20100735 Ver 1_Stormwater Info_20101023

•
•
PRE- AND POST-DEVELOPMENT
STORMWATER MANAGEMENT CALCULATIONS
For
FIRST CHOICE EYECARE
PARCEL # 08324002
STALLINGS, NORTH CAROLINA
Prepared For:
First Choice Eye Care
c/o Kevin and Margaret Bigham
7800 Stevens Mill Road
Matthews, North Carolina 28104
Prepared By:
Amicus Engineering, PC
7714 Matthews-Mint Hill Road
Charlotte, North Carolina 28227
SEALS ;.
032006
G it
Original Submi t?l - September 2010
#'?@Cc7 ??' - -
OrT2?1QlO
eftvoy
• Amicus Engineering Project No: 17-10-033
•
APPENDIX I CALCULATIONS
•
0

SEDIMENT TRAP CALCULATIONS
0
0
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Sediment Traps ST-1
OBJECTIVE:
Design sediment traps ST-1 to detain runoff during Phase III of the construction
process.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Proposed Erosion Control Plan" by Amicus Engineering PC, 06/16/10.
3. Charlotte Mecklenburg Stormwater Design Manual, 1993.
TERMS:
Q i o = 10-year peak flow, (ft3/s)
C = runoff coefficient
i = rainfall intensity, (in)
A = drainage area, (acres)
tc = time of concentration, (min)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Drainage area for sediment trap ST-1 = 1.28 acres
TRAP DIMENSIONS ST-1
Height to spillway = 3.0 ft = 3.0 ft therefore ok.
Height of embankment = 5 ft = 5 ft therefore ok.
Ilil/
A
i
'HESS/G
-Q- SEAL
032006 ;
"'*GIN
???•??
lillll
Q?-16-1a [Ref: 1]
[Ref: 2]
Exterior embankment side slope = 3:1 > 2:1 therefore ok.
Interior embankment side slope = 3:1 > 2:1 therefore ok.
Weir length = 6 feet > 4 feet therefore ok.
Spillway depth = 2.0 ft > 2.0 ft therefore ok.
Top width of embankment = 5 ft > 5 ft therefore ok.
CALCULATIONS:
[Ref: 1 ]
[Ref: 1]
[Ref: 1 ]
[Ref: 1 ]
[Ref: 1 ]
[Ref: 1 ]
[Ref: 1 ]
Determine if trap ST-1 is adequate to handle the 10-year storm during
construction.
- Use rational method to determine peak flow based on conservatism and
drainage area being less than 200 acres [Ref: 3]
a. Assume maximum time of concentration is 5 minutes
- Total drainage area = 1.28 acres
b. Determine rainfall intensity based on t..
- i = 7.03 inches/hour [Ref: 3, Table 2-3]
Amicus Engineering

Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Sediment Traps ST-1
c. Determine runoff coefficient, C
- 46% Impervious area C = 0.95
- 54% Smooth bare packed soil C = 0.60
- Weighted runoff coefficient C = 0.76
d. Determine peak flow
Qo = CiA
Q,o = (0.76)(7.03in / hr)(1.28acres) = 6.84cfs
e. Check sediment trap volume
Volume for '-,erlimPnt
ST-1
[Ref: 1, Table 8.03b]
[Ref: 1, Table 8.03b]
[Ref: 3, Eq. 2-1]
Total basin volume to spillway (elev. 680.00 ft) = 7,531 ft
Minimum required basin volume = 3,600 ft3/acre
Total volume required = (3,600 ft3/acre)(1.28 acres) = 4,608 ft3
4,608 ft3 < 7,531 ft3 therefore ok.
f. Determine minimum surface area of sediment trap
- Minimum surface area = (435 sq. ft.) x (Q10)
(435 sq. ft.) x (6.84 efs) = 2,976 sq. ft.
- 2,976 sq. ft.< 3,749 sq. ft. therefore ok.
[Ref: 1 ]
[Ref: 1 ]
0
Practice Standards and Specifications
•
Y
l(:' ?
Definition A small, temporary ponding basin formed by an embankment or excavation
to capture sediment.
11
? IC Lh I
J
Purpose To detain sediment-laden runoff and trap the sediment to protect receiving
streams, lakes, drainage systems, and protect adjacent property.
Conditions Where Specific criteria for installation of atemporary sediment trap are as follows:
Practice Applies • At the outlets of diversions, channels, slope drains, or other runoff
conveyances that discharge sediment-laden water.
• Below areas that are draining 5 acres or less.
• Where access can be maintained for sediment removal and proper
disposal.
- In the approach to a stormwater inlet located below a disturbed area as
part of an inlet protection system.
• Structure life limited to 2 years.
A temporary sediment trap sbould not be located in an intermittent or
perennial stream.
Planning Select locations for sediment traps during site evaluation. Note natural
Considerations drainage divides and select trap sites so thaf runoff from potential sediment-
sediment-
producing areas can easily be diverted into the traps. Ensure the drainage
areas for each trap does not exceed 5 acres. Install temporary sediment traps
before land disturbing takes place within the drainage area
Make traps readily accessible for periodic sediment removal and other
necessary maintenance. Plan locations for sediment disposal as part of trap
site selection. Clearly designate all disposal areas on the plans.
In preparing plans for sediment traps, it is important to consider provisions to
protect the embankment from failure from storm runoff that exceeds the design
capacity- Locate bypass outlets so that flow will not damage the embankment.
Direct emergency bypasses to undisturbed natural, stable areas- If a bypass is
not possible and failure would have severe consequences, consider alternative
sites.
E Rev. 6/06

Sediment trapping is achieved primarily by settling within a pool formed by
an embankment. The sediment pool may also be formed by excavation, or by
a combination of excavation and embankment. Sediment-trapping efficiency
is a function of surface area and inflow rate (Practice 6.61, Sediment Basin).
Therefore, maximize the surface area in the design. Because porous baffles
improve flow distribution across the basin, high length to width ratios are not
necessary to reduce short-circuiting and to optimize efficiency.
Because well planned sediment traps are key measures to preventing off
site sedimentation, they should be installed in the first stages of project
development.
6.60.1
Lf-If, ?]

r
Design Criteria Summary:
Primary Spillway:
Maximum Drainage Area:
Minimum volume:
Minimum Surface Area:
Minimum L/W Ratio:
Minimum Depth:
Maximum Height:
Dewatering Mechanism:
Minimum Dewatering Time:
Baffles Required:
Temnoran, Sediment TrU
it lway
5 acre
3600 cub feet per acre of disturbed area
435 square feet per cfs of Q10 peak inflow
2:1
3.5 feet, 1.5 feet excavated below grade
Weir elevation 3.5 feet above grade
Stone Spillway
N/A
Storage capacity Provide a minimum volume of 3600 f'/acre of disturbed
area draining into the basin. Required storage volume may also be determined
by modeling the soil loss with the Revised Universal Soil Loss Equation or
other acceptable methods. Measure volume to the crest elevation of the stone
spillway outlet-
Trap cleanouf-Remove sediment from the trap, and restore the capacity
to original trap dimensions when sediment has accumulated to one-half the
design depth.
0
Trap efficiency-The following design elements must be provided for
adequate trapping efficiency:
Provide a surface area of 0.01 acres (435 square feet) per cfs based on the
10-year storm;
Convey runoff into the basin through stable diversions or temporary slope
drains;
Locale sediment inflow to the basin away from the dam to prevent short
circuits from inlets to the outlet;
Provide porous bafi9es (Practice 6.65, Porous Babes);
• Excavate 1.5 feet of the depth of the basin below grade, and provide
minimum storage depth of 2 feet above grade.
Enabanloment--Ensure that embankments for temporary sediment traps do
not exceed 5 feet in height. Measure from the center line ofthe original ground
surface to the top of the embankment. Keep the crest of the spillway outlet
a minimum of 1.5 feet below the settled top of the embankment. Freeboard
may be added to the embankment height to allow flow through a designated
bypass location. Construct embankments with a minimum top width of 5 feet
and side slopes of 2:1 or flatter. Machine compact embankments.
Excavation-Where sediment pools are formed or enlarged by excavation,
keep side slopes at 2:1 or flatter for safety.
Outlet section-Construct the sediment trap outlet using a stone section of
the embankment located at the low point in the basin. The stone section serves
two purposes: (1) the top section serves as a non-erosive spillway outlet for
flood flows; and (2) the bottom section provides a means of dewatering the
basin between runoff events.
i
6.60.2
Stone size-Construct the outlet using well-graded stones with a d50 size of g
inches (Class B erosion control stone is recommended,) and a maximum stone
Rev. 6106
C z v,1?
Practice Standards and Spec f cations
size of 14 inches. The entire upstream face of the rock structure should be
covered with fine gravel (NCDOT #57 or #5 wash stone) a minimum of I foot
thick to reduce the drainage rate.
Side slopes-Keep the side slopes of the spillway section at 2:1 or flatter.
To protect the embankment, keep the sides of the spillway at least 21 inches
thick.
Depth-The basin should be excavated 1.5 feet below grade.
Stone spillway height-The sediment storage depth should be a minimum of
2 feet and a maximum of 3.5 feet above grade.
Protection from piping-Place filter cloth on the foundation below the riprap
to prevent piping. An alternative would be to excavate a keyway trench across
the riprap foundation and up the sides to the height of the dam.
Weir length and depth-Keep the spillway weir at least 4 feet long and sized
to pass the peak discharge of the I0-year storm (Figure 6.60a). A maximum
flow depth of six inches, a minimum freeboard of 1 foot, and maximum side
slopes of 2:1 are recommended. Weir length may be. selected from Table 6.60a
shown for most site locations in North Carolina.
Cross-Section 12° min. of NCDO T #5
or #57 washed stone min
b.- -.?-• ------
- --------------
A V
3 600 cu f", /acre;
ry ,t-'--
- max
1-p . filter
'v
1AMMIn
MME - fabric
Design settled 2p
top Overfill 6° for
ml?- settlement I'll - - `? Plan View °`•?.a,?, 5 -,?,. ??.. 4' Emergency by-
Ft ass below
----? ..`. max e 1 a min.settled top of
4 f .t+ a s a ?+? ?.t dam
2' to 3.5' °p 3 N fill V??( N y, rt
--Irk y indL?r ?nr ,ri m „?rrra?p?li j1$f 1
Natural
fitter Ground
fabric min_
Figure 6.60a Plan view and cross-section view of a temporary sediment trap.
Rev. 6106
6.60.3

- M -,
• Table 6.60a Drainage Area Weir Length'
Design of Spillways (acres) (ft)
1 4.0
2 6.0
3 8.0
4 10.0
5 12.0
'Dimensions shown are minimum.
Construction 1. Clear, grub, and strip the area under the embankment of all vegetation and
Specifications root mat. Remove all surface soil containing high amounts of organic matter,
and stockpile or dispose of it properly. Haul all objectionable material to the
designated disposal area.
2. Ensure that fill material for the embankment is free of roots, woody
vegetation, organic matter, and other objectionable material. Place the fill in
lifts not to exceed 9 inches, and machine compact it_ Over fill the embankment
b inches to allow for settlement.
3. Construct the outlet section in the embankment. Protect the connection
between the riprap and the soil from piping by using filter fabric or a keyway
cutoff trench between the riprap structure and soil.
- Place the filter fabric between the riprap and the soil. Extend the fabric
across the spillway foundation and sides to the top of the dam, or
- Excavate a keyway trench along the center line of the spillway foundation
extending up the sides to the height of the dam. The trench should be at
least 2 feet deep and 2 feet wide with 1:1 side slopes.
4. Clear the pond area below the elevation of the crest of the spillway to
facilitate sediment cleanout_
5. All cut and fill slopes should be 2:1 or flatter.
6. Ensure that the stone (drainage) section of the embanlanent has a
minimum bottom width of 3 feet and maximum side slopes of 1:1 that extend
to the bottom of the spillway section-
7. Construct the minimum finished stone spillway bottom width, as shown
on the plans, with 2:1 side slopes extending to the top of the over filled
embankment. Keep the thickness of the sides of the spillway outlet structure
at a minimum of 21 inches. The weir must be level and constructed to
grade to assure design capacity.
S. Material used in the stone section should be awell-graded mixture of stone
with a d. size of 9 inches (class B erosion control stone is recommended) and
a maximum stone size of 14 inches. The stone may be machine placed and the
smaller stones worked into the voids of the larger stones. The stone should be
hard, angular, and highly weather-resistant.
9. Discharge inlet water into the basin in a manner to prevent erosion. Use
temporary slope drains or 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).
6.60.4
Rev. 6106
F)C tF:IJ

Table 8.03b Land Use C
Value of Runoff Coefficient Land Use
C
(C) for Rational Formula Business: Lawns:
Downtown areas 0.70-0.95
Neighborhood Sandy soil, flat, 2% 0.05-0.10
areas 0.50-0.70 Sandy soil, ave., 0.10-0.15
Residential: 2-7%
Single-family areas 0.30-0
50 Sandy soil, steep, 0.15-0.20
.
Multi units, detached 0.40-0.60
Multi units, Attached 0.60-0
75 Heavy soil, flat, 2% 0.13-0.17
.
Suburban
0.25-0
40 Heavy soil, ave., 0.18-0.22
. 2-7%
Industrial: Heavy soil, steep,
Light areas 0.50-0.80 7% 0.25-0.35
Heavy areas 0.60-0.90
Agricultural land:
Parks, cemeteries 0.10-0.25 Bare packed soil
Smooth 0.3 -0.60
Playgrounds 0.20-0.35 Rough 0.20-0.50

Railroad yard areas 0.20-0.40 Cultivated rows
Heavy soil no crop
0.30-0.60
Unimproved areas 0.10-0.30 Heavy soil with
crop 0.20-0.50
Streets: Sandy soil no crop 0.20-0.40
Asphalt 0 70-0 95 Sandy soil with
Concrete 0.80-0 .95 crop 0.10-0.25
Brick 0.70-0.85 Pasture

Drives and walks 0.75-0.85 Heavy soil
Sandy soil 0.15-0.45
0.05-0.25
ROOTS 07
r85 Woodlands 0.05-0.25
NOTE: The designer must use judge ment to select the appropriate C
value within the range for the appropriate land use. Generally
larger
ar
eas with permeable soils, flat slope
have lowest C val s, and dense vegetati ,
on should
ues. Smaller areas with slowly permeable soils, steep
slopes
and sparse v
t
i
,
ege
at
on should be assigned highest C values.
Source: American Society of Civil Engi neers
0 8.03.6
Rev. 6106
3.5 Design Frequency .
•
Design
Frequencies
3.5.1
Rainfall
Intensity
3.5.2
Table 3-3
Rainfall Intensities - Charlotte, North, Carolina
Storm Duration Rainfall Intensity(r_ in /hr
Return Period (Years)
h
0
•
ours minutes 2 3 5
10
0 5 5.03 5.60 6.30 1

6
`1-78
5.33
6.02 Pi
7 4.55 5.09 5.76 6
49
8 4.34 4.88 5:53 .
6
26
9 4.16 4-68 5.32 .
6
04
10 3-99 4-50 5.12 .
5
8
15 3.33 3.79 4.35 .
5
03
16 3.23 3-67 4.22 .
4
89
17 3.13 3-57 4.10 -
4
77
18 .3.04 3.47 3.99 .
4
65
19 2.96 3.37 . 3.89 .
4
53
20 2.88 3.29 3.79 .
4
43
21 2.80 3-20 3.70 .
4
32
22 2.73 3.12 3.61 .
4
23
23 2-66 3.05 3.53 .
4
14
24 2.'60 2.98 3-45 .
4
D5
25 2.54 2.91 3.37 .
3
96
26 2.48 2.85 3.30 .
3
88
27 2.43 2.79 3.23 .
3
81
28 2-38 2.73 3.17 .
3
73
29 2.33 2..68 3.11 .
3
66
30 2.28 2.62 3.05 .
3
60
40 .1.90 2.20 . 2:57 .
3
05

1 50 1.64 1.90 2.23 .
2.66

2 1.45 1.68 1.98 2.36

3 0-88 1.03 1.21;
1.45

6 0.65 -0-76 0.90 1 .07

12 0.38 0.44 0-53 0.62

. 24 0.22 0.26 0.37'
0.36
0.13 0.15 0.18 0.20
Taken from equati on f
or OF curve f or Charlo tte, N.C.

1-, n
75 50 100
8.21 9.D0 9-92
7.89 8.65 9.53
7.59 8.32 9.17
7.31 8.03 8.84
7.06 7.75 8-54
6.83 7.50 8.26
5-B7 6.46 7.11
5.72 6.29 6.S2
5.57 6.13 6.74
5.43 , 5-97 6.57
5.30 5.83 6.41
5.17 5.69 6.26
5.05 5-56 6.12
4.94 5.44 5.98
4.83 . 5.32 5.85
4.73 '5.21 5.73
.4-63 5.10 5.61
4-54 5.00 5-50
4.45 4.90 5.39
4-36 4.81 S.29-
4.28 4.72 5-19
4.20 4.64 5.09.
3.56. 3.93 4.32
3.10 3.43 3.76
2:76. 3.05 3.34
1.70 1.89 2.06
1,25 1.40 1.52
0.73 0.82 0.89
0.42 0.47 0.51
0.24 0.27 0.29
SStcarrr, 1?F'?rer- ,?er-v?src?<?
•
•
3.6 Rational Method
Introduction
3.6
1 When 'using the rational method some precautions should b

. e considered.
• In determining the C value (land use) for the drainage area, hydrologic analysis
should take into ac
count future Land use changes. Drainage facilities should
be designed for future land
o
use c
nditions as specified in the County and City
Land Use Plans.
• Since the rational method uses a composite C value for the entire drainage
area, if the distribution
f l
o
and uses within the drainage basin will affect the
results of hydrologic analysis, then the basin should be divided i
nto two or
more sub-drainage basins for analysis.
The charts, graphs, and tables included in this section are given to assist the
engineer in appl
in
h
y
g t
e rational method. The engineer should use good
engineering judgement in applying these desi
n aid
d
g
s an
should make
appropriate adjustments when specific site characteristics dictate that these
adjustments are a
i
ppropr
ate.
Runoff
Equation The rational formula estimates the: peak rate of runoff at any location in a
watershed as a fun
i

3.6.2 ct
on of the drainage area, runoff coefficient, and mean rainfall
intensity for a duration equal to the time of conc
i
f
entrat
on (the time required for
water to flow from the most remote point of th
b
i
e
as
n to the location being
analyzed). The rational formula is expressed as foIIOVVS:

(3.1)
Where_ Q = maximum rate of runoff (cfs)
C = runoff.coefficient representin
i
g a rat
o of runoff to rainfall
I = average rainfall intensity for a duration equal to the time of
concentration (in/hr)
A = drainage area contributing to the' design location (acres)
•
Infrequent
Storms
3.6.3
The coefficients given in Table 3-5 are applicable for storms of 2-yr to 10-yr
frequencies. ......
; :M-! .' %::. = Y; , „C aoiustment of the rational
method for use with major storms 'can be made by multiplying the right side of
the rational formula by a frequency factor C;. The rational formula now becomes:
a = C C,lA

3-11
(3.2)
. -
•
SKIMMER SEDIMENT TRAP
CALCULATIONS
0
0
Project No: 17-10-033 Sheet No: of
y Date: 06-16-2010
1 Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Skimmer Sediment Trap
OBJECTIVE:
Design Skimmer Sediment Trap SST-1 to contain 10-year peak runoff. The sediment
basin shall be a skimmer type sediment structure as per the North Carolina Erosion
and Sediment Control Handbook. The sediment basin shall be designed for Phase II
development conditions.
THEORY/DESIGN CONSIDERATIONS:
The structure was designed as a skimmer type sediment trap based on the drainage
area being less than 5 acres.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Phase II Erosion Control Plan; Valencia Subdivision," by Amicus Engineering
PC, 06/16/10.
3. Charlotte Mecklenburg Storm Water Design Manual, 1993.
4. Faircloth Skimmer Sizing (www.fairclothskimmer.com/skimmer.html)
TERMS: C
Q I o_ 10-year peak flow, (ft'/s) s
Qp = minimum flow through principal spillway, (ft/s) ?y
Qe =minimum flow through emergency spillway, (ft'/s) - SEAL cfs = cubic feet per second 0 3 2 0 0 6 =
C = runoff coefficient 5-
G i NE
i = rainfall intensity, (in/hr)
A = drainage area, (acres) tip/AII i I
db-i6-la
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year [Ref: 1 ]
CALCULATIONS FOR SKIMMER SEDIMENT TRAP SST-1
1. Basin Dimensions
Height of embankment = 5 ft < 5 ft therefore ok. [Ref: 1 ]
Exterior embankment side slope = 3:1 > 2:1 therefore ok. [Ref: 2]
Interior embankment side slope = 3:1 > 2:1 therefore ok. [Ref: 2]
Length to width ratio > 2:1 therefore ok. [Ref: 1]
Spillway side slope = 3:1 therefore ok. [Ref: 1]
Spillway depth = 2.0 ft > 2.0 ft therefore ok. [Ref: 2]
Top width of embankment = 8 ft therefore ok. [Ref: 1]
0
Project No: 17-10-033 Sheet No: of
Date: 06-16-2010
ti-, > Calcs Performed By: JLM
M Calcs Checked By: NRP
Amicus Ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Skimmer Sediment Trap
2. Determine peak flow for basin drainage area
- Use rational method to determine peak flow based on conservatism and
drainage area being less than 200 acres [Ref: 3]
a. Determine time of concentration
- t, = 5 minutes [Ref: 3, Fig. 3 -1]
- conservative assumption
b. Determine rainfall intensity based on t,.
- do = 7.03 inches/hour [Ref: 3, Table 3-3]
c. Determine runoff coefficient, C
- Total drainage area =1.58 acres
o Assume smooth bare packed soil, C = 0.60 [Ref: 1, Table 8.03b]
d. Determine i 0-year peak flow
Qio = CiA
Q,o = (0.60)(7.03in / hr)(1.58acres) = 6.66 ft's [Ref: 3, Eq. 3.1]
3. Determine Basin Volume
Volume for Skimmer Sediment Trap SST-1
Elevation (ft) Area (ft ) Height (ft) Volume (ft
)
[Ref: 21 [Ref: 2]
679 23,503
678 21,005 1 22,254
677 13,791 1 17,398
1 10,149
676 6,507
a. Total basin volume to principle spillway = 49,801 ft
b. Determine required basin volume
Minimum required basin volume = 3,600 ft3/acre [Ref: 1]
Total volume required = (3,600 ft3/acre)(1.58 acres) = 5,688 ft3
- 5,688 ft3 < 49,801 ft3 therefore ok.
c. Determine minimum surface area of skimmer sediment trap
- Minimum surface area = (435 sq. ft.) x (Qlo) [Ref: 1]
• - (435 sq. ft.) x (6.66 cfs) = 2,897 sq. ft.
2,897 sq. ft.< 23,503 sq. ft. therefore ok.
Project No: 17-10-033 Sheet No: of
Date: 06-16-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amim engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Skimmer Sediment Trap
d. Determine if actual surface area of skimmer sediment trap is adequate for the
50-yr storm event
Qso = CiA
Qso = (0.60)(9.00in l hr)(1.58acres) = 8.53 ft3Is
- Minimum surface area = (435 sq. ft.) x (Q50)
(435 sq. ft.) x (8.53 cfs) = 3,711 sq. ft.
3,711 sq. ft.< 23,503 sq. ft. therefore ok.
4. Design emergency spillway
a. Determine required capacity for emergency spillway
- Qe=Qio=6.66 cfs
- Elevation of bottom of spillway = 679.00 ft
- Assume excavated soil in spillway is erosion resistant
- Bottom width of spillway = 12.0 ft
- Depth of emergency spillway = 2.0 ft
- Stage = 0.69 ft <2.0 ft therefore ok.
5. Design Skimmer
a. Required water storage volume = 5,688 ft3
b. Desired dewatering time = 1 days
c. A 2.0-inch skimmer is required
d. A 0.9-inch orifice radius is required
e. A 1.8-inch orifice diameter is required
[Ref: 3, Eq. 3.1]
[Ref: 1 ]
[Ref: 1 ]
[Ref: 1, Table 8.07c]
[Ref: 1, Table 8.07c]
[Ref: 4]
[Ref: 4]
[Ref: 4]
0

•
•
N
Design Criteria Summary: Temporary Sediment Trap
Primary Spillway: Stone Spillway
Maximum Drainage Area: 5 acres
Minimum Volume: 3600 cubic feet per acre of disturbed area
Minimum Surface Area: 435 square feet per efs of Q 0 peak inflow
Minimum L/W Ratio: 2:1
Minimum Depth: 3.5 feet, 1.5 feet excavated below grade
Maximum Height: Weir elevation 3.5 feet above grade
Dewatering Mechanism: Stone Spillway
Minimum Dewatering Time: N/A
Baffles Required: 3
Storage capacity-Provide a minimum volume of 3600 f0/acre of disturbed
area draining into the basin. Required storage volume may also be determined
by modeling the soil loss with the Revised Universal Soil Loss Equation or
other acceptable methods. Measure volume to the crest elevation of the stone
spillway outlet.
Trap cleanout-Remove sediment from the trap, and restore the capacity
to original trap dimensions when sediment has accumulated to one-half the
design depth.
Trap efficiency-The following design elements must be provided for
adequate trapping efficiency:
• Provide a surface area of 0.01 acres (435 square feet) per cfs based on the
10-year storm;
• Convey runoff into the basin through stable diversions or temporary slope
drains;
• Locate sediment inflow to the basin away from the dam to prevent short
circuits from inlets to the outlet;
• Provide porous baffles (Practice 6.65, Porous Baffles);
• Excavate 1.5 feet of the depth of the basin below grade, and provide
minimum storage depth of 2 feet above grade.
Embankment-Ensure that embankments for temporary sediment traps do
not exceed 5 feet in height. Measure from the center line of the original ground
surface to the top of the embankment. Keep the crest of the spillway outlet
a minimum of 1.5 feet below the settled top of the embankment. Freeboard
may be added to the embankment height to allow flow through a designated
bypass location. Construct embankments with a minimum top width of 5 feet
and side slopes of 2:1 or flatter. Machine compact embankments.
Excavation-Where sediment pools are formed or enlarged by excavation,
keep side slopes at 2:1 or flatter for safety.
Outlet section-construct the sediment trap outlet using a stone section of
the embankment located at the low point in the basin. The stone section serves
two purposes: (1) the top section serves as a non-erosive spillway outlet for
flood flows; and (2) the bottom section provides a means of dewatering the
basin between runoff events.
Stone size-Construct the outlet using well-graded stones with a d50 size of 9
inches (Class B erosion control stone is recommended,) and a maximum stone
6.60.2
Rev. 6/06

Table 8.07c
Design Table for Vegetated Spillways Excavated in Erosion Resistant Soils
(side slopes-3 horizontal:1 vertical)
•
Discharge Slope Range Bottom Stage
Q
CFS Minimum
Percent Maximum
Percent Width
Feet Feet
15 3-3 12.2 -91 .83
3.5 18.2 12 ) 69
3.1 8.9
20 3.2 13.0 12 .81
3.3 17.3 16 .70
2.9 7.1 8 1.09
25 3.2 9.9 12 .91
3.3 13.2 16 .79
3.3 17.2 20 .70
2.9 6.0 8 1.20
30 3.0 8.2 12 1.01
3.0 10.7 16 .88
3.3 13.8 20 .78
2.8 5.1 8 1.30
2.9 6.9 12 1.10
35 3.1 9.0 16 .94
3.1 11.3 20 .85
3.2 14.1 24 .77
2.7 4.5 8 1.40
2.9 6.0 12 1.18
40 2.9 7.6 16 1.03
3.1 9.7 20 .91
3.1 11.9 24 .83
2.6 4.1 8 1.49
2.8 5.3 12 1.25
45 2.9 6.7 16 1-09
3.0 8.4 20 .98
3.0 10.4 24 .89
2.7 3.7 8 1.57
2.8 4.7 12 1.33
50 2.8 6.0 16 1.16
2.9 7.3 20 1.03
3.1 9.0 24 .94
2.6 3.1 8 1.73
2.7 3.9 12 1.47
60 2.7 4.8 16 1.28
2.9 5.9 20 1.15
2.9 7.3 24 1.05
3.0 8.6 28 .97
2.5 2.8 8 1.88
2.6 3.3 12 1.60
70 2.6 4.1 16 1.40
2.7 5.0 20 1.26
2.8 6.1 24 1.15
2.9 7.0 28 1.05
2.5 2.9 12 1.72
80 2.6 3.6 16 1.51
2.7 4.3 20 1.35
Discharge Slope Range Bottom
Sta
e
Q
CFS Minimum
Percent Maximum
Percent Width
Feet g
Feet
2.8 5.2 24 1.24
80 2.8 5.9 28 1.14
2.9 7.0 32 1.06
2.5 2.6 12 1.84
2.5 3.1 16 1.61
90 2.6 3.8 20 1.45
2.7 4.5 24 1.32
2.8 5.3 28 1.22
2.8 6.1 32 1.14
2.5 2.8 16 1.71
2.6 3.3 20 1.54
100 2.6 4.0 24 1.41
2.7 4.8 28 1.30
2.7 5.3 32 1.21
2.8 6.1 36 1.13
2.5 2.8 20 1.71
2.6 3.2 24 1.56
120 2.7 3.8 28 1.44
2.7 4.2 32 1.34
2.7 4.8 36 1.26
2.5 2.7 24 1.71
2.5 12 28 1.58
140 2.6 3.6 32 1.47
2.6 4.0 36 1.38
2.7 4.5 40 130
2.5 2.7 28 1.70
2.5 3.1 32 1.58
160 2.6 3.4 36 1.49
2.6 3.8 40 1.40
2.7 4.3 44 1.33
2.4 2.7 32 1.72
180 2.4 3.0 36 1.60
2.5 3.4 40 1.51
2.6 3.7 44 1.43
2.5 2.7 36 1.70
200 2.5 2-9 40 1.60
2.5 3.3 44 1.52
2.6 3.6 48 1.45
2.4 2.6 40 1.70
220 2.5 2.9 44 1.61
2.5 3.2 48 1.53
2.5 2.6 44 1.70
240 2.5 2.9 48 1.62
2.6 3.2 52 1.54
260 2.4 2.6 48 1.70
2.5 2.9 52 1.62
280 2.4 2.6 52 1.70
300 2.5 2.6 56 1-69
Example of Use
Given: Discharge, Q = 87 c.f.s. Spillway slope, Exit section (from profile) = 4%
Find: Bottom width and Stage in Spillway
• Procedure: Enter table from left at 90 c.f.s. Note that Spillway slope (4%) falls within slope ranges corresponding to
bottom widths of 24, 28, and 32 ft. Use bottom width, 32 ft, to minimize velocity. State in Spillway will be
1.14 ft.
Note: Computations based on: Roughness coefficient, n = 0.40. Maximum velocity 5.50 ft. per sec.
8.07.8 Rev. 6/06
Calculate Skimmer Size
Basin Volume in Cubic Feet
Days to Drain*
In NC assume 3 days to drain
•
5;688 Cu.Ft
2 Days
Skimmer Size 2.0 Inch
Orifice Radius 0.9 Inch[es]
Orifice Diameter 9.8 Inch[es]
•
E-ILL , j
Practice Standards and Specifications
•
?= ? ,;;
Definition A small, temporary ponding basin formed by an embankment or excavation
to capture sediment.
Purpose To detain sediment-laden runoff and trap the sediment to protect receiving
streams, lak=es, drainage systems, and protect adjacent property.
Conditions Where Specific criteria for installation of atemporary sediment trap are as follows:
Practice Applies - At the outlets of diversions, channels, slope drains, or other runoff
conveyances that discharge sediment-laden water-
Below areas that are draining 5 acres or less.
• Where access can be maintained for sediment removal and proper
disposal.
In the approach to a storm-water inlet located below a disturbed area as
part of an inlet protection system-
- Structure life limited to 2 years.
A temporary sediment trap should not be located in an intermittent or
perennial stream.
Planning Select locations for sediment traps during site evaluation- Note natural
Considerations drainage divides and select trap sites so that runoff from potential. sedimenci-
producing areas can easily be diverted into the trans. Ensure the drainage
areas for each trap does not exceed 5 acres. Install temporary sediment zaps
before land disturbing tal=es place within ite drainage area
Male traps readily accessible for periodic sediment removal and other
necessary maintenance. Plan locations for sediment disposal as part of trap
site selection. Clearly designate all disposal areas on the plans-
In preparing plans for sediment traps, it is important to consider provisions to
protectthe embanlanentfrom failure from storm runoff that exceeds the design
capacity. Locate bypass outlets so that flow will not damage the embankment-
Direct eme ,ency bypasses to undisturbed natural, stable areas. If a bypass is
not possible and failure would have severe consequences, consider alternative
sites.
Sediment trapping is achieved primarily by settling within a pool formed by
an embankment- The sediment pool may also be formed by excavation, or by
a combination of excavation and embankment. Sediment-trapping efficiency
is a function of surface area and inflow rate (Practice 6.61, Sediment Basin).
Therefore, maximize the surface area in the design. Because porous baffles
improve flow distribution across the basin, high length to width ratios are not
necessary to reduce short-circuiting and to optimize efficiency-
Because well planned sediment traps are key measures to preventing o$=
site sedimentation, they should be installed in the first stages of project
development.
Rev. 6/06

Design Criteria Summary: TemnorarySedimentTra1
Primary Spillway: illway
Maximum Drainage Area: 5 acre
Minimum volume: 3600 cub feet per acre of disturbed area
Minimum Surface A
rea: 435 square feet per cfs of Quo peak inflow
Minimum L/W Ratio: 2:1
Minimum Depth: 3.5 feet, 1.5 feet excavated below grade
Maximum Height: 'Weir elevation 3.5 feet above grade
Dewatering Mechanism: Stone Spillway
Minimum Dewatering Time: N/A
Baffles Required: 3
Storage capacity Provide a minimum volume of 3600 ft3/acre of disturbed
area draining into the basin. Required storage volume may also be determined
by modeling the soil loss with the Revised Universal Soil Loss Equation or
other acceptable methods. Measure volume to the crest elevation of the sto
ne
spillway outlet.
Trap cleanout- Zemove sediment from the trap, and restore the capacity
to original trap dimensions when sediment has accumulated to one-half the
design depth.
Trap efficiency-The following design elements must be provided for
adequate trapping efficiency:
- Provide a surface area of 0.01 acres (435 square feet) per cfs based on the
10-year storm;
- Convey runoff into -the basin through stable diversions or temporary slope
drains,-
- sediment inflow to the basin away from the dam to prevent short
circuits from inlets to the owlet;
• Provide porous baffles (Practice 6.65, Porous Beres);
- Excavaie 1.5 feet of the depth of the basin below grade, and provide
minimum storage depth of 2 feet above grade.
Ewbanl;ment--Ensure that embankments for temporary sediment traps do
not exceed 5 feet in height. Measure from the center line ofthe original ground
surface to the top of the emban ment_ Keep the crest of the spillway outlet
a minimum of 1.5 feet below the settled top of the embanlonent_ Freeboard
may be added to the emb
k
an
ment height to allow flow through a designated
bypass location- Construct embankments with a mi
i
t
n
mum
op width of 5 feet
and side slopes of 2:1 or flatter. Machine compact embanlanents_
Excavation-Where sediment pools are formed or enlarged by excavation,
keep side slopes at 2:1 or flatte
f
r
or safety.
Outlet section--Construct the sediment trap outlet using a stone section of
the embankment located at the low point in the basin. The stone section serves
two purposes: (1) the top section serves as a non-erosive spillway outlet for
flood flows; and (2) the bottom
ti
sec
on provides a means of dewatering the
basin between runoff events-
Stone size-Construct the outlet using well graded stones with a d50 size of 9
inches (Class B erosion control sto
i
ne
s recommended) and a maximum stone
6.60.2
Rev- 6106

,Practice Standards and Speclfcations
•

Side slopes-Keep the side slopes of the spillway section at 2:3 or flatter.
To protect the embankment, keep the sides of the spillway at least 21 inches
thick.
Depth-The basin should be excavated 1.5 feet below grade.
Stone spillway` beight-The sediment storage depth should be a minimum of
2 feet and a maximum of 3.5 feet above grade.
Protection from piping -place filter cloth on the foundation below the riprap
to prevent piping. An alternative would be to excavate a keyway trench across
the riprap foundation and up the sides to the height of the dam.
Weir lengtb and depth-Keep the spillway weir at least 4 feet long and sized
to pass the peak discharge of the I 0-year storm (Figure 6.60a)_ A maximum
flow depth of six inches, a minimum freeboard of I foot, and maximum side
slopes of 2:1 are recommended. Weir length may be selected from Table 6.60a
shown for most site locations in North Carolina.
Cross-Section 12" min. of NCDOT#5
or #57 washed stone
•
360D cu L/acre
size of 14 inches. The entire upstream face of the rock structure should be
covered with fine gravel (NCDOT #57 or 45 wash stone) a minimum of I foot
thick to reduce the drainage rate.

MIM- filter
1 :1 fabric
Design settled
top
2' to 35
----I-----------
Plan View
-------.1 -------------------------
?_ , 1.5' min.
..
5'
7'K max
Overfill 6° for
r settlement
xi
5i' 4'-? Emergency by-
,. pass 6" below
max min.?"?611
!PM
fillf? - ?t13F--msettled top of
dam
filter 3'
fabric min.
Figure 6.60a Plan view and cross-section view of a temporary sediment trap.
Rev 6/06
Natural
Ground
6.603

U-
0
Table 6.60a Drainage Area
Design of Spillways (acres) Weir Length'
) (ft)
1 4-0
2 6.0
3 8.0
4 10.D
5 12.0
Lons shown are minimum.
Constructlon 1- Clear, grub, and strip the area underthe embankment of all vegetation and
Specifications root mat. Remove all surface soil containing high amounts of organic matter and stockpile or dispose of it properly. Haul all objectionable material to the
designated disposal area.
Ensure that fill material for the embankment is free of roots, woody
vegetation, organic matter, and other objectionable material. Place the fill in
lifts not to exceed 9 inches, and machine compact it. Over fill the embankment
b inches to allow for settlement.
•
3. Construct the outlet section in the embankment. Protect the connection
between the riprap and the soil from piping by using filter fabric or a keyway
cutoff trench between the riprap structure and soil.
• Place the filter fabric between the riprap and the soil- Extend the fabric
across the spillway foundation and sides to the top of the dam; or
- Excavate a ley4vay trench along the center line of the spillway foundation
extending up the sides to the height of the darn- The trench should be at
least 2 feet deep and 2 feet wide with 1:1 side slopes.
4. Clear tie pond area below the elevation of the cre.s of the spillway to
facilitate sediment cleanout_
:5- All cut and fill slopes should be 2:1 or flatter.
0.60.4
6- Ensure tt,at the stone (drainage) section of the embauhment has a
minimum bottom width of 3 feet and maximum side slopes of 1:1 that extend
to the bottom of the spillway section-
7- Construct the minimum finished stone spillway bottom .width as shown
on the plans, with 2:1 side slopes extending to the top of the over filled
embaakment. Keep the thickness of the sides of the spillway outlet structure
at a minimum of 21 inches. The weir must be level and constructed to
grade to assure design capacity.
s- Material used in the stone section should be a well-graded mixture of stone
witb a d5, size of 9 inches (class B erosion control stone is recommended) aad
a maximum stone size of 14 inches. The stone may be machine placed and the
smaller stones worked into the voids of the larger stones. The stone should be
hard, angular, and highly weather-resistant-
9. Discharge inlet water into the basin in a manner to prevent erosion- Use
temporary slope drains or 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).
Rev. 6106
/Z ?F: IJ

Table 8.03b Land Use C
Value of Runoff Co
ff
i Land Use
C
e
ic
ent
Business:
(C) for Rational Formul
a
Downtown areas 0.70-0.95
Neighborhood a Lawns:
Sandy soil, flat, 2%
0.05-0.10
reas 0.50-0.70 Sandy soil, ave., 0.10-0.15
Residential: 2-7%
Single-family areas 0.30-0
50 Sandy soil, steep, 0.15-0.20
.
Multi units, detached 0.40-0
60
.
Multi units, Attached 0.60-0
75 Heavy soil, flat, 2% 0.13-0.17
.
Suburban 0.25-0
40 Heavy soil, ave_, 0.18-0.22
. 2-7 /°
Industrial: Heavy soil, steep,
Light areas 0.50-0.80 7% 0.25-0.35
Heavy areas 0.60-0.90 Agricultural land:
Parks, cemeteries 0.10-0.25 Bare packed soil

Playgrounds 0.20-0.35 Smooth
Rough 0.3 -0.60
0.20-0.50

Railroad yard areas 0.20-0.40 Cultivated s
Heavy soil no crop
0.30-0.60
Unimproved areas 0.10-0.30 Heavy soil with
crop 0.20-0.50
Streets: Sandy soil no crop 020-0.40
Asphalt 0 70-0 95 Sandy soil with
Concrete 0.80-0.95 crop 0.10-0.25
Brick 0.70-0.85 Pasture

Drives and walks 0.75-0-85 Heavy soil
Sandy soil 0.15-0.45
0.05-0.25
Roots 0.75--0_85 Woodlands 0.05-0.25
NOTE: The designer must use judgement to select the app
value within the range for the ropriate C
appropriate land use. Generally, larger
areas with permeable soils, fiat siopes, and dense vegetation sh
h
ould
ave lowest C values. Smaller areas with slowly permeable soils, steep
slopes
and sparse v
,
egetation should be assigned highest C values-
Source: American Society of Civil Engineers
8.03.6
Rev_ 6/06
•

•
3.S Design Frequency
Design
Frequencies
3.5.1 .

b 4.78 5.33 6
02. J o" i S. DO
6 9.92
7 .
4.55 5.09 5 76 . 5
6
49 7.89 8.65 9.53

8
4.34 4.88 5.53 .
6
26 7.59 8.32 9.17

9
4.76 4.68 5.3
2 .

6
04 7-31 8.03
8.84
10 3 ag 4 50
5.12 .
5
84 7.06 7.75 8.54
.15 .
3.33 3.79
4.35 .
5
03 6.83 7.50 8.26
16
3.23 3.67 4.22 .
4
89 5.87 6.46 7.11
17
3.13 3.57 4.10 .
4
77 5.72 6.29 6.92

-
18

.
3. 3.47 3.39 .

4.65 5
.57
5
43
6.13
6.74

- 79

20 2
.96 6 3.37. 3.89
4.53 .

5.30 . 5.97

5
83 6.57

21
2.88 3.29 3.79
2-80 3
20
4.43
5.17 .
5.69 6.41
6.26

22 .
3-70,
2.73 3.12 3
67 4.32 5.05 5.56 6.12

23 .
2.66 3.05 3.53 4.23
14 4.94 5.44 5.98

24

2.'60 2.98 3.45
.
4
4
05
4.83
5.32
'
5.85

25
2.54 2.91 3.37 .
3
96 4.73
4 5.21 5.73

26
2.48 2.85 3.30 .
3
88 .
.63 5.10 5.61

27
2.43 2.79 3.23 .

3
81 4.54 5.00 5.50
28
2.38 2.73 3.17 .
3
73 4.45
3 4.90 5.39
29
2.33 2..68 3.11; .
3
65 4.
6 4.81 5-29-

30
2.28 .2.62 3.05 .
3
60 4.28 4.72 5.19

40
.1.90 2.20 .2:57 .
3
05 4.20 4.64 5.09.

1
50
1.64 1.90 2.23 .
2
66 3.56. 3.93 4.32

2
1.45 1.68 1.98 .

2-36 3.10

2
76 3.43 3.76

.
.
3 0.88 1.03 1.21; 1.45 :
.
1
70 3.05 3.34

6
0.65 -0.76 0.90
'

1.07 .

1
25 1.89

1
40 2.06

1

12 •
0.38
0.44 0.53
0
22
0.62 .
-0.73 .
0.82 .52
0
89
24 .
0.26 . 0.31:
0.73 0.1
5 0
18 0.36 0.42 0.47 .
0.51
.
. 0,20 0.24 0.27 0.29
Taken from equati on for OF curve for Ch
l -
ar
o LTe, N. C.

S(Orrr, T ' fei Se.;-V'
:
17J
3.6 Rational Method

Introduction When using the rational method soiree precautions should be considered.
3.6. 7
• In determining the C value (land use) for the drainage area, hydrologic analysis
should take into account future lend use changes. Drainage facilities should
be designed for future land use conditions as specified in the County and City
Land Use Plans.
Since the rational method uses a composite C value for the entire drainage
area, if the distribution of land uses within the drainage basin will affect the
results of hydrologic analysis, then the basin should be divided into two or
more sub-drainage basins for analysis-
' The charts, graphs, and tables included in this section are given to assist the
engineer to applying the rational method. The engineer should use good
engineering judgement in applying these design aids and should make
appropriate adjustments when specific site characteristics dictate that these
adjustments are appropriate.
•
Runo s I ne' ra-bonal formula estimates the: peak rate of runoff at any location in a
Equation watershed as a function of the drainape area, runoff coeffiicient, and mean rainfall
3.6.2 intensity fora duration equal to the time of concentration (the time required for Y
vrater to flow from the mosi remote point cf the basin to the location being
analyzed). The rational formula is expressed as follows:
Q = CiA -
Where: Q = maximum rate of runoff (cfs)
C = runoff.coefficient representing a ratio of runoff to rainfall
1 = average rainfall intensity for a duration equal to the time of
concentration (in/hr)
A = drainage area contributing to The design location (acres)
LJ
Infrequent
Storms
3.6.3
The coefficients given in Table 3-5 are applicable for storms of 2-yr to 1 O-yr
frequencies. .:::, :................
..,Y r.,»?a._af. i ne aolustment of the rational
method for use with major storms can be made by multiplying the right side of
the rational formula by a frequency factor Ci. The rational formula now becomes:
a = C C,IA
(3.2)
3-1 1
•
HYDROLOGIC
EVALUATION
•
0
•
•
•
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
®
ln%> ? Calcs Performed By: JLM
V Calcs Checked By: NRP
Amu; Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
OBJECTIVE:
Determine the overall hydrologic conditions, both pre-developed and post-developed,
for the proposed professional building at Lawyer's Road.
DESIGN CONSIDERATIONS:
This site requires structures to control and maintain water quality and runoff volume.
Because of the lot size and the owner's need to maximize usable space, there will be
two water quality structures to provide the treatment portion of the storm water
system. These structures will be designed to treat and control the 1St inch for water
quality as well as maintain pre-developed flow conditions for the 1-year, 24-hour, 10-
year, 6-hour, the 25-year, 6-hour, and the 50-year, 24-hour storm events. The
structures will also be designed to accommodate and safely pass the 50-year, 24-hour
storm event.
REFERENCES:
1. City of Stallings Post Construction Ordinance for Phase II Stormwater
2. "Manual of Storm Water Best Management Practices," by The North Carolina
Department of Environment and Natural Resources, 2007.
3. "Precipitation-Frequency Atlas of the United States," National Oceanic and
Atmospheric Administration Atlas 14, Volume 2, Version 3.
4. "Pre-Developed Drainage Map," by Amicus Engineering, 06/16/2010.
5. Design Hydrology and Sedimentology for Small Catchments, by C.T. Haan,
1994.
6. HEC-HMS version 3.3 Developed by the Army Corps of Engineers, 2008.
7. Web Soil Survey
8. "Post-Developed Drainage Map," by Amicus Engineering, 09/01/2010.
9. Charlotte Mecklenburg Storm Water Design Manual, 1993.
TERMS:
P. = x-year 24-hour rainfall, (in)
A = drainage area, (acres)
n = manning's coefficient
L = flow length, (ft)
S = slope, (ft)
v = velocity, (ft/s)
tL = SCS lag time, (hrs)
CN = SCS curve number
Q, = x-year flow, (ft3/s)
a = surface flow coefficient
tc = time of concentration, (hrs)
CA,
'a ScAL T*
032006
11;!94AS 'R
??I1111141\ \
0Y_.0/- /O
•
•
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Amim Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
GIVEN/REQUIREMENTS:
Treat and control runoff for the 1" inch [Ref: 1]
Maintain pre-developed runoff rates for 1-yr, 24-hr storm [Ref: 1]
Maintain pre-developed runoff rates for 10-yr, 6-hr storm [Ref: 1 ]
Maintain pre-developed runoff rates for 25-yr, -hr storm [Ref: 1]
Safely pass the 50-year, 24-hour storm [Ref: 2]
Minimum freeboard = 6-inches [Ref: 2]
P1 = 2.79 inches [Ref: 3]
P2 = 3.12 inches [Ref: 9]
P10 = 3.55 inches [Ref: 3]
P25 = 4.20 inches [Ref: 3]
P50 = 6.54 inches [Ref: 3]
Soil type = Bab, ScA [Ref: 7]
Soil Hydrologic Group = B, C [Ref: 7]
1. PRE-DEVELOPED FLOW CALCULATIONS:
1. Calculate composite Curve Number and Time of Concentration for pre-
developed conditions
Subbasin 1
a. Subbasin 1 = 2.44 acres [Ref: 4]
b. Composite curve number for Subbasin 1
Soil Type
[Ref: 7] Land Cover Area (acres)
[Ref: 4] % Total
Drainage Area Curve Number
[Ref: 2, Table 3-5]
B Wooded 0.30 12 60
C Wooded 0.30 12 73
B Grassed 0.58 24 69
B Impervious 0.04 2 98
B Pond 0.10 4 100
C Pond 1.12 46 100
Pre-developed weighted UN = 84
c. Determine physical properties of various flow semnents
Sheet
flow
Coefficient [Ref: 5, Tables 3.20, 3.21 ] 0.24
Slope (ft/ft) [Ref: 4] 0.085
Length (ft) [Ref: 4] 199
•
d. Determine t,, associated with sheet flow.
0.007 (nL)0-8
t? - P0.5s0.4
2
0.007 [(0.24) (199 ft)]'*'
= 0.23hrs
(3.12in)0-5 (0.085)0.4
[Ref: 5, Eq. 3.50]
•

b. Composite curve number for Rrnhhg6n 1
[Ref: 5, Eq. 3.52]
[Ref: 6]
[Ref: 8]
Soil Type
[Ref: 7] Land Cover Area (acres)
[Ref 81 % Total
Drainage Area Curve Number
[Ref: 2, Table 3-5]
B Grassed 0.28 55 69
C Grassed 0.01 2 79
B Impervious 0.20 39 98
C
T Impervious 0.02 4 98
I VOL-uC;VUW JCU WC1g11LM1 1..1V = 6/_
c. Determine physical properties of various flow segments
Sheet
flow
Coefficient [Ref: 5, Tables 3.20, 3.21] 0.011
Slope (ft/ft) [Ref 8] 0.043
Length (ft) [Ref: 8] 94
d. Determine tc associated with sheet flow.
• 0.007(nL)0"8 _ 0.007[(0.011)(94ft)]°_a
t? - l o.sso.4 (3.12in)0-5 (0.043)°4 - 0.01hrs
V
Amlo Ingineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Cales Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
e. Detennine total pre-developed time of concentration
t,, = 0.23 hrs
tL = 0.6(t,) = 0.6(0.23 hrs) = 0.14 hrs
II. PRE-DEVELOPED HYDROLOGIC CONDITIONS:
1. Subbasin 1
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 4.37
10-yr, 6-hr 6.43
25-yr, 6-hr 8.24
50-yr, 6-hr 14.86
III. POST-DEVELOPED FLOW CALCULATIONS:
1. Calculate composite Curve Number and Time of Concentration for post-
developed conditions
Subbasin 1
a. Subbasin 1 = 0.51 acres
[Ref 5, Eq. 3.50]

Amlo Engineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Cales Performed By: JLM
Cales Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
e. Determine total post-developed time of concentration
t,? = 0.01 hrs
tL = 0.6(Q = 0.6(0.01 hrs) = 0.01 hrs
Subbasin 2
a. Subbasin 2 = 1.28 acres

Soil Type
[Ref: 7]
Land Cover
Area (acres)
[Ref: 8]
% Total
Drainage Area - -,
Curve Number
[Ref: 2, Table 3-5]
B Grassed 0.36 28 69
C Grassed 0.33 26 79
B Impervious 0.40 31 98
C Impervious 0.19 15 98
re5L -aeveiopea weigntea (_:N = r)
b. Determine nhvsical nronerties of vm in„s flow CAorm P. 1tz
•
Sheet V
flow Shallow
flow
Coefficient [Ref: 5, Tables 3.20, 3.21] 0.011 20.3
Slope (ft/ft) [Ref: 8] 0.029 0.029
Length (ft) [Ref: 8] 100 38
c. Determine t, associated with sheet flow.
0.007(nL)0-8 0.007 [(0.011)(100ft)] 0.8
tl = o s o a = o s o.a = 0.02hrs [Ref 5, Eq. 3.50]
P S (3.12in) (0.029)
d. Determine t,, associated with 2nd segment shallow concentrated flow.
v = aS0-5 = (20.3) (0.029)05 = 3.46 ft l s [Ref: 5, Eq. 3.48]
_ L _ 38ft _
O.Ohrs [Ref: 5, Eq. 3.47]
3600v 3600(3.46ftls)
e. Determine total post-developed time of concentration
t, = tl + t2 = 0.02hrs + O.Ohrs = 0.02 hrs
tL = 0.6(t,) = 0.6(0.02 hrs) = 0.01 hrs [Ref: 5, Eq. 3.52]
U
Subbasin 3
a. Subbasin 3 = 0.90 acres
b. Comllosite curve nnmher fnr Riihbn6n q
Mpf• R1
[Ref: 8]
Soil Type Land Cover Area (acres) % Total Curve Number
[Ref: 7] [Ref: 81 Drainage Area [Ref: 2, Table 3-5]
C
T 1 Grassed 0.90 100 79
[Ref: 5, Eq. 3.52]
wL -uavclvpuu weigntea l:lV = /y
•
Amicus ingineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
c. Determine physical properties of various flow sements
Sheet
flow
Coefficient [Ref: 5, Tables 3.20, 3.21] 0.24
Slope (ft/ft) [Ref: 8] 0.176
Length (ft) [Ref: 8] 37
d. Determine t, associated with sheet flow.
t _ 0.007(nL)0' _ 0.007[(0.24)(37ft)] 08 =0.05hrs
1 - PO.5sO.4 (3.12in)1.5 (0.176)0.4
e. Determine total post-developed time of concentration
t, = 0.05 hrs
tL = 0.6(t,) = 0.6(0.05 hrs) = 0.03 hrs
[Ref: 5, Eq. 3.50]
[Ref: 5, Eq. 3.52]
2. Determine storage volume available in the proposed bioretention areas and
landscaped detention area.
•
a. Bioretention Area BR-1
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft)
682.00 1,865
1.00 1,586
681.00 1,306
1. Total volume available in Bioretention Area BRA (elev. 682.00 ft) = 1,586 ft'
b. Bioretention Area BR-2
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft)
681.00 4,683
1.00 4,216
680.00 3,749
i. Total volume available in Bioretention Area BR-2 (elev. 681.00 ft) = 4,216 ft'
0

w
Amicus ingineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Cales Performed By: JLM
Cales Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
c. Pronosed Extended Drv Detention Area DDA-1
•
Elevation (ft)
[Ref: 3] Area (ft)
[Ref: 3] Height (ft) Volume (ft)
679.00 20,465
1 17,874
678.00 15,282
1 12,832
677.00 10,381
1 6,260
676.00 2,138
0.5 535
675.50 0
a. Total volume available in LDA-1 (elev. 679.00 ft) = 37,501 ft'
b. Total pond volume to overflow spillway = (elev. 678.00 ft) = 19,627 ft3
IV. POST-DEVELOPED HYDROLOGIC CONDITIONS:
1. Subbasin 1
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 1.11
10-yr, 6-hr 1.65
25-yr, 6-hr 2.15
50-yr, 24-hr 3.96
2. Subbasin 2
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 3.22
10-yr, 6-hr 4.66
25-yr, 6-hr 5.93
50-yr, 24-hr 10.52
3. Subbasin 3
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 1.61
10-yr, 6-hr 2.51
25-yr, 6-hr 3.32
50-yr, 24-hr 6.37
L`
4. Pronosed Bioretention Area BR-1
[Ref: 4]
[Ref: 4]
[Ref: 4]
[Ref: 4]
Storm Event Peak Inflow
(cfs) Peak Outflow
(cfs) Peak Storage
(acre-ft) Peak Elev.
(ft)
1" inch 0.08 0.00 0.00 681.13
4"?M>
Amim Ingineering
•
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
5. Proposed Bioretention Area BR-2
Storm Event Peak Inflow
(cfs) Peak Outflow
(cfs) Peak Storage
(acre-ft) Peak Elev.
(ft)
1St inch 0.35 0.00 0.02 680.19
6. Proposed Extended Dry Detention Area DDA-1
7.
Storm Event Peak Inflow
(cfs) Peak Outflow
(cfs) Peak Storage
(acre-ft) Peak Elev.
(ft)
1-yr, 24-hr 1.61 0.57 0.02 676.10
10-yr, 6-hr 2.51 0.66 0.04 676.22
25-yr, 6-hr 3.32 0.74 0.05 676.33
50-yr, 24-hr 6.37 1.00 0.12 676.82
Total Post-Devel oped Runoff Flowinj
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 0.57
10-yr, 6-hr 0.66
25-yr, 6-hr 0.74
50-yr, 24-hr 1.00
Off Site
8. Check Regulatory Requirements
For Commercial Site
Qi(post) = 0.57 cfs < Ql(pre) = 4.37 therefore ok.
Qlo(post) = 0.66 cfs < Q1o(pre) = 6.43 therefore ok.
Q25(post) = 0.74 cfs < Q25(pre) = 8.24 therefore ok.
Q50(post) = 1.00 cfs < Q50(pre) = 14.86 therefore ok.
For Extended Dry Detention Area DDA-1
Peak elev. For 50 year storm = 676.82 ft < 679.00 ft
Free board = 2.18 feet > 0.50 feet therefore ok.
[Ref: 4]
[Ref: 4]
[Ref: 4]

NCDENR Stormwater BMP Manual
Chapter Revised 06-16-09
. The type of ground cover at a given site greatly affects the volume of runoff.
Undisturbed natural areas, such as woods and brush, have high infiltration potentials
whereas impervious surfaces, such as parking lots and roofs, will not infiltrate runoff at
all. The ground surface can vary extensively, particularly in urban areas, and Table 3-5
lists appropriate curve numbers for most urban land use types according to hydrologic
soil group. Land use maps, site plans, and field reconnaissance are all effective methods
for determining the ground cover.
Table 3-5
Runoff curve numbers in urban areas for the SCS method (SCS , 1986)
Cover Description Curve Numbers for

Fully developed urban areas
A Hydrologic Soil Group
B C
D
Open Space (lawns, parks, golf courses, etc.)
Poor condition (< 50% grass cover) 68 79 86 89
Fair condition (50% to 75% grass cover) 49 69 79 84
Good condition (> 75% grass cover) 39 61 74 80
Impervious areas:
Paved parking lots, roofs, driveways, etc. 98 98 98 98
Streets and roads:
Paved; curbs and storm sewers 98 98 98 98
Paved; open ditches 83 89 98 98
Gravel 76 85 89 91
Dirt 72 82 85 88
Developing urban areas
Newly graded areas 77 86 91 94
Pasture (< 50% ground cover or heavily grazed) 68 79 86 89
Pasture (50% to 75% ground cover or not heavily grazed) 49 69 79 84
Pasture (>75% ground cover or lightly grazed) 39 61 74 8o
Meadow - continuous grass, protected from grazing and 30 58 71 78
generally mowed for hay
Brush (< 50% ground cover) 48 67 77 83
Brush (50% to 75% ground cover) 35 56 70 77
Brush (>75% ground cover) 30 48 65 73
Woods (Forest litter, small trees, and brush destroyed by 45 66 77 83
heavy grazing or regular burning)
Woods (Woods are grazed but not burned, and some forest 36 60 73 79
litter covers the soil)
Woods (Woods are protected from grazing, and litter and 30 55 70 77
brush adequately cover the soil)
Most drainage areas include a combination of land uses. The SCS Curve Number Model
should be applied separately: once for areas where impervious cover is directly
connected to surface water via a swale or pipe and a second time for the remainder of
the site. The runoff volumes computed from each of these computations should be
added to determine the runoff volume for the entire site.
For the portion of the site that is NOT directly connected impervious surface, a
composite curve number can be determined to apply in the SCS Curve Number Model.
The composite curve number must be area-weighted based on the distribution of land
• uses at the site. Runoff from impervious areas that is allowed to flow over pervious
Storm water Management and Calculations 3-9 July 2007

Stallings Post-Construction Storm Water Ordinance ...................September 18, 2007
0 (1) Storm Water Quality Treatment Volume
Storm water quality treatment systems shall treat the difference in the
storm water runoff from the predevelopment and post-development
conditions for the 1-year, 24-hour storm.
(2) Storm Water Quality Treatment
All structural storm water treatment systems used to meet these
requirements shall be designed to have a minimum of 85% average annual
removal for Total Suspended Solids.
(3) Storm Water Treatment System Design
General engineering design criteria for all projects shall be in accordance
with 15A NCAC 2H .1008(c), as explained in the Design Manual.
(4) Stream Buffers
Perennial streams shall have a 200-foot undisturbed buffer and
intermittent streams shall have a 100-foot undisturbed buffer in the Goose
Creek Watershed. Buffer widths shall be measured horizontally on a line
perpendicular to the surface water, landward from the top of the bank on
each side of the stream.
(5) Storm Water Volume Control
Storm water treatment systems shall be installed to control the difference
in the storm water runoff from the pre-development and post-development
conditions for the 1-year, 24-hour storm. Runoff volume drawdown time
shall be a minimum of 24 hours, but not more than 120 hours.
(6) Storm Water Peak Control
For developments greater than or equal to 10% built upon area, peak
control shall be installed for the 10-yr and 25-yr, 6-hr storms. Controlling
the 1-year, 24-hour volume achieves peak control for the 2-year, 6-hour
storm. The emergency overflow and outlet works for any pond or wetland
constructed as a storm water BMP shall be capable of safely passing a
discharge with a minimum recurrence frequency as specified in the Design
Manual. For detention basins, the temporary storage capacity shall be
restored within 72 hours. Requirements of the Dam Safety Act shall be
met when applicable.
•
20
Precipitation Frequency Data Server ufn ; 33 Page 1 of 4
3 POINT PRECIPITATION
FREQUENCY ESTIMATES
l:µ FROM NOAA ATLAS 14
CHARLOTTE MT CITY, NORTH CAROLINA (31-1695) 35.2333 N 80.85 W 711 feet
from "Precipitation-Frequency Atlas of the United States" NOAA Atlas 14, Volume 2, Version 3
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NO" National Weather Service, Silver Spring, Maryland, 2004
Extracted: Fri Jan 30 2009
?J
C ,gidencemLimits' Seasonallry `,; Lbcatlon Maps Other Info` GIS data`; Maps' "D'ocs
Precipitation Frequency Estimates (inches)
U& 2 24ARI* _ 60 2 4S hr (years) ;<run mtn min gRH hr hr da
d
y
ay c
0.40 0.64 0.80 1.09 1.36 1.58 1.69 2.04 2.41 2.79 326 3.66 4.20 4.82 6.47 7.98 10.03 11
0.47 0.76 0.95
I- I 1'.31 1.65 1.91 2.04 2.46 2.91 3.36 3.93 4.39 5.01 5.73 7.63 9.38 11.75
L J0,55...0_$8 1_l 1.58 2.03 2.38 .2.54.; 3x07 3.65 4.22 4.89 5.41 6.10 6.89 9.01 10.91 1 -1
13.42
10- DO 0..93 17.1 1 7 23 2 3 253 3_$5? $23 4.89 5.65 6.22 6.96 7.80 10.10 12.09 14.71
3?M6 4.:20 5`.04 5.81 6.68 7.33 8.16 9.02 11.56 13.64 16.37
50 " 0.71 1 1 237' 293' 33 - 81 432< 5.70 6.54 7.50 8.21 9.10 9.98 12.71 14.84 17.64
100 0.75 1.20 1.51 2.32 3.19 3.87 29 5.24 6.37 7.28 833 9.10 10.07 10.94 13.86 16.03 18.86
200 0.79 1.25 1.58 2.45 3.44 4.21 4.72 5.79 7.07 8.04 9.18 10.02 11.06 1192 15.02 17.21 20.06 C
500 0.83 1.31 1.65 2.62 3.76 4.65 5.30 6.53 8.05 9.08 10.34 11.28 12.41 13.24 16.59 18.78 21.62
1000 0.85 1.35 1.69 2.74 4.00 4.99 5.76 7.12 8.83 9.89 11.24 12.26 13.46 14.26 17.81 19.97 22.79 C
I
`These precipitation frequency estimates are based on a partial duration series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting forces estimates near zero to appear as zero.
Upper bound of the 90% confidence interval
Precipitation Frequency Estimates (inches)
30[ (Aye rs) min min min min min lmin hr hr F r hr hr ][]F
day F ay day 11 day 11 d y day
?? 0.43 0.69 0.86 1.18 1.47 1.73 1.85 1 224 2.64 3.00 3.51 3.93 .49 5.16 6.87 8.44 10.55 C
0.51 0.82 1.03 1.42 1.78 2.10 2.23 2.70 3.19 3.63 4.24 4.71 536 6.13 8.10 9.93 12.33
0.60 095 1.21 1.71 2.20 2.61 2.79 337 3.99 4.55 5.27 5.81 6.52 7.36 9.56 11.54 14.09
10 0.65 1.05 1.32 1.92 2.50 2.98 3.21 3.88 4.62 5.28 6.08 6.67 7.44 8.32 10.71 12.79 15. A 1
25 0.72 1.15 1.46 2.16 2.88 3.48 3.79 4.58 5.49 6.25 7.18 7.86 8.72 9.63 12.27 14.43 17.20 E
® 0.77 1.23' 1.55 2.34 3.17 3.85 .24 5.14 6.19 7.03 8.06 8.81 9.74 10.65 13.48 15.71 18.54
100 0.81 129 1.63 2.50 3.44 4.23 4.69 5.71 6.91 7.83 8.95 9.78 10.78 11.69 14.71 16.98 19.85
200 0.85 1.35 1.70 2.65 3.72 4.61 5.17 6.31 7.66 8.66 9.88 10.77 11.85 12.74 15.95 18.25 21.12
00 0.90' 1:42 1:79 2.84 046@571 0 681j 8.71 E? 124 13,13 13.3 14.127 17.64 19.94 24:0
®?0?2,
The upper bound of the confidence intervalat 90% confidence level is the value which 5%-of the simulated quantile values for a given frequency are greater than. . .
_.,..
't a ?EJ6!Pl ggA ?f@NgeAEd &6?il !?? riF? ,&g gR g partial oura{*9 sgrE S ?? RV&f?9d ?g60FFgR6@ (ftt@R?31..
Please refer to NOAA Atlas 14 Document for more information. NOTE:.Formatting prevents estimates near zero to appear as zero.
* Lower bound of the 90% confidence interval
h".//hdsc.nws.noaa.Rov/cpi-bin/hdse/buildout.nerl?tvDe=Df&units=us&series=nd&.tAtena... 1/30/9,009
Precipitation Frequency Data Server Page 2 of 4
F 10 0-56 0.89 1.13 1.63 2.12 2.48 2.67 3.24 3.87 4.54 525 5.78 6.50 7.28 9.51 11.43 13.97 E
25 0.61 0.98 1.24 1.83 2.44 2.88 3.13 3.81 4.58 537 6.19 6.78 7.59 8.39 10.86 12.87 15.53 if
50 0.65 1.03 1.31 1.97 2.67 3.18 3-49 426 5.13 6.03 6.93 7.57 8.46 927 11.91 13.97 16.70 Eic
?. 100 0.68 1.08 12 2.89 3.47 3.84 4.70 5.68 6.70 7.68 8.39 933 10.15 12.96 15.05 17.83 L`_`
200 0.71 1.12 1.42 2.21 3.10 3.75 4.19 5.13 6.24 7.37 8.44 921 1022 11.03 14.00 16.12 18.94 21
-1 500 o.74 1.17 1.47 2.34 3.35 4.10 4.63 5.71 6.99 8.30 9.47 10.33 11.42 12.21 15.42 17.54 20.36 2
1000 0.76 1.19 1.50 2.42 3.53 4.35 4.98 6.15 7.56 9.02 10.26 11.20 12.35 13.13 16.52 18.61 21.43 E,
The lower bound of the confidence interval at 90% confidence level is the value which 5% of the simulated quantile values for a given frequency are less than.
-These precipitation frequency estimates are based on a partial duration maxima series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting prevents estimates near zero to appear as zero.
s' _ jL)q verslorl of tables
Partial duration based Point Precipitation Frequency Estimates - Version: 3
35.2333 N 80.85 W 711 ft

S
i'
e)
ra
0
i_P
L
U
i
rL
•
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
s
7
6
5
4'
3i
2
1!
0
,
I
I i I I
_
-
I I ! I I - I _ --1 I
I I _
=
I - I _ - 1 1 I- -? "1 I I J --- ?-
I 1-J - 1 - 1 1
1
_ I I =_ -- _i I = ? I T I L_
= I I I _? -1 = _ i I I T I I I I

1
I - ` I I 1 I

- -~ I ! - - I --I -- 1 ? -

I

1 2 3 4 5 6 7 8 910 20 30 40 50 80 100 140 200 300 500 700 1000
Average Recurrence Interval (years)
Fri Jan 30 16:53:36 2009
Duration
5-min 0-rn -?- 4d-hr 30-day -?-
1 0-rr, i n- 3-hr --+-
4-day -°-
45-Clan -=
15-ruin -? 6-hr ?- 7-dau- 60-day -
30-rain -B- 12-fir -+- 10-day -{-
60-min -E 24-hr --a- 20-dais -e-
httn://hdse.nws.noaa.t?ov/cizi-binlhdsc/buildout.nerl?tvne==Df&units=us&series=nd&,3tatena..-. 111019.009

i k vation 75
15-min Unit Hydrograph from S-Curve
r rve
fs) Smoothed
S-curve Displaced
S-curve, UH'
(cfs) UH
smoothed
0 0 0 0 0
9 29 0 58 58
8 68 29 78 78
2 122 68 loft 112
S 168 122 92 100
L, .n7 217 168 98 96
7 251 217 68 85
5 285 251 68 64
5 305 285 40 44
3 331 305 52 36
7 342 331 22 28
9 355 342 26 20
360 355 10 14
2 368 360 16 12
3 375 368 14 10
-- ___%A79 377 375 4 6
- 6 378 377 2 4
.3 379 378 2 2
9 382 379 6 0
S 383 382 2 0
- -? 0 383 383 0 0
6 383 383 0 0
---- -s (D 383 383 0 0
6 383 383 0 0
s 0 383 383 0 0
Sum 769
) - S(t-D')]D/D' = [S(t) - S(t-15)130/15.
-- ?e and generally prevent direct derivation of
zaphs .for small catchments. Unit hydro-
resent direct stormwater runoff. Baseflow
and water discharges to streams must be
m the flow record before unit hydrographs
i iined from the record. Linsley et al. (1982)
__.:. sulted or details. For small catchments,
-=u1it hydrographs are generally used. Syn-
hydrographs are discussed .in detail in the
- - --•• •..:ections of this chapter- Several synthetic
raph models have been proposed. Gener-
-ovide the ordinates of the unit hydrograph
zl of the time to peak, tp, peak flow rate,
athematical or empirical shape description.
After presenting procedures for estimating these at-
tributes, several unit hydrograph models are presented.
Estimation of Time Parameters
This section deals with the estimation of the time
parameters D, tL, tp, and tb as shown in Fig. 3.22 and
the time of concentration, t,. Several methods for
estimating these parameters are available. The method
that produces results consistent with good engineering
judgement should be selected for a particular study
area.
The time of concentration is the time it takes for
flow to reach the basin outlet from the hydraulically
most remote point on the watershed. For some areas,
this parameter can be estimated by summing the flow
time for the various flow segments as the water travels
toward the watershed outlet. These segments generally
are overland flow, shallow channel flow toward larger
channels, and flow in open channels, both natural and
improved. The travel time in these various flow seg-
ments depends on the length of travel and the flow
velocity.
Once the velocity in each flow segment is deter-
mined, the time of concentration is determined from
n Li
(3-47)
i=1 Vi
where n is the number of flow segments and L; is the
length and vi the flow velocity for the ith segment.
Flow velocity of overland flow and shallow channel
flow can be estimated using results such as those of
3zzard (1946), Regan and Duru (1972), Overton and
Meadows (1976), or from the relationship
v = aS1/2 (3-48)
based on information in SCS (1975), where S is in ft/ft
and v is in fps. The coefficient a is contained in Table
3.20-
Regan and Duru (1972) present a method for esti-
mating travel time, tt, over a plane surface based on
the kinematic wave equation [Eq- (3.40)]. The equation
is valid for turbulent flow or when the product of the
rainfall excess intensity, ie, in iph and the flow length,
L, in feet is greater than 500. The equation is
0.0155 (nL)o.6
tt = ie0ASos (3.49)
e
where tt is in hours, n is Manning's n, L is in feet, ie
is in iph, and S is the slope in ft/ft. Table 3.21
presents some values for n for overland flow surfaces.
The Soil Conservation Service (1986) presents a rela-
tionship attributed to Overton and Meadows (1976) for
-Z -7
7, 77
771 7 _
0
Chapter 3. Rainfall-Runoff Estimation in Storm Water Computations
3.20 Coefficient a for Eq. (3.48)1
:e a
tnd flow
-st with heavy ground litter 2.5
; meadow 2.5
;h fallow; minimum tillage 5.1
tour; strip cropped 5.1
>dland 5.1
rt grass 7.0
ight row cultivation 8.6
untilled 10.1
:d 20.3
x concentrated flow
vial fans 10.1
std waterways 16.1
11 upland gullies 20.3
cults in fps; multiply by 0.305 to get m/sec
N. 02 Is n for Travel Time Computations for
to Surfaces (Soil Conservation Service, 1986)
Jescription n°
(concrete, asphalt,
soil 0.011
ie) 0.05
<70% 0.06
>20% 0.17
airie 0.15
b 0.24
0.41
0.13
0.40
0.80
3 are a composite of information compiled by Engman
obstacles such as litter, crop residue, ridges, and rocks-,
and the erosion and transport of sediment. These n
values are for very shallow flow depths of about 0.1 ft
or so. Table 3.21 gives Manning's n values for these
conditions. The relationship for travel time is
0.007(nL) o-s
Ti = P0,5So.4 (3.50)
where P, is the 2-year, 24-hr rainfall in inches and the
other terms are as defined for Eq. (3.49). This relation-
ship is based on shallow, steady, uniform flow-, a con-
stant rainfall excess intensity; and minor effects from
infiltration.
In urban areas, the travel time may have to be based
on a travel time to a storm drain inlet plus the travel
time through the storm drain itself. Inlet travel time
can generally be computed as the sum of overland flow
and shallow channel flow travel times. Flow in storm
drains would be considered as open channel flow with
the storm drain pipe flowing full. Often large storms
produce runoff rates that exceed the capacity of the
storm drains and some of the runoff bypasses the
drains in the form of concentrated surface flow as open
channel flow. Such flow should be considered in com-
puting the time of concentration.
Undersized culverts and bridge openings can cause
ponding of flow and a reduction in the average flow
velocity. For small ponds and situations where water is
passing through the pond with little or no storage build
up, the actual travel time through the pond may be
very small. If significant storage results, the travel time
is lengthened over that for normal channel flow, and
flow routing as discussed in Chapter 6 must be used.
Flow velocity for open channels can be estimated
from Manning's equation, which is treated in detail in
Chapter 4.
Other methods are available in the form of empirical
equations for estimating t, One such relationship that
is widely used but based on limited data is expressed by
Kirpich (1940)
:ies such as weeping lovegrass, bluegrass, buffalo grass,
and native grass mixtures.
,ig n, consider cover to a height of about 0.1 ft. This is the
(ant cover that will obstruct sheet flow.
r 0 flow over plane surfaces based on
uation and a kinematic approximation to
tions. The equation is for flow lengths of
ft. The friction value or Manning's n is
roughness coefficient that includes the
drop impact; drag over plane surfaces-,
t, = 0.0078L°.77(L/H) 0.385' (3.51)
where t, is in minutes, L is the maximum length of
flow in feet, and H is the difference in elevation in feet
between the outlet of the watershed and the hydrauli-
cally most remote point in the watershed. Obviously,
Eq. (3.51) does not consider flow resistance in the form
of overland flow and channel roughness-
Several methods for estimating the lag time of a
watershed are available. One simple method for lag
Runoff Estimati
time estimatic
The SCS (1
on natural wa
LO-8
tL = -
1
where tL is tl
of the waters
number by Ec
in percentage
an antecedes
being used as
runoff potenti
Many local
shed physical
example, Putr
North Carolir
where tL is t
the main wat
slope in feet
area. Here tL
of mass of r
Before an ec
exercised to
equation was
est.
The duratii
ally associate
fifth to one-tt
is given by Et
Epsey et t
from 41 wate
North Caroli
2; Mississipp
The watersht
acres (3.5 to
tion equatiol
hydrographs
1
1
where tP is t.
channel leng
feet, S is the
terms of len€
omputati Runoff LSTimarlon
and roc time estimation is (Soil Conservation Service, 1973)
t- These IL = 0.6t,. (3.52)
bout 0.1
' for the The SCS (1975) has developed a lag equation based
s on natural watersheds
Los(S + 1)0.7
t = (50 < CN 5 95), (3.53)
(3.50 L 1900Y1.5
where tL is the lag in hours, L is the hydraulic length
and the of the watershed in feet, S is related to the curve
-elation,: number by Eq. (3.22), and Y is the average land slope
a con-: in percentage. The S in Eq. (3.53) should be based on
is from` an antecedent condition II curve number- since it is
being used as a measure of surface roughness and not
based' runoff potential.
travel ii Many local studies relating tL or tp or t, to water-
s time I shed physical characteristics have been conducted. For
1 flow, example, Putnam (1972) in a study of 34 watersheds in
'torn North Carolina, presented the relationship
with L 0.50
Drms j tL = 0.49( I-0.57 (3.54)
the
the
pen j where tL is the basin lag in hours, L is the length of
lm s the main water course in miles, S is the main stream
slope in feet per mile, and I is fraction of impervious
use ? area. Here tL was defined as the time from the center
)W of mass of rainfall to the center of mass of runoff.
i? Before an equation like (3.54) is used, care must be
0 exercised to see that the conditions under which the
e equation was developed match the conditions of inter-
est.
j The duration, D, of the rainfall excess that is gener-
ally associated with a unit hydrograph should be one-
fifth to one-third of the time to peak. The time to peak
is given by Eq. (3.26) as
tp = tL + D/2.
Epsey et al. (1977) studied rainfall-runoff records
E from 41 watersheds located in several states (Texas, 16;
North Carolina, 9; Kentucky, 6; Indiana, 4; Colorado,
2; Mississippi, 2; Tennessee, 1; and Pennsylvania, 1).
The watersheds ranged in size from about 9 to 9600
acres (3.5 to 3900 hectares). They developed an estima-
tion equation for the time to peak of 10-min unit
hydrographs as
tp = 3.1L0.23S-o.z5l-0.18(D 1.57 (3.55)
where tP is the time to peak in minutes, L is the main
channel length from the upper watershed boundary in
feet, S is the slope in feet per foot of the lower 80% (in
terms of length) of the main channel, I is the percent-
L
Table 3.22 cp Values for Eq. (3.55) (Epsey et al., 1977)
Manning's n
Percentage imp. 0.015 0.03 0.05 0.10 0.15
0 0.82 0.86 0.93 1.15 1.30
20 0.74 0.80 0.88 1.09 1.27
40 0.65 0.72 0.81 1.03 1.22
60 0.60 0.68 0.79 1.00 1.19
age impervious area with an assumed minimum value
of 5% for an undeveloped area, and (D is a conveyance
factor that depends on the percentage impervious area
and Manning's n for the main channel. Table 3.22
contains some representative values for (D.
The base time of a unit hydrograph is somewhat
arbitrary. Some hydrologists use a base time of five
times the time to peak. Some unit hydrograph models
have a recession limb that asymptotically approaches
q = 0, so that the base time is theoretically infinity.
Estimation of Peak Flow Parameters
The peak flow rate of a unit hydrograph is often
given by an equation of the form
qP = K4/tp. (3.56)
Based on a triangular unit hydrograph with a base
time of 2.67tp, the SCS (1972) estimates the peak flow
of a unit hydrograph from the equation
484A
9P = (3.57)
tp
where qP is the peak flow in cfs, A is the basin area in
square miles, and tp is the time to peak in hours.
Epsey et al. (1977) recommend that for 10-min unit
hydrographs, the relation
qP = 31620(A096/tp°7) (3.58)
be used where qP is in cfs, A is the drainage area in
square miles, and tp is the time to peak in minutes-
As was the case for lag time, many studies have been
conducted in an effort to relate qP to watershed physi-
cal conditions. Before any of these empirically derived
equations are used, their applicability should be care-
fully determined.

?i
the F J
Runoff Estimation
fable 3.79 i>-niin Linii HVdre32n2Dh 1_rOri S-Cur.'t
itrs- t;N- tT

_
ec'a
133
{v i_z trc 1^? tie M)
`- ? I 95 4b
- t)
25 i 23?
-e.
68
\5

7; G
=_- _ 1,
52

=s
s 50
if]
i 93
3 F,

--- =?= 3.
tel. ?j . ?? --

_._ 3S.
.
'!j

a ae L''.?terLSl?'L' and Cyltra11v prevent direct tieritaiion e,
unit b?dro_,-aph qtr =mall catchments- Lrsi h?•tro-
!?raphs renrt:e3t dircz[ siorrntwaier runoff. Pase:,f]a.v
arid; or mound vat?-r discharges,to , -au,; must be
re;xio3,=- d from the flow record b,co re: unit h drographs
can bi!,, defined from the record. L.inLlcl ci a1_ (3982)
call be rons7-ItP-d or detail,. For small catchmcnis,
synthetic unit h drographs are :zenerall; used- Svn-
tbetic unit hydrographs are discussed in detail in the
follo,Ying sections of this cbztpter. Several s_ynihctic
unit liYdrograph models have been proposed- Gencr-
ally tbey provide the ordinates of file unit hyd.rograph
as a function of the tine to peck};; 1r. ge<i.L fiOr: rate,
qn,_ and a mathematical or ernpirical shape description-
0
75
?te.r pres;:ntin? procudtirc:; fr.?- estim:uine t}Ia;c at-
trihute?. =several unit hydrograph models arc vestint d.
Estimation of Time Forarneiers
This section deals with the estimation of the tirn?-
parame,ters D. 'tL, rte, anci r. as shown. in 322 and
the time. of conceniratitin; Scteral rnetliod for
e_tin231in2 Chest parameters arc 2vail-Ale. Tllc. method
.that prod;,c s results consisicni with -good tnRinczTInn
judocm; nt sho id bL- sefeciCd for a particular salJdV
artia.
11t tirse of cuncentraiion i-. thtime it take, filr
flow- to reach the basin outlet from the. hpdraulicau':
mcr;t remotc ooini or ihe. watershed. For tonic: area::
thiC -rarainLtCr can C tSli-MatCd bi' SummnE Ih-,t»'-
t1nY fUr Itie I aWIOUS tlCl SP.JlIen1S HS the vvattr try'- els
ioward rho ivaicrsled o -lei. Th=Sc sC nm.?,-P_ s
zz ovc_land Bow., SballCc': s:.hH=1 -3 iiO-'% IUr•::?r?i I,;S?.r
chanre?C end Po-w in oDi zm V 7 % nzOS-both naiar2d P?cl
ave] iim,= ]n &tst .anous S==-
3?n3rC?ved. 1;':v 77
=nents dc?Dcnes on. the lzn_un Of and ;hc- flkn'
vtlochtv.
-nce iDe 5'iIOG-: in t aLh flow s==i!;-jn: z
hL thne O Ccr:i-l iDn 1_ >=n nod fie--?
?), • L nv of fkyw s c arit, L, ,2.C
Ier_Lh and -? - Holy., :':acir° for zih s =7-r1?_
) _'; c=?y t_e_!ard ii and -,-=tc _ a l
L.Cadorvs ='.
bzs.ed on in'ormLtion in SCS (197?=-`acre S is in i
aid is in LDS- T 31C Co5mcieni v is con-La:ned in Tai l_
Rcgar; a_ncd DurL+ 8.19;28 prescm a mc.thod for Esti-
mating, tra,:ei ri-i?t, t-_ over a plane suriacc LLiScd can
the kinematic wzly^ equation [Eq_ Thc ccuati;)P
is valid for rurbiilcni iov,, or 3•>h;--n thr product of ihti
rainfall e%cc=-< intensir _ i, ; in iph and she iflu 1en__h7
L. in feet is grt:.ater Than f@D- The equation is
t-%he.re r; is in hours, n is ManninR's dl. L is in Peer, r_
is in iph; and ti- is the slope in i-t ffi_ Tabic 5.21
presents some values for n for overland f cro % surfaces.
The Soil Consep-ation Service ( 19' 6) preknts a rela-
tionship aitributed ko Overton and Mcado*xs (1976) for

Choppar 3_ RCinfoll-Punor Estimoiiorl in 5iorrn V,ater
TobJe 3.20 C:er icacn; a for Ec. i `,;_

O: ?a"ci ?]SC

mc_?'a
Hay:
'-=
' 1 i?iti 6? 1 ?:+: fii io. ,J ?f ST'iit_5 ' - t

ser_ts_4„ nlxculfwa:ion ? b

S':?,u?•:: ;J::c??,?-?-'??.mss:' ,

JS.;

fvs:
Table -3-21 1a7_3__'_ :: o_ 1 _ '-: tt -1: Cu 3-D" ZzLi

JCL- --?--
Li D: _3
'3:-i_3a=?c PT??_?-• <-1C1'7 2? :...?J1 ?_' 'sal°c1a__ 711'0=' =C?. ?.i?.
>r!l1-_^?:c
'1 -- -
[ra%;el time for skied f-l(wr twcr plane surfaces based on
ManniaL's equation zar)d a kinenlatic apprommation to
the fioly equations- The e=quation is for lcn:zLlls of
less than 300 ft_ The 1-rictien ;slue or ManninEZ`s-r is
an, efcctivc roughness coefficient that includes the
ctiLtt o` raindrop impact= drag over plane surfaces;
Y'
ahslaele-..LlCfJ a> litter, Crnl? i - C?L3 . rl?°_v5. Win =CL
anu ti[ . eros[ora auto rrLnsllor o- sclirr eot. The>.
x
;akues are. for >eri- sha;ln::' So;, do the of about
.or o_ Table 331. ?i?'es l??cFlniS-; r values for ch
:;r;, ; F
cendiiions. The relationship for trscl ti tic is
0.00-1, P,1_ j
T. = P- - QZ?51.1-- 1.
u:hers P, i; the 2-1°car. -.L hr rainfi]l in inches and
other tons are as ddined ?o. 1 q- (? 191. q'hls rz] ?v
ship is based oil shallCS?-L teady: unifl:)rIr1 ?7olr 2 Ca-
J
S[%nL Fair all CXCess in_ien57r._ anti iJ1L[3D7 za?iC irC
mi? 1 Crtttor=.
In urban -3 Tr'.-s, tk?e :U2i`e.= ilr [ naafi' have iU be bati
the t
on a travel tiL?E W a s>oJ7+ drain irlct ,1L..s . th
t)??z ti}LDu:Lb LPL sto=gy Lr n iLelf_ lni_t -L r c= i-
irh nu &0
tan _C31c.z ail\' be cUJ+1DLicd as _ .:7° SUM Of a1 ;
a .ay-1 t:r.-I=:.;_ _ Floe: in =_.
r,d hallol=° ci ar:nel u., t
Lirpln: ;vould b= considt_7eU a_`OD-Cn ci-lerlilci !1O ;r-
iht _i+.3rril drain pipes = L?1t+ii7__ `L+}=- O.Icr] larLc c-,--
+ze ca:?'rCif 0?
?r!..L -zcccv l .-
i?rLLL"ii L:3L`r` riii°_ ? - _
-)"'_i-+- Z-1 1u w ._ L? ih? _1511?i= bvr)as?27
-
1-_ C inLe-n-r 2li. [; Su [aCZ = ov,7 as
lira rn5 in =.? _ ?-_r.. '- -
5`_aLld INC CODSidc-ed _i-
s?;: -
.hc?r!=?. fill ?Lrch ?DgE
=tin=crarzts^=?-
P - = - --`
=--
ti
h LO.I'? i:1L ?3 _1l'? 1° i JiL:?C ..-
-.
E5C fr..
-=Sii i5. c!
ove? 3 7- lc-,`1 f_C4 norj-L -L_n11tl =[";
7p - _Crr_j?1_ as d€Sti_?C inn Ci?2?tyr t) 17!1+5: hut usaa
'or o -)°- C1arinels can v_.
'? ,`J?DCsr_-
7,70n? 3?Tu1ln.=$ cGL'?i30 whicll 15 l_renrlld 311 LJ-?i3
- Cnapi:r ;.
- -,
OlLer r.I= t i:- in !Lhe for-lix i)i ?t:-r--
:C;Lat3ons 107 u12,2:UDg OnL such relataeiISj-. t:
ls'Wideh+ °ul? d but ba_cd on liuiiied n2La 1S CXDr?S=_3
Kirpkln f 3 S-'. 0)
n ?7 (;_
LA
R'17Fr? l? 3i1 s]?InlliCS ?: i:5 th-- I13 - iril i17 lens:-.-
flow in feet- and H is the LifferLncc in elevation in
beu,,-Een thL outlet of the i.>a[crshe?l and Lbe hvdra
ealh+ most remote pains 111 th t?'atet hed_ Ob. ioL
.
Eq_ (151) does not con.[d°r r,.t.?_;;' ,c.5[stance int?ic fc
of m.-crland flo+- and channet roughness.
Several methods for estimating the la-2 time c
N,-ater_hed are availab1c_ O?ie sample method for
77
Piunc'ii E= rna#ior: _
ti- MC estimation is (Sail Consulz:liiall Ser:=ict' 3973)
0.6
Tbu SCS (19:,_ has de:veioped a iag equnlion bascJ
on natural ticalersheds
il. 1900}; r.; (50 < CN < 95.)
*? crc ;L is the la- in }lULr-z; L is tl3e hvdraulic length
of ihv waiershed in _ee#. S L related ti) the cLn c
numb=- bi° Eq_ (iaed ?' is ihv avinaac land slope
in Dercezitan2._ Tbt S in Eq. (3-53;", shuLld be based on
__ anl2Cidz!nl condiii-on Ii cu-vt nllmGc sin C= ;i is
iE?g used as a ?=measure ofsuri'Lct rou_'}incsS and nag
ii,
L-1 -n
_r=a!!1' local SmdLe' relaiing r Or r_ or .T. to wat2r-
ch2i3 n :yi: i Cha+ i:`i ?- di For
p =a_ laci_rt.c_c n2 bz.en ci.ndocee -
Lep12, PLL1am ;19:2) In a study o 3- wai_ szheds mn
North C2rJlin?_ i7r;_scnted the rely ?Oitshin

tr; =S i? i -sin L S. .1?e
c?? _ :n Lip= L"l_-ZC in
-1-i=- is =?2 ;;:-_
L`Aljf- and. .1 of L= zn.ii)Uzz
it eJ,! ae Ci 25 111:: !i-?U ^!G-ice 1i1? COMlea
_a== of == Rfzdj Ii= the Cci-C C'1 =te rL,u
?ue- ti+?i'-ie iht
Cti?-?=4tl aL? SC= =hc !h"= Col-Clti0-'= 11_
eoa _ wz G eicped -1ztca the coo-6;6 n- S of 17ic--
- pile dur?tio7, j7, of ih-e ra' li ail C. ti2?_ ?3_L = -vDe=-
al_h' a=scLlared T:rib ii L- it h!`drfl_iaph ? o'?li t 2 C1ne-
_i>? it.? Cie-il3trr'i n; ihle ili7e -;o v..?k _ 11? - Tim2 iC? ?fl.3::
o-?- lq.(3?6) as -
-
ED=.i?: 2? LII_ (19717) SLUdic-d rainfall-rLd101 reCOy-dS
irola =1 ,uaicr,heds loci?id in stlifral Siaies Mxa=; lb_
North Carotin ; 9; KtmLlckv- 6: Indiana, ColoT.-ado:
_; Mississippi; 3eru3esse 1. and PennS)°l?ania, 1)_
jlc rrarersheds ranged in =iZe irL)m about 9 is 9600
acres U-5 Lo 3900 }i dare l_ They dtve.loped an esiima-
wri cqu21, -ii for the time t{3 peal,: of 10-ruin Lnii
hydrograpb-sl as

i1'172re 1. i? the iirne. t0 peak in minutes. L i< the remain
ehaaael length from the upper v-atcrshcd bot iidar:i in
feet. S is the slope in feet lacr iuut Of the lo.•;er $!?<<: On
terms of JcngCh) na the main channel, I'is the percent-
Table 3.22 0Vahiz„orEr.i3_?)!En >e
0.0 ]h i)?
,' U"

,L._
-
!A5
?;l L SiJ 0,S

aee inner'!oi!& a_ca ?=.iih an qssLmed nininnum glue
of 1Lr an Unde-vf-113D.'.d area, ;ind () iti a
n 7^rc ni.a=- 1737-Ci+'tULs 272;1
e
falno. th2C t.r.ends oil ih-?
3711 '47;_tL?i_rlr_ J. for i13i: I'Tealn channel_ 12hle
r anti So ni21i values e)-
•T;12 h2=2 =iTL: i3i'a unil. its drG_r,?•}7 IS ?t?T?2?':17i
St)7-c hl'il_v1o2i:-S L
i7-nits the. ii_` t-L Dfal:- so'T Lnli h_'?ir?=rap?= cGe;_
ha--- =8i=cssiorl hilt tr u?'-7:Oil~c;a_ ??r03 1c
= d)LSi3 ire; Z=!c I?c- °_3Tt. iS iilcLr2ii=? i Ill; t-''-

1 =Ut? o - C
-int
=iY Ta y 'iia? ii

'?_. IInir ','trO r.'. ?.5 a bas=
?.+??tL on ---_ _
I:-M tnC 5t S f ?`: _? e:i1.n]3T_::S ir!e n-taK = OT:
-""rap iy'- aiiC13
U= L L ii }°? IUc?pi7-!L•1!! cite

tY132r:. Cfr ?s Yli-c L!Can dtmi°: In ci.?_ :-1 i_ i[72 i?i3lr, cT::a i7
Square mues; and d_. 7 Lhe iinn rO Pe-d, in i3C)Ur`.
EpseV el 7!_ reconmiend ;ilai for 1(-rain Unit
h °dro raphs_ iha relation

be used mrilere. q,, of- in cfs, A is the drainage area in
square railes- and iV is [he time to peak in miruies_
s -vv-a?s ih Last. for lag time, maiw- studies have beef,,
rondt!c.ted in an effort to relaie qa to -l:atershe.d physi-
cal condiiions_ Before a:nv of these empirically dcri\°ed
equations are used. their applicaLility should be care-
fulll, de ni 3lm-il_

•
Project : First Choice Eye Care
Basin Model : Pre-Developed
HEC-HMS Jun 15 15:05:23 EDT 2010
r
Subbasin-1
Sink-1

Project: First Choice Eye Care Simulation Run: Pre-Developed 1-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 1-yr, 24-hr
Compute Time: 15Jun2010, 12:24:02 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 4.37 13Apr2009, 12:02 1.35
Subbasin-1 0.0038125 4.37 13Apr2009, 12:02 1.35
•
40
0 Project: First Choice Eye Care Simulation Run: Pre-Developed 10-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 10-yr, 6-hr
Compute Time: 15Jun2010, 12:24:14 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 6.43 13Apr2009, 12:02 1.98
Subbasin-1 0.0038125 6.43 13Apr2009, 12:02 1.98
E
0
• Project: First Choice Eye Care Simulation Run: Pre-Developed 25-yr, 6-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 25-yr, 6-hr
Compute Time: 15Jun2010, 12:24:24 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 8.24 13Apr2009, 12:02 2.55
1 Subbasin-1 0.0038125 8.24 13Apr2009, 12:02 2.55
•
0
0 Project: Project 1 Simulation Run: Pre-Developed 50-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 50-yr,24-hr
Compute Time: 21Ju12010, 13:17:50 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 14.86 13Apr2009, 12:01 4.70
1 Subbasin-1 0.0038125 14.86 13Apr2009, 12:01 4.70
0
Irl
r1
Project : First Cho Care
ice Eye
Basin Model : Post-Developed
HEC-HMS Jun 15 15:08:11 EDT 2010
1.
Subbasin-2
Diversion-2
BR-2 ??--
Subbasin-3
Subbasin-1
Diversion-1--
F;A
. `BR-1
LDA-1
.J
, Sink-1

Project: Project 1 Simulation Run: Post Developed 1st inch
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 1st inch
Compute Time: 21 Jul2010, 13:03:13 Control Specifications: Control Specifications
CJ
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 0.08 13Apr2009, 11:56 0.11
Diversion-2 0.0020000 0.35 13Apr2009, 11:55 0.17
LDA-1 0.0042031 0.00 13Apr2009, 00:00 0.00
Sink-1 0.0042031 0.00 13Apr2009, 00:00 0.00
Subbasin-1 .000796875 0.08 13Apr2009, 11:56 0.11
Subbasin-2 0.0020000 0.35 13Apr2009, 11:55 0.17
Subbasin-3 0.0014062 0.05 13Apr2009, 12:00 0.07
•
•
Project: Project 1
Simulation Run: Post Developed 1st inch Reservoir:
Start of Run: 13Apr2009, 00:00 Basin Model:
End of Run: 14Apr2009, 12:00 Meteorologic Model:
Compute Time: 21 Ju12010, 13:03:13 Control Specifications:
Volume Units: IN
-Computed Results- ----- -
Peak Inflow : 0.08 (CFS)
Peak Outflow : 0.00 (CFS)
Total Inflow: 0.11 (IN)
Total Outflow : 0.00 (IN)
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
BR-1
Post-Developed
1st inch
Control Specifications
13Apr2009, 11:56
13Apr2009, 00:00
0.00 (AC-FT)
681.13 (FT)
?il
l __d
•
Project: Project 1
Simulation Run: Post Developed 1st inch Reservoir:
Start of Run: 13Apr2009, 00:00 Basin Model:
End of Run: 14Apr2009, 12:00 Meteorologic Model:
Compute Time: 21,102010, 13:03:13 Control Specifications:
Volume Units: IN
-Computed Results- ------------------
Peak Inflow : 0.35 (CFS)
Peak Outflow : 0.00 (CFS)
Total Inflow : 0.17 (IN)
Total Outflow : 0.00 (IN)
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
BR-2
Post-Developed
1st inch
Control Specifications
13Apr2009, 11:55
13Apr2009, 00:00
0.02 (AC-FT)
680.19 (FT)
0
Project: Project 1 Simulation Run: Post-Developed 1-yr, 24-hr

Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21Ju12010, 13:02:19
Volume Units: IN
Basin Model:
Meteorologic Model:
Control Specifications
Post-Developed
1-yr, 24-hr
Control Specifications
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 1.11 13Apr2009, 11:54 1.22
Diversion-2 0.0020000 3.22 13Apr2009, 11:53 1.41
LDA-1 0.0042031 0.51 13Apr2009, 12:04 0.30
Sink-1 0.0042031 0.51 13Apr2009, 12:04 0.30
Subbasin-1 .000796875 1.11 13Apr2009, 11:54 1.22
Subbasin-2 0.0020000 3.22 13Apr2009, 11:53 1.41
Subbasin-3 0.0014062 1.61 13Apr2009, 11:55 1.04
•
•
Project: Project 1
Simulation Run: Post-Developed 1-yr, 24-hr Reservoir: LDA-1
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 1-yr, 24-hr
Compute Time: 21Ju12010, 13:02:19 Control Specifications: Control Specifications
Volume Units: IN
•
-Computed Results_ ._.___..........
..._....___..
Peak Inflow : 1.61 (CFS)
Peak Outflow : 0.51 (CFS)
Total Inflow : 0.35 (IN)
Total Outflow : 0.30 (IN)
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
13Apr2009, 11:55
13Apr2009, 12:04
0.03 (AC-FT)
677.03 (FT)
0
• Project: Project 1 Simulation Run: Post-Developed 10-yr, 24-hr
Start of Run : 13Apr2009 , 00:00 Basin Model: Post- Developed
End of Run: 14Apr2009 , 12:00 Meteorologic Model: 10-yr 6-hr
Compute Time: 21Jul2010, 13:01:14 ,
Control Specifications: Control Specifications
Volume Unit s: IN
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (M12) (C FS) (IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 1.65 13Apr2009, 11:53 1.82
Diversion-2 0.0020000 4.66 13Apr2009, 11:53 2.06
LDA-1 0.0042031 0.58 13Apr2009, 12:04 0.49
Sink-1 0.0042031 0.58 13Apr2009, 12:04 0.49
Subbasin-1 .000796875 1.65 13Apr2009, 11:53 1.82
Subbasin-2 0.0020000 4.66 13Apr2009, 11:53 2.06
Subbasin-3 0.0014062 2.51 13Apr2009, 11:55 1.60

•
Project: Project 1
Simulation Run: Post-Developed 10-yr, 24-hr Reservoir: LDA-1
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 10-yr, 6-hr
Compute Time: 21 Ju12010, 13:01:14 Control Specifications: Control Specifications
Volume Units: IN

-Conputed Results- -------.__.___-.-.
Peak Inflow : 2.51 (CFS)
Peak Outflow : 0.58 (CFS)
Total Inflow : 0.54 (IN)
Total Outflow : 0.49 (IN)
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
13Apr2009, 11:55
13Apr2009, 12:04
0.04 (AC-FT)
677.11 (FT)

Project: Project 1 Simulation Run: Post Developed 25-yr, 6-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 25-yr, 6-hr
Compute Time: 21Ju12010, 12:59:49 Control Specifications: Control Specifications
Volume Units: IN

Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)

BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00

Diversion-1 .000796875 2.15 13Apr2009, 11:53 2.37

Diversion-2 0.0020000 5.93 13Apr2009, 11:53 2.64

LDA-1 0.0042031 0.64 13Apr2009, 12:05 0.67

rSink-1 0.0042031 0.64 13Apr2009, 12:05 0.67

ubbasin-1 .000796875 2.15 13Apr2009, 11:53 2.37

Subbasin-2 0.0020000 5.93 13Apr2009, 11:53 2.64

Subbasin-3 0.0014062 3.32 13Apr2009, 11:55 2.13
0
r1
ICJ
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 25-yr, 6-hr
Compute Time: 21 Ju12010, 12:59:49 Control Specifications: Control Specifications
Project: Project 1
Simulation Run: Post Developed 25-yr, 6-hr Reservoir: LDA-1
Volume Units: IN
0
;"' Computed Results -- -------
Peak Inflow : 3.32 (CFS)
Peak Outflow : 0.64 (CFS)
Total Inflow:
0.71 (IN)
Total Outflow : 0.67 (IN)
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
13Apr2009, 11:55
13Apr2009, 12:05
0.06 (AC-FT)
677.19 (FT)
0
Project: Project 1 Simulation Run: Post-Developed 50-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 50-yr,24-hr
Compute Time: 21Ju12010, 13:19:30 Control Specifications: Control Specifications
Volume Units: IN
•
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.31 13Apr2009, 12:26 2.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 3.96 13Apr2009, 11:53 4.49
Diversion-2 0.0020000 10.52 13Apr2009, 11:53 4.81
LDA-1 0.0042031 0.84 13Apr2009, 12:28 1.73
Sink-1 0.0042031 0.84 13Apr2009, 12:28 1.73

Subbasin-1 .000796875 3.96 13Apr2009, 11:53 4.49
Subbasin-2 0.0020000 10.52 13Apr2009, 11:53 4.81
Subbasin-3 0.0014062 6.37 13Apr2009, 11:55 4.17
0
•
•
Project: Project 1
Simulation Run: Post-Developed 50-yr, 24-hr Reservoir: LDA-1
Start of Run: 13Apr2009, 00:00 Basin Model:
End of Run: 14Apr2009, 12:00 Meteorologic Post-Developed
Compute Time: 21JU12010, 12:58:14 Control Speciflications: Co troi Shr
Volume Units: IN
Computed Results
Peak Inflow : 6.37 (CFS)
Peak Outflow : 0.84 (CFS)
Total Inflow. 1.77 (IN)
Total Outflow : 1.73 (IN)
He, cations
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
13Apr2009, 11:55
13Apr2009, 12:28
0.13 (AC-FT)
677.50 (FT)
0
0
0
0
• Project: Project 1
Simulation Run: Post-Developed 50-yr, 24-hr Reservoir: LDA-1
Start of Run: 13Apr2009, 00:00 Basin Model:
End of Run: 14Apr2009, 12:00 Post-Developed
Meteorologic Model: 50-yr,24-hr
Compute Time: 21 Ju12010, 12:58:14 Control Specifications: Control Specifications
Volume Units: IN
Computed Results- ------------
Peak Inflow : 6.37 (CFS)
Peak Outflow : 0.84 (CFS)
Total Inflow : 1.77 (IN)
Total Outflow : 1.73 (IN)
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
13Apr2009, 11:55
13Apr2009, 12:28
0.13 (AC-FT)
677.50 (FT)
I?
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Page 1 of 2
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M; 77
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•

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Unified Soil Classification (Surfa
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1, V
Warning: Soil Ratings Map may not be valid at this scale.
!Lu have zoomed in beyond the scale at which the soil map for this area is
intended to be used. Mapping of soils is done at a particular scale. The soil
surveys that comprise your A01 were mapped at 1:24,000. The design of
map units and the level of detail shown in the resulting soil map are
dependent on that map scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting soils that
could have been shown at a more detailed scale.
Tables - Hydrologic Soil Group - Summary By Map Unit

Summary by Map Unit -Union County
North Carolina _._--
, O!
Map unit Map unit name Rating Acres in Percent of AOI
symbol AOI
BaB Badin channery silt B 13-8 49.6%!
loam, 2 to 8 percent
slopes
BaC Badin channery silt B 0.3 1.0%
loam, 8 to 15 percent
slopes
...
ScA Secrest-Cid complex, 0 C 13.7 49.3%'.
to 3 percent slopes
Totals for Area of Interest 27.8; 100.01/6
Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to
one of four groups according to the rate of water infiltration when the soils are not
protected by vegetation, are thoroughly wet, and receive precipitation from long-duration
storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and three dual
classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet.
These consist mainly of deep, well drained to excessively drained sands or gravelly sands.
These soils have a high rate of water transmission.
http://websoilsurvey.nres-usda.gov/app/WebSoilSurvey.aspx 6/3/2010
tMap - Hydrologic Soil Group F ?'!: m? 1_I SCate., -(not to scaicj
Soil Map-Union County, North Carolina
•
•
Map Unit Legend
Union County, North Carolina (NC179)
Map Unit Symbol Ma p Unit Name Acres in AOI Percent ofAO1
aaB Badin channery silt loam, 2 to 8 percent 13
8 %

slopes . °
49.6
BaC Badin channery sift loam, 8 to 15 0
3

percent slopes . 1.0%
ScA Secrest-Cid complex, 0 to 3 percent 13
7

slopes . 49.3%
Totals for Area of Interest 27
8
. 100.0%
0
USDA Natural Resources
? Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/3/2010
Page 3 of 3
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81,
BIORETENTION-WATER QUALITY
CALCULATIONS
•
'Ile

V
Amim Engineering
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject:_Bioretention - Water Quality
OBJECTIVE:
Determine required water quality volume for the proposed bioretention area.
DESIGN CONSIDERATIONS:
The Manual of Storm water Best Management Practices requires the design volume
of the bioretention structure be based on treating the first inch of runoff using the
Simple Method. Per a previous draft of the manual, a general rule of thumb states
that the surface area of the bioretention area should be between 3% and 8% of the
total drainage area. This rule of thumb was used as a starting point for the design.
REFERENCES:
1. "Manual of Storm Water Best Management Practices," by The North Carolina
Department of Environment and Natural Resources, 2007.
2. "Bioretention Drainage Map," by Amicus Engineering PC, 06/16/10.
CALCULATIONS
1. Bioretention Area RR-1
•
•
Elevatio
(ft) Area (ft-) Height (ft) Volume (ft')
[Ref: [Ref: 2]
j
682. 1,865
1.00 1,586
681.0
T 1,306
1. 1 otai volume available in Bioretention Area BR-1 (elev. 682.00 ft) =1,586 ft
Determine surface area required
a. Total drainage area = 0.51 acres [Ref: 2]
b. Surface area of BR-1 = 1,306 ft2 = 0.03 acres [Ref: 2]
c. Percent of area = (0.03 ac./0.51 ac.) = 0.06 or 6% therefore ok
2. Determine water quality volume required for area draining to BR-1
a.
The runoff volume calculations in the "Simple Method" as described
by Schueler (1987) will be used. [Ref: 1]
Rv = 0.05 + 0.009(I) >wI I'l i?/.
Rv = runoff coefficient = storm runoff (inches) / storm rainfaarzcs) y•
;

I =percent impervious portion of the drainage area = 44% ?
_
a s A L r • =
-
- 032006 ;
Rv = 0.05 + 0.009(44)
Rv = 0.45 (in. / in.) c: <z
% h
0
?
i
N1111111111??\

4mim Engineering
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject:_Bioretention - Water Quality
b. For the volume that must be controlled:
Volume = (design rainfall) (Rv) (drainage area)
Volume = 1.00 inch rainfall * 0.45 (in. / in.) * 1/12 (feet / inch) * 22,327 ft2
Volume = 837 ft3
Volume available in BR-1 = 1,586 ft3
837 ft3 < 1,586 ft3 therefore ok.
3. Compute Filter Media Capacity
a. Media Capacity = (Af)(k)(hf+df)/df [Ref: 3]
b. Media Capacity = (1,306 ft)(3.Oft/day)(1.0-ft + 2-ft)/(2.0 ft)
c. Media Capacity = 0.05 cfs
4. Design Inlets and Underdrain System for BR-1
a. Compute minimum dawdown discharge
0
Water Quality volume = 1,586 ft3
Drawdown = 1,586 ft3/[(24 hours)(3,600sec/hour)]
= 0.018 cfs
b. Compute perforation capacity
i. Number of Perforations= (149 lf)(2 rows/ft)(4 holes/row) = 1,192 holes
50 percent of perforations = 596 holes
Capacity of one hole = CA(2gh)o.5
= (0.6)(3.1416)[(3/8in)(l/24)]2[(64.4)(5.Oft)]o.s
= 0.0083 cfs
Total capacity = (0.0083 cfs)(596) = 4.95 cfs
ii. 4.96 cfs > 0.018 cfs > 0.05 cfs therefore ok.
c. Compute underdrain pipe capacity
i. For 8-inch PVC underdrain pipe at 0.005 ft/ft slope:
Capacity of pipe = 0.93 cfs [Ref 2]
Fifty percent assuming clogging = 0.47 cfs
ii. 0.47 cfs > 0.018 cfs > 0.05 cfs therefore ok
0
•
V
Amicus Ingineering
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Cales Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Bioretention - Water Quality
4. Bioretention Area RR-7.
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft)
681.00 4,683
1.00 4,216
680.00 3,749
F
Mal vwunic avaiiame in tsioretennon area t3x-2 (elev. M 1.00 tt) = 4,216 ft'
Determine surface area required
a. Total drainage area = 1.28 acres [Ref: 2]
b. Surface area of BR-2 = 3,749 ft2 = 0.11 acres [Ref: 2]
c. Percent of area = (0.09 ac./1.28 ac.) = 0.07 or 7% therefore ok
E
5. Determine water quality volume required for area draining to BR-2
The runoff volume calculations in the "Simple Method" as described
by Schueler (1987) will be used. [Ref: 1]
a. Rv = 0.05 + 0.009(I)
Rv = runoff coefficient = storm runoff (inches) / storm rainfall (inches)
I = percent impervious portion of the drainage area = 66%
Rv = 0.05 + 0.009(66)
Rv = 0.64 (in. / in.)
b. For the volume that must be controlled:
Volume = (design rainfall) (Rv) (drainage area)
Volume = 1.00 inch rainfall * 0.64 (in. / in.) * 1/12 (feet / inch) * 55,626 ft2
Volume = 2,967 ft3
Volume available in BR-2 = 4,216 ft3
2,967 ft3 < 4,216 ft3 therefore ok.
E

Project No: 17-10-033 Sheet No: of
194 Date: 06-16-10
-4n?> Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus ingineering Project Name: Proposed Professional Buildin at Lawyer's Road
Subject: Bioretention - Water Quality
6. Compute Filter Media Capacity
a. Media Capacity = (Af)(k)(hf+df)/df [Ref: 3]
b. Media Capacity = (3,749 ft2)(3.0ft/day)(1.0-ft + 2-ft)/(2.0 ft)
c. Media Capacity = 0.20 cfs
7. Design Inlets and Underdrain System for BR-2
b. Compute minimum drawdown discharge
ii. Water Quality volume = 4,216 ft3
Drawdown = 4,216 ft3/[(24 hours)(3,600sec/hour)]
= 0.05 cfs
•
c. Compute perforation capacity
ii. Number of Perforations = (454 lf)(2 rows/ft)(4 holes/row) = 3,632 holes
50 percent of perforations = 1,816 holes
Capacity of one hole = CA(2gh) 0-5
= (0.6)(3.1416)[(3/8in)(1/24)]2[(64.4)(5.Oft)]o.s
= 0.0083 cfs
Total capacity = (0.0083 cfs)(1,816) = 15.07 cfs
ii. 15.07 cfs > 0.20 cfs > 0.05 cfs therefore ok.
d. Compute underdrain pipe capacity
ii. For 8-inch PVC underdrain pipe at 0.005 ft/ft slope:
Capacity of pipe = 0.93 cfs [Ref: 5]
Fifty percent assuming clogging = 0.47 cfs
ii. 0.47 cfs > 0.20 cfs > 0.005 cfs therefore ok
0
l
NCDEMR Stormva,ater BMP Manua]
Revised 09-28-07
• allows the user to select from one of NOAA's numerous data stations throughout the
state. Then, the user can ask for precipitation iztensity and view a table that displays
precipitation intensity estimates for various annual return intervals (ARIs) (1 year
through 1000 years) and various storm durations (5 minutes.through 60 days).
The requirements'of the applicable stormwater program will determine the appropriate
values for ARI and storm duration. If the design is for a level spreader that is receiving
runoff directly from the drainage area, then the value for I should simply be one inch
per hour (more information on level spreader design in Chapter 8).
0- R-Unoff ITOlume
Many stormwater programs have a volume control requirement, that is, capturing the
first I or 1.5 inches of stormwater and retaining it for 2 to 5 days. There are two primary
methods that can be used to determine the volume of runoff from a given design storm:
the Simple Method (Schueler, 2987) and the discrete SCS Curve Number Method (_NRCS,
1956). Both of these methods are intended for use at the scale of a single drainage area.
Stormwates Bh2s shall be designed to treat a volume that is at least as large as the
volume calculated using the Simple Method. i= the SCS Method yields a greater v olume,
then it can also be used.
3.3.1. Simple Method
The Simple Method uses a n idz gal amount of i_nrormation such as watershed drainage
area, rmpezv3DUS area, and design storm depth to estimate the volume OI rtflDff_ The
Simple Method was developed by measuz-m; the runoff from many watersheds with
Lmov'n imp-a v ious areas and curve-fr tzg a relationshup between percent
1peli%10iSnesS and the fraC?i Dn of ra_Zal? COnve Led to rLZ3o- (the runo z cfl?iclellt).
This relationship is prese-cited bell ow:
Rv = 0-05 +-0.9 * 1:3
Where: Rv = 'Runoff coefficient [storm runoff (in)/storm rainfall (in)], unitless
IA = Impervious fraction [impervious portion of drainage area (ac)/
drainage area (ac)], unitless.
Once the runoff coefficient is determined, the volume of runoff that must be controlled is
oven by the equation below:
V= 3630 * RD * Rz, * A
Where: V = Volume of runoff that must be controlled for the design storm (ft3)
RD = Design storm rainfall depth (in) (TW7icaily,1_0" 07 '1.5")
A = Watershed area (ac) '
•
'>tormwatez Management and Calculations ?3 July 2007
NCDEI\TR Stormwater BlvfP Manual Chapter Revised 09-28-07
11
12 fizo.Tetention
Description
Bioretention is the use of plants and soils for removal of pollutants from stormwater runoff via
adsorption, filtration, sedimentation, volatilization, ion exchange, and biological decomposition.
In addition, bioretention provides landscaping and habitat enhancement benefits.
•
•
Regulatory Credits Feasibility CORSiderations
Pozzutant F--Mmal
85% Total Suspended Solids High Land Requirement
35 % Total Nitrogen Med-High Cost of Construction
Z % Total- Phosphorus Med-High Maintenance Burden
Water Quantity Small Treatable Basin Size
yes Peal- Runoff Attenuation Med Possible Site Constraints
possible Runoff Volume Reduction Med-High Community Acceptance
Advantages
Ef3cient rear_oval method for suspe-nded
solids, heavy metals, adsorbed pollutant,
nitrogen, ph horus, paihogans, and
i? Tatire.
Irprovidiinglnal'LTaLoninapprD -ia 2.Coil
concLibo-T1s it can, of eC7Eve(y reduce peLk
rl?no_ rates for zelativ-ly frequent Stour m5,
reduce runo1 volumes, and redha=ge
a 0T.Lndwater.
rle `?jie aaap ?L30 n t0 urban reTolu-
Indi-I "PI units are well suited - Dr USe in
small areas, and muitrple, distribur.?i uriitr
can provide treatment in large drainage
areas.
Natural integration into landscaping for
urban landscape enhancement.
Disadvantages
- Surface soil layer may clog over time
(though it can be restored).
- Frequent trash removal may be required,
espedaliy m ll-dcgh traffic areas.
v7j ?itnce =n pr{)Lacting t? Le b1 OreL`1 LDn
area du-,71g construction is ase_naal.
- Su gle urdt can only we've a s
dra- age area
- RequhTes iaquenni.r-! tainte- aZce or }planti
material and -?`lchlaye--
Bioretention
12-1
July 2007
NCDEINTR Stormwater EI\Cl Manual
Mal_ orEesi'n Elements
Revised 09-28-07
° shall ire into account all runoff at ultimate build-out including off-site
i a rrc
slopes stabilized with vegetation shall be no steeper than 3:1_
1bMP shall be located in a recorded drainage easement jqith a recorded access
asement to a public right of Tay (ROI9.
Volume in excess of the design volume, as determined from the design storm, shall
by-pass the bioretention cell-
v fume in excess of the design volume, as determined from the design storm, shall be
'enly distributed across a minimum 30 feet long vegetated filter strip. (_A 50-ft filter
required in some locations.) If this can not.be attained, altzxmte designs will be
onsidered on a case by case basis.
iDretention facilities shall not be used where the seasonally high water table less than
feet balow bottom of MT-
f' [!"ectia PEmeab'llity- of 0.52-6"PE- hou_T is required, l-2 in Pr hour is prefe-Tred_
e des3 ts_ !? }}? ?oC?teda, i, i r ^ L r
T1iLTl Ol JO feel!_OTi su ace waters, and 30 feet
s S=A waters- .
PFh?e esign shall be located a _nuLmum of 100 feet from water supply wells.
10 Ibioretention facilities shall not be used where slopes greater than 20%, or in non-
anently stabilized drainage areas.
11 ?oz'" must be Sheet floznT (1 ft/sec) or utilize energy dissipating devices-
? ?t'onding depth shall be 12 inches or less. Nine inches is preferred.
3 edia depth shall be speed for the vegetation used- For grassed cells, use 2 feet
um. For shrubs or trees use 3 feet mimmum-
1 e geometry of the cell shall be such that no dimension is less than 10 feet (width,
ength, or radius).
Media should be specified as listed in this section.
e phosphorus index (P-index) for the soil must be low, between 10 and 30_ This is
nough phosphorus to support plant growth without exporting phosphorus from the
ell.
ect water shall completely drain into the soil within 12 hours.
of 24 inches below the soil surface in a maximum of 48 hours-
Bioretention
12-2
It shall drain to a
July 2007
NCDENR Stormwater BI\P- Manual Chapter Revised 09-2cS-07
• An underdrain shall be T icall installed if in-situ soil drainage is less than 2 in lu or
P Y b /
78 if there is in situ loamy soil (-12% or more of fines). This is usually the case for soil
tighter than sandy loam -Or if there has been significant soil compaction from
construction.
X17 ?_iean-out pipes must be provided if underdrains are required. .
12-1- General Characteristics and Purpose
A bioretention cell consists of a depression in the ground filled with a soil media
mixture that supports various types of water-tolerant vegetation. The surface of the BMP
is depressed in bioretention facilities to allow for ponding of runoff that filters through
the BAI.P media.' Water exits the bioretention area via exfiltration into the surrounding
soil, flow out an underdram, and evapotranspiration. The surface of the cell is protected
from weeds, mechanical erosion, and desiccation by a layer of mulch. Bioretention is an
efficient method for removing a wide variety of pollutants, such as suspended solids,
heavy metals, nutrients, parhogero, and temperature (NC Cooperative E'ate-nsion, 20Do
Bioretention areas provide some nutrient uptake in addition to physical filtration. If
located at a site with appropriate soil conditions to pi-mdde infiltration, biorete-n.tion can
a3so be effective in reducing peal: o rates, reducing runoff volumes, and recharging
groundwater.
Many develop=nen t pro- -is present a challenge to the design of conve_zuoaal
stormvs-ater f;i i s because of physical site constraints. Bioretention areas are intended to
address t??e spatial constraints that can be found in densely developed urban areas
where ;he dr ; age areas are highly mpe_T--?7jous (see Fi-ire 12-3). They can be used on
uTbzn sates tZat-would not normally support the hydrolo % of a wet detention
pond and where the soils would not allow for an infiltration device. Median strips,
ramp loops, traffic circles, and parl3ng lot islands are good examples of typical locations
for bioretention areas. See Section 12.3.1 for more illustrated examples of the versatility
of bioretention facilities.
Bioreteation units are ideal for distributing several units throughout a site to provide
treatment of larger areas- Developments that incorporate this decentralized approach to
stormwater management can achieve savings by. eliminating stormwater management
ponds; reducing pipes, inlet structures, curbs and gutters; and having less grading and
clearing- Depending on the type of development and site constraints, the costs for using
decentralized bioretention stormwater management methods can bereduced by 10 to
25 percent compared to stormwater and site development using other BMPs (Coffman et
al., 1998).
Bioretention facilities are generally most effective if they receive runoff as close as
possible to the source- Reasons for this include- minimizing the concentration of flow to
reduce entry velocity; reducing the need for inlets, pipes, and downstream.controls; and
allowing for blending of the facilities with the site (e-g-, parking median facilities). For
sites where infiltration is being utilized, it also avoids excessive groundwater mounding.
Where bioretention takes the place of required green space, the landscaping expenses
Bioretention 72_3 July 2007
•
NCDENR Stormwater BMP Manual
Revised 09-28-07
that would be required in the absence of bioretention should be subtracted when
determining the actual cost .(Low Impact Development Center, 2003). Bioretention cells
may also address landscaping/green space requirements of some local governments
(Wossink and Hunt, 2003)-
Figure 12-1
Bioretention in Parking Lot Island
0 To ob iZ a -ie-- Tu- to construct a bioretent: on cell in No rth Ca_Tolina, the loretanition cell
12?- Meeting Regulatory Requirements
rust meet a it of the ReGl.u-re-mer'Lts specified in t-+ie Major Dasig Elements located at f-
-be-of this Sects Gn-
PoZZutont PE?T2OVL11 Cn.lculotions
The pollutantremoval calculations for bioretention facilities ale as described in Section
3-4, and use the pollutant removal rates provided in Table 4-2 in Section 4-0-
Construction of a Bioretention cell also passively lowers nutrient loading since it is
counted as pervious surface when calculating nutrient loading-
VOZU7ne Control CaZC-UZations
A bioretention cell can sometimes be designed with enough storage to provide active
storage control (calculations for which are provided in Section 3.4), however, some may
not have enough water storage to meet the volume control requirements of the
particular storrrmwater program (since its storage potential is limited because the
ponding depth is limited) so they may need to be used in series with another BMP with
volume control capabilities- All bioretention facilities provide some passive volume
control capabilities by providing pervious surface and therefore reducing the total
runoff volume to be controlled-
Bioretention
xz-4
July 2007
BIORETENTION CELL
SUPPLEMENT SHEETS
•
40
Permit Number:
(to be provided by DWQ)
aaF wArF9
- ? a 9r
NCDENR
• STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
BIORETENTION CELL SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information
1I. PROJECTJNFORMATION
Project name Proposed Professional Building at Lawyer's Road
Contact name Nicholas R. Parker, PE
Phone number 704-5731621
Date October 11, 2010
Drainage area number 1
L DESIGN 1NFORMATION
Site Characteristics
Drainage area 22,328 ft2
Impervious area 9,825 ft2
Percent impervious 44.0% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? y (Y or N)
1-yr, 24-hr runoff depth 2.9 in
1-yr, 24-hr intensity 0.12 in/hr
Pre-development 1-yr, 24-hr peak flow 0"100 ft3/sec
st-development 1-yr, 24-hr peak flow 1.110 ft3/sec
re/Post 1-yr, 24-hr peak control 1.010 ft3/sec
Storage Volume: Non-SA Waters
Minimum volume required 837.0 ft3
Volume provided 1,586.0 ft3 OK
Storage Volume: SA Waters
1.5" runoff volume ft3
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required 0 ft3
Volume provided ft 3
Cell Dimensions
Ponding depth of water 12 inches OK
Ponding depth of water 1.00 ft
Surface area of the top of the bioretention cell 1,865.0 ft2 OK
Length: 74 ft OK
Width: 32 ft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 6 hr OK
Drawdown time, to 24 inches below surface 18 hr OK
Drawdown time, total: 24 hr
In-situ soil:
Soil permeability n/a in/hr OK
ting media soil.
it permeability 1.50 in/hr OK
Soil composition
% Sand (by volume) 87% OK
% Fines (by volume) 8% OK
Form SW401-Bioretention-Rev.8
June 25, 2010
Parts I and II. Design Summary, Page 1 of 3
Permit Number:
°
/° Organic (by volume) 5% OK (to be Provided by DWQ)
Total: 100%
Phosphorus Index (P-Index) of media 20 (unitless) OK
C?
r?
I• J
E
Form SW401-Bioretention-Rev.8
June 25, 2010
Parts I and II. Design Summary, Page 2 of 3
Basin Elevations
Temporary pool elevation
682.00 fmsl
Type of bioretention cell (answer "Y" to only one of the two following
questions):
•
Is this a grassed cell?

Is this a cell with trees/shrubs? y (Y or N)
n/a (Y or N)
Planting elevation (top of the mulch or grass sod layer) 681 fmsl
Depth of mulch 0 inches
Bottom of the planting media soil 679 fmsl
Planting media depth 2 ft
Depth of washed sand below planting media soil 0.67 ft
Are underdrains being installed? y (Y or N)
How many clean out pipes are being installed? 3
What factor of safety is used for sizing the underdrains? (See
BMP Manual Section 12.3.6) 2
Additional distance between the bottom of the planting media and
the bottom of the cell to account for underdrains 1 ft
Bottom of the cell required 677.33 fmsl
SHWT elevation 670 fmsl
Distance from bottom to SHWT 7.33 ft
Permit Number:
(to be provided by DWQ)
OK
Insufficient mulch depth, unless installing grassed cell.
OK
OK
OK
Internal Water Storage Zone (IWS)
Does the design include IWS n (Y or N)
Elevation of the top of the upturned elbow fmsl
Separation of IWS and Surface 681 ft
Planting Plan
Number of tree species 0
Number of shrub species 0
umber of herbaceous groundcover species 3
W OK
d
ditional Information
Does volume in excess of the design volume bypass the
bioretention cell? y (Y or N) OK
Does volume in excess of the design volume flow evenly distributed
through a vegetated filter? y (Y or N) OK
What is the length of the vegetated filter? nla ft
Does the design use a level spreader to evenly distribute flow? n (Y or N) Show how flow is evenly distributed.
Is the BMP located at least 30 feet from surface waters (50 feet if -
SA waters)? y (Y or N) OK
Is the BMP located at least 100 feet from water supply wells? y (Y or N) OK
Are the vegetated side slopes equal to or less than 3:1? y (Y or N) OK
Is the BMP located in a proposed drainage easement with access to
a public Right of Way (ROW)? y (Y or N) OK
Inlet velocity (from treatment system) ft/sec
Is the area surrounding the cell likely to undergo development in the
future? n (Y or N) OK
Are the slopes draining to the bioretention cell greater than 20%? n (Y or N) OK
Is the drainage area permanently stabilized?
Pretreatment Used
(Indicate Type Used with an "X" in the shaded cell)
Gravel and grass
flinches gravel followed by 3-5 ft of grass)
ssed swale
orebay
Other
Form SW401-Bioretention-Rev.8
June 25, 2010
y (Y or N) OK
X
0 OK
,0
- n
Parts I and II. Design Summary, Page 3 of 3
M
NCDENR
•
Permit Number:
(to be provided by DWQ)
of wn rF
?? RAG
O ~
Y
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
BIORETENTION CELL SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part Ill) must be printed, filled out and submitted along with all of the required infnrmatinn
1. "PROJEG7NFORMATION ---
Project name Proposed Profession. 6uildi,iy 0t Lawyers Road
Contact name
Phone number Nicholas R. Parker, P.E.
Date 704-573-1621
October 11, 2010
Drainage area number 2
Fl., : MIUN;INI-VWTION
Site Characteristics -
Drainage area

Impervious area 55,626 ft2

Percent impervious 36,714 ft2

Design rainfall depth 66.0% %
--
1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required?
1-yr, 24-hr runoff depth y or N )
1-yr, 24-hr intensity _2 in
.9 in
Pre-development 1-yr, 24-hr peak flow --- 0.12 in/hr

st-development 1-yr, 24-hr peak flow 3X240 ft /sec

/Post 1-yr, 24-hr peak control 3220 '
ft /sec

Storage Volume: Non-SA Waters 2.980 ft3ISeC
Minimum volume required
Volume provided - 0 ft3

Storage Volume: SA Waters 4,,216216..0 ft3 OK
1.5" runoff volume

Pre-development 1-yr, 24-hr runoff 3
----ft

Post-development 1-yr, 24-hr runoff ft3
--

Minimum volume required 3
---- -ft
Volume provided ------ W

Cell Dimensions ft3
Ponding depth of water
Ponding depth of water 12 inches OK
Surface area of the top of the bioretention cell 0 ft

Length: 4,683.0 ft2
OK
Width: 130 ft OK
-or- Radius 40 ft OK

Media and Soils Summary ft
Drawdown time, ponded volume
Drawdown time, to 24 inches below surface ---- 6 hr OK
Drawdown time, total: _18 hr OK
In-situ soil: 24 hr
Soil permeability
Planting media soil. Na in/hr OK
rmeability
composition 1•50 in/hr OK
% Sand (by volume)
% Fines (by volume) 87% OK
- __8% OK
Form SW401-Bioretention-Rev.8
June 25, 2010
Parts I and II. Design Summary, Page 1 of 3
Permit Number:
Organic (by volume) 5% OK (to be provided by DWQ)
Total: 100%
Phosphorus Index (P-Index) of media
0
is
•
Form SW401-Bioretention-Rev.8
June 25, 2010
20 (unitless) OK
Parts I and II. Design Summary, Page 2 of 3
Permit Number:
(to be provided by DWQ)
Basin Elevations
Temporary pool elevation 681.00 fmsl
Type of bioretention cell (answer "Y" to only one of the two following
• questions):
Is this a grassed cell? y (Y or N) OK
Is this a cell with trees/shrubs? nla (Y or N)
Planting elevation (top of the mulch or grass sod layer) 680 fmsl
Depth of mulch 0 inches Insufficient mulch depth, unless installing grassed cell.
Bottom of the planting media soil 678 fmsl
Planting media depth 2 ft
Depth of washed sand below planting media soil 0.67 ft
Are underdrains being installed? y (Y or N)
How many clean out pipes are being installed? 5 OK
What factor of safety is used for sizing the underdrains? (See
BMP Manual Section 12.3.6) 2 OK
Additional distance between the bottom of the planting media and
the bottom of the cell to account for underdrains 1 ft
Bottom of the cell required 676.33 fmsl
SHWT elevation fmsl
Distance from bottom to SHWT 676.33 ft OK
Internal Water Storage Zone (IWS)
Does the design include IWS n (Y or N)
Elevation of the top of the upturned elbow fmsl
Separation of IWS and Surface 680 ft
Planting Plan
Number of tree species 0
Number of shrub species 0
umber of herbaceous groundcover species
W 3 OK
d
ditional Information
Does volume in excess of the design volume bypass the
bioretention cell? y (Y or N) OK
Does volume in excess of the design volume flow evenly distributed
through a vegetated filter? y (Y or N) OK
What is the length of the vegetated filter? n/a ft
Does the design use a level spreader to evenly distribute flow? n (Y or N) Show how flow is evenly distributed.
Is the BMP located at least 30 feet from surface waters (50 feet if
SA waters)? y (Y or N;
Is the BMP located at least 100 feet from water supply wells? y (Y or N)
Are the vegetated side slopes equal to or less than 3:1? y (Y or N)
Is the BMP located in a proposed drainage easement with access to
a public Right of Way (ROW)? y (Y or N)
Inlet velocity (from treatment system) ft/sec
Is the area surrounding the cell likely to undergo development in the
future? n (Y or N)
Are the slopes draining to the bioretention cell greater than 20%? n (Y or N)
Is the drainage area permanently stabilized? y` (Y or N)
Pretreatment Used
(Indicate Type Used with an "X" in the shaded cell)
Gravel and grass
inches gravel followed by 3-5 ft of grass) 0
ssed swale 0
orebay
0
Other
n
Form SW401-Bioretention-Rev.8
June 25, 2010
OK
OK
OK
OK
OK
OK
OK
Parts I and II. Design Summary, Page 3 of 3
•
PIPE HYDRAULICS AND
GRATE CAPACITY
CALCULATIONS
•
0
•
4A_ IvIk
w
Amicus Ingineering
OBJECTIVE:
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Pipe Hydraulics & Grate Capacity
Design a series of storm drainage pipes to adequately convey runoff during and after
construction. Verify the grate capacity of all catch basins.
REFERENCES:
1. Charlotte Mecklenburg Stormwater Design Manual
2. "Proposed Grading Plan," by Amicus Engineering PC, 09/01/10.
3. FHWA Urban Drainage Design Program, HY - 22.
4. "Water Resources Engineering," by Mays, Larry W., 2001.
5. Charlotte Mecklenburg Land Development Standards
6. "Hydrologic Evaluation," by Amicus Engineering PC, 09/01/10.
•
TERMS:
Q10 = 10-year peak flow, (ft3/s)
Q1 = 1St-inch peak flow, (ft3/s)
Qf = first flush peak flow, (ft3/s)
Q; = inlet capacity, (ft3/s)
C = runoff coefficient
Co = orifice coefficient
d = depth of water ponded over grate, (ft)
g = acceleration due to gravity, (ft/s2)
i = rainfall intensity, (in/hr)
A = drainage area, (acres)
a = clear opening area of a grate, (ft)
t? = time of concentration, (min)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
CALCULATIONS:
I. Determine grate capacity for catch basins
a. Determine maximum inflow for 10-yr storm for catch basins
C 1(??
0
:,Q- SEAL
032006
GIN
AS R
1111111
oS- v/-lo
[Ref: 1 ]
0
4K?>
V
Amicus Engineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Pipe Hydraulics & Grate Capacity
Catch Total 10-yr Rainfall Weighted 10-yr
Basin/ Drainage Intensity, i, Runoff Flow,
Inlet Area (in/hr) Coefficient, C Qio
(Acres), A [Ref: 1, [Ref: 1, (cfs)
[Ref: 2] Table 3-3] Table 3-5]
CB-1 0.32 7.03 0.95 2.14
CB-2 0.71 7.03 0.95 4.74
b. Determine grate capacity for catch basin CB-1 and CB-2
Since inlets are in sag locations, assume orifice control and 50% clogging by
debris. The maximum ponding depth will be evaluated as 0.S foot.
Qi = COA(2gd)0-5 [Ref: 4, Eq. 16.1.33]
Opening ratio = 0.46 [Ref 5, CLDS 20.02B]
- Co = 0.67 [Ref: 41
Grate capacity for aforementioned structures
r?
LJ
o Qi =(0.67)[(0.46)x(6sq.ft)][(2)x(32.2 ftIs2 )x(0.5ft)]0' =10.49 ft3ls
(50%) Q, =(0.50)x(10.49 ft31s)=5.25 ft3/s
o The grate capacity far exceeds the calculated ten year flows
2. Determine pipe sizes for pipes PI - P8, Temp. CPP, and Roof Drain
Collection Pipes [Ref: 3]
Drain
Pipe

F Contributing
Flow
[Ref•2] Flow,
Q
(cfs)
mTempCPP . CB-2
4.74
RD1 Roof Drain 0.86
RD2 Roof Drain 0.86
PI LDA-1 1.00°
P2 CB-2 4.74
P3 CB-1 2.14
P4 Existing 36" Pipe 32.31
P5 Existing 36" Pipe 32.31
P6 1st-inch to BR-1 0.085
P7 1St-inch to BR-2 0.355
P8 Roof Drain 0.86
a. Based on hydrologic evaluation
b. Existing flow based on analysis from FHWA Urban
Drainage Design Program
c. 50-year outflow from Landscaped Detention System
[Ref: 6]
[Ref. 3]
[Ref: 6]
•
0
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Y Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus [ngineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Pipe Hydraulics & Grate Capacity
Drain
Pipe Flow,
Q
(cfs) Slope, S
(ft/ft) Manning's
Coefficient, C Required
Diameter (in)
[Ref: 3] Actual
Diameter
(in) Velocity
(ft/s)a
[Ref: 3]
Temp. CPP 4.74 0.169 0.020 12 12 11.92
RD I 0.86 0.007 0.012 12 12 3.42
RD2 0.86 0.007 0.012 12 12 3.42
P1 1.00 0.004 0.012 12 12 2.87
P2 4.74 0.008 0.012 15 15 5.53
P3 2.14 0.012 0.012 12 12 5.38
P4 32.31 0.007 0.012 30 36 8.52
P5 32.31 0.002 0.012 36 36 5.20
P6 0.08 0.005 0.012 12 12 1.52
P7 0.35 0.005 0.012 12 12 2.31
P8 0.86 6007 0.012 12 12 3.42
0
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zcl Pr¢c:se ;a z rriirla I.r rl .a r.] requires juagame. zinc uppers.1zr-foir3.g Qn jhe:pari
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---
----------

FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 06/09/2010
Project No. .
Project Name :
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0020
2. Pipe Diameter (in) 36.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 32.314
OUTPUT RESULTS
Full Flow Conditions
Depth of Flow (ft) 3.00
Velocity (ft/sec) 4.57
•
0
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.1690
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.020
4. Discharge (cfs) 4.740
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.50
Velocity (ft/sec) 11.92
0
•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.007
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.860
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.35
Velocity (ft/sec) 3.42
0
E
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.007
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.860
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.35
Velocity (ft/sec) 3.42
•
•

FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No.
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0040
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 1.000
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.45
Velocity (ft/sec) 2.87
•
r?r- - SJ z
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
is Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.008
2. Pipe Diameter (in) 15.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 4.740
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.81
Velocity (ft/sec) 5.53
•
•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0120
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 2.140
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.50
Velocity (ft/sec) 5.38
0

FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0070
2. Pipe Diameter (in) 30.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 32.310
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 1.79
Velocity (ft/sec) 8.52

•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0020
2. Pipe Diameter (in) 36.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 32.310
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 2.46
Velocity (ft/sec) 5.20
is
0
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No.
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0050
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.080
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.11
Velocity (ft/sec) 1.52
•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No_
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0050
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.350
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.24
Velocity (ft/sec) 2.31
is
0
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0070
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.860
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.35
Velocity (ft/sec) 3.42

•
-7777 777
'642 Chapter to Sto,-mivater:Control: Street and 3liahcna5 Drainage and Culverts
Tt?e.interception capacity of the:curb-opening inlet is fnen
0; .E0 = (0.41)(8) = 328 -cfs
To:.cdinput? iheinterception capacity of'th g-rar?et $quarion (16.1 7)is use3
.
The flaw at the y rate is then 0 = 8 -.328 =.a.72 cis::IT? nQ in s flow.race the.spread'3x.,,can k-COL,
puled with equation
s.,l
0-56. V2 513.,S13
?- Y - O=-;S Sz 1r;
s 73
4.:12 = O5ti (0 01)11'-(0 O5j5131,sr
. ` QOM
T, = 3122 -[ -
-NPM the. velocity can:be.pommuted:;or.use; in.dttrrmioinz'k from?Fir? 16_i S,so Stl1
z? It v --014
T F-vm Figure 16.U, J 1:D..Tbe sidey7ow.:nt megdon rfficiency Is .coirpu?d .Rm-Q a_s
-?
1 ,l
0.ID-(3.DDpg - =G
125(2)
?v -s rstal-;1ow ratio 3.s co?;.ed n=:?`.?uayn? (56.3 21}= ? = F.7)
=0-4i
. iat 7tiOn .capa-i3 is -ihw
- rte- - - _
a; =.?(1;a _ R,(1 -! = 4_?i•Y.:D_41 = 01(1 j] 9.1 cam. -
lbt-. tai inlerccphouk a. °. 0?= - - 0 bc? _ Z21 3 2S cf'_
M- -
1fiA Interception Capacity and lMdenev of.IWets is S:* Durations
.?: Inleti'that. ?. piac?i ut saa,.Iacarions n . `? = ? ':
_ L :. p?atc;'as ueir.:tancl?r>iow'heads'and as oii<?cz~:icr'?..,? ,.???`
h-ass.'The tuilsi.tiau b?twecn weir flow:and orifice fiowcannot be oc-ratcJy.defin„ d, as t-J? .-
ma3-alucuiate'back-andfoith betuV?n these :two'cbnirols_ All r{cnoff that eaters .sags mrst j t
#kimugbthe:inlet-. As aconsequence, the,?rTcieucy of iniets.in:sw in:passwgdebns.is.soxuv?eh - -
q MiticaL Combination inlets.and.curb-op?una roles ara recommended.ifOr Sag;locations, as grtc p c
inlets 3iave clo,--trig tendencies.
7j s
tx`
16.27-:5.1 Viaie Inlets in z Eng. Lvcmwn ..
r= 3e.capacitS .of. grate ?nlcts..?? lIndZl:•S6]i.CDIliC?11S
16.1 Drainage of Street and Hehv,,ay Pavements 643
where C, is the:weirroefncient 3.0 for U.S.,enstomary units (1.66 for Sl units),.P is the grate
perimeter disregardine bars and the curb side is ft.{m), and d is the depfa of water over the:inlet
in ft.(m). The.capacity of.rate ialats.under orifice. ZDptrol is
F -- :0 CO A(2?djos
rr where:C'fl is 0.67 A is the dIear.openmg aria cif the grate., ft'- (n i ), and g.as'tbe:aceeleration due:#o
t y gravity,
-32.16 fr/s2-(9:$1 m1s2).aurz :16.1.9 proyjdes a design solution for equations {15.1.32)
aad.(16.1.33)_

^`
' `
F'

m..
"
.,.?
,?
a
.
Consider a sy etdcal znc?al cure (grifh a cmbj w3ih vpal

b}pass irom
inlets upgade of
lhe
.
.
low pouv D'
tezmme.i e gat .size .for.a dssioa Q of.6.it3/s nd xhe cart d
- -
pa
m--,ut
clog??g of -the :ate the d?si'sprznd is T - L
- di, :S = 0 $_ fU25:f -and:n = 0
u
015
Wh
t
r r
;9F- Rf .
.
a
haPp?w whzn'ihe :flow late is S fiNs?
- i

@

?r O T y,'?? T

Liil LO }'

ccording to Fines 16=l-9,a Vale must have a
edm
t
f
-

t ti
ME P
e
cr:o
12 f
, Wing '.d ° T,;i; = T?{0.075) =..03
#t.and.?J =.=0-,S- Assuming 50pti--nt Clog
gin
b
clebri
th
x
-
g
y
s:.
e e
ec e pedmeLez is reduced b3 ,60
Pe- C IIi ASSam? the use of f-a graie would mezt ttL,.pedmeL.rrequimmearv
th
d
b
-
2
a
ou
le
Ift X J f{,aci; .

a
3 ?
= UB
Q
n

you ?v :5D 64 ,SD .'f'Ui
?"?gare 16.19 ,fisrale 3miet.;Faparsity in sump ?ondifions :(#com Johnson :end .Chang {I9.8?)),
D2 n 53
i
-

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N
a 3
?i
c -
d
i

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.O

-LLJ
c r-)
i 7r
UD
::D
W
-C:
•
RIPRAP APRON
CALCULATIONS

0
•
r:
OBJECTIVE:
Design Riprap Apron (RA-1) to dissipate the 50-year flow discharging from pipe P1.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
r
Project No: 17-10-033 Sheet No:_ o?_
-In Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Arnim Engineering Project Name:_Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
TERMS:
Qso = 50-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
dso = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
L. = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vso = 50-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 50-year
Pipe Pi
Qso = 1.00 cfs
Vso = 2.87 ft/s
do = 12"
Assume minimum tailwater conditions
CALCULATIONS:
L Determine median and maximum stone diameter
a. Determine median stone diameter
- dso = 4"
b. Determine maximum stone size
- dmax = 1.5 x dso = 1.5(4") = 6.0"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
La =8ft
b. Determine width of riprap apron
- Upstream width = ado = 3(1.0 ft) = 3.0 ft
- Downstream width of apron
0 W=do+La=1.0+8.0ft=9.0ft
o\ 111111)
.. SEAL
032006 _
??G' G r N Eti?'??
ASlRtip
[Ref, 1 ]
[Ref: 2]
[Ref. 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1 ]
[Ref 1, Fig. 8.06a]
[Ref, 1, Fig. 8.06a]
Amim Engineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
C. Determine thickness of apron
- T = 1.5(dm.) = 1.5(6.0") = 9.0"
- Use T = 11.25"
Use appropriate filter fabric underneath apron
0
[Ref. 1
0

Appendices
•
Riprap (large stones of various sizes) is often used to prevent erosion at the ends
of culverts and other pipe conduits. It converts high-velocity, concentrated
pipe flow into low-velocity, open channel flow. Stone should be sized and the
apron shaped to protect receiving channels from erosion caused by maximum
pipe exit velocities. Riprap outlet structures should meet all requirements in
Practice Standards and Specifications: 6. 41, Outlet Stabilization Structure.
Several methods are available for designing riprap outlet structures. The
method presented in this section is adapted from procedures used by the USDA
Soil Conservation Service. Outlet protection is provided by a level apron of
sufficient length and flare to reduce flow velocities to nonerosive levels.
•
Design Procedure for The following procedure uses two sets of design curves: Figure 8.06a is used
Riprap Outlet for minimum tailwater conditions, and Figure 8.06b for maximum tailwater
conditions.
Protection
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter, it is classified minimum tailwater condition.
If it is greater than half the pipe diameter, it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a minimum tailwater condition unless reliable flood stage elevations
show otherwise.
Step 2. Based on the tailwater conditions determined in step 1, enter Figure
8.06a or Figure 8.06b, and determine d, riprap size and minimum apron length
(L). The dso size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at the pipe outlet, the apron shape, and the
apron width at the outlet end from the same figure used in Step 2.
Step 4. Determine the maximum stone diameter:
dmax = 1.5 x d50
Step 5. Determine the apron thickness:
Apron thickness = 1.5 x d
max
Step 6. Fit the riprap apron to the site by making it level for the minimum
length, La, from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
•
Rev. 12/93
8.06.1
•
M
Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary (Appendix 8.05). Where overfalls exist at
pipe outlets or flows are excessive, a plunge pool should be considered, see
page 8.06.8.
•
•
8.06.2
•

t?
0
•
Outlet
pipe W 00 + l a
diameter (Lb)
?a ---W
T ilwater < 0. 51),
30
AO,
ok C?0: L Ut? f'-GS

Discharge (ft3/sec)
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
Rev. 12/93
Appezzdices
2 N
U)
C-
M
a
rr
0
LO
a
A(.
Cup !?± ? `?
8.06.3
n
L --A
4le
AmIcui Engineering
OBJECTIVE:
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Cales Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
Design Riprap Apron (RA-2) to dissipate the 10-year flow discharging from pipe P-2.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS
Q 1 o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d5o = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vio = 10-year peak velocity, (ft/s)
•
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-2
Qio = 4.74 cfs
Vio = 5.53 ft/s
do = 15"
Assume minimum tailwater conditions
CALCULATIONS:
L Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 5"
b. Determine maximum stone size
- dma,, = 1.5 x d50 = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=8ft
b. Determine width of riprap apron
- Upstream width = 3do = 3(1.25 ft) = 3.75 ft
• - Downstream width of apron
0 W= do + La = 1.25 + 8.0 ft = 9.25 ft
[Ref: 1 ]
[Ref: 2]
[Ref 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1 ]
[Ref. 1, Fig. 8.06a]
[Ref: 1, Fig. 8.06a]

0
AMIM Engineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's=
Subject:_RinRap Apron
c. Determine thickness of apron
T = 1.5(dnaX) = 1.5(7.5") = 11.25"
Use T = 11.25"
Use appropriate filter fabric underneath apron
[Ref: 1 ]

Ja-Z
i r L Appendices
Outlet W I j ?. II
pipe - Do + La
t(DO)
diameter j i
I,.
La ---•l 80 li:
?_ T ilwater 0.5D i; 117 i
D l I I I j?l i; I i I it
al?t? 7 j
I I 1 i. _, L , ?I ?
o? QQ?°50 gar !i l ? ' I+ F I ? ; ? 4,
r I# I I I I
a F F II I!'I? ' Ii ' i ! ' ° a
a
•t1 i?.? I?`-:.#I I _?_ Ijl,l I .,? a' i} j 1 II tl
20
l,.i! I I{i l I 3
10 fi? I+ I f } i
;?? I 4 I
I i I ? III a• ! ? II? IILi! ,? i iI_ Ij I ' - .}. Z V ,? ( I a D ?
0
2 N
f ! i •??- i IE_. ; l.i.? ! it I•VI III:II ?I' ?O _ F ' 1 Cl
4 '' `1:20 ! .I I? _ ' L
Ii I' ?1 V a
v c in A
1-7 T
3 5 10
20 50 100 200 D
Discharge (ft3/sec) 500 1000
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
E

Rev. 12/93
8.06.3
•
U
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
4A, , Calcs Performed By: JLM
Calcs Checked By: NRP
Amim Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-3) to dissipate the 10-year flow discharging from pipe P-3.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q i o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d5o = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vio = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-3
Qio=2.14 cfs
Vio = 5.38 ft/s
do = 12"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- 5"
- dso -
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine miminum length of riprap apron
- La = 8 ft
b. Determine width of riprap apron
- Upstream width = 3do = 3(1.0 ft) = 3.0 ft
- Downstream width of apron
o W= do + La = 1.0 + 8.0 ft = 9.0 ft
[Ref 1]
[Ref: 2]
[Ref 2]
[Ref: 2]
[Ref: 1, Fig. 8.06x]
[Ref: 1 ]
[Ref: 1, Fig. 8.06a]
[Ref: 1, Fig. 8.06a]
•
v
Amicus Ingineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
T = 1.5(d,naX) = 1.5(7.5") = 11.25"
Use T = 11.25"
- Use appropriate filter fabric underneath apron
•
[Ref: 1 ]
0
•
0
I4 ?- {
rm` t v??
•

Appendices
Lit 0
30
Outlet IW = Do + La
diameter (Dc))
pipe i
La -- W
==a, &T ilwater < 0.5130

Du luu
Discharge (0/sec)
a?
2 N
Q
(LS
Q
Ir
O
1 ?
1000
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
Rev. 12/93
of Pp 60 }
I;I 59
e i
8.06.3

Amicus Ingineering
OBJECTIVE:
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
Design Riprap Apron (RA-4) to dissipate the 10-year flow discharging from pipe P-5.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q i o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d50 = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vio = 10-year peak velocity, (ft/s)
•
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-5
Qio = 32.31 cfs
Vio = 5.20 ft/s
do = 36"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d5o = 7"
b. Determine maximum stone size
- dmax = 1.5 x d50 =1.5(7') = 10.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=9.Oft
b. Determine width of riprap apron
Upstream width = 3do = 3(3.0 ft) = 9.0 ft
- Downstream width of apron
0 W=do+La=3.0+9.0ft=12.0ft
[Ref: 1 ]
[Ref: 2]
[Ref 2]
[Ref. 2]
[Ref: 1, Fig. 8.06a]
[Ref. 1 ]
[Ref. 1, Fig. 8.06a]
[Ref 1, Fig. 8.06a]
x
Amia Engineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name:-Proposed Professional Buildin at Lawyer_ s Road
Subject: RipRap Apron
c. Determine thickness of apron
T = 1.5(dmax) = 1.5(10.5") = 15.75"
- Use T = 11.25"
Use appropriate filter fabric underneath apron
c:
[Ref: 1 ]
•
044
?u
ici'
10
0
ou 1uu
scharge (0 /sec) '
2i
N
3' Z N_
Cn
a
c?
I Q'
tr
O
1 ?
l' 6
jl;.
0
0
1000
Curves may not be extrapolated. P o - 37,? ( C
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
•
3 0
Outlet W = D0 + La
diameter (Do)
pipe
La - W
T ilwater < 0.5D0

nor l?al`?l,
gar o? Pp 50 I d
JI
59
Appendices
Rev. 12/93
8.06.3
n
L _A
•
0
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-5) to dissipate the 10-year flow discharging from pipe P-6.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q1o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d5o = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vio = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-6
Qio = 0.08 cfs
Vio = 1.52 ft/s
do = 12"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 5"
b. Determine maximum stone size
- dmax = 1.5 x d5o = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=8ft
b. Determine width of riprap apron
Upstream width = 3do = 3(1.0 ft) = 3.0 ft
- Downstream width of apron
o W= do + La = 1.0 + 8.0 ft= 9.0 ft
[Ref: 1 ]
[Ref 2]
[Ref: 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1 ]
[Ref 1, Fig. 8.06a]
[Ref: 1, Fig. 8.06x]
•
v
Amicus ingineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010 --
Cafes Performed By: JLM
Cafes Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
T = 1.5(dmaX) = 1.5(7.5") = 11.25"
Use T = 11.25"
Use appropriate filter fabric underneath apron
•
[Ref: 1]
0
f
a
a
3 0
Outlet W = Do + La
pipe
diameter (qo)
La -
?_? T ilwater 0.5DO
to F
o? Pp 60 I ,.
5 l? it
4 I I I II'l i' III{I? fi 'I it
` j! l? !i lit
ll ILL II_ 1f ;.j: li? ?? I t
3Q it t f?l II? I!r I -r -I1-F I ?I rig' ill ?I I'+!
iii i I Ii! 1 ? ? I 1.1- I ?I 1ff I' .I i I ? 21d '
i
?OLr l
(4/,, ?
•
Appendices

?y
4
11 nr, ; i hl' !,
} > -i ?
r 3
10 - i

I li ' I 1 y 2
Q
l - -- I zs '' ? a , ?
1
+
i i i i 15v t
-a
YV.

5 10 20 50
Discharge (ft3/sec) 100 200 0
500 loon

Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection fro m a round pipe flowing full, minimum tailwater condition M, < 0.5 diameter).
Rev. 12/93
80-I. li ,I
J..:., _
T_ ;I ilk
,I
= f _1 :j.
II
8.06.3
•

Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-6) to dissipate the 10-year flow discharging from pipe P-7.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Qio = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
dso = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vio = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-7
Qio = 0.35 cfs
V i o = 2.31 ft/s
do = 12"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- dso = 5"
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=8ft
b. Determine width of riprap apron
Upstream width = 3do = 3(1.0 ft) = 3.0 ft
• - Downstream width of apron
0 W= do + La = 1.0 + 8.0 ft= 9.0 ft
[Ref: 1 ]
[Ref: 2]
[Ref. 2]
[Ref: 2]
[Ref. 1, Fig. 8.06a]
[Ref: 1 ]
[Ref. 1, Fig. 8.06a]
[Ref, 1, Fig. 8.06a]

Amicus Ingineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject:_RipRap Apron
c. Detennine thickness of apron
T = 1.5(dmax) = 1.5(7.5") = 11.25"
Use T = 11.25"
- Use appropriate filter fabric underneath apron
c:
[Ref: 1 ]
40
£•90'8

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wal uoiloalojd uolloaloid lallno jo u61saa a90 g ain6i j
pa}a?od??lxa aq lou Aew sanano
(oas/£0) a6?Byosia
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saxpuaddv
1 = o ??

DRAWDOWN
CALCULATIONS
9
0
E
4 _0
n?>
4micus engineering
OBJECTIVE:
Design a skimmer structure SST-2 that will efficiently drawdown an existing man-
made pond in approximately 7 days.
ASSUMPTIONS/DESIGN CONSIDERATIONS:
It is assumed that the existing man-made pond is spring fed. But until the pond has
been drained and exact spring locations are located, a factor of safety of two will be
used in determining the volume of water that is to be drained by the skimmer
structure.
REFERENCES:
1. "Existing Site Conditions," by Amicus Engineering PC, 06/16/10.
2. Faircloth Skimmer Sizing (www.fairclothskimmer.com/skimmer.html)
CALCULATIONS FOR SHIMMER STRUCTURE DESIGN
Project No: 17-10-033
Date: 09-01-2010
Sheet No: of
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Drawdown Calculations
1. Determine Basin Volume
•
Volume of existinE man-made pond
Elevation (ft)
[Ref: 1 ] Area (ft)
[Ref: 1] Height (ft) Volume (ft )
679 49,847
1 46,604
678 43,361
1 39,052
677 34,743
1 30,196
676 25,649
1 15,105
675 4,560
1 3,587
674 2,613
1 1,651
673 689
a. Total basin volume to principle spillway (679.00 ft) = 136,195 ftb. Total basin volume to principle spillway (679.00 ft) with
factor of safety included = 272,390 ft3
•
l c lei.
2. Design Skimmer Structure SST-2

a. Required water storage volume = 272,390 ,
ft3 \ ?• . Ir- /. 7
b. Desired dewatering time = 7 days - a S E A L
c. A 6.0-inch skimmer is required 0 3 2 0 0 6 _ [Ref. 2]
d. A 2.6-inch orifice radius is required
A 5
2
i
h •, ,?. • •4 . [Ref: 2]
£? •
??
e.
.
-
nc
orifice diameter is required .y IN
%
[Ref: 2]

09-61-10
•
0
Calculate Skimmer Size
Basin Volume in Cubic Feet 272,390 Cu.Ft Skimmer Size 6.0 Inch
Days to Drain* 7 Days Orifice Radius 2.6 Inch[es]
Orifice Diameter 5.2 Inch[es]
'In NC assume 3 days to drain

•
APPENDIX II
SOILS REPORT
•
0
U
TM
lz??,6300@
REPORT OF PRELIMINARY
SUBSURFACE EXPLORATION
FIRST CHOICE EYE CARE
STALLINGS, NORTH CAROLINA
ECS PROJECT NO. 08-7117
September 10, 2010
•
ECS CAROLINAS LLP "Settirl the Standard for Service"
Geofechnical * Construction Materials* Environmental a Facilities NC Registered Engineering Firm F-1078
September 10, 2010
•

Mr. Nick Parker
Amicus Engineering
4400 Morris Park Drive
Suite J
Mint Hill, North Carolina 28227
Reference: Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
ECS Project No. 08-7117
Dear Mr. Parker:
ECS Carolinas, LLP (ECS) has completed a preliminary subsurface exploration for the above
referenced project. This project was authorized and performed in general accordance with ECS
Proposal No. 08-11795P. This report presents the results of our preliminary subsurface
exploration and our evaluation of those conditions with regard to foundation support and general
site development. This report presents our findings along with our preliminary conclusions and
recommendations for design and construction geotechnical aspects. of the project.
ECS Carolinas, LLP appreciates the opportunity to assist
you have questions concerning this report, please contact
Respectfully,
ECS CAROLINAS, LLP
Kevin D. Orr, E.I.
Staff Project Manager
o
z ',':ir
a
t,.
Ri+ard L. Nance, P.E.
Pri pal Engineer
NC Registration No. 7234
of the project. If
8702 Rod Oak Blvd., Suite A, Charlotte, HC 28217 s [phone],*Fax [phone] • www.ecslimited.com
Ashavilk, NC+Chalone, NC-0-0 b .'NC-Grcmvilk, SC.YWagh, NC+S.%rW ro, NC.%kningloq NC
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings„ North Carolina Page 1
1. INTRODUCTION
1.1 Project Information
The site is located to the east of the intersection of Lawyers Road and Millwright Lane in Stallings,
Union County, North Carolina. A site visit indicated existing timber framed structures, a pond and
wooded portions. Topographic information indicates that the site ranges in elevation from 677 to
692 feet above mean sea level (MSL). Review of a grading plan provided by you dated June 8,
2010 proposes a one-story structure, 9,462 square feet in size, to be located on the property. The
structure will be timber framed with a finished floor elevation of approximately 688 feet. The
existing pond onsite is proposed to be drained and the placement of engineered fill will occur within
a portion of the drained pond.
Project information also indicates that the site will contain two bioretention structures and
associated pavements. No structural information was provided at the time of the proposal. ECS
anticipates that structural loads for the building will not exceed 75 kips with wall loads not
exceeding 5 kips per linear foot.
1.2 Scope of Services
Our scope of services included a preliminary subsurface exploration with soil test borings,
laboratory testing, engineering analysis of the foundation support options and preparation of this
report with our recommendations. The subsurface exploration included six (6) soil test borings
(B-1 through B-5, and B-1-A). The borings were performed at the approximate locations shown
on the Boring Location Diagram, Figure 2 in the Appendix, and advanced to depths ranging
from 3.6 to 13.8 feet below the existing ground surface with an ATV mounted drill rig using
16 continuous-flight, hollow-stem augers.
0
•

Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
3. LABORATORY SERVICES
ECS Project No. 08-7117
September 10, 2010
Page 3
Soil samples were collected from the borings and examined in our laboratory to check field
classifications and to determine pertinent engineering properties. Data obtained from the
borings and our visual/manual examinations are included on the respective boring logs in the
Appendix.
A geotechnical engineer classified each soil sample on the basis of color, texture, and plasticity
characteristics in general accordance with the Unified Soil Classification System (USCS). The
soil engineer grouped the various soil types into the major zones noted on the boring logs. The
stratification lines designating the interfaces between earth materials on the boring logs and
profiles are approximate; in situ, the transition between strata may be gradual in both the
vertical and horizontal directions. The results of the visual classifications are presented on the
Test Boring Records included in Appendix.
0

Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
ECS Project No. 08-7117
September 10, 2010
Page 5
borings generally sampled as Silty SAND, exhibiting SPT N-values between 50 blows over 4.5
inches and 50 blows over 1 inch.
Materials hard enough to cause auger refusal or rock were encountered in borings B-1, B-1-A,
and B-3. Refusal depths ranged between 6.5 and 12.0 feet below the ground surface. Refusal is
defined as negligible penetration of the augers under the weight and down pressure of the drill
rig.
4.4 Groundwater Observations
Groundwater level readings were attempted during the time of drilling and after termination of
drilling. Groundwater was not recorded within the borings performed on-site. Fluctuations in the
groundwater elevation should be expected depending on precipitation, run-off, utility leaks, and
other factors not evident at the time of our evaluation. Normally, highest groundwater levels
occur in late winter and spring and the lowest levels occur in late summer and fall.
0

Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 7
5.3 Site Classification for Seismic Design
The 2006 Edition of the North Carolina Building Code (NCBC) requires that the stiffness of the
top 100-ft of soil profile be evaluated in determining a site seismic classification. Alternately,
designers can default by Code to a Site Class "D" site assumption, unless soils data further
reduces the site to an "E" classification. The data available to date indicates that a Site Class
°C" is appropriate for the project.
5.4 Slab-On-Grade Support
•
0
A proposed slab-on-grade floor system can be adequately supported on undisturbed residual
soils, partially weathered rock, or on new, properly placed fill overlying residual soils or partially
weathered rock provided the site preparation and fill recommendations outlined herein are
implemented. For a properly prepared site, a modulus of subgrade reaction (k) for the soil of
100 pounds per cubic inch for the soil can be used. ECS recommends that a granular material
be placed immediately beneath the floor slab to provide a capillary barrier and to increase the
load distribution capabilities of the floor slab system.
ECS recommends the slabs-on-grade be underlain by a minimum of 4 inches of granular
material having a maximum aggregate size of 1%2 inches and no more than 2 percent fines.
This granular layer will facilitate the fine grading of the subgrade and help prevent the rise of
water through the floor slab. Prior to placing the granular material, the floor subgrade soil
should be properly compacted, proofrolled, and free of standing water, mud, and frozen soil.
Before the placement of concrete, a vapor barrier may be placed on top of the granular material
to provide additional moisture protection. However, special attention should be given to the
surface curing of the slab in order to minimize uneven drying of the slab and associated
cracking.
5.6 Cut and Fill Slopes
We recommend that permanent cut slopes less than 10 feet tall through undisturbed residual
soils be constructed at 2:1 (horizontal: vertical) or flatter. Permanent fill slopes be constructed
using controlled fill at a slope of 2.5:1 or flatter. A slope of 3:1 or flatter may be desirable to
permit establishment of vegetation, safe mowing, and maintenance. The surface of all cut and
fill slopes should be adequately compacted. All permanent slopes should be protected using
vegetation or other means to prevent erosion.
The outside face of building foundations and the edges of pavements placed near slopes should
be located an appropriate distance from the slope. The North Carolina Building Code lists the
following requirements:
• Buildings or pavements placed at the top of fill slopes should be placed at distance equal to
at least 1/3 of the height of the slope behind the crest of the slope, but that distance need
not be more than 40 feet.
• Buildings or pavements near the bottom of a slope should be located at least '/z of the height
of the slope from the toe of the slope, but the distance need not be more than 15 feet.
Slopes with structures located closer than these limits or slopes taller than the height limits
indicated, should be specifically evaluated by the geotechnical engineer and may require
approval from the building code official.
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 9
6. CONSTRUCTION CONSIDERATIONS
6.1 Site Preparation and Earthwork Operations
ECS understands that the on-site pond will be drained and a portion of the pond will be filled
with compacted engineered fill. ECS recommends once the pond is completely drained that
the pond surface soils be examined by an engineer or engineering technician prior to
engineered fill placement. ECS anticipates saturated or soft soil will be encountered at the
base of the pond and will need to be undercut to reach a stable subgrade prior to
engineered fill placement.
Alluvial soils may be encountered near the pond area of the site. Remediation to the
ground surface may be required prior to the placement of engineered fill for slopes or
pavement. Isolated undercutting or stabilization with geosynthetics may be required and
should be budgeted for.
Exposed subgrade in areas to receive fill should be proofrolled with a loaded dump truck or
similar pneumatic-tired vehicle having a loaded weight of approximately 25 tons. After
excavation, the exposed subgrades in cut areas should be similarly proofrolled. Proofrolling
operations should be performed under the observation of a geotechnical engineer or their
authorized representative. The proofrolling should consist of two (2) complete passes of the
exposed areas, with each pass being in a direction perpendicular to the preceding one.
Areas which deflect, rut or pump during the proofrolling, and fail to be remedied with
successive passes, should be undercut to suitable soils and backfilled with controlled fill.
Drying of wet soils, if encountered, may be accomplished by spreading and discing or by other
mechanical or chemical means. The ability to dry wet soils, and therefore the ability to use
them for fill, will be reduced if earthwork is performed during late winter or spring.
6.2 Excavation
The results of our exploration indicate that some excavations on-site will likely encountered
very dense soils and partially weathered rock. ECS recommends that equipment capable of
heavy excavation be used during grading activities. Auger refusal Indicating potential rock
was encountered in borings B-1, B-1-A, and B-3 at depths ranging from 6.5 to 12.0 feet
below the ground surface. ECS anticipates that non-rippable rock may be encountered
during installation of utilities on-site. If desired, seismic refraction can be performed to aid in
evaluating utility elevations and the underlying soil and rock stratums.
Partially weathered rock can occasionally be excavated without blasting. It has been our
experience that subsurface material with a Standard Penetration Resistance value of 50/6,
50/5, and 50/4 inches of penetration can likely be loosened and ripped using a D-8 dozer
equipped with a single-tooth ripper. For confined excavations, such material can be removed
with a John Deer 120C or equivalent excavator equipped with rock teeth. The ease of
excavation depends on the quality of grading equipment, skill of the equipment operators and
geologic structure of the material itself, such as the direction of bedding, planes of weakness
and spacing between discontinuities. Therefore, a conservative approach concerning budget
estimates for utility excavations is recommended. Subsurface material that exhibited a
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 11
per 1 foot of fill thickness, whichever results in more tests. We recommend at least one test
per 1 foot thickness of fill for every 100 linear feet of utility trench backfill.
Density tests in the field shall be performed using the Drive Tube Method (ASTM D 2937),
the Sand Cone Method (ASTM D 1556) or the Nuclear Method (ASTM D 2922). If the
Nuclear Method is used, the moisture content determined by the nuclear density equipment
shall be verified by performing one moisture content test per (ASTM D 2216) for every five
nuclear density tests. Good site drainage should be maintained during earthwork operations
to prevent ponding water on exposed subgrades.
Where fill will be placed on existing slopes, we recommend that benches be cut in the
existing slope to accept the new fill. All fill slopes should be overbuilt and then cut back to
expose compacted material on the slope face.
6.5 Footing Observations
Foundation excavations should be tested to confirm adequate bearing prior to installation of
reinforcing steel or placement of concrete. ECS recommends testing shallow foundations to
confirm the presence of foundation materials similar to those assumed in the design. ECS
recommends the testing consist of hand auger borings supplemented with Dynamic Cone
Penetrometer testing performed by an engineer or engineering technician.
Where soft or unsuitable materials are encountered, they should be undercut and replaced
• with properly compacted fill or lean concrete. If soil or aggregate is used as backfill, the
undercut excavation should be oversized 1-foot horizontally beyond each edge of the
footing for every 2 feet of undercut performed below the design bottom of footing level.
Over sizing is not required if lean concrete is used as backfill for the undercut excavation.
Bearing surfaces for foundations should not be disturbed or left exposed during inclement
weather; saturation of the onsite soils can cause a loss of strength and increased
compressibility. If construction occurs during inclement weather, and concreting of the
foundation is not possible at the time it is excavated, a layer of lean concrete should be
placed on the bearing surface for protection.
0
•
APPENDIX
Figure 1 - Site Location Map
Figure 2 - Boring Location Diagram
Soil Test Boring Logs - B-1 through B-5
Unified Soil Classification System
Reference Notes for Boring Logs
ASFE Reference Document
•
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o z w
° n
o BORING LOCATION DIAGRAM First Choice Eye Care
$ g Stallings, North Carolina
z
CLIENT
Amicus Engineering
PROJECT NAME
First Choice Eye Care
SITE LOCATION
Stallings, North Carolina
W
a

5
JOB # BORING # SHEET
08-7117 B-1-A 1 OF 1 E?N
ARCHITECT-ENGINEER -LP
GAROLI NAS
--o- CAMRATED PENETROMETER
TONS/FT. 2
1 2 3 4 5+
PLAMC WATER UQUM
LIMIT % CONTENT % LIMIT %
DESCRIPTION OF MATERIAL ENGLISH UNITS _ X ----? --?

x w
V2 a ROCK QUAIM DESIGNATION do RECOVERY
a
a BOTTOM OF CASING LOSS OF CIRCULATION 100X o RQO%- - - REC.9:
< -20%-40X-60%-80X-1 00%-
SURFACE ELEVATION F' ® STANDARD PENET

?0.
688
¢
w RATION
BLOWS/VT
Topsoil Depth 2"
AUGER PROPE TO 8.5 FEET
PARTIALLY WEATHERED ROCK -
1 Sampled as Light Brown and
White, Silty Fine SAND, Moist,
(PWR)
• AUGER REFUSAL @ 12.0'
1
3
80
10 20 30 40 50+
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES IN-SITU THE TRANSITION NAY BE GRADUAL
7 WL G N E WS OR ® BORING STARTED
09/02/10
?WL(BCR) ,LWL(ACR> BORING COMPLETED 09/02/10
CAVE IN DEPTH 6 10.3'
-TWL
RIG SIMCO 2400FOREww PRESLEY
DRIId.IIdG METHOD HSA
CLIENT
JOB # BORING # SHEET
Amicus Engineering 08-7117 B-3 1 OF 1
rm"i
PROJECT NAME ARCHITECT-ENGINEER c

First Choice E
e Car LLP
y
e CAROLINAS
SITE LOCATION CALIBRA

Stallings, North Carolina TED PENETROMETER
TONS/FTT.2

3
1 2 4 6t

PLASTIC WATER LIQUID
LDHT % CONTENT % LIMIT %
4 _ DESCRIPTION OF MATERIAL ENGLISH UNITS m
w F
., ROCK QUALITY DESIGNATION do RECOVERY

z =
a
BOTTOM OF CASING W- LOSS OF CIRCUTATION 100% z
o ROD%- - - REC.X
i 20X-40%-60 80%100X
ca a
1 a °o SURFACE ELEVATION

'
682 ® STANDARD PENETRATION
BLOWS
i

0 w /
T.
] 0 20 30 40 50+
Topsoil Depth 2"

1 SS 18 10 RESIDUAL - Dense to Very Dense, 680 :(ID-I2-22) 34
Light Brown and White, Silty
Fine SAND
Moist
(SM) = =
,
,

5 2 SS 18 12 (19-24-M))
54
-

3 SS 9 9 PARTIALLY WEATHERED ROCK -
50
Sampled as Light Brown and 4 -50/3)
675 3
White, Silty Fine SAND, Moist, =
PWR
( )
: (?/1): 10
1 AUGER REFUSAL ® 8.0' =
F6701
1
66
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES IN-SITU THE TRANSITION MAY BE GRADUAL °
SPI, GNE WS OR ® BORING STARTED 09/02/10
YWL(BCR) ZWL(ACR) BORING COMPLETED 09/02/10 CAVE IN DEPTFI a 6,3' s
Y'n luGsIMCO 2400FOREMAN PRESLEY DRLLIJZTG METHOD HSA
CLIENT
JOB # BORING #
SHEET
Amicus Engineering 08-7117 g -5 1 of 1
PROJECT NAME ARCHITECT-ENGINEER ECY

First Choice
Eye Care LLP
SITE LOCATION CA ROLII.fAS
Stallings, Norfh Carolina -o- o??``TED PENETROMETER
TONS/FT. 2
1 2 3 4 6+
PLASTIC WATER LIQUID
LDBT % CONTENT % LIMIT X
DESCRIPTION OF MATERIAL ENGLISH UNITS vo x -------?

..
0
z a

BOTTOM OF CASIN
a
ROCK QUALITY DESIGNATION k RECOVERY
R
G.-- LOSS OF CIRCULATION 100% o OD%- - - REC.X
a

M

SURFACE ELEVATION (?
a
20%-40%-60% 80% tOOX-
02 688 PENETRATION
® STANDARD
BLOWS/n.

Topsoil Depth 2" 10 ?.0 30 40 50+
1 SS 18 9 RESIDUAL - Medium Dense to
Dense
Light Brow
d W
21 (?10-11)
,
n an
hite, =
Silty Fine SAND, Moist, (SM) 685
2 SS 18 8 =
5 (12-18-30 48
END OF BORING @ 5.0
1
•
1
2
THE STRATIFICATION LINES REPRESENT THE APPRID(IMATE BOUNDARY LINES RETVEEN SOIL TYPES IN-SITU THE TRANSITION MAY BE GRADUAL
GNE WS OR ® BORING STARTED g
09/02/10 =
_TWL(BCR) IWL(ACR) BORING COMPLETED 09/02/10 CAVE IN DEPTH ®3.2'
-TWL RAG SIMCO 2400 FOREMAN
P R ES LEY DRILI"G METIiOD HSA $
•
REFERENCE NOTES FOR BORING LOGS
Drilling Sampling Symbols
SS
RC Split Spoon Sampler
Rock Core, NX, BX, AX ST
PM Shelby Tube Sampler
Pressuremeter
DC Dutch Cone Penetrometer RD Rock Bit Drilling
BS
HSA Bulk Sample of Cuttings
Hollow Stem Au
er PA
WS Power Auger (no sample)

REC g
Rock Sample Recovery %
RQD Wash sample
Rock Quality Desi
natio
%
g
n
II. Correlation of Penetration Resistances to Soil Properties
Standard Penetration (blows/ft) refers to the blows per foot of a 140 lb. hammer falling 30
inches on a 2-inch OD split-spoon sampler, as specified in ASTM D 1586. The blow count is
commonly referred to as the N-value.
A. Non-Cohesive Soils (Silt, Sand, Gravel and Combinations)
•
Do
Under 4 blows/ft
5 to 10 blows/ft
11 to 30 blows/ft
31 to 50 blows/ft
Over 51 blows/ft
)nsity
Very Loose
Loose
Medium Dense
Dense
Very Dense
Relative Properties
Adjective Form 12% to 49%
With 5% to 12%
Particle Size ldentifrcation
Boulders 8 inches or larger
Cobbles 3 to 8 inches
Gravel Coarse 1 to 3 inches
Medium '/ to 1 inch
Sand Fine
Coarse % to % inch

Medium 2.00 mm to''/< inch (dia. of lead pencil)

Fine 0.42 to 2.00 mm (dia. of broom straw)

Silt and Clay 0.074 to 0.42 mm (dia. of human hair)
0.0 to 0.074 mm
particles cannot be seen
B. Cohesive Soils (Clay, Silt, and Combinations)

Blows/ft
Consistency Unconfined
Comp. Strength Degree Plasticity
Qp (tst] Plasticity y Index
Under 2
3 to 4 Very Soft Under 0.25 None to slight 0-4

5 to 8 Soft
Medium Stiff 0.25-0.49 Slight 5-7
0.50-0.99 Mediu

9 to 15

16 to 30
Stiff

Very Stiff m
8-22
1.00-1.99 High to Very High Over 22

31 to 50
Hard 2.00-3.00
4.00-8
00
Over 51 Very Hard .
Over 8.00
III. Water Level Measurement Symbols
WL Water Level BCR Before Casing Removal DCI Dry Cave-In
WS While Sampling ACR After Casing Removal WCI Wet Cave-In
WD While Drilling V Est. Groundwater Level
8 Est. Seasonal High GWT
The water levels are those levels actually measured in the borehole at the times indicated by the
symbol. The measurements are relatively reliable when augering, without adding fluids, in a granular
soil. In clay and plastic silts, the accurate determination of water levels may require several days for
the water level to stabilize. In such cases, additional methods of measurement are generally applied.

A Report's Recommendations Are Not Final
Do not overrely on the construction recommendations included
in your report. Those recommendations are not final, because
geotechnical engineers develop them principally from judgment
and opinion. Geotechnical engineers can finalize their recom-
mendations only by observing actual subsurface conditions
revealed during construction. The geotechnical engineer who
deveioped your report cannot assume responsibility or liability for
the report's recommendations if that engineer does not perform
construction observation.
A Geotechnical Engineering Report is Subject
To Misinterpretation ?.
Other design team members' misinterpretation of geotechnical
engineering reports has resulted in costly problems. Lower
that risk by having your geotechnical engineer confer with
appropriate members of the design team after submitting the
report. Also retain your geotechnical engineer to review perti-
nent elements of the design team's--plans and specifications.
Contractors can also misinterpret a geotechnical engineering
report Reduce that risk by having your geotechnical engineer
participate in prebid and preconstruction conferences, and by
providing construction observation.
Do Not Redraw the Engineer's Logs
Geotechnical engineers prepare final boring and testing logs
based upon their interpretation of field logs and laboratory
data. To prevent errors or omissions, the logs included in a.
geotechnical engineering report should never be redrawn for
inclusion in architectural or other design drawings. Only photo-
graphic or electronic reproduction is acceptable, but recognize71
that separating logs from the report can elevate risk.
Give Contractors a Complete
Report and Guidance
Some owners and design professionals mistakenly believe they
can make contractors liable for unanticipated subsurface condi-
tions by limiting what they provide for bid preparation. To help
prevent costly problems, give contractors the complete geotech-
nical engineering report, but preface it with a clearly written let-
ter of transmittal. In that letter, advise contractors that the report
was not prepared for purposes of bid development and that the
report's accuracy is limited; encourage them to confer with the
geotechnical engineer who prepared the report (a modest fee
may be required) and/or to conduct additional study to obtain
the specific types of information they need or prefer. A prebid
conference can also be valuable. Be sure contractors have suffi-
cient time to perform additional study. Only then might you be in
a position to give contractors the best information available to
you, while requiring them to at least share some of the financial
responsibilities stemming from unanticipated conditions.
Read Responsibility Provisions Closely
Some clients, design professionals, and contractors do not
recognize that geotechnical engineering is far less exact than
other engineering disciplines. This lack of understanding has
created unrealistic expectations that have led to disappoint-
ments, claims, and disputes. To help reduce such risks, geot-
echnical engineers commonly include a variety of explanatory
provisions in their reports. Sometimes labeled "limitations",
many of these provisions indicate where geotechnical engi-
neers responsibilities begin and end, to help others recognize
their own responsibilities and risks. Read these provisions
closely. Ask' questions. Your geotechnical engineer should
respond fu1Ly and frankly.
Geoenviponmental Concerns Are Not Covered
The equipment, techniques, and personnel used to perform a
geoenvironmentaf study differ significantly from those used to
perform a geotechical study. For that reason, a geotechnical
engineering report does not usually relate any geoenvironmen-
tal findings, conclusions, or recommendations; e.g., about the
likelihood of encountering underground storage tanks or regu-
lated contaminants. Unanticipated environmental problems have
led to numerous project failures. If you have not yet obtained
your own geoenvironmental information, ask your geotechnical
consultant for risk management guidance. Do not rely on an
environmental report prepared for someone else.
Rely on Your Geotechnical Engineer top
Additional Assistance
Membership in ASFE exposes geotechnical engineers to a wide
array of risk management techniques that can be of genuine ben-
efit for everyone involved with a construction project. Confer with
your ASFE-member geotechnical engineer for more information.
PROFESSIONAL
A FIRMS PRACTICING
F=EIN THE GEOSCIENCES
8811 Colesville Road Suite G106 Silver Spring, MD 20910
Telephone: [phone] Facsimile: 301-589-2017
email: [e-mail] www.asfe.org
Copyright 1998 by ASFE, Inc. Unless ASFE grants written permission to do so, duplication of this document by any means whatsoever is expressly prohibited.
Reuse of the wording in this document. in whole or in part, also is expressly prohibited, and may be done only with the express permission of ASFE or for purposes
• of review or scholarly research.
IIGER06983.51V1
•
APPENDIX III
CONSTRUCTION
DRAWINGS
r
0