.11-9.28)
(9.14-10.5)
(10.2-11.9)
( 11.4-13.3)
( 12.9-15.3)
( 14.2-17.0)
4.77
5.71
7.01
8.0 6
10.7
12.0
13.3
15.1
16.6
10-day
��69.53
(4.48-5.10 )
(5.37-6.10)
(6.58-7.48 )
(7.55-8.60)
(8.89-10.2 )
(9.96-11.4)
(11.1-12.8)
(12.2-14.2)
(13.8-16.2)
(15.0-17.8)
6.43
7.65
9.20
10.4
12.1
13.4
14.7
16.1
17.9
19.3
20-day
(6.05-6.85)
(7.21-8.16)
(8.66-9.81)
(9.79-11.1)
(11.3-12.9)
(12.5-14.3)
(13.7-15.7)
(14.9-172)
(16.4-19.2)
(17.6-20.8)
30-day
7.95
9.40
11.1
12.3
14.0
15.3
16.5
17.7
19.3
20.5
(7.53-8.41)
(8.91-9.94)
(10.5-11.7)
(11.7-13.0)
(13.2-14.8)
(14.4-16.2)
(15.5-17.5)
(16.6-18.8)
(18.0-20.5)
(19.0-21.9)
45-day
10.0
11.8
13.7
15.2
17.1
18.5
19.8
21.1
22.8
24.0
(9.48-10.6)
(11.2-12.5)
(13.0-14.5)
(14.4-16.0)
(16.1-18.0)
(17.4-19.5)
(18.6-21.0)
(19.8-22.4)
(21.3-24.2)
(22.3-25.6)
12.0
14.0
16.1
17.7
19.7
21.2
22.6
23.9
25.6
26.8
60-day
( 114-12.6) 1
(13.4-14.8) 1
U-15-3-1-7.0) I
(16.8-18.6) 1
U-18-7-2-o.7) 1
(20.0-22.3) 1
U-21-3-2-3.8) 1
(22.5-25.2) J
(24.0-27.1) 11
(25.1-28.4)
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90 % confidence interval. The probability that precipitation frequency estimates (for a
given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5 % . Estimates at upper bounds are not
checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
Page 2 of 3
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— 30-min —
7-4ay
— Btr-cnin —
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— 2-11"lr —
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— 34il —
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— "t —
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http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Precipitation Frequency Data Server
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hvdroloaic Develooment
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions(a)noaa.aov
Disclaimer
http://hdsc.nws.noaa.gov/hdse/pfds/pfds printpage.html?lat=3 6.4999&lon=-79.7013 &data... 9/15/2014

Energy Dissipater and Stone Gabion Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 1 of 4
12/9/2016 (Initial submittal)

Calculation Title:
Energy Dissipater and Stone Gabion Calculation
Summary:
The energy dissipaters and stone gabion mattresses were designed for stability and capacity
for a Type II 100-year, 24-hour design storm event of 8.20 inches while maintaining channel
lining stability.

Notes:

Revision Log:
No. Description Originator Verifier Technical Reviewer
0

Initial submittal –
12/9/2016

Chris Jordan Stephanie Stanwick Cedric H. Ruhl

Energy Dissipater and Stone Gabion Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 2 of 4
12/9/2016 (Initial submittal)

OBJECTIVE:
The objective of this calculation is to design riprap energy dissipaters and stone gabions that will
be constructed during decommissioning of the Primary and Secondary Ash Basin dams at Duke
Energy’s Dan River Steam Station.
METHOD:
The riprap energy dissipaters and stone gabions were designed for a 100-year storm event in
accordance with the North Carolina Department of Environment and Natural Resources
(NCDENR) “Erosion and Sediment Control Planning and Design Manual”.
DEFINITION OF VARIABLES:
A = drainage area;
AC = cross-section area of flow through channel;
b = bottom width of flow through channel;
d = depth of flow through channel;
D0 = bottom width or diameter;
d50 = minimum riprap size;
dmax = maximum riprap size;
CN = curve number;
D = channel depth;
i = rainfall depth;
La = minimum apron length;
W = downstream apron width;
n = Manning’s roughness co-efficient for flow through channel;
P = wetted perimeter of flow through channel;
Q = discharge flow;
R = hydraulic radius of flow through channel;
S = longitudinal slope of the channel flow;
T = top width of flow through channel;
V = velocity of flow through channel; and
Z = channel side slope.
CALCULATIONS:
1.0 Design riprap energy dissipaters
Riprap energy dissipaters will be located at the outlet of slope drains and culverts that convey
stormwater flow from upstream tributary areas to the footprint of the decommissioned
impoundment. The 48-inch diameter culvert, 54-inch diameter culvert, and 36-inch diameter slope
drain all discharge directly to a longitudinal ditch with riprap lining and are designed in the “Final
Conditions Stormwater Calculation”. Peak flows to each dissipater were calculated for a 100-year,
24 hour design storm event.

Riprap energy dissipaters for minimum tailwater conditions were calculated as follows:

Energy Dissipater and Stone Gabion Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 3 of 4
12/9/2016 (Initial submittal)

𝑃𝑚𝑟𝑟𝑟𝑍𝑍𝑚 𝐴𝑚𝑟𝑚𝑚 𝑃�ℎ𝑍𝑟�=3𝐷0

𝑃=𝐷0 +𝐿𝑎

Riprap energy dissipaters for maximum tailwater conditions were calculated as follows:

𝑃𝑚𝑟𝑟𝑟𝑍𝑍𝑚 𝐴𝑚𝑟𝑚𝑚 𝑃�ℎ𝑍𝑟�=3𝐷0

𝑃=𝐷0 +0.4𝐿𝑎

Apron Thickness is calculated as follows:

𝐴𝑚𝑟𝑚𝑚 𝑃𝑖ℎ𝑍𝑘𝑚𝑍𝑟𝑟=1.5𝑍𝑚𝑎𝑥

The riprap energy dissipaters will have the dimensions shown in the following table:

Outlet ID Dissipater ID Tailwater
Condition
Discharge
(cfs)
Diameter
{D0}
(in)
Minimum
Riprap Size
{d50}
(in)
[Ref. 1]
Selected
Riprap Class
[Ref. 2]
Maximum
Riprap Size
{dmax}
(in)
[Ref. 2]
Apron
Thickness
(in)
Minimum Apron
Length
{La}
(ft)
[Ref. 1]
Upstream Apron
Width
(ft)
[Ref. 1]
Downstream
Apron Width
{W}
(ft)
[Ref. 1]
SD-4 RD-1 minimum 12.2 18 7.2 B 10.8 16.2 16 4.5 17.5
SD-5 RD-2 minimum 16.6 36 7.2 B 10.8 16.2 20 9 12
SD-6 RD-2 minimum 9.6 18 4.8 B 7.2 10.8 12 4.5 13.5
SD-7 RD-3 minimum 4.2 18 4.8 B 7.2 10.8 12 4.5 13.5
Table 1: Riprap Energy Dissipater Dimensions

2.0 Design gabion outlet protection
Four gabions will be constructed to convey stormwater flow from the footprint of the
decommissioned impoundment to the Dan River. The gabion mattresses were analyzed for
capacity as a rectangular channel using Manning’s equation and the discharge from the “Outlet
Channel Calculation” package as the peak runoff.

2.1 Gabion Capacity
The gabion mattress capacity was assumed to be a rectangular channel with dimensions as
presented in the following table:
Gabion ID
Bottom Width
{b}
(ft)
MIN. Depth
{D}
(ft)
Left Side Slope
{Z1H:V}
Right
Side
Slope
{Z2H:V}
Top
Width
{T}
(ft)
Upstream
Invert
(ft)
Downstream
Invert
(ft)
Length
{L}
(ft)
Longitudinal
Slope
{S}
(ft/ft)
G-1 15 1.5 0 0 15 497.0 480 38 0.447
G-2 21 2 0 0 21 496.0 480 33 0.485
G-3 21 1.5 0 0 21 497.0 480 27 0.630
G-4 15 2 0 0 15 495.0 480 15 1.000
Table 2: Gabion Mattress Dimensions

The capacity of each gabion was evaluated using Manning’s equation [Ref. 1] as presented in the
following equation:
Energy Dissipater and Stone Gabion Calculation Dam Decommissioning Plan
Duke Energy – Dan River Steam Station

Amec Foster Wheeler Project No. 7810-14-0065 4 of 4
12/9/2016 (Initial submittal)

𝑃=1.49
𝑚𝑃2/3 𝑃1/2
Where n is Manning’s coefficient, R is hydraulic radius and S is the longitudinal slope of
the stormwater flow.
The total discharge was given by:
𝑃=𝐴𝐶𝑃
The flow cross-section area “AC” and wetted perimeter “P” were calculated based on the
geometry of a trapezoidal channel with a flow depth “d”, bottom width “b”, left side slope
“Z1”, and right side slope “Z2”, using the following relationships:

𝐴𝐶=𝑍𝑍+0.5𝑍1 𝑍2 +0.5𝑍2 𝑍2
𝑃=𝑍+√[(𝑍1 𝑍)2 +𝑍2 ]+√[(𝑍2 𝑍)2 +𝑍2 ]
Each gabion was assumed to have rip-rap lining and was evaluated in flow capacity for the 100-
year, 24-hour design storm event. The trial flow depth and Manning’s n were iteratively modified
until the channel capacity exceeded the predicted peak runoff for the conditions modeled. Gabion
capacity estimated for the channel grade is shown in the following table:

Gabion
ID
Channel
Lining
Manning's
n
{n}
Trial Flow
Depth
{d}
(ft)
Flow
Area
{A}
(ft2)
Wetted
Perimeter
{P}
(ft)
Hydraulic
Radius
{R}
(ft)
Velocity
{V}
(ft/s)
Channel
Capacity
{Q}
(cfs)
Peak
Runoff
{Q}
(cfs)
Channel Capacity > Peak
Runoff?
Freeboard
(in)
G-1 rip rap 0.03 0.26 3.9 15.5 0.3 13.2 51.45 49.75 yes 14.9
G-2 rip rap 0.03 0.58 12.2 22.2 0.5 23.1 281.88 280.99 yes 17.0
G-3 rip rap 0.03 0.43 9.0 21.9 0.4 21.8 196.86 190.27 yes 12.8
G-4 rip rap 0.03 0.28 4.2 15.6 0.3 20.7 86.89 81.99 yes 20.6
Table 3: Gabion Mattress - 100 years Long-Term Conditions

The hydraulic analyses indicate that the gabion outlets have capacity to pass the 100-year, 24-
hour design storm.
DISCUSSION:
The energy dissipaters and stone gabion mattresses for the Dan River dam decommissioning
were designed for stability and capacity for a Type II 100-year, 24-hour design storm event of
8.20 inches while maintaining channel lining stability.
REFERENCES:
1. North Carolina Department of Environment and Natural Resources, “Erosion and
Sediment Control Planning and Design Manual”, Revised May 2013.
2. North Carolina Department of Transportation. Standard Specification for Roads and
Structures. Raleigh, 2012.
REFERENCE 1

North Carolina Department of Environment and Natural Resources, “Erosion and
Sediment Control Planning and Design Manual”, Revised May 2013.

Appendices
8.05.5
8
8.05.6 Rev. 12/93
Design Procedure-
Permissible Velocity
The following is a step-by-step procedure for designing a runoff conveyance
channel using Manning’s equation and the continuity equation:
Step 1. Determine the required flow capacity, Q, by estimating peak runoff
rate for the design storm (Appendix 8.03).
Step 2. Determine the slope and select channel geometry and lining.
Step 3. Determine the permissible velocity for the lining selected, or the
desired velocity, if paved. (see Table 8.05a, page 8.05.4)
Step 4. Make an initial estimate of channel size—divide the required Q by the
permissible velocity to reach a “first try” estimate of channel flow area. Then
select a geometry, depth, and top width to fit site conditions.
Step 5. Calculate the hydraulic radius, R, from channel geometry (Figure
8.05b, page 8.05.5).
Step 6. Determine roughness coefficient n.
Structural Linings—see Table 8.05b, page 8.05.6.
Grass Lining:
a. Determine retardance class for vegetation from Table 8.05c, page
8.05.8. To meet stability requirement, use retardance for newly
mowed condition (generally C or D). To determine channel capacity,
use at least one retardance class higher.
b. Determine n from Figure 8.05c, page 8.05.7.
Step 7. Calculate the actual channel velocity, V, using Manning’s equation
(Figure 8.05a, pg. 8.05.3), and calculate channel capacity, Q, using the
continuity equation.
Step 8. Check results against permissible velocity and required design
capacity to determine if design is acceptable.
Step 9. If design is not acceptable, alter channel dimensions as appropriate.
For trapezoidal channels, this adjustment is usually made by changing the
bottom width.
Table 8.05b
Manning’s n for Structural
Channel Linings
Channel Lining
Recommended
n values
Asphaltic concrete, machine placed
Asphalt, exposed prefabricated
Concrete
Metal, corrugated
Plastic
Shotcrete
Gabion
Earth
0.014
0.015
0.015
0.024
0.013
0.017
0.030
0.020
Source: American Society of Civil Engineers (modified)
Appendices
Rev. 12/93 8.06.3
8
8.06.4 Rev. 12/93
REFERENCE 2

North Carolina Department of Transportation. Standard Specification for Roads and Structures.
Raleigh, 2012.
Section 1043

10-62
All stone shall meet the approval of the Engineer. While no specific gradation is required, 1
there shall be equal distribution of the various sizes of the stone within the required size 2
range. The size of an individual stone particle will be determined by measuring its long 3
dimension. 4
Stone or broken concrete for rip rap shall meet Table 1042-1 for the class and size 5
distribution. 6
TABLE 1042-1
ACCEPTANCE CRITERIA FOR RIP RAP AND STONE FOR EROSION CONTROL
Required Stone Sizes, inches Class Minimum Midrange Maximum
A 2 4 6
B 5 8 12
1 5 10 17
2 9 14 23
No more than 5.0% of the material furnished can be less than the minimum size specified nor 7
no more than 10.0% of the material can exceed the maximum size specified. 8
SECTION 1043 9
AGGREGATE FROM CRUSHED CONCRETE 10
1043-1 GENERAL 11
Aggregate from crushed concrete is a recycled product made by crushing concrete obtained 12
from concrete truck clean out, demolition of existing concrete structures or pavement, or 13
similar sources and transported from a crushing facility. It does not include concrete 14
pavements that are rubblelized, broken or otherwise crushed in place on the roadway. 15
The crushed material must meet all sources approval requirements described in Sections 1005 16
and 1006 with the exception of the sodium sulfate test requirement. Deleterious materials 17
shall not be more than 3%. 18
Sampling and acceptance for the determination of gradaction, LL and PI will be performed as 19
described in the Aggregate QC/QA Program Manual and the Aggregate Sampling Manual. 20
1043-2 AGGREGATE BASE COURSE 21
The material shall meet the ABC gradation. The LL of the material shall be raised 5 points to 22
no more than 35. 23
1043-3 AGGREGATE SHOULDER BORROW 24
The material shall meet Section 1019. 25
1043-4 CLEAN COARSE AGGREGATE FOR ASPHALT 26
The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 27
shall be approved by the Engineer, and the mix shall meet all requirements. 28
1043-5 CLEAN COARSE AGGREGATE FOR CONCRETE 29
The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 30
is restricted to Class B concrete mixes only. Use of the material shall be approved by the 31
Engineer, and the concrete shall meet all requirements. 32
SECTION 1044 33
SUBSURFACE DRAINAGE MATERIALS 34
1044-1 SUBDRAIN FINE AGGREGATE 35
Subdrain fine aggregate shall meet No. 2S or 2MS in Table 1005-2. 36
NCDOT 2012 Standard Specifications
err7[
for ter
M ieeier
AMEC Design Calculation or Analysis Cover Sheet
Project
Duke Energy Coal Combustion Residual Management Program
CalciAnalysis No.
AMEC Project No.
Reconstitution Design of Ash Basins - Dan River Steam Station
H-001
7810-14-0150
Title
Primary (ROCK]-237-H) and Secondary (ROCKI-238-H) Ash Ponds
- Hydrologic and Hydraulic (H&H) Analysis
Computer Software and Version No.
HydroCADTm
Purpose and Objective
Hydrologic and Hydraulic (H&H) Analysis to assess if the combined spillway capacity is sufficient to pass the inflow
design flood (IDF) in a safe and non -erosive manner while maintaining required freeboard and without overtopping the
embankment. The IDF hydrograph shall be calculated as the flow resulting from the design flood storm event falling on
the watershed upstream of the impoundment and the impoundment itself and process flows.
Summary of Conclusion
Based on the results of this study and assumptions made, AMEC concludes that bath the Primary and Secondary Ash
Ponds have sufficient hydraulic capacity to safety store/pass the 3/4 PMP design storm in a safe and non -erosive
manner. Both the Primary and Secondary Ash Ponds pass the design storm without overtopping the embankment in
accordance with the design criteria presented in the North Carolina Administrative Code and Duke's Programmatic
Document. The Primary Ash Pond will have 0.66 feet of freeboard and the Secondary Ash Pond will have 5.56 feet of
freeboard based on the hydraulic capacity analyses. The majority of the Primary Ash Pond dike is at elevation 540
and the maximum water surface is more than 8 feet below this elevation which means that the water surface is shielded
from wind -generated wave setup and run-up by the surrounding dike. The Secondary Ash Pond is shielded from direct
wind action by adjacent landforms (the ash stack and the Primary Ash Pond) and the maximum water surface is over
6 feet below the lowest point on the dike, therefore wind -generated wave run-up and setup is not applicable. The
existing spillways for the Primary and Secondary Ash Ponds will discharge 80% of the inflow from the design storm
within 15 days of the peak.
Revision Log
Rev.
Revision Description:
No.
0
Initial Issue
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Rev.
Originator (Print) ` �' '.,
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Independent Technical Reviewer (Print)
No.
Richard L Hiner w
Joshua M. Bell, ?F,,CFM
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TABLE OF CONTENTS

Section
Page
1. EXECUTIVE SUMMARY ...................................................................................................................... 3
2. SCOPE OF INVESTIGATION ................................................................................................................ 4
3. ASSUMPTIONS .................................................................................................................................. 5
4. COMPUTER PROGRAM IDENTIFICATION .......................................................................................... 5
5. DESCRIPTION OF FACILITIES AND POTENTIALLY IMPACTED AREA ................................................... 6
6. CALCULATION APPROACH AND INPUT ........................................................................................... 10
7. SUMMARY OF METHODS AND APPROACH ..................................................................................... 14
8. CONCLUSIONS AND DISCUSSIONS .................................................................................................. 16
9. REFERENCES .................................................................................................................................... 18
10. ABBREVIATIONS .............................................................................................................................. 19

Tables
Table 1 – Administrative Information - Primary (ROCKI-237-H) Ash Basin & Dam
Table 2 – Administrative Information - Secondary (ROCKI-238-H) Ash Basin & Dam
Table 3 – Stage-Storage Data for Dry Fly Ash Basin
Table 4 – Stage-Storage Data for Primary (ROCKI-237-H) Ash Basin
Table 5 – Stage-Storage Data for Secondary (ROCKI-238-H) Ash Basin
Table 9 – HydroCAD™ Model Inputs for Dry Fly Ash Basin
Table 10 –HydroCAD™ Model Inputs for Primary (ROCKI-237-H) Ash Basin
Table 11 –HydroCAD™ Model Inputs for Secondary (ROCKI-238-H) Ash Basin
Table 12 –HydroCAD™ Output Summary for the Dry Fly Ash, Primary (ROCKI-237-H) Ash, and
Secondary (ROCKI-238-H) Ash Basins

Figures
Figures 1a & 1b – Scaled Topographic Map of the Contributing Watersheds
Figure 2 – Basin Contours - Primary (ROCKI-237-H) and Secondary (ROCKI-238-H) Ash Basins
Figures 3a & 3b – Soil Map - Primary (ROCKI-237-H) and Secondary (ROCKI-238-H) Ash Basins

Appendix
15A NCAC 2K .0205 – Spillway Design
Time of Concentration Calculations
SCS Type II 6-hour Rainfall Distribution
Curve Number Calculations
Stage-Storage Calculations
Stage-Discharge Calculations
Rainfall Reference for PMP (Figure 18 from HMR51)
HydroCAD™ Output for ¾ PMP Analysis
PREPARED
BY
DATE CHECKED
BY
DATE JOB NUMBER 7810-14-0150
Source: USDA-NRCS Digital Raster Graph Mosaic, dated 2007.
ST770
ST87
£¤311
Rockingham County
NN OO RR TT HH CC AA RR OO LL II NN AA
VV II RR GG II NN II AA
Eden
Sources: Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO,
USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey,
Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, ©
OpenStreetMap contributors, and the GIS User Community
DAN RIVER ASH PLANT - DUKE ENERGYEDEN, NORTH CAROLINA
±
JMS 8/31/2016 RLH 8/31/2016
EXHIBIT 1PROJECT LOCATION
^_
NORTH CAROLINA
Copyright:© 2013 National
Geographic Society, i-cubed
Project Location
0 10,000 20,0005,000
Feet
ASH BASIN
Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 3 of 20

RCN: BFHR-0084.0

1. EXECUTIVE SUMMARY

The Primary (ROCKI-237-H) and Secondary (ROCKI-238-H) Ash Basins at the Duke Energy Dan
River Steam Station are considered to be large high-hazard structures (based on the existing
NCDENR hazard-rating criteria). The Primary (ROCKI-237-H) Ash Basin Dam was originally
constructed in 1951 and was modified in 1968. It is a 40-foot high earthen dam and the reservoir
has a normal surface area of approximately 7.40 acres (at elevation 532) and a maximum
hydraulic storage capacity of approximately 37 acre-feet (at elevation 532). The Secondary
(ROCKI-238-H) Ash Basin Dam was constructed in 1976. It is a 30-foot high earthen dam and
the reservoir has a normal surface area of approximately 4.83 acres (at elevation 515) and a
maximum hydraulic storage capacity of approximately 130.16 acre-feet (at elevation 528.52). The
purpose of this report is to demonstrate compliance with Section 15A of the North Carolina
Administrative Code, Subchapter 2K, section .0205 (15A NCAC 2K .0205) with regards to spillway
capacity (Part .0205 is excerpted in the Appendix). This report summarizes the methodology and
results of the ¾ PMP spillway analysis completed for the Primary (ROCKI-237-H) and Secondary
(ROCKI-238-H) Ash Basin Dams. Data for the hydrologic and hydraulic analyses were obtained
from a combination of publicly available information, information provided by Duke Energy, and
field data collection.

Design documentation indicates that the constructed top-widths of both the Primary (ROCKI-237-
H) and Secondary (ROCKI-238-H) Ash Basin Dams are 15 feet. The original design crest
elevations were approximately 540 feet (Primary – ROCKI-237-H) and 530 feet (Secondary –
ROCKI-238-H). According to recent survey data, in the lowest point on the current crest of the
Secondary Ash Pond Dam is at elevation 528.52 and the dike breech area for the Primary Ash
Pond Dike is at elevation 532 (the remainder of the Primary Ash Pond Dam is at approximately
elevation 540). The design side slopes are 2 foot horizontal to 1 foot vertical (2H:1V) on the
interior and 2H:1V on the exterior for both structures. The maximum height of the Primary
(ROCKI-237-H) and Secondary (ROCKI-238-H) Ash Basin Dams are 40 feet and 30 feet,
respectively, measured from the crest to the downstream toe. The hydrologic design criterion for
both structures is three-quarters of the Probable Maximum Precipitation (¾ PMP) for the spillway
design flood.

The hydrologic analysis of the ¾ PMP storm was completed using HydroCAD™ 10.0, Build 18.
Basin areas, land use classifications, soil hydrologic groups, flow lines, and topographical
information were obtained for the Primary (ROCKI-237-H) and Secondary (ROCKI-238-H) Ash
Basin dam watersheds. The Full PMP event for the 6-hour duration at this location was
interpolated as 29.2 inches according to Hydro-Meteorological Report No. 51 (HMR-51) issued
by the National Weather Service in June, 1978. A 6-hour, ¾ PMP storm of 21.9 inches (29.2*0.75)
was used in this analysis. Based on the project location and using Figure B-2 from Appendix B
of the TR-55 manual, an SCS Type II rainfall distribution was used for this analysis. This rainfall
distribution concentrates the bulk of the rainfall in the ½ hour surrounding the center of the storm
duration (between 2:45 and 3:15). This distribution was developed by the Natural Resource
Conservation Service (NRCS, formerly SCS) in 1986 and is a synthetic distribution based on
observed precipitation events.

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 4 of 20

The following analysis demonstrates that the existing spillway system meets the requirements of
15A NCAC 2K .0205. The Primary (ROCKI-237-H) Ash Basin Dam is not overtopped during the
¾ PMP storm event. No emergency spillway is required for the Primary (ROCKI-237-H) Ash
Basin Dam. Therefore, the frequency of use requirements in 15A NCAC .0205 (b) are not
applicable to this facility.

The analysis also demonstrates that the Secondary (ROCKI-238-H) Ash Basin Dam is not
overtopped during the ¾ PMP storm event. Both the Primary (ROCKI-237-H) Ash Basin and the
Dry Fly Ash Basin discharge directly into the Secondary (ROCKI-238-H) Ash Basin and the
existing principal spillway meets the requirements of 15A NCAC 02K .0205. The dam is not
overtopped in the ¾ PMP design storm event and no emergency spillway is required for the
Secondary (ROCKI-238-H) Ash Basin Dam. Therefore, the frequency of use requirements in 15A
NCAC .0205 (b) are not applicable to this facility.
2. SCOPE OF INVESTIGATION
AMEC performed the analysis of the Primary (ROCKI-237-H) and Secondary (ROCKI-238-H) Ash
Basins to determine whether the existing spillway systems can safely pass the ¾ PMP event in
compliance with 15A NCAC 2K .0205. Topographic information showing the current configuration
of the interior of the ash basins was available from Duke Energy. The remaining contour data for
the ash basin watersheds was developed for this analysis using a combination of LiDAR (Light
Detection And Ranging) data and data from WSP Sells.
The analysis of the Primary (ROCKI-237-H) and Secondary (ROCKI-238-H) Ash Basins for the
¾ PMP event was performed using HydroCAD™ and included the Primary (ROCKI-237-H)
and Secondary (ROCKI-238-H) Ash Basins, the associated spillway/outfall structures,
and the Dry Fly Ash Basin. No analysis of downstream structures or inundation was
performed was performed for the Dan River as part of this analysis. The rainfall depth for the
design event was obtained by determining the PMP event from the HMR 51 and multiplying
it by 0.75. Lesser storms (500-yr, 100-yr, etc.) were not analyzed as part of this task.
The contributing drainage areas for the Primary (ROCKI-237-H) and Secondary (ROCKI-238-H)
Ash Basins were determined using a combination of topographic information developed for Duke,
recent bathymetric data for the Secondary Ash Basin, recent topo of the stack area within the
Primary Ash Basin, and LiDAR data as necessary to fill in any missing areas. A detailed
survey was not performed for the remainder of the contributing watershed as part of this contract.
The stage-storage information for the basins was determined from the topographic data provided
by Duke Energy as part of this contract. The stage-discharge relationship was calculated
dynamically within the HydroCAD program based on the structure data from the original design
drawings.
The following deliverables were prepared and are included in this report:
 Scaled topographic map of the contributing watershed;
 Time-of-concentration calculations;
 Curve number calculations;

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 5 of 20

 Rainfall reference information for PMP (HMR 51); and
 Stage-storage and stage-discharge calculations.
3. ASSUMPTIONS
For the analysis of the secondary ash pond, a number of assumptions have been established and
are listed below.
 The normal pool level of the secondary pond has been lowered to elevation 514 to
improve the stability of the dam structure and to provide additional storage during the
design event.
 The stage-storage information for the Secondary Ash Pond is based on previously
provided aerial topographic data and new bathymetric survey information obtained as
part of the plan to lower the operating water level (OWL) in the Secondary Pond.
 The discharge structure input data for the Secondary Ash Pond is based on original
design drawings for the spillway as well as previously provided survey information and
the stage-discharge relationship is computed dynamically within the HydroCAD program.

For the analysis of the primary ash pond, a number of additional assumptions have been
established and are listed below.
 The normal pool level of the primary pond can be lowered to provide additional storage
during the design event.
 The elevation of the containment dike at the breach can be raised to contain the peak
stage during the ¾ PMP event.
 The stage-storage information for the primary ash pond is based on topographic survey
information obtained for and used in the previously approved report (3/4 PMP Spillway
Capacity Analysis for Primary (ROCKI-237-H) Ash Pond Dam and Secondary (ROCKI-
238-H) Ash Pond Dam) in addition to topographic information obtained following the
failure of the pipe under the primary ash pond.
 The discharge structure input data for the Primary Ash Pond is based on original design
drawings for the spillway as well as previously provided survey information and the stage-
discharge relationship is computed dynamically within the HydroCAD program.

4. COMPUTER PROGRAM IDENTIFICATION
The table below indicates the computer hardware, operating system, and software used by AMEC
for the data analysis and/or calculations presented herein.
User
(Computer Name)
Computer Hardware
(Service Tag No.)
Operating System Computer Software
Richard Hiner

Dell Latitude M4800
(LG750870)
Microsoft Windows
7 Professional
Microsoft Office Word
2007, HydroCAD™ 10.0,
Build 18

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 6 of 20

5. DESCRIPTION OF FACILITIES AND POTENTIALLY IMPACTED AREA
1.1 General Information – Primary Ash Pond Dam
The Primary (ROCKI-237-H) Ash Pond at the Dan River Station is not currently used for ash
discharge. Information describing the characteristics of the impoundment, maximum dam
sections and spillway facilities are provided in Table 1.
Table 1 - Administrative Information - Primary (ROCKI-237-H) Ash Basin & Dam
Basic Dam Information
Name Primary (ROCKI-237-H) Ash Basin Dam
National ID Number NC05945
State Dam ID Number ROCKI–237
Current Hazard Classification Large, High Hazard
Status Impounding
Type Earthen
Purpose Ash sluicing operations
Year Constructed 1968
Baseflow ( cfs ) 0.00
Owner's contact information
Owner's name and address DAN RIVER STEAM STATION
ROCKINGHAM COUNTY
900 SOUTH EDGEWOOD DRIVE
EDEN, NC, 27288
336-623-0415
Engineer's name and address AMEC E&I, Inc.
2801 Yorkmont Road
Charlotte, NC 28208
704.357.8600
Geographic coordinates, location and specific dam features
Latitude, Longitude (NAD83 decimal
degrees)
N36.48830, W79.71480
County/NCDENR Region Rockingham/WSRO
USGS Quadrangle Name Southeast Eden
Name of Impounded Stream Unnamed tributary of Dan River
Name of Receiving Stream Dan River
River Basin Roanoke
Nearest City Eden
Distance to Nearest City ( miles ) 2.8

Specific information about the dam, including its construction and drainage area.
Structural Height3 ( feet ) 40
Normal Freeboard4 ( feet ) 12

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 7 of 20

Hydraulic Height5 ( feet ) 28
Crest Length ( nearest foot ) 1,944
Crest Width ( nearest foot ) 15
Upstream Slope, XH:1V 2H:1V
Downstream Slope, XH:1V 2H:1V
Normal Pool Elevation 528.0
Pond Surface Area (acres ) 7.40 (area of ash)
Normal Pool Capacity (acre·feet ) 0.00 (no impoundment)
Hydraulic Capacity (acre-feet) 36.48
Bottom Drain Yes
Bottom Drain Operable Unknown
Drainage Area ( acres )2 27.4
Principal (ROCKI-237-H) Spillway Details1
 Type Riser/Barrel
 Size Outlet: 36 inch diameter RCP
 Material CIP Concrete
 Total Weir Length ( feet ) 8 (2-4 foot weirs)
 Weir details Removable 4’ Concrete Stop Logs
 Total Drop ( feet ) 9
 Invert Elevations, Weir/Outlet Barrel 528.0 ( current/min ) /526.2
Emergency Spillway Type None
Emergency Spillway Details Not Applicable
Notes:
1. Based on data provided by Duke Energy Corporation, Feb. 2011
2. Based on map–based drainage area calculations by AMEC, Apr. 2011
3. Estimated vertical distance from lowest point on crest to point at which breech would fail at
toe.
4. Difference between structural height and hydraulic height.
5. Distance from normal pool to lowest point on downstream toe.
Elevations in feet, NAVD 1988

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 8 of 20

1.2 General Information – Secondary Ash Pond Dam
The Secondary (ROCKI-238-H) Ash Pond at the Dan River Station is currently used for final
clarification of the ash discharge. Information describing the characteristics of the impoundment,
maximum dam sections and spillway facilities are provided in Table 2.

Table 2 - Administrative Information - Secondary (ROCKI-238-H) Ash Basin & Dam
Basic Dam Information
Name Secondary (ROCKI-238-H) Ash Basin
Dam
National ID Number NC05946
State Dam ID Number ROCKI–238
Current Hazard Classification Large, High Hazard
Status Impounding
Type Earth
Purpose Ash sluicing operations
Year Constructed 1976
Baseflow ( cfs ) 0.00
Owner's contact information
Owner's name and address DAN RIVER STEAM STATION
ROCKINGHAM COUNTY
900 SOUTH EDGEWOOD DRIVE
EDEN, NC, 27288
336-623-0415
Engineer's name and address AMEC E&I, Inc.
2801 Yorkmont Road
Charlotte, NC 28208
704.357.8600
Geographic coordinates, location and specific dam features
Latitude, Longitude (NAD83 decimal
degrees)
N36.49190, W79.71140
County/NCDENR Region Rockingham/WSRO
USGS Quadrangle Name Southeast Eden
Name of Impounded Stream Unnamed tributary of Dan River
Name of Receiving Stream Dan River
River Basin Roanoke
Nearest City Eden
Distance to Nearest City ( miles ) 2.8

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 9 of 20

Specific information about the dam, including its construction and drainage area.
Structural Height3 ( feet ) 30
Normal Freeboard4 ( feet ) 16
Hydraulic Height5 ( feet ) 14.0
Crest Length ( nearest foot ) 1364
Crest Width ( nearest foot ) 15
Upstream Slope, XH:1V 2H:1V
Downstream Slope, XH:1V 2H:1V
Normal Pool Elevation 515.0
Pond Surface Area ( acres ) 7.07
Normal Pool Capacity ( acre·feet ) 29.56
Hydraulic Capacity (acre-feet) 130.16
Bottom Drain Yes
Bottom Drain Operable Yes
Drainage Area ( acres )2 29.4 (119.616*)
Principal (ROCKI-237-H) Spillway Details1
 Type Riser/Barrel
 Size ( Outlet ) 33 inches (36” RCP with 1.5” lining)
 Material ( Riser ) CIP Concrete
 Total Weir Length ( feet ) 16
 Weir details Removable 4’ Concrete Stop Logs
 Total Drop ( feet ) 16
 Invert Elevations, Weir/Outlet Barrel 515 ( current ), 502.2 ( min )/498.0
Emergency Spillway Type None
Emergency Spillway Details Not Applicable
Notes:
1. Based on data provided by Duke Energy Corporation, Feb. 2011
2. Based on map–based drainage area calculations by AMEC, Apr. 2011 – *The area of 29.4
acres is the area which contributes by direct runoff. Since the Dry Fly Ash Basin and the
Primary Ash Basin both discharge into the Secondary Ash Basin and are part of the
watershed, the total area of the watershed 119.7 acres.
3. Estimated vertical distance from lowest point on crest to point at which breech would fail at
toe.
4. Difference between structural height and hydraulic height.
5. Distance from normal pool to lowest point on downstream toe.
Elevations in feet, NAVD 1988

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 10 of 20

6. CALCULATION APPROACH AND INPUT
6.1 Drainage Area Delineation
The contributing watersheds for the Dry Fly Ash Basin, are based on a delineation prepared for
this analysis using a combination of WSP-Sells contour data provided by Duke Energy and USGS
data for areas not covered by the WSP-Sells data. This USGS data came from the 2001-2003
1/9-Arc Second National Elevation Dataset for the State of North Carolina and was published in
2008. The watershed drainage areas measured from this delineation are approximately 62.9
acres (0.0983 mi2) for the Dry Fly Ash Basin, 27.4 acres (0.0428 mi2) for the Primary (ROCKI-
237-H) Ash Basin and 29.4 acres (0.0459 mi2) for the Secondary (ROCKI-238-H) Ash Basin. The
outflows from both the Dry Fly Ash Basin and the Primary (ROCKI-237-H) Ash Basin discharge
directly into the Secondary (ROCKI-238-H) Ash Basin. Please refer to Figure 1 in this report for
the drainage area delineation.
6.2 Time-of-Concentration/Lag-Time Calculations
The time-of-concentration for the watershed was computed using the methodology in the NRCS
(formerly SCS) publication Urban Hydrology for Small Watersheds (Technical Release 55). This
methodology, like many others, requires the delineation of the longest flow path. This path is then
broken down into three typical flow regimes; Sheet flow or overland flow, shallow concentrated
flow, and channel/pipe flow. Once the flow path and flow regimes are identified, travel time for
each segment is computed and then added together to determine the total time-of-concentration.
Once this is determined, the lag-time is computed as 60% of the total time-of-concentration.
While it has been common practice when modeling small ponds to assume a near instantaneous
Tc of 0.01 hours, the large size of the pond renders this assumption inappropriately conservative.
In addition to the overland flow, it is reasonable to assume that it will take some time for the inflow
to propagate across the pond. For our analyses, the single wave solution of the Kortweg-de Vries
equation (cp=SQRT(g(h+H), where g=32.2 ft/sec2, h is the average depth, and H is the wave
height) was used to determine the wave propagation speed. Assuming an average water depth
of 5 feet and a wave height of 0.5 feet, yields a computed wave propagation speed of
approximately 13.3 ft/sec. This value will be used to determine the travel time across the pond
for both ash basins.
For the Dry Fly Ash Basin, the flow path is approximately 1670 feet in length and has an upper
elevation of 628 feet and a lower elevation of 530 feet for an average slope of 5.87%. Since the
shallow swales along the flow path are unpaved, the shallow concentrated flow calculations
assume an unpaved condition. The time-of-concentration computed for this watershed is 9.0
minutes.
Since the contributing watershed for the Primary (ROCKI-237-H) Ash Basin is limited to the basin
itself, the 1,694 foot flow path consists of a short distance of sheet flow followed by the shallow

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 11 of 20

concentrated flow across the ash. The time-of-concentration computed for this watershed is 43.2
minutes.
For the Secondary (ROCKI-238-H) Ash Basin, the flow path is approximately 2502 feet in length
and has an upper elevation of 591 feet and a lower elevation of 530 feet for an average slope of
2.44%. Since the shallow swales along the flow path are unpaved, the shallow concentrated flow
calculations assume an unpaved condition. The time-of-concentration computed for this
watershed is 22.1 minutes. The full calculations for the time-of-concentration are included in the
HydroCAD™ output. Please refer to Figures 1a and 1b in this report for a depiction of the flow
path.
6.3 Rainfall Reference Information
The Dan River Steam Station is located approximately 45 miles northeast of Winston-Salem,
North Carolina and approximately 4 miles south of the Virginia state line. The rainfall depth
information for this analysis was obtained from HMR-51 using the 6-hour, 10 mi2, All-Season
PMP Isopluvial Map (Figure 18). Interpolation from this figure yields a full PMP event for the 6-
hour duration of approximately 29.2 inches. Therefore, the 6-hour, ¾ PMP storm would be 21.9
inches and this value was used in the analysis and was distributed using a 6-hour duration SCS
Type II distribution. Figure 18 from HMR-51 is included for reference in the appendix of this report.
6.4 Curve Number Information
For the curve number computations, TR-55 methodology was used and several general
assumptions were necessary to ensure consistency in the results. The first was the assumption
that the normal pool area in each of the basins was impervious. The second was that the land
use was considered as “open space with fair grass cover”. Curve numbers were then selected
based on the distribution of soil types within the watershed. For Type B soils, a curve number of
69 was selected and for Type C soils, a curve number of 79 was selected. Impervious areas
(ponded water) were modeled with a curve number of 98. The selected curve numbers are
conservative given that much of the watersheds are used for ash stacking operations and coal
ash deposits are highly pervious and would actually have an effective curve number much lowe r
than the native soil in these areas. It is appropriate, however, for this type of analysis, to take a
somewhat more conservative position since curve numbers for coal ash deposits have not been
firmly established.
The drainage area for the Dry Fly Ash Basin includes both the original dry fly ash stacking area
and the former dredge pond. Both of these areas have been filled with coal ash deposits and no
longer have any hydraulic storage capacity, but do drain to the remaining basin area between
them. For the Dry Fly Ash Basin watershed, the weighted curve number was computed as 75
and the watershed was divided fairly evenly between Type B and Type C soils. The basin itself
does not have a normal pool elevation as it is not intended to store water on a normal basis, so
this watershed had no impervious percentage associated with it.

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 12 of 20

The drainage area for the Primary (ROCKI-237-H) Ash Basin consists of the ash basin itself and
the basin has no permanent pool. The area of the basin is primarily Type C soil with a very small
amount of Type B. A weighted curve number of 79 was computed for this basin. The contributing
watershed for the Secondary (ROCKI-238-H) Ash Basin consists of about 49% Type B soils, 34%
Type C soils, and 16% Ponded Water which results in a weighted curve number of 77. The normal
pool area in the basin was modeled with a curve number of 98. Please refer to Figures 3a and
3b in this report as well as the calculations in the appendix for further information about the soil
distribution in the watershed.
6.5 Stage-Storage Calculations
LDSI performed an aerial survey of the Primary (ROCKI-237-H) Ash Basin in February 2014 and
a bathymetric survey of the Secondary (ROCKI-238-H) Ash Basin for Duke Energy in September
2014. A CAD drawing of these surveys was provided by Duke Energy for this analysis. The
contours in this drawing were used to create a triangulated irregular network (TIN – a vector based
representation of the physical land surface) from which stage-storage data could be developed.

Table 3: Stage-Storage Data for Dry Fly Ash Basin

Elevation (ft) Surface Area
(acres)
Volume (acre-feet)
530 0 0
535 0.29 0.13
540 2.34 8.39
545 3.67 23.77
550 4.98 45.32
555 6.50 73.97
558.2 7.66 96.36

Table 4: Stage-Storage Data for Primary (ROCKI-237-H) Ash Basin

Elevation (ft) Surface Area
(acres)
Volume (acre-feet)
528 7.40 0
529 8.22 7.81
530 9.13 16.48
531 9.82 25.96
532 11.22 36.48

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Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
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Table 5: Stage-Storage Data for Secondary (ROCKI-238-H) Ash Basin
Elevation (ft) Surface Area
(acres)
Volume (acre-feet)
515 7.07 0
516 7.47 7.27
517 7.87 14.94
518 8.14 22.95
519 8.34 31.19
520 8.52 39.62
521 8.68 48.22
522 8.85 56.99
523 9.15 65.99
524 9.81 75.46
525 11.60 86.17
526 12.24 98.09
527 12.50 110.45
528 13.04 123.22
528.52 13.38 130.09
529 13.69 136.58

6.6 Stage-Discharge Calculations
The stage-discharge calculations are based on the physical characteristics of the principal
spillway system. The spillway for the Dry Fly Ash basin consists of a riser tower with provisions
for stop logs which is connected to a 24-inch diameter outfall pipe. Since this is not maintained
as a wet basin, there are no stop logs in place and the spillway is free draining through the culvert.
The spillway for the Primary (ROCKI-237-H) Ash Basin consists of a concrete riser tower with
stop logs on two sides. The stop logs for the Primary principal spillway are placed at elevation
535 to maintain the normal pool. These stop logs can be removed down to the invert elevation of
the outfall pipe if it is necessary to drain the pond. The spillway for the Secondary (ROCKI-238-
H) Ash Basin consists of a concrete riser tower with stop logs on four sides. The stop logs for the
Secondary principal spillway are placed at elevation 515 to maintain the normal pool. These stop
logs can be removed down to the invert elevation of the outfall pipe if it is necessary to drain the
pond. At very low flows (less than about 2 ft of head), the weir flow over the riser will control the
discharge. Once the depth exceeds about 2 feet, orifice flow through the outfall pipe will control
the discharge. HydroCAD™ computes the discharge dynamically at each elevation based on the
physical characteristics of the riser structure and outfall pipe which are entered as input data. The
stage-discharge characteristics can be viewed as part of the HydroCAD™ output data.

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
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7. SUMMARY OF METHODS AND APPROACH
7.1 Hydrologic and Hydraulic Analysis
Both the hydrologic and hydraulic analyses completed for this study were based on application of
HydroCAD™ 10.0, build 18. HydroCAD™ is a general application, hydrologic and hydraulic
model that can perform unsteady flow routing through storage areas and dams (an unsteady flow
analysis deals with flow conditions that vary both temporally and spatially) in addition to
performing hydraulic calculations for the outlet structures and discharge pipes.
In accordance with 15A NCAC 2K .0205, the hydrologic analyses completed for this study were
based on the guidelines presented in the National Weather Service (NWS) Hydro-Meteorological
Report No. 51 (HMR-51, 1978). These guidelines were used to develop a Probable Maximum
Precipitation (PMP) event for the project watershed.
SCS methods were used for the rainfall-runoff analyses. The input parameters for the SCS
hydrologic method for each basin were determined by analyses of the hydrologic soil group data
provided by the NRCS.
The full PMP event for the 6-hour duration at this location was interpolated as 29.2 inches
according to HMR-51. Therefore, a 6-hour, ¾ PMP rainfall depth of 21.9 inches was used in this
analysis and was distributed using a 6-hour duration SCS Type II distribution. The resulting
hydrologic model simulates the runoff produced by the ¾ PMP event for the Primary (ROCKI-
237-H) and Secondary (ROCKI-238-H) Ash Pond watershed and the resulting discharge
hydrographs were routed through the basin to determine the peak stage during the ¾ PMP event.
The HEC-1 models developed for this analysis are included in the appendix and the basic input
data is summarized in the following tables.

Table 9. HydroCAD™ Model Inputs for the Dry Fly Ash Basin
Input Value
Basin Area (acres) 62.9
Time-of-Concentration(minutes) 9.0
SCS Curve Number 75
Unit Hydrograph SCS
Rainfall Distribution SCS Type II
Rainfall Duration 6 hours
Precipitation (inches) for ¾ PMP 21.9
Computation time increment (minutes) 3

Design Calculation or Analysis
Title: Dan River Primary and
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AMEC Project No: Calculation No: Rev No: Page:
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Table 10. HydroCAD™ Model Inputs for the Primary (ROCKI-237-H) Ash Basin
Input Value
Basin Area (acres) 27.39
Time-of-Concentration (minutes) 43.2
SCS Curve Number 79
Unit Hydrograph SCS
Rainfall Distribution SCS Type II
Rainfall Duration 6 hours
Precipitation (inches) for ¾ PMP 21.9
Computation time increment (minutes) 3

Table 11. HydroCAD™ Model Inputs for the Secondary (ROCKI-238-H) Ash Basin
Input Value
Basin Area (acres) 29.42
Time-of-Concentration (minutes) 22.1
SCS Curve Number 77
Unit Hydrograph SCS
Rainfall Distribution SCS Type II
Rainfall Duration 6 hours
Precipitation (inches) for ¾ PMP 21.9
Computation time increment (minutes) 3

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
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8. CONCLUSIONS AND DISCUSSIONS
8.1 HydroCAD™ Modeling Results
The results of the HydroCAD™ analysis are summarized in the following table (the full
HydroCAD™ output is included in the appendix).

Table 12. HydroCAD™ Output Summary for the Dry Fly Ash, Primary (ROCKI-237-H), and
Secondary (ROCKI-238-H) Ash Basins
Dry Fly Ash Basin Primary (ROCKI-237-
H) Ash Basin
Secondary
(ROCKI-238-H)
Ash Basin
6-hour, ¾ PMP
(inches)
21.9 21.9 21.9
Total Loss 3.55 2.9 3.33
Total Excess 18.35 19.0 18.57
Peak Inflow to Basin
(cfs)
2,363.41 469.95 891.47
Time of Peak Inflow
(hours)
3.00 3.39 3.15
Total Storm Volume
(ac-ft)
96.197 43.377 185.289
Peak Stage Elevation
(ft)
553.28 531.34 522.96
Overtopping Elev. (ft) 558.2 532 528.52
Maximum Storage
(ac-ft)
96.4 36.48 136.58
Remaining Freeboard 4.92 0.66 5.56
Peak Storage Volume
(ac-ft)
64.142 29.582 65.634
Peak Discharge (cfs) 112.32 65.24 138.89
Time of Peak Outflow
(hours)
4.24 4.63 9.63
Time to Drain Basin
(hours)
~14 ~17 ~36

The results of the HEC-1 analysis for the Primary Ash Pond spillway indicate that with the
operating water level at elevation 528 and the primary dike breach at elevation 532, sufficient
storage capacity exists to safely pass the ¾ PMP storm event with approximately 0.66 feet of
freeboard and in compliance with the requirements of 15A NCAC 2K .0205. The details from the
HEC-1 model are captured in the following table:
The results of the HEC-1 analysis of the Secondary Ash Pond spillway indicate that with an
operating level of 514 in the Secondary Ash Pond, sufficient storage capacity exists to safely pass

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
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the ¾ PMP storm event with approximately 5.56 feet of freeboard and in compliance with the
requirements of 15A NCAC 2K .0205.
8.2 Adequacy of Existing Spillway System
As demonstrated through the above analysis, the existing spillway systems meet the
requirements of 15A NCAC 2K .0205. The Primary (ROCKI-237-H) Ash Basin Dam is not
overtopped during the ¾ PMP storm event. No emergency spillway is required for the Primary
(ROCKI-237-H) Ash Basin Dam. Therefore, the frequency of use requirements in 15A NCAC
.0205 (b) are not applicable to this facility. The existing spillway system will also drain 80% of the
stored water in less than 1 days.
The Secondary (ROCKI-238-H) Ash Basin Dam is not overtopped during the ¾ PMP storm event
and the existing spillway system meets the requirements of 15A NCAC 02K .0205. No emergency
spillway is required for the Secondary (ROCKI-238-H) Ash Basin Dam. Therefore, the frequency
of use requirements in 15A NCAC .0205 (b) are not applicable to this facility. The existing spillway
system will also drain 80% of the stored water in less than 2 days.
The majority of the Primary Ash Pond dike is at elevation 540 and the maximum water surface is
531.34 which means that the water surface is shielded from wind-generated wave setup and run-
up by the surrounding dike. The majority of the Secondary Ash Pond dike is at elevation 530 and
the maximum water surface is 522.96 which means that the water surface is shielded from wind-
generated wave setup and run-up by the surrounding dike. Wind-generated wave run-up and
setup should not be an issue at this site.

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
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9. REFERENCES
National Weather Service, June 1978. Hydrometeorological Report No. 51, Probable Maximum
Precipitation Estimates, United States East of the 105th Meridian.

USDA NRCS June 1986. Technical Release 55 - Urban Hydrology for Small Watersheds

WSP-Sells AutoCAD drawing (x_topo-final.dwg) provided by Duke Energy on 03/22/2011

LDSI AutoCAD drawing (3074Bathymetric.dwg) provided by LDSI, Inc. on 10/23/2014

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
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10. ABBREVIATIONS

AF acre-feet
cfs cubic feet per second
ft feet
GIS geographic information system
NCDENR North Carolina Department of Environment and Natural Resources
NGVD National Geodetic Vertical Datum of 1929
NRCS Natural Resource Conservation Service (formerly SCS)
PMP Probable Maximum Precipitation
SCS Soil Conservation Service
LIDAR LIght Detection And Ranging

Design Calculation or Analysis
Title: Dan River Primary and
Secondary Ash Pond H&H Analyses
AMEC Project No: Calculation No: Rev No: Page:
7810-14-0150 H - 001 0 20 of 20

APPENDIX

D an
R i v e r
62.9 AC
29.4 AC
27.4 AC
PRIMARYASHPOND
SECONDARYASHPOND
DRY FLY ASHBASIN
FLOWPATHL=1,669.6 FT
FLOWPATHL=2,502.0 FT
630620610600
580
570
560
550
640
590
560
55
0
54
0
530
520
610600590
620610
600
61
0
600
560
550
53
05
2
0
540530
530 5
2
0
5
2
0
5
1
0
500
490
5
9
0
58
0
590
580
5
1
0
620
550
54
0
540
52
0
610
600
580
570
580
5
7
0
560
550
530 530
530
530
520
510
560
530
530
530
0 200 400 600100
Feet
27.4 AC
$
DAN RIVER ASH PLANTDUKE ENERGYEDEN, NORTH CAROLINA
FIGURE 1ADRAINAGE AREA ANDFLOWPATH
Prepared By:
Date:
Checked By:
Date:
Job #: 7810-14-0150
JMS 8/31/2016 RLH 8/31/2016
LEGEND
MAJOR CONTOUR (10FT)
MINOR CONTOUR (2FT)
FLOWPATH
POST-DEVELOPMENT DRAINAGE AREA
Data Source: Topographic Data from LDSI.
D a n R i v e r
29.4 AC
27.4 AC
PRIMARYASHPOND
SECONDARYASHPOND
57
0
5
4
0
520
51
0
580
5
5
0
560
53
0
500
490
530
5
3
0
560
510
5
3
0
520
540
540
530
5
4
0
56
0
530
530
530
510
520
530
500
530
51
0
500
530
520
520
520
530
540
530
5
4
0
510
540
520
520
520
530
510
51
0
550
510
530
520
55
0
5
1
0
520
530
53
0
0 200 400 600100
Feet
$
DAN RIVER ASH PLANTDUKE ENERGYEDEN, NORTH CAROLINA
FIGURE 1BDRAINAGE AREA ANDFLOWPATH
Prepared By:
Date:
Checked By:
Date:
Job #: 7810-14-0150
LEGEND
POST-DEVELOPMENT DRAINAGE AREA
FLOWPATH
MAJOR CONTOUR (10FT)
MINOR CONTOUR (2FT)
Data Source: Topographic Data from LDSI.
FLOWPATHL=1,693.9 FT
JMS 9/1/2016 RLH 9/1/2016
D a n R i v er500
520 530
5
2
0
5
8
0
510
510
610
520
530
61
0
51
0
530
500
530
580
530
520
520
5
3
0 510
51
0
5
1
0
56
0
510
54
0
530
530
510
540
55
0
5
1
0
5
7
0
5
1
0
550
590
530
5
8
0
53
0
540
6
0
0
530
5
3
0
5
3
0
590
520
5
3
0
5
3
0
530
510
560
500
520
6
1
0
5
4
0
62
0
5
3
0
60
0
600
59
0
5
2
0
6
4
0
520
550
630
530
530
540
500
540
560
62
0
5
2
0
490
5
8
0
540
61
0
510
580
6
0
0
590
55
0
5
2
0
520
510
56
0
550
540
57
0
53
0
NC OneMap, NC Center for Geographic Information and Analysis, NC 911 Board
0 200 400 600100
Feet
$
DAN RIVER ASH PLANTDUKE ENERGYEDEN, NORTH CAROLINA
FIGURE 2BASIN CONTOURS
Prepared By:
Date:
Checked By:
Date:
AMEC Foster Wheeler Job #: 7810-14-0150
LEGEND
BASIN OUTLINE
MAJOR CONTOUR (10FT)
MINOR CONTOUR (2FT)
Data Source: Aerial Topographic Survey obtained from
LDSI; NAIP Aerial Photography, dated 2010.
Bottom of Basin 509'
Bottom of Basin 505'
Top of Dam 528.52'
Top of Dam 540'Primary Dike Breach at 532'
SECONDARYASHPONDNORMAL POOL ELEV. = 514
PRIMARYASH POND
Bottom of Basin 530'
DRY FLYASHBASIN
OVERTOPPINGELEV. 558.2'
JMS 8/31/2016 RLH 8/31/2016
D an
R i v e r
62.9 AC
29.4 AC
27.4 AC
PRIMARYASHPOND
SECONDARYASHPOND
DRY FLY ASHBASIN
59
0
560
54
0
640
630
60
0
620
530
610
5
5
0
57
0
510
520
580
500
490
510
550
600
570
580
5
3
0
5
1
0
52
0
590
530
61
0
59
0
5
1
0
56
0
54
0
58
0
520
620
570
56
0
600
53
0
58
0
600
54
0
590
55
0
520
530
620
590
550
610 610
520
530
560
530
55
0
610
520
530
550
530
510
600
52
0
58
0Ud
CmB AyF
W
CmD
AyC
DaA
SvD SvB
NC OneMap, NC Center for Geographic Information and Analysis, NC 911 Board
0 200 400 600100
Feet
$
DAN RIVER ASH PLANTDUKE ENERGYEDEN, NORTH CAROLINA
FIGURE 3ANRCS SOILS
Prepared By:
Date:
Checked By:
Date:
Job #: 7810-14-0150
LEGEND
POST-DEVELOPMENT DRAINAGE AREA
SOIL BOUNDARY
MAJOR CONTOUR (10FT)
MINOR CONTOUR (2FT)
FLOW PATH
SOIL TYPES WITHIN DRAINAGE AREAS
DRY FLY ASH BASIN
B (26.94 AC)
C (35.96 AC)
SECONDARY ASH POND
B (14.45 AC)
C (10.14 AC)
N/A (4.83 AC)
Data Source: USDA NRCS Soil Survey Geographic
(SSURGO) database for Rockingham County, North
Carolina, dated 2009; NAIP Aerial Photography for
Rockingham County, dated 2010.
Soil Symbol Description Type
AyF Ayersville gravelly loam, 15 to 45 percent slopes B
CmB Clover sandy loam, 2 to 8 percent slopes B
CmD Clover sandy loam, 8 to 15 percent slopes B
DaA Dan River loam, 0 to 2 percent slopes, frequently flooded B
Ud Udorthents, loamy C
W Water NA
JMS 9/1/2016 RLH 9/1/2016
D a n R i v e r
29.4 AC
27.4 AC
PRIMARYASHPOND
SECONDARYASHPOND
57
0
5
4
0
520
51
0
580
5
5
0
560
53
0
500
490
530
5
3
0
560
510
5
3
0
520
540
540
530
5
4
0
56
0
530
530
530
510
520
530
500
530
51
0
500
530
520
520
520
530
540
530
5
4
0
510
540
520
520
520
530
510
51
0
550
510
530
520
55
0
5
1
0
520
530
53
0
Ud
DaA
W
AyC
CsA
CmD
HbA
CmB AyF
NC OneMap, NC Center for Geographic Information and Analysis, NC 911 Board
0 200 400 600100
Feet
$
DAN RIVER ASH PLANTDUKE ENERGYEDEN, NORTH CAROLINA
FIGURE 3BNRCS SOILS
Prepared By:
Date:
Checked By:
Date:
Job #: 7810-14-0150
LEGEND
POST-DEVELOPMENT DRAINAGE AREA
SOIL BOUNDARY
MAJOR CONTOUR (10FT)
MINOR CONTOUR (2FT)
FLOW PATHSOIL TYPES WITH DRAINAGE AREA
PRIMARY ASH POND
B (O.45 AC)
C (26.94 AC)
Data Source: USDA NRCS Soil Survey Geographic
(SSURGO) database for Rockingham County, North
Carolina, dated 2009; NAIP Aerial Photography for
Rockingham County, dated 2010.
Soil Symbol Description Type
AyF Ayersville gravelly loam, 15 to 45 percent slopes B
CmB Clover sandy loam, 2 to 8 percent slopes B
CmD Clover sandy loam, 8 to 15 percent slopes B
DaA Dan River loam, 0 to 2 percent slopes, frequently flooded B
Ud Udorthents, loamy C
W Water NA
JMS 9/1/2016 RLH 9/1/2016

15A NCAC 02K .0205 SPILLWAY DESIGN
(a) All dams shall have a spillway system with capacity to pass a flow resulting from a design storm indicated in (e) of this
Rule for a hazard classification appropriate for the dam, unless the applicant provides calculations, designs, and plans to show
that the design flow can be stored, passed through, or passed over the dam without failure occurring.
(b) A vegetated earth or unlined emergency spillway will be approved when computations indicate that it will pass the design
storm without jeopardizing the safety of the structure. The risk of recurring storms, excessive erosion, and inadequate
vegetative cover will be considered acceptable in such a spillway when its average frequency of use is predicted to be no
more frequent than once in 25 years for existing class B and for class A dams except for small class A dams designed in
accordance with all design criteria established by the U.S.D.A, Soil Conservation Service, and as contained in Engineering
Standard 378 of the U.S.D.A., Soil Conservation Service; once in 50 years for new class B, small and medium new class C,
and existing class C dams; and once in 100 years for large and very large new class C dams. The dam sizes referred to in this
Subsection are defined in (e) of this Rule.
(c) Lined Spillways and Channels. The design report shall include design data criteria for open channel, drop, ogee, and
chute spillways and other spillway types that include crest structures, walls, channel lining, and miscellaneous details. All
masonry or concrete structures shall have joints that are relatively water-tight and shall be placed on foundations capable of
sustaining applied loads without undue deformation. Provisions must be made for handling leakage from the channel or
underseepage from the foundation which might cause saturation of underlying materials or uplift against the undersurfaces.
(d) Within 15 days following passage of the design storm peak, the spillway system shall be capable of removing from the
reservoir at least 80 percent of the water temporarily detained in the reservoir above the elevation of the primary spillway.
(e) It is recognized that the relationships between valley slope and width, total reservoir storage, drainage area, other
hydrologic factors, and specific cultural features have a critical bearing on determining the safe spillway design flood.
Rational selection of a safe spillway design flood for specific site conditions based on quantitative analysis is acceptable. The
spillway should be sized so that the increased downstream damage resulting from overtopping failure of the dam would not be
significant as compared with the damage caused by the flood in the absence of dam overtopping failure. A design storm more
frequent than once in 100 years will not be acceptable for any class C dam. In lieu of quantitative analysis, the following
tables shall be used as criteria for spillway design storms and permissible velocities for vegetated earth spillways:
CRITERIA FOR SPILLWAY DESIGN STORM
SIZE CLASSIFICATION
Size Total Storage (Ac-Ft)1 Height (ft)1
Small less than 750 less than 35
Medium equal to or greater than 750 and less than 7,500 equal to or greater than 35 and less than 50
Large equal to or greater than 7,500 and less than 50,000 equal to or greater than 50 and less than 100
Very Large equal to or greater than 50,000 equal to or greater than 100

1 The factor determining the largest size shall govern

MINIMUM SPILLWAY DESIGN STORMS
Hazard Size Spillway Design Flood (SDF)
Low (Class A) Small
Medium
Large
Very Large
Medium
50 year
100 year
1/3 PMP
1/2 PMP
1/3 PMP
Intermediate (Class B) Small
Large
Very Large
100 year
1/2 PMP
3/4 PMP
High (Class C) Small
Medium
Large
Very Large
1/3 PMP
1/2 PMP
3/4 PMP
PMP

PERMISSIBLE VELOCITIES FOR VEGETATED EARTH SPILLWAYS
Permissible velocity1 feet per second
Erosion resistant soils Easily erodible soils
Slope of exit channel Slope of exit channel
Percent Percent
Vegetation 0 to 5 5 thru 10 0 to 5 5 thru 10
Bermuda Grass
Bahia grass
8 7 6 5
Tall fescue
Kentucky bluegrass
Reed canary
7 6 5 4
Sod forming
grass mixture
5 4 4 3
Lespedeza sericea
Weeping lovegrass
Alfalfa
Crabgrass
3.5 Do not use 2.5 Do not use

2 Increase values 10 percent when the anticipated average use of the spillway is not more frequent than once in 50 years or 25
percent when the anticipated average use is not more frequent than once in 100 years.

History Note: Authority G.S. 143-215.26; 143-215.27; 143-215.31;
Eff. June 15, 1980.

15A NCAC 02K .0206 CONDUITS
(a) A conduit shall be provided to drain each reservoir. The conduit design shall include the computation of the minimum
time required to drain the reservoir.
(b) All pipe conduits shall convey water at the design velocity without damage to the interior surface.
(c) Protection shall be provided to prohibit unsafe seepage along conduits through the dam, abutments, and foundation. The
specific design for seepage protection along conduits shall be shown in the drawings and specifications.
(d) Adequate allowances shall be incorporated in the design to compensate for differential settlement and possible elongation
of the pipe conduit.
(e) Trash racks shall be installed at the intake of conduits to prevent clogging the conduit.
(f) Pipe Conduit Spillway Materials
(1) Pipe conduits shall be designed to support the total external loads in addition to the total internal hydraulic
pressure without leakage.
(2) Reinforced or Prestressed Concrete Pipe Conduits
(A) All conduits are to be designed and constructed to remain watertight under maximum anticipated
hydraulic pressure and maximum probable joint opening, including the effects of joint rotation
and extensibility.
(B) Provisions for safe movement of the barrel are to be provided at each joint in the barrel and at the
junction of the barrel and riser or inlet. Cradles are to be articulated if constructed on a yielding
foundation.
(C) The engineer shall submit the final design details of the proposed pipe to be used for all class A
dams where the height of the dam exceeds 35 feet and all class B and C dams.
(3) Corrugated Metal Pipe Conduits
(A) Corrugated metal pipe shall not be used in class A dams over 35 feet high or in class B and C
dams, except for special cases when the design engineer can adequately demonstrate satisfactory
performance.
(B) Corrugated metal pipe may be used in class A dams which are less than 35 feet high.
(C) Corrugated metal conduits shall have watertight connecting bands designed and installed to
remain watertight under maximum anticipated hydrostatic head and joint rotation.
(D) Flange type couplings shall not be used for corrugated metal pipe or corrugated steel pipe where
the diameter exceeds 12 inches unless the applicant produces computations to verify that the
flanges and the pipe conduit are of such design to safely support the total external loads in
addition to the total internal hydraulic pressure without leakage.
(g) Dissipating Devices. All gates, valves, conduits and concrete channel outlets shall be provided with a dissipator designed
and constructed to control erosion and prevent damage to the embankment or the downstream outlet or channel.
Dan River Ash Basin Watersheds
Prepared by: F. Hammers Dated: 05. Apr, 2011 Checked by: R. Hiner Dated: April 8, 2011
TC_ TR55-Method Basin ID:Dry Fly Ash (Condition: Developed)
SHEET FLOW SEG #1 SEG #2 Roughness coefficents for sheet flow
2- Year, 24- HR. Rainfall (in)3.80 3.80 Smooth Surface 0.01
Manning's "n"0.13 Range (Natural)0.13
Flow Length (ft)100 Prairie grass 0.15
Elevation Up (ft)628.0 Dense grass (Lawns)0.24
Elevation Down (ft)610.0 Bermuda grass 0.41
Land Slope (ft/ft)0.1800 0.0000 Woods - Light 0.40
Time Of Concentration (mins)3.3 0.0 3.3 Woods - Medium 0.60
Woods - Dense 0.80
SHALLOW CONCENTRATED FLOW SEG #1 SEG #2
Surface Description (P OR U)U U U
Flow Length (ft)593 P
Elevation Up (ft)610.0
Elevation Down (ft)556.0
Watercourse Slope (ft/ft)0.0911 0.0000
Average Velocity (ft/sec)4.869 0.000
Time Of Concentration (mins)2.0 0.0 2.0
CHANNEL FLOW SEG #1 SEG #2 SEG #3 SEG #4
Bottom Width (ft)2.0
Depth (ft)2.0
Side Slopes (?H:1V) (ft)6.0
Flow Length (ft)977
Elevation Up (ft)556.0
Elevation Down (ft)530.0
Manning's "n"0.055
Area (sq. ft)28.000 0.000 0.000 0.000
Wetted Perimeter (ft)26.331 0.000 0.000 0.000
Hydraulic Radius (ft)1.063 0.000 0.000 0.000
Channel Slope (ft/ft)0.0266 0.0000 0.0000 0.0000
Average Velocity (ft/sec)4.606 0.000 0.000 0.000
Time Of Concentration (mins)3.5 0.0 0.0 0.0 3.5
CIRCULAR PIPE FLOW (Gravity)SEG #1 SEG #2 SEG #3 SEG #4
Pipe Diameter (in)
Flow Length (ft)
Elevation Up (ft)
Elevation Down (ft)
Manning's "n"
Area (sq. ft)0.000 0.000 0.000 0.000
Wetted Perimeter (ft)0.000 0.000 0.000 0.000
Hydraulic Radius (ft)0.000 0.000 0.000 0.000
Channel Slope (ft/ft)0.0000 0.0000 0.0000 0.0000
Average Velocity (ft/sec)0.000 0.000 0.000 0.000
Time Of Concentration (mins)0.00 0.00 0.00 0.00 0.0
Total Length of Flow Path (feet)1669.60
Total Time Of Concentration (Minutes)8.89
Total Time Of Concentration (Hours)0.1482
Lagtime (Hours)0.0889
Dan River Ash Basin Watersheds
Prepared by: F. Hammers Dated: 05. Apr, 2011 Checked by: R. Hiner Dated: April 8, 2011
TC_ TR55-Method Basin ID:Primary Ash Basin (Condition: Developed)
SHEET FLOW SEG #1 SEG #2 Roughness coefficents for sheet flow
2- Year, 24- HR. Rainfall (in)3.80 Smooth Surface 0.01
Manning's "n"0.13 Range (Natural)0.13
Flow Length (ft)50 Prairie grass 0.15
Elevation Up (ft)542.0 Dense grass (Lawns)0.24
Elevation Down (ft)538.0 Bermuda grass 0.41
Land Slope (ft/ft)0.0800 0.0000 Woods - Light 0.40
Time Of Concentration (mins)2.6 0.0 2.6 Woods - Medium 0.60
Woods - Dense 0.80
SHALLOW CONCENTRATED FLOW SEG #1 SEG #2
Surface Description (P OR U)U U U
Flow Length (ft)50 P
Elevation Up (ft)539.0
Elevation Down (ft)536.0
Watercourse Slope (ft/ft)0.0600 0.0000
Average Velocity (ft/sec)3.952 0.000
Time Of Concentration (mins)0.2 0.0 0.2
CHANNEL FLOW SEG #1 SEG #2 SEG #3 SEG #4
Bottom Width (ft)200.0
Depth (ft)1.0
Side Slopes (?H:1V) (ft)20.0
Flow Length (ft)1594
Elevation Up (ft)536.0
Elevation Down (ft)535.0
Manning's "n"0.003
Area (sq. ft)220.000 0.000 0.000 0.000
Wetted Perimeter (ft)240.050 0.000 0.000 0.000
Hydraulic Radius (ft)0.916 0.000 0.000 0.000
Channel Slope (ft/ft)0.0006 0.0000 0.0000 0.0000
Average Velocity (ft/sec)12.139 0.000 0.000 0.000
Time Of Concentration (mins)2.2 0.0 0.0 0.0 2.2
CIRCULAR PIPE FLOW (Gravity)SEG #1 SEG #2 SEG #3 SEG #4
Pipe Diameter (in)
Flow Length (ft)
Elevation Up (ft)
Elevation Down (ft)
Manning's "n"
Area (sq. ft)0.000 0.000 0.000 0.000
Wetted Perimeter (ft)0.000 0.000 0.000 0.000
Hydraulic Radius (ft)0.000 0.000 0.000 0.000
Channel Slope (ft/ft)0.0000 0.0000 0.0000 0.0000
Average Velocity (ft/sec)0.000 0.000 0.000 0.000
Time Of Concentration (mins)0.00 0.00 0.00 0.00 0.0
Total Length of Flow Path (feet)1693.90
Total Time Of Concentration (Minutes)5.04
Total Time Of Concentration (Hours)0.0841
Lagtime (Hours)0.0504
Dan River Ash Basin Watersheds
Prepared by: F. Hammers Dated: 05. Apr, 2011 Checked by: R. Hiner Dated: April 8, 2011
TC_ TR55-Method Basin ID:Secondary Ash Basin (Condition: Developed)
SHEET FLOW SEG #1 SEG #2 Roughness coefficents for sheet flow
2- Year, 24- HR. Rainfall (in)3.80 Smooth Surface 0.01
Manning's "n"0.13 Range (Natural)0.13
Flow Length (ft)100 Prairie grass 0.15
Elevation Up (ft)591.0 Dense grass (Lawns)0.24
Elevation Down (ft)590.0 Bermuda grass 0.41
Land Slope (ft/ft)0.0100 0.0000 Woods - Light 0.40
Time Of Concentration (mins)10.6 0.0 10.6 Woods - Medium 0.60
Woods - Dense 0.80
SHALLOW CONCENTRATED FLOW SEG #1 SEG #2
Surface Description (P OR U)U U U
Flow Length (ft)1550 P
Elevation Up (ft)590.0
Elevation Down (ft)532.0
Watercourse Slope (ft/ft)0.0374 0.0000
Average Velocity (ft/sec)3.121 0.000
Time Of Concentration (mins)8.3 0.0 8.3
CHANNEL FLOW SEG #1 SEG #2 SEG #3 SEG #4
Bottom Width (ft)200.0
Depth (ft)1.0
Side Slopes (?H:1V) (ft)20.0
Flow Length (ft)748
Elevation Up (ft)526.0
Elevation Down (ft)525.0
Manning's "n"0.010
Area (sq. ft)220.000 0.000 0.000 0.000
Wetted Perimeter (ft)240.050 0.000 0.000 0.000
Hydraulic Radius (ft)0.916 0.000 0.000 0.000
Channel Slope (ft/ft)0.0013 0.0000 0.0000 0.0000
Average Velocity (ft/sec)5.139 0.000 0.000 0.000
Time Of Concentration (mins)2.4 0.0 0.0 0.0 2.4
CIRCULAR PIPE FLOW (Gravity)SEG #1 SEG #2 SEG #3 SEG #4
Pipe Diameter (in)60
Flow Length (ft)104
Elevation Up (ft)532.0
Elevation Down (ft)530.0
Manning's "n"0.013
Area (sq. ft)19.625 0.000 0.000 0.000
Wetted Perimeter (ft)15.700 0.000 0.000 0.000
Hydraulic Radius (ft)1.250 0.000 0.000 0.000
Channel Slope (ft/ft)0.0192 0.0000 0.0000 0.0000
Average Velocity (ft/sec)18.457 0.000 0.000 0.000
Time Of Concentration (mins)0.09 0.00 0.00 0.00 0.1
Total Length of Flow Path (feet)2502.00
Total Time Of Concentration (Minutes)21.38
Total Time Of Concentration (Hours)0.3563
Lagtime (Hours)0.2138

SCS Type II 6 hour Rainfall Distribution
Time (min)Time (hrs)Cum. %
1 0 0 0.0000
2 7.5 0.125 0.0053
3 15 0.25 0.0108
4 22.5 0.375 0.0164
5 30 0.5 0.0223
6 37.5 0.625 0.0284
7 45 0.75 0.0347
8 52.5 0.875 0.0414
9 60 1 0.0483
10 67.5 1.125 0.0555
11 75 1.25 0.0632
12 82.5 1.375 0.0712
13 90 1.5 0.0797
14 97.5 1.625 0.0887
15 105 1.75 0.0984
16 112.5 1.875 0.1089
17 120 2 0.1203
18 127.5 2.125 0.1328
19 135 2.25 0.1467
20 142.5 2.375 0.1625
21 150 2.5 0.1808
22 157.5 2.625 0.2042
23 165 2.75 0.2351
24 172.5 2.875 0.2833
25 180 3 0.6632
26 187.5 3.125 0.7351
27 195 3.25 0.7724
28 202.5 3.375 0.7989
29 210 3.5 0.8179
30 217.5 3.625 0.8380
31 225 3.75 0.8538
32 232.5 3.875 0.8676
33 240 4 0.8801
34 247.5 4.125 0.8914
35 255 4.25 0.9019
36 262.5 4.375 0.9115
37 270 4.5 0.9206
38 277.5 4.625 0.9291
39 285 4.75 0.9371
40 292.5 4.875 0.9446
41 300 5 0.9519
42 307.5 5.125 0.9588
43 315 5.25 0.9653
44 322.5 5.375 0.9719
45 330 5.5 0.9777
46 337.5 5.625 0.9836
47 345 5.75 0.9892
48 352.5 5.875 0.9947
49 360 6 1.0000
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
0 1 2 3 4 5 6 7
SCS Type II -6-hour
SCS Type II
4/18/2011 Dan River Ash Basins Page 1 of 1
SCS CURVE NUMBER CALCULATIONS
Dry Fly Ash Basin
Land Use Type Soil Type Area (acres)% of Perv.SCS CN Weighted CN
Open Space (Fair)B 26.94 42.83%69 29.55
Open Space (Fair)C 35.96 57.17%79 45.16
Open Water (Impervious)N/A 0 100 100.00
Pervious Area 62.9 Weighted CN*74.72
Total Area 62.9 % Impervious 0.00%
*Weighted Curve Number does not include impervious area
Primary Ash Basin
Land Use Type Soil Type Area (acres)% of Perv.SCS CN Weighted CN
Open Space (Fair)B 5.21 92.05%69 63.51
Open Space (Fair)C 0.45 7.95%79 6.28
Open Water (Impervious)N/A 21.74 100 100.00
Pervious Area 5.66 Weighted CN*69.80
Total Area 27.4 % Impervious 79.34%
*Weighted Curve Number does not include impervious area
Secondary Ash Basin
Land Use Type Soil Type Area (acres)% of Perv.SCS CN Weighted CN
Open Space (Fair)B 14.45 71.39%69 49.26
Open Space (Fair)C 5.79 28.61%79 22.60
Open Water (Impervious)N/A 9.13 100 100.00
Pervious Area 20.24 Weighted CN*71.86
Total Area 29.37 % Impervious 31.09%
*Weighted Curve Number does not include impervious area
Chaptar 2 Estimating B cineff
Tall le ME Runoillaurw narnl En foi uil anaram 1t
Taahnilial Raliase 115
Url an lIldralog I fa i Small Watanil ads
Q urva nuiul ars fc ii
----_�_•._ __. -. .-.-_ ._••_ Q c vE ii da i c riptic n------------ —--•-----liydre lol lie sc it grc lull_ --
Couch type and hildiolc gia aondillon
FUlllyl daveJhpad i LrI an areas (vagatatian astahiltihi i
.Miei age psrcan I
impervia us ara 2 21 A 13 C D
Open sipa co (lawns, parks, gc If aouises, aen et( ies, ate.):
I c on condition (gaass aoue n < al %)..........................................
No itaondltii n (gsassaouei 1(%t( 799) ................................ -
Ga c d aon ditia n (I lnai s a oiii : 71191.........................................
In pervious aveas :
Paged paillrinll lc ts, 11114 i va ways, E tl .
(axaludingright cf-via,0.............................................................
Sti eel! an d iced: :
II aw d; curbs and store novauri (exaludinl
night-c 1wialo................................................................................
Raved; og an diti hes (iiicludin €l rillht-i &way) ..........................
GmveI (inaludlnll rigl t-of-A aSl).................................................
Dirt (fin cluding ill ht-c I-vea10......................................................
weeiten des art unbar aness:
Nate ial deset landsaol inl (parvioi is areas onI)f a .....................
Ar lifiaial deaart laildsaapinll (iniperviou E m(d barrio r,
deEiart ehn b miitll 1-to 9-inah a and a i gnaval n Wet
and basin 1 c iii ......................................................................
Unl an disitriats:
Con meraial and t us inc ss.................................................................
Induiitrial.............................................................................................
It (sidanl is distrii is t y aw sal a lol aise:
I/8aer4 on le asQtcwit heuaici)..........................................................
I/4 a cna................................................................................................
I/3 a cne................................................................................................
1/2 acaa................................................................................................
Iacre...................................................................................................
Iaares................................................................................................-
Lkive aping i A aai areas
Nev ly glaa ad arias
(pervia u a are as on ly, ni ve go tall is n)1i I................................................................
Idle lands ijCN's are determined to sing aoiieii types
sim'lar t( 1he se in tal le 2-1a).
18
19
all 89
Z19
19
79 84
39
III
41 aQ
98
la
91 98
98
98
A 98
a
19
91 91
16
8a
f1 91
12
82
81 81
43
13
81 88
96
96
91 �Q
811 89
92
9,1 �1
ill f l
88
9:1 91
(� 17
35
94 �1
211 6.1
15
(9 81
31 97
12
81 f 1
25 F�-
10
84 F1
21 9.1
98
19 811
11 Z16
15
11 81
ill 86 9J 9'1
1 Avaimgo nunafYaanditian, and I.= 9.2S.
2 T] a a inraIlepirivatirrmperviaueana itawawaa use dt-odavclan the aalupositE QIN's.Othaaass iurnpt'onsare as la ]Iaws:fmperviausaraa: all
direatll aoni tc tl111 dr, isalle system, inpcivic us azaashavE a ON r f 118, and 1crviaus anus asa aaasids ied 4quinialiinttc a)lan apace in
good 1 ydrola Ilia soadit'on. (IN's far athaii asml biotic is of canditicns mall be aamnuted insilill figure 2-2 a
a CN's sl own ale 04valentto thane oppmtura. Composite 4111 maybe rrosxlutrd fosethcr aanlinaL'oni of opiii sl ace
sovertyge.
e Ce inn osita MA's fa- i natural dese rt loin dseall h i g should bE cc mg ute d using fi€lure s 2-2 a. i 1-4 bas , i d a n the img ervia us a re a pa, ices talta
(ON =18) ai i d the g i n is us ara a ON. ' 1 c pa rvic l is arc a CN's am as sums d e q aims 14 nt to de Bert st rut in p oa r 1 ydrola 1 lie CO n dition.
G Cc inn osite VI's tc us e. for ttlr i le sip I of to mg orary me as ura s duaing grading and ion tructian sl ould 1 a as inn ute cl i is iri l I llrgurE i-9 a r 2 4
based antheeleFneofdavalajmant(irnparviou■areajeraenta;le)gridttli ON' firtharawlygradEd gerviausareas.
(210.VI-TR4J, 8 aaaA Ed., Juna 1980) 2-11

Dan River Dry Fly Ash Basin Stage-Storage
Elevation Area (SF)Area (acres)]Volume (CF)Volume (AF)
530.0 0.00 0.00 0.00 0.00
531.0 9.05 0.00 5.18 0.00
532.0 14.73 0.00 17.28 0.00
533.0 266.84 0.01 231.10 0.01
534.0 385.17 0.01 555.88 0.01
535.0 12477.58 0.29 5547.74 0.13
536.0 41896.87 0.96 31290.19 0.72
537.0 72821.75 1.67 99408.19 2.28
538.0 83705.98 1.92 177524.38 4.08
539.0 93968.59 2.16 267543.21 6.14
540.0 101822.07 2.34 365443.14 8.39
541.0 118702.41 2.73 479138.31 11.00
542.0 128290.50 2.95 602677.41 13.84
543.0 139051.80 3.19 736958.86 16.92
544.0 148490.61 3.41 880740.25 20.22
545.0 159753.12 3.67 1035211.15 23.77
546.0 170278.65 3.91 1200230.93 27.55
547.0 181759.79 4.17 1376702.33 31.60
548.0 192937.58 4.43 1563990.92 35.90
549.0 205045.32 4.71 1763408.20 40.48
550.0 216804.04 4.98 1974282.62 45.32
551.0 230283.96 5.29 2198687.93 50.47
552.0 242428.06 5.57 2435005.26 55.90
553.0 254995.56 5.85 2684110.41 61.62
554.0 267189.85 6.13 2945161.77 67.61
555.0 283274.13 6.50 3222135.36 73.97
556.0 295942.24 6.79 3511736.84 80.62
557.0 309962.55 7.12 3815344.20 87.59
558.0 322761.35 7.41 4131697.31 94.85
558.2 333600.47 7.66 4197344.84 96.36
Dan River Steam Station
Stage-Storage Data
Primary Ash Basin
Elevation Area (sf)Area (ac)Inc. Vol. (cf)Cum. Vol. (cf)Cum. Vol. (af)
528 322,373.24 7.40 0 0 0.00
529 357,889.78 8.22 340131.51 340131.51 7.81
530 397,708.17 9.13 377798.975 717930.485 16.48
531 427,934.59 9.82 412821.38 1130751.865 25.96
532 488,917.54 11.22 458426.065 1589177.93 36.48
Secondary Ash Basin - 515
Elevation Area (sf)Area (ac)Inc. Vol. (cf)Cum. Vol. (cf)Cum. Vol. (af)
505 14,470.76 0.33 0 0 0.00
506 30,808.92 0.71 0 0 0.00
507 71,914.41 1.65 0 0 0.00
508 93,084.25 2.14 0 0 0.00
509 111,062.61 2.55 0 0 0.00
510 131,750.59 3.02 0 0 0.00
511 145,539.80 3.34 0 0 0.00
512 160,997.92 3.70 0 0 0.00
513 170,799.03 3.92 0 0 0.00
514 210,489.95 4.83 0 0 0.00
515 307,892.76 7.07 0 0 0.00
516 325,532.50 7.47 316712.63 316712.63 7.27
517 342,965.03 7.87 334248.765 650961.395 14.94
518 354,636.67 8.14 348800.85 999762.245 22.95
519 363,320.39 8.34 358978.53 1358740.775 31.19
520 371,083.28 8.52 367201.835 1725942.61 39.62
521 378,179.73 8.68 374631.505 2100574.115 48.22
522 385,521.98 8.85 381850.855 2482424.97 56.99
523 398,408.40 9.15 391965.19 2874390.16 65.99
524 427,168.80 9.81 412788.6 3287178.76 75.46
525 505,379.05 11.60 466273.925 3753452.685 86.17
526 533,029.28 12.24 519204.165 4272656.85 98.09
527 544,347.19 12.50 538688.235 4811345.085 110.45
528 567,885.15 13.04 556116.17 5367461.255 123.22
528.52 582,716.70 13.38 299156.481 5666617.736 130.09
529 596407.37 13.69 582146.26 5949607.515 136.58
Note: Stage-Storage Data based on new topo obtained by LDSI (2014)
1S
Dry Fly Ash Basin DA
3S
Primary Ash Basin DA
5S
Secondary Ash Basin
DA
2P
Dry Fly Ash Pond
4P
Primary Ash Basin Pond
6P
Secondary Ash Basin
Pond-515
Routing Diagram for Dan_River_Phase_2-515
Prepared by AMEC, Printed 10/12/2016
HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 2HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Area Listing (all nodes)
Area
(acres)
CN Description
(subcatchment-numbers)
41.390 69 Pasture/grassland/range, Fair, HSG B (1S, 5S)
46.100 79 Pasture/grassland/range, Fair, HSG C (1S, 5S)
0.450 69 Pasture/grassland/range, Poor, HSG B (3S)
26.940 79 Pasture/grassland/range, Poor, HSG C (3S)
4.830 98 Ponded Water (5S)
119.710 76 TOTAL AREA
Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 3HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Soil Listing (all nodes)
Area
(acres)
Soil
Group
Subcatchment
Numbers
0.000 HSG A
41.840 HSG B 1S, 3S, 5S
73.040 HSG C 1S, 3S, 5S
0.000 HSG D
4.830 Other 5S
119.710 TOTAL AREA
Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 4HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Ground Covers (all nodes)
HSG-A
(acres)
HSG-B
(acres)
HSG-C
(acres)
HSG-D
(acres)
Other
(acres)
Total
(acres)
Ground
Cover
Subcatchment
Numbers
0.000 41.390 46.100 0.000 0.000 87.490 Pasture/grassland/range, Fair 1S,
5S
0.000 0.450 26.940 0.000 0.000 27.390 Pasture/grassland/range, Poor 3S
0.000 0.000 0.000 0.000 4.830 4.830 Ponded Water 5S
0.000 41.840 73.040 0.000 4.830 119.710 TOTAL AREA
Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 5HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Pipe Listing (all nodes)
Line# Node
Number
In-Invert
(feet)
Out-Invert
(feet)
Length
(feet)
Slope
(ft/ft)
n Diam/Width
(inches)
Height
(inches)
Inside-Fill
(inches)
1 5S 0.00 0.00 104.0 0.0192 0.013 60.0 0.0 0.0
2 2P 530.00 525.00 200.0 0.0250 0.024 36.0 0.0 0.0
3 4P 526.17 524.00 50.0 0.0434 0.013 36.0 0.0 0.0
4 6P 498.00 495.00 150.0 0.0200 0.013 33.0 0.0 0.0
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 6HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Time span=0.00-72.00 hrs, dt=0.05 hrs, 1441 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=62.900 ac 0.00% Impervious Runoff Depth=18.35"Subcatchment 1S: Dry Fly Ash Basin DA
Flow Length=1,670' Tc=9.0 min CN=75 Runoff=2,363.41 cfs 96.197 af
Runoff Area=27.390 ac 0.00% Impervious Runoff Depth=19.00"Subcatchment 3S: Primary Ash Basin DA
Flow Length=1,694' Tc=43.2 min CN=79 Runoff=469.95 cfs 43.377 af
Runoff Area=29.420 ac 16.42% Impervious Runoff Depth=18.68"Subcatchment 5S: Secondary Ash Basin
Flow Length=2,502' Tc=22.1 min CN=77 Runoff=762.01 cfs 45.804 af
Peak Elev=553.28' Storage=64.142 af Inflow=2,363.41 cfs 96.197 afPond 2P: Dry Fly Ash Pond
36.0" Round Culvert n=0.024 L=200.0' S=0.0250 '/' Outflow=112.32 cfs 96.197 af
Peak Elev=531.34' Storage=29.582 af Inflow=469.95 cfs 43.377 afPond 4P: Primary Ash Basin Pond
Outflow=65.24 cfs 43.288 af
Peak Elev=522.96' Storage=65.634 af Inflow=891.47 cfs 185.289 afPond 6P: Secondary Ash Basin
Outflow=138.89 cfs 185.209 af
Total Runoff Area = 119.710 ac Runoff Volume = 185.378 af Average Runoff Depth = 18.58"
95.97% Pervious = 114.880 ac 4.03% Impervious = 4.830 ac
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 7HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: Dry Fly Ash Basin DA
Runoff = 2,363.41 cfs @ 3.00 hrs, Volume= 96.197 af, Depth=18.35"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"
Area (ac) CN Description
26.940 69 Pasture/grassland/range, Fair, HSG B
35.960 79 Pasture/grassland/range, Fair, HSG C
62.900 75 Weighted Average
62.900 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.5 100 0.1800 0.47 Sheet Flow, Sheet Flow
Range n= 0.130 P2= 3.40"
2.0 593 0.0911 4.86 Shallow Concentrated Flow, Shallow Concentrated
Unpaved Kv= 16.1 fps
3.5 977 0.0266 4.59 128.64 Channel Flow, Channel Flow
Area= 28.0 sf Perim= 26.3' r= 1.06' n= 0.055
9.0 1,670 Total
Subcatchment 1S: Dry Fly Ash Basin DA
Runoff
Hydrograph
Time (hours)
7065605550454035302520151050
Fl
o
w

(
c
f
s
)
2,600
2,400
2,200
2,000
1,800
1,600
1,400
1,200
1,000
800
600
400
200
0
Runoff=2,363.41 cfs @ 3.00 hrs
Type II
6-hr
3/4 PMP Rainfall=21.90"
Runoff Area=62.900 ac
Runoff Volume=96.197 af
Runoff Depth=18.35"
Flow Length=1,670'
Tc=9.0 min
CN=75
2,363.41 cfs @ 3.00 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 8HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 3S: Primary Ash Basin DA
Runoff = 469.95 cfs @ 3.39 hrs, Volume= 43.377 af, Depth=19.00"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"
Area (ac) CN Description
* 0.450 69 Pasture/grassland/range, Poor, HSG B
* 26.940 79 Pasture/grassland/range, Poor, HSG C
27.390 79 Weighted Average
27.390 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.2 100 0.0100 0.15 Sheet Flow, Sheet Flow
Range n= 0.130 P2= 3.40"
32.0 1,594 0.0069 0.83 Shallow Concentrated Flow, Shallow Concentrated
Nearly Bare & Untilled Kv= 10.0 fps
43.2 1,694 Total
Subcatchment 3S: Primary Ash Basin DA
Runoff
Hydrograph
Time (hours)
7065605550454035302520151050
Fl
o
w

(
c
f
s
)
500
450
400
350
300
250
200
150
100
50
0
Runoff=469.95 cfs @ 3.39 hrs
Type II
6-hr
3/4 PMP Rainfall=21.90"
Runoff Area=27.390 ac
Runoff Volume=43.377 af
Runoff Depth=19.00"
Flow Length=1,694'
Tc=43.2 min
CN=79
469.95 cfs @ 3.39 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 9HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 5S: Secondary Ash Basin DA
Runoff = 762.01 cfs @ 3.14 hrs, Volume= 45.804 af, Depth=18.68"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"
Area (ac) CN Description
14.450 69 Pasture/grassland/range, Fair, HSG B
10.140 79 Pasture/grassland/range, Fair, HSG C
* 4.830 98 Ponded Water
29.420 77 Weighted Average
24.590 83.58% Pervious Area
4.830 16.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.2 100 0.0100 0.15 Sheet Flow, Sheet Flow
Range n= 0.130 P2= 3.40"
8.3 1,550 0.0374 3.11 Shallow Concentrated Flow, Shallow Concentrated Flow
Unpaved Kv= 16.1 fps
2.5 748 0.0013 5.06 1,112.30 Channel Flow, Channel Flow
Area= 220.0 sf Perim= 240.0' r= 0.92' n= 0.010
0.1 104 0.0192 18.38 360.88 Pipe Channel, RCP_Round 60"
60.0" Round Area= 19.6 sf Perim= 15.7' r= 1.25'
n= 0.013
22.1 2,502 Total
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 10HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Subcatchment 5S: Secondary Ash Basin DA
Runoff
Hydrograph
Time (hours)
7065605550454035302520151050
Fl
o
w

(
c
f
s
)
800
700
600
500
400
300
200
100
0
Runoff=762.01 cfs @ 3.14 hrs
Type II
6-hr
3/4 PMP Rainfall=21.90"
Runoff Area=29.420 ac
Runoff Volume=45.804 af
Runoff Depth=18.68"
Flow Length=2,502'
Tc=22.1 min
CN=77
762.01 cfs @ 3.14 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 11HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 2P: Dry Fly Ash Pond
Inflow Area = 62.900 ac, 0.00% Impervious, Inflow Depth = 18.35" for 3/4 PMP event
Inflow = 2,363.41 cfs @ 3.00 hrs, Volume= 96.197 af
Outflow = 112.32 cfs @ 4.24 hrs, Volume= 96.197 af, Atten= 95%, Lag= 74.2 min
Primary = 112.32 cfs @ 4.24 hrs, Volume= 96.197 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
Peak Elev= 553.28' @ 4.24 hrs Surf.Area= 0.000 ac Storage= 64.142 af
Plug-Flow detention time= 254.4 min calculated for 96.130 af (100% of inflow)
Center-of-Mass det. time= 254.5 min ( 449.8 - 195.3 )
Volume Invert Avail.Storage Storage Description
#1 530.00' 96.400 af Custom Stage Data Listed below
Elevation Cum.Store
(feet) (acre-feet)
530.00 0.000
535.00 0.130
540.00 8.400
545.00 23.800
550.00 45.300
555.00 74.000
558.20 96.400
Device Routing Invert Outlet Devices
#1 Primary 530.00'36.0" Round Culvert
L= 200.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 530.00' / 525.00' S= 0.0250 '/' Cc= 0.900
n= 0.024, Flow Area= 7.07 sf
Primary OutFlow Max=112.32 cfs @ 4.24 hrs HW=553.28' TW=520.83' (Dynamic Tailwater)
1=Culvert (Barrel Controls 112.32 cfs @ 15.89 fps)
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 12HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Pond 2P: Dry Fly Ash Pond
Inflow
Primary
Hydrograph
Time (hours)
7065605550454035302520151050
Fl
o
w

(
c
f
s
)
2,500
2,000
1,500
1,000
500
0
Inflow Area=62.900 ac
Inflow=2,363.41 cfs @ 3.00 hrs
Primary=112.32 cfs @ 4.24 hrs
Peak Elev=553.28'
Storage=64.142 af
36.0"
Round Culvert
n=0.024
L=200.0'
S=0.0250 '/'
2,363.41 cfs @ 3.00 hrs
112.32 cfs @ 4.24 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 13HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 4P: Primary Ash Basin Pond
Inflow Area = 27.390 ac, 0.00% Impervious, Inflow Depth = 19.00" for 3/4 PMP event
Inflow = 469.95 cfs @ 3.39 hrs, Volume= 43.377 af
Outflow = 65.24 cfs @ 4.63 hrs, Volume= 43.288 af, Atten= 86%, Lag= 74.2 min
Primary = 65.24 cfs @ 4.63 hrs, Volume= 43.288 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
Peak Elev= 531.34' @ 4.63 hrs Surf.Area= 0.000 ac Storage= 29.582 af
Plug-Flow detention time= 286.7 min calculated for 43.258 af (100% of inflow)
Center-of-Mass det. time= 288.6 min ( 513.9 - 225.4 )
Volume Invert Avail.Storage Storage Description
#1 528.00' 36.480 af Custom Stage Data Listed below
Elevation Cum.Store
(feet) (acre-feet)
528.00 0.000
529.00 7.810
530.00 16.480
531.00 25.960
532.00 36.480
Device Routing Invert Outlet Devices
#1 Primary 526.17'36.0" Round Culvert
L= 50.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 526.17' / 524.00' S= 0.0434 '/' Cc= 0.900
n= 0.013, Flow Area= 7.07 sf
#2 Device 1 528.00'4.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s)
#3 Device 1 528.00'4.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s)
Primary OutFlow Max=65.24 cfs @ 4.63 hrs HW=531.34' TW=521.20' (Dynamic Tailwater)
1=Culvert (Inlet Controls 65.24 cfs @ 9.23 fps)
2=Sharp-Crested Rectangular Weir (Passes < 66.62 cfs potential flow)
3=Sharp-Crested Rectangular Weir (Passes < 66.62 cfs potential flow)
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 14HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Pond 4P: Primary Ash Basin Pond
Inflow
Primary
Hydrograph
Time (hours)
7065605550454035302520151050
Fl
o
w

(
c
f
s
)
500
450
400
350
300
250
200
150
100
50
0
Inflow Area=27.390 ac
Inflow=469.95 cfs @ 3.39 hrs
Primary=65.24 cfs @ 4.63 hrs
Peak Elev=531.34'
Storage=29.582 af
469.95 cfs @ 3.39 hrs
65.24 cfs @ 4.63 hrs
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 15HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 6P: Secondary Ash Basin Pond-515
Inflow Area = 119.710 ac, 4.03% Impervious, Inflow Depth = 18.57" for 3/4 PMP event
Inflow = 891.47 cfs @ 3.15 hrs, Volume= 185.289 af
Outflow = 138.89 cfs @ 9.63 hrs, Volume= 185.209 af, Atten= 84%, Lag= 389.0 min
Primary = 138.89 cfs @ 9.63 hrs, Volume= 185.209 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
Peak Elev= 522.96' @ 9.63 hrs Surf.Area= 0.000 ac Storage= 65.634 af
Plug-Flow detention time= 263.9 min calculated for 185.209 af (100% of inflow)
Center-of-Mass det. time= 262.5 min ( 667.2 - 404.7 )
Volume Invert Avail.Storage Storage Description
#1 515.00' 136.580 af Custom Stage Data Listed below
Elevation Cum.Store
(feet) (acre-feet)
515.00 0.000
516.00 7.270
517.00 14.940
518.00 22.950
519.00 31.190
520.00 39.620
521.00 48.220
522.00 56.990
523.00 65.990
524.00 75.460
525.00 86.170
526.00 98.090
527.00 110.450
528.00 123.220
529.00 136.580
Device Routing Invert Outlet Devices
#1 Primary 498.00'33.0" Round Culvert
L= 150.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 498.00' / 495.00' S= 0.0200 '/' Cc= 0.900
n= 0.013, Flow Area= 5.94 sf
#2 Device 1 515.00'4.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s)
#3 Device 1 515.00'4.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s)
#4 Device 1 515.00'4.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s)
#5 Device 1 515.00'4.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s)
Primary OutFlow Max=138.89 cfs @ 9.63 hrs HW=522.96' (Free Discharge)
1=Culvert (Inlet Controls 138.89 cfs @ 23.38 fps)
2=Sharp-Crested Rectangular Weir (Passes < 176.84 cfs potential flow)
3=Sharp-Crested Rectangular Weir (Passes < 176.84 cfs potential flow)
4=Sharp-Crested Rectangular Weir (Passes < 176.84 cfs potential flow)
5=Sharp-Crested Rectangular Weir (Passes < 176.84 cfs potential flow)
Type II 6-hr 3/4 PMP Rainfall=21.90"Dan_River_Phase_2-515
Printed 10/12/2016Prepared by AMEC
Page 16HydroCAD® 10.00-18 s/n 00996 © 2016 HydroCAD Software Solutions LLC
Pond 6P: Secondary Ash Basin Pond-515
Inflow
Primary
Hydrograph
Time (hours)
7065605550454035302520151050
Fl
o
w

(
c
f
s
)
900
800
700
600
500
400
300
200
100
0
Inflow Area=119.710 ac
Inflow=891.47 cfs @ 3.15 hrs
Primary=138.89 cfs @ 9.63 hrs
Peak Elev=522.96'
Storage=65.634 af
891.47 cfs @ 3.15 hrs
138.89 cfs @ 9.63 hrs