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STORMWATER IMPACT ANALYSIS
DUNN OPERATIONS CENTER & MOBILE SUBSTATION STORAGE/ DKE-22052/OCTOBER 2023
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MCADAMS

DUNN OPERATIONS CENTER & MOBILE
SUBSTATION STORAGE
DUNN, NORTH CAROLINA
STORMWATER IMPACT ANALYSIS
STORMWATER PERMIT: SW6230701
PROJECT NUMBER: DKE-22052
DESIGNED BY: J. WOOSTER, PE
A. THIERER, PE
S. FERRITER, El
DATE: JUNE 2023
REVISED: OCTOBER 2023
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621 HILLSBOROUGH STREET, SUITE 500
RALEIGH, NC 27603
NC LIC. # C-0293

�J MCADAMS NARRATIVE > DKE-22052
DUNN OPERATIONS CENTER & MOBILE SUBSTATION STORAGE
Stormwater Impact Analysis
SITE HISTORY& PROJECT DESCRIPTION
Located on the north side of Jonesboro Road (S.R. 1808), at its intersection with Wise Road (S.R. 1799), the project
area consists of a +/-34.96 acre parcel currently under contract for purchase by Duke Energy Progress, LLC, which is
further described by Harnett County Parcel Identification Number(PIN) 1527-91-9952.000.The site is located within
the jurisdiction of Harnett County,just outside the Dunn Extra-Territorial Jurisdiction (ETJ) and is primarily zoned RA-
20M (Residential/Agricultural District) with a small portion on the north side of the property zoned RA-30
(Residential/Agricultural District).
Development on this site will consist of approx. 18,500 sq ft. of office workspace, along with an adjacent 15,000 sq ft.
of warehouse / garage and (6) truck bays to support approximately 55 permanent staff. The new Mobile Substation
building will be a (14) bay pull through Pre-engineered Metal Building (PEMB). The proposed development will also
include a new lay down yard to support both the operations center and mobile storage business unit requirements,
along with parking, utility, and stormwater management infrastructure. Two stormwater control measures (SCM) are
proposed with this project.
The proposed development is not located within a Nutrient Management Watershed (NMS).
Per Harnett County regulations, stormwater management on this site shall meet the stormwater management
performance standards for development set forth in Section 2.5 Stormwater Management Statement of the Harnett
County Unified Development Ordinance.
The regulations are as follows:
2.5 Stormwater Management Statement
A preliminary subdivision plat or site plan (except for minor site plans as defined by this
Ordinance)for a commercial or residential subdivision shall include a stormwater management
statement, submitted as part of the required Conceptual Plan. A stormwater management
statement shall include the following:
A. Development name and location
B. Developer/owner and consultant contact information
C. Site description including the following:
1.Vicinity map
2. USGS Topographic Map and Harnett County Soil Survey indicating area of development
3. Description of all water courses, impoundments, and wetlands on or adjacent to the site or into
which stormwater directly flows
D. Statement noting whether the site is located within the conservation zoning or a watershed district.
E. Impervious area calculations
F. A description of the proposed stormwater management system including:
1. Best Management Practices (BMPs) and preliminary sizes and locations, including post
development drainage map delineating the flows diverted to each BMP.
2. Description and concept for diversion of off-site stormwater
3. Pre-development and post-development discharges for the 10 year and 25 year storms. If the
increase in the pre-development discharge is less than 10 percent(10%), then an additional may
not be required unless deemed necessary by the DRB.
G. Downstream Analysis, if required:
creating experiences through experience 621 Hillsborough Street,Suite 500,Raleigh,NC 27603/919.361.5000

MCADAMS NARRATIVE > DKE-22052
1. Provide topography with the following identified:
a. Drainage areas for the development
b. Drainage areas for downstream drainage structures
c. Provide photographs of downstream structures
2. For existing streams and ditches, the analysis should focus on increases in velocity and flooding
within the stream.
3. For existing culverts, the analysis should focus on increases in headwater and flooding at the
structure.
4. Identify the point at which the drainage area of the development or redevelopment becomes less
than 10 percent (10%) of the total watershed.
5.All negative impacts of existing improvements and developments shall be identified, if there are
no negative impacts,the analysis specifically state and demonstrate that there are not adverse
impacts in the increase in site runoff.
6. If downstream measures are found to be inadequate, detention or other improvements will be
required to minimize downstream impacts.
CALCULATION METHODOLOGY
■ Rainfall data for this area in the Dunn, NC region is from NOAA Atlas 14. This data contains a depth-duration-
frequency(DDF)table describing rainfall depth versus time for varying return periods in the area. These rainfall
depths are input into the meteorological model within PondPack for peak flow rate calculations. Please
reference the precipitation information within the Miscellaneous Site Information section of this report for
additional information.
■ Using WebSoil Survey, the on-site soils were determined to be hydrologic soil group (HSG) 'A' and 'D' soils.
Since the method chosen to compute pre- and post-development peak flow rates and runoff volumes is
dependent upon the soil type, care was taken when selecting the appropriate Soil Conservation Service Curve
Number(SCS CN).
- An approximate proportion was determined, a composite SCS CN was computed for each cover
condition with a sub-basin.
- A composite SCS Curve Number was calculated for both the pre- and post-development condition for
each indirectly connected (IC) impervious area in each subbasin using SCS curve numbers and land
cover conditions.
■ Land cover conditions for the pre-development condition were taken from survey data obtained by McAdams.
Land cover conditions for the post-development condition were taken from the proposed layout. Off-site areas
draining to a proposed SCM are assumed to be 100% impervious to account for future development.
■ The time of concentration for each subbasin was calculated using SCS TR-55 (Segmental Approach, 1986).The
Tc flow path can be divided into four segments: overland flow,concentrated flow, channel flow, and pipe flow.
The travel time was then computed for each segment, from which the overall time of concentration was
determined by taking the sum of each segmental time.
■ Existing topographic information used in this analysis is from survey data obtained by McAdams.
■ PondPack Version 10.02.00.01 was used in determining the pre-& post-development peak flow rates for the
1-, 10-, and 25-year storm events as well as routing calculations for the proposed stormwater control
measures.
creating experiences through experience 2 of 4

�J MCADAMS NARRATIVE > DKE-22052
creating experiences through experience 3 of 4

�J MCADAMS NARRATIVE > DKE-22052
DISCUSSION OF RESULTS
PEAK FLOW ANALYSIS
As shown in the Summary of Results in this report, the proposed stormwater control measures provide the necessary
peak runoff control such that there are no predicted increases in the 1-, 10-, and 25-year storm events at any of the
four points of analysis (POAs)from the pre-development to post-development condition.
CONCLUSION
If the development on this tract is built as proposed within this report, then the requirements set forth in Harnett
County regulations will be met without additional stormwater management facilities. However, modifications to the
proposed development may require that this analysis be revised. Some modifications that would require this analysis
to be revised include:
1. The proposed site impervious surface exceeds the amount accounted for in this report.
2. The post-development watershed breaks change significantly from those used to prepare this report.
The above modifications may result in the assumptions within this report becoming invalid.The computations within
this report will need to be revisited if any of the above conditions become apparent as development of the proposed
site moves forward.
creating experiences through experience 4of4

1 MISCELLANEOUS SITE INFORMATION
2 PRE-DEVELOPMENT HYDROLOGIC
CALCULATIONS
I
3 POST-DEVELOPMENT HYDROLOGIC
CALCULATIONS
4 STORMWATER CONTROL MEASURE 'A'
IPRELIMINARY DESIGN CALCULATIONS
5 STORMWATER CONTROL MEASURE 'B'
PRELIMINARY DESIGN CALCULATIONS

DUNN OPERATIONS CENTER AND MOBILE SUMMARY OF RESULTS S.FERRITER,El
SUBSTATION STORAGE 10/12/2023
DKE22052
RELEASE RATE MANAGEMENT RESULTS
—
POINT OF ANALYSIS#1
Return Period Pre-Dev Post-Dev %Increase
[cfs] [cfs] [%]
1-Year 2.74 1.56 -43%
10-Year I 13.22 I 10.57 I -20%
25-Year I 18.44 I 17.13 I -7%
POINT OF ANALYSIS#2
Return Period Pre-Dev Post-Dev %Increase
[cfs] [cfs] [%]
1-Year I 4.89 I 4.67 I -4%
10-Year 19.55 12.85 -34%
25-Year 26.50 16.20 -39%
POINT OF ANALYSIS#3
Return Period Pre-Dev Post-Dev %Increase
. [cfs] [cfs] [%] a
1-Year 3.57 0.01 -100%
10-Year I 14.97 I 0.60 I -96%
25-Year I 20.42 I 1.33 I -93%
POINT OF ANALYSIS#4
Return Period Pre-Dev Post-Dev %Increase
[cfs] [cfs] ['Al —
1-Year I 0.58 I 0.12 I -79%
10-Year 5.06 1.90 -62%
25-Year 7.72 3.22 -58%

DUNN OPERATIONS CENTER AND MOBILE SUMMARY OF RESULTS S.FERRITER,El
SUBSTATION STORAGE SCM A 10/12/2023
DKE22052
STORMWATER CONTROL MEASURE'A'SUMMARY
Design Drainage Area= 22.01 ac
Design Impervious Area= 18.84 ac
%Impervious= 85.6%
Top of Dam= 222.50 ft
NWSE= 215.50 ft
Average Depth= 3.88 ft
WQv Ponding Elevation= 217.53 ft
Required Surface Area at NWSE= 24,973 sf
Provided Surface Area at NWSE= 30,777 sf
WQv Orifice Diameter= 3.50 in
WQv Orifice Invert Elevation= 215.50 ft
Riser Size= 4'x 4'
Riser Crest= 220.50 ft
Number of Orifices= 1
Orifice Invert Elevation= 217.75 ft
Orifice Diameter= 3'L x 0.5' H
Number of Weirs= 1
Weir Invert Elevation= 219.60 ft
Weir Length= 3.00 ft
Barrel Diameter= 30 in
#of Barrels= 1
Upstream Invert= 215.50 ft
Downstream Invert= 215.00 ft
Length= 49 ft
Slope= 0.0102 ft/ft
STORMWATER CONTROL MEASURE ROUTING RESULTS
Return Period Inflow Outflow Max.WSE Freeboard
[cfs] [cfs] [ft] [ft]
1-Year 45.10 0.45 217.75 4.75
10-Year 106.86 9.29 219.48 3.02
25-Year 130.81 18.08 220.42 2.08
100-Year 165.72 45.20 221.25 1.25

DUNN OPERATIONS CENTER AND MOBILE SUMMARY OF RESULTS S.FERRITER,El
SUBSTATION STORAGE SCM B 10/12/2023
DKE22052
STORMWATER CONTROL MEASURE'B'SUMMARY
Design Drainage Area= 6.12 ac
Design Impervious Area= 4.19 ac
%Impervious= 68.5%
Top of Dam= 232.00 ft
NWSE= 227.00 ft
Average Depth= 3.60 ft
WQv Ponding Elevation= 227.56 ft
Required Surface Area at NWSE= 5,877 sf
Provided Surface Area at NWSE= 20,722 sf
WQv Orifice Diameter= 2.75 in
WQv Orifice Invert Elevation= 227.00 ft
Riser Size= 4'x 4'
Riser Crest= 231.00 ft
Orifice 1 Diameter= 3.00 in
Orifice 1 Invert Elevation= 227.75 ft
Barrel Diameter= 24 in
#of Barrels= 1
Upstream Invert= 227.00 ft
Downstream Invert= 226.00 ft
Length= 144 ft
Slope= 0.0069 ft/ft
STORMWATER CONTROL MEASURE ROUTING RESULTS MMII
Return Period Inflow Outflow Max.WSE Freeboard
[cfs] [cfs] [ft] [ft]
1-Year 18.16 0.24 227.97 4.03
10-Year 35.87 0.54 229.20 2.80
25-Year 42.20 0.64 229.82 2.18
100-Year 51.24 0.78 230.88 1.12

MISCELLANEOUS SITE INFORMATION
Dunn Operations Center& Mobile Substation Storage
DKE-22052

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A DUNN OPERATIONS CENTER & MOBILE SUBSTATION STORAGE 'IA
SITE AERIAL MAP
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1"=500' Feet CITY OF DUNN,HARNETT COUNTY,NORTH CAROLINA
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USGS TOPOGRAPHIC MAP
PROJECT#: DKE-22052
0 250 500 1,000 1,500 CITY OF DUNN,HARNETT COUNTY, NORTH CAROLINA
1 =500' Feet MCADAMS/

CAPE FEAR RIVER BASIN
Name of Stream Subbasin Stream Index Number Map Number Class
Mill Creek CPF17 18-77-1-1 J26SE9 C;Sw
Mill Creek CPF17 18-81-6-1 K26SE4 C;Sw
Mill Creek(Betts Creek) CPF24 18-87-14 J28SW2 SA;HQW
Mill Creek(Warrior Lake,Crystal Lake) CPF14 18-23-11-(2) G21NE2 WS-III,B;HQW:@
Mill Pond CPF23 18-74-33-5 127NE8 C;Sw
Mill Run CPF19 18-68-2-7 H26NW2 C;Sw
Mill Run CPF23 18-74-55-8 J26NE5 C;Sw
Mill Swamp CPF19 18-68-1-17-6 G25SW4 C;Sw
Mill Swamp CPF19 18-68-2-2 G26SW4 C;Sw
Millers Creek CPF19 18-68-2-10-3 H26NE7 C;Sw
Millers Creek CPF22 18-68-2-10-3 H26NE7 C;Sw
Millstone Creek CPF09 17-19 E2ONE4 C
Mine Creek CPF02 16-14-7-(1) C21NW5 WS-II;HQW,NSW
Mine Creek CPF02 16-14-7-(2) C21NW7 WS-II;HQW,NSW,CA
Mineral Springs Branch CPF23 18-74-63-2-1 K27NW2 C;Sw
Mines Creek CPF16 18-38-1-(2) H23SE4 WS-IV
Mines Creek(Pages Lake) CPF16 18-38-1-(1) H23SE4 WS-IV,B
Mingo Swamp CPF18 18-68-12-2 F24NE7 C;Sw
Mire Branch CPF13 18-20-13-2 F22SE4 C
Mire Branch CPF21 18-74-7 G27SW3 C;Sw
Moadams Creek(Latham Lake) CPF02 16-18-7 C21SE2 WS-V;NSW
Moccasin Branch CPF19 18-68-1-12 H25NW3 C;Sw
Moccasin Creek CPF03 16-19-9 C21SW9 WS-V;NSW
Molasses Creek CPF17 18-88-9-2-5 L26NE8 SA;HQW
Molly Branch CPF13 18-20-28 F23SE1 WS-IV
Moore Branch CPF14 18-23-16-8-6-1 F22SW7 WS-III
Moore Creek CPF17 18-86-1 K26SE9 C;Sw
Moores Creek CPF02 16-11-3 C19NW8 WS-III;NSW
Moores Creek CPF20 18-68-18 126SE1 C;Sw
Moores Creek CPF23 18-74-33-1 128NW5 C;Sw
Morgan Branch CPF17 18-81-7 K26NE5 C;Sw
Morgan Creek CPF06 16-41-2-(1) D22NW3 WS-II;HQW,NSW
Morgan Creek CPF06 16-41-2-(5) D22NE7 WS-V;NSW
Morgan Creek CPF06 16-41-2-(5.5) D22NE8 WS-IV;NSW
Morgan Creek(including the Morgan Creek Arm of CPF05 16-41-2-(9.5) D22SE3 WS-IV;NSW,CA
New Hope River Arm of B.Everett Jordan Lake)
Morgan Creek(including the Morgan Creek Arm of CPF06 16-41-2-(9.5) D22SE3 WS-IV;NSW,CA
New Hope River Arm of B.Everett Jordan Lake)
Morgan Creek(University Lake) CPF06 16-41-2-(1.5) D22NE7 WS-II;HQW,NSW,CA
Morgans Creek CPF23 18-74-55-12 J27NW7 C;Sw
Morris Branch CPF05 16-41-1-17-3-1 D23SW6 WS-IV;NSW
Motes Creek(Newland Creek) CPF04 16-25 D21NE2 WS-V;NSW
Mott Creek(Todds Creek) CPF17 18-82 K27NW9 C;Sw
Motts Channel CPF24 18-87-24-2 K27NE2 SB:#
Mount Pleasant Creek CPF09 17-16-3 D20SE4 WS-III
Mountain Creek CPF05 16-41-1-5 D22NE1 WS-V;NSW
Mud Creek CPF05 16-41-1-10 C23SW7 WS-V;NSW
Mud Lick Creek CPF12 17-43-6-(0.5) D21SW5 WS-III
Mud Lick Creek CPF12 17-43-6-(2) D21SW4 WS-III;CA
Muddy Creek CPFO8 17-9-(1) D19NW9 WS-IV:*
Muddy Creek CPF08 17-9-(2) D19NW9 WS-IV;CA:*
Muddy Creek CPF02 16-11-14-1-3 C19SE6 WS-V;NSW
Muddy Creek CPF22 18-74-25 H27SE2 C;Sw
Muddy Creek(Overhills Lake) CPF14 18-23-26 F22SE8 C
Muddy Slough CPF17 18-88-7 L27NW7 SA;HQW
Page 19 of 30 2016/03/03 8:47:23

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Hydrologic Soil Group—Harnett County, North Carolina PI
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
NoA Norfolk loamy sand,0 to A 24.8 71.2%
2 percent slopes
NoB Norfolk loamy sand,2 to A 2.1 6.1%
6 percent slopes
Ra Rains sandy loam,0 to A/D 7.9 22.7%
2 percent slopes
Totals for Area of Interest 34.9 100.0%
Description
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.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential)when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
USDA Natural Resources Web Soil Survey 8/16/2022
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group—Harnett County, North Carolina pl
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff:None Specified
Tie-break Rule: Higher
USDA Natural Resources Web Soil Survey 8/16/2022
Conservation Service National Cooperative Soil Survey Page 4 of 4

8/16/22,3:21 PM Precipitation Frequency Data Server
NOAA Atlas 14,Volume 2,Version 3
iewoe�, Location name: Dunn,North Carolina,USA* � '�"
V Latitude:35.3201°,Longitude:-78.5651° noan
Elevation:229.47 ft**
source:ESRI Maps
'"source:USGS "`"'"`
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley
NOAA,National Weather Service,Silver Spring,Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Average recurrence interval(years)
Duration - -
1 2 5 10 25 50 100 200 500 __ 1000
5-min 0.436 10.512 0.592 0.659 0.736 0.794 I 0.850 I 0.902 0.966 1.02
(0.399-0.478) (0.469-0.561) (0.541-0.649) (0.602-0.721) (0.669-0.804) (0.720-0.867) (0.765-0.927) (0.808-0.984) (0.857-1.05) (0.898-1.12)
10-min 0.696 0.819 0.948 1.05 1.17 1.26 1.35 1.43 1.53 I 1.61
(0.637-0.764)1(0.750-0.898) (0.867-1.04) (0.962-1.15) (1.07-1.28) (1.15-1.38) I (1.22-1.47) I (1.28-1.56) (1.36-1.67) (1.41-1.76)
15-min 0.870 1.03 1.20 1.33 1.49 I 1.60 1.71 1.80 I 1.92 2.02
(0.796-0.955) (0.943-1.13) (1.10-1.31) (1.22-1.46) (1.35-1.62) (1.45-1.75) (1.54-1.86) (1.62-1.97) (1.71-2.10) (1.77-2.20)
30-min 1.19 1.42 1.70 1.93 2.20 2.41 2.61 2.81 3.06 3.26
_ (1.09-1.31) (1.30-1.56) (1.56-1.87) (1.76-2.11) (2.00-2.40) (2.19-2.63) (2.35-2.85) (2.52-3.06) (2.72-3.34) (2.87-3.57)
60-min 1.49 1.79 2.19 2.52 2.93 3.27 3.60 3.94 4.39 4.76
(1.36-1.63) (1.64-1.96) (2.00-2.39) I (2.30-2.75) (2.66-3.20) (2.96-3.57) (3.24-3.93) (3.53-4.30) (3.90-4.79) (4.19-5.21)
2-hr 1.75 2.11 2.62 3.06 3.64 4.12 4.61 5.13 5.84 6.45
(1.58-1.95) (1.91-2.34) (2.37-2.91) (2.76-3.40) (3.26-4.04) (3.68-4.57) (4.09-5.11) (4.52-5.68) (5.10-6.46) (5.58-7.14)
3-hr 1.85 2.24 2.79 3.29 3.96 4.53 5.12 5.76 6.67 7.46
(1.68-2.07) (2.03-2.50) (2.53-3.12) (2.97-3.67) (3.55-4.40) (4.03-5.03) (4.53-5.69) (5.06-6.40) (5.78-7.41) (6.40-8.30)
6-hr 2.21 2.67 3.34 3.94 4.75 5.45 6.19 6.99 -
8.13 9.13
(2.01-2.46) (2.42-2.96) (3.03-3.71) (3.56-4.36) (4.26-5.25) (4.86-6.03) (5.47-6.84) (6.12-7.70) (7.02-8.96) (7.79-10.1)
12-hr 2.60 3.13 3.94 4.67 5.67 6.56 7.49 8.51 9.99 11.3
(2.35-2.90) (2.84-3.49) (3.56-4.40) (4.20-5.21) (5.06-6.30) (5.80-7.27) (6.56-8.29) (7.37-9.42) _ (8.52-11.1) (9.49-12.5)
24-hr 3.05 3.70 4.74 5.58 6.77 7.75 8.79 9.90 11.5 12.8
(2.78-3.36)_ (3.38-4.07) (4.31-5.21) i (5.07-6.13) (6.12-7.44) i (6.97-8.53) (7.88-9.67) (8.82-10.9) (10.2-12.7) (11.2-14.2)
2-day 3.57 4.31 5.47 6.41 7.74 8.83 9.98 11.2 13.0 l 14.4
(3.27-3.89) (3.96-4.71) (5.01-5.97) (5.86-7.00) (7.04-8.44) (7.98-9.64) (8.98-10.9) (10.0-12.3) (11.5-14.3) (12.7-15.9)
3-day 3.79 4.58 5.78 6.74 8.10 9.21 10.4 11.6 13.4 14.8
(3.49-4.13) (4.22-4.98) (5.31-6.28) (6.18-7.32) (7.39-8.80) (8.36-10.0) (9.37-11.3) (10.4-12.7) (11.9-14.6) (13.1-16.3)
4-day 4.02 4.85 6.08 7.07 8.46 9.59 10.8 12.0 13.8 15.3
(3.72-4.36) (4.48-5.26) (5.61-6.59) (6.51-7.64) (7.74-9.15) , (8.74-10.4) i (9.77-11.7) 1 (10.8-13.1) I (12.3-15.0) (13.5-16.7)
7-day 4.66 5.59 6.94 8.01 9.50 I 10.7 I 11.9 I 13.3 15.1 1 16.6
(4.30-5.06) (5.16-6.07) (6.39-7.53) (7.36-8.68) (8.69-10.3) (9.76-11.6) (10.8-13.0) (12.0-14.4) (13.5-16.5) (14.8-18.2)
-
10-day 5.32 6.37 7.77 8.87 10.4 11.6 12.8 14.1 I 15.8 17.3
(4.96-5.72) (5.93-6.84) (7.22-8.35) (8.23-9.52) (9.59-11.1) (10.7-12.4) (11.7-13.8) (12.9-15.2) (14.4-17.1) (15.6-18.7)
20-day 7.17 8.52 10.2 11.6 13.4 14.9 16.3 17.8 19.9 21.5
(6.68-7.71) (7.94-9.16) (9.52-11.0) (10.7-12.4) (12.4-14.4) I (13.7-16.0) , (15.0-17.6) 1 (16.3-19.2) (18.1-21.5)1 (19.5-23.3)
30-day 8.94 10.6 12.5 14.0 15.9 1 17.4 18.9 20.5 22.5 1 24.1
(8.35-9.60) (9.88-11.4) (11.6-13.4) (13.0-15.0) (14.8-17.1) (16.1-18.7) (17.5-20.4) (18.8-22.0) (20.6-24.3) (22.0-26.0)
45-day 11.3 13.4 15.5 17.2 19.4 21.0 22.7 24.3 26.5 28.1
(10.7-12.1) (12.6-14.3) (14.6-16.6) (16.1-18.3) (18.1-20.7) (19.6-22.4) (21.1-24.2) (22.6-26.0) (24.5-28.4) (25.9-30.2)
60-day 13.6 16.0 18.4 20.2 22.6 24.4 26.1 27.8 30.1 31.8
(12.8-14.4) (15.0-17.0) 1 (17.3-19.5) 1 (19.0-21.5) (21.2-24.0) 1 (22.8-25.9) (24.4-27.8) 1 (25.9-29.7) (27.9-32.2)1 (29.4-34.1)
1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for
a given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are
not checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information. _
Back to Top
PF graphical
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?Iat=35.3201&Ion=-78.5651&data=depth&units=english&series=pds 1/4

8/16/22,3:21 PM Precipitation Frequency Data Server
PDS-based depth-duration-frequency (DDF) curves
Latitude: 35.3201°, Longitude: -78.5651°
35 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Average recurrence
30 interval
(years)
• 25 - — 1
a 2
v 20 - — 5
c — 10
o • • •
0 15 — 25
a — 50
u — 100
a — 200
500
5 — 1000
0
EEE E r s lsb t� v v v -or-6
ry �o vo v v
o io NN1
or-1 l0 4I- oo o v p
Duration
35
30 -
S 25 Duration
t
o.
• 20 _ — 5�rtin — 2-day
c — 10-min — 3-day
• •
° 16--min — 4-day
O 15 - — 30-min — 7-day
a
v — 60-min — 10-day
li 10 - — 2-nr — 20-day
— 3-hr — 30-day
5 = • — 641r - 45-day
T - — 12-hr — 60-day
0 - 1 I i t 1 I I I — 24-hr
1 2 5 10 25 50 100 200 500 1000
Average recurrence interval (years)
NOAA Atlas 14,Volume 2,Version 3 Created(GMT):Tue Aug 16 19:19:15 2022
Back to Top
Maps & aerials
Small scale terrain
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?Iat=35.3201&Ion=-78.5651&data=depth&units=english&series=pds 2/4

8/16/22,3:21 PM Precipitation Frequency Data Server
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https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3201&Ion=-78.5651&data=depth&units=english&series=pds 3/4

8/16/22,3:21 PM Precipitation Frequency Data Server
inston-Salem
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
National Water Center
1325 East West Highway
Silver Spring,MD 20910
Questions?:[e-mail]
Disclaimer
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3201&Ion=-78.5651&data=depth&units=english&series=pds 4/4

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This digital Flood Insurance Rate Map(FIRM)was produced through a unique
cooperative partnership between the State of North Carolina and the Federal
Emergency Management Agency(FEMA). The State of North Carolina has
implemented a long term approach to floodplain management to decrease the
costs associated with flooding.This is demonstrated by the States commitment
to map flood hazard areas at the local level.As a part of this effort,the State of
North Carolina has joined In a Cooperating Technical State agreement with
FEMA to produce and maintain this digital FIRM.
FLOOD HAZARD INFORMATION NOTES TO USERS SCALE
E SEE FIS REPORT FOR ZONE DESCRIPTIONS AND INDEXMAP NORTH CAROLINA FLOODPLAIN MAPPING PROGRAM
For information and questions about this map,available products associated with this FIRM Including Map Projection:
NATIONAL FLOOD INSURANCE PROGRAM
hlalodc versions of this Map Information
order products or the National Hood Insurance Program in general, ) ( 3200) ...el 'OOD INSURANCE RATE MAP
THE INFORMATION DEPICTED ON THIS MAP AND SUPPORTING e North Carolina State Plane Protection Feet Zone
please call the FEMA Map Irdormati0n eXchange at 1-8]]-FEMA-MAP(1-8]]-336-262])or visit the FEMA Map Datum:NAD 1983 H )
DOCUMENTATION ARE ALSO AVAILABLE IN DIGITAL FORMAT AT Service Center websiteathtlplimsc.fema.gov.An accompanying Flo.Insurance Study report,Letter of Map orizontal),NAVD1988(Vertical
Revision(LOMR)or Letter of Map Amendment(LOMA)revising portions of this panel,and digital versions of this
HTTP://FRIS.NC.GOV/FRIS FIRM may beavelable.Vsit the North Carolina Floodplain Mapping Program webeteal httpaloonvo cfloodmaps.com 'On NORTH CAROLINA trl
or contact the FEMA Map Servce Center 1 Ieeh-5DD feet 1:6,000 OWithout Base Flood Elevation(BFE) Communities annexing land on adjacent FIRM panels mustobtain a wnent copy of the adjacent panel as well as 0 250 500 1,000 ' PANEL 1527 _ZDne A, A99 the cunenl FIRM Index.These may be ordered directly from the Map Service Center at the pumper listed above.With BFE or Depth Zone AE,AO,AH,VE,AR Feet r4R �
For community and Countywide map dates refer to the Flood Insurance Study revert for this jurisdiction. CI
Meters W l�
SPECIAL FLOOD Regulatory To determine if flcod insurance is available in the community,contact your Insurance agent or call the National 0 75 150 300 -1-I�'�%,
HAZARD AREAS Flood Insurance Program at 1-800-838e620. a°
0.2%Annual Chance Flood Hazard,Areas Base map information shown on this FIRM was provided in digital format by the North Carolina Floodplain
Mapping Program(NCFMP).The source of this Information can be determined from the antedate available In the PANEL LOCATOR a Ilel Contains:
of 1%Annual Chance Flood with Average digital FLOOD database and in the Technical Support Data Notebook(TSDN). '1 t
Depth Less Than One Foot or With Drainage ACCREDITED LEVEE NOTES TO USERS:If an accredited levee note appears on this panel check with your local , 1 COMMUNITY CID PANEL SUFFIX
Areas of Less Than One Square Mile zone x communitytnobtainmoreinformation,suchastheestimatedlevelofprotectionprovided(whichmayexceedthe ,.' 4 DUNN,CITY OF 370264 1527 J
1-percent-annualchance level)and Emergency Action Plan,on the levee systems)shown as providing protection. n ,a'� v/ HARNETT COUNTY 370328 1527 J
Future Conditions 1%Annual To negate flood ask In residual risk areas,property owners and residents are encouraged to consider flood
insurance and floodproofing m other protective measures.For more information on flood insurance,interested i
Chance Flood Hazard Zone x parties should yea the FEMA Website at http://www.fema.gov/business/nfipandex.shtm. CHATHAM COUNTY
OTHER AREAS OF —Area with Reduced Flood Risk due to Levee PROVISIONALLY ACCREDITED LEVEE NOTES TO USERS:If a Provisionally Accredited Levee(PAL)note / WAKE COUNTY
FLOOD HAZARD appears on this panel,check with your local community to obtain more informaton,such as the estimated level of -
See Notes Zone x protection provided(which may exceed the 1-percent-annual-chance level)and Emergency Action Plan,on the
OTHER levee system(s)shown as providing protection.To maintain accreditation,the levee owner or community is r �' �'l •.,6626 -
-Areas Determined to be Outside the required to submit the data and documentation necessary to comply with Section 65.10 of the NFIP regulations. t 0646 0
AREASIf the community or owner does not provide the necessary data and documentation or if the data and documentation 'I_/
0.2%Annual Chance Floodplain zone x indicates the levees t does not comply with Section 85.10 requirements.FEMA will revise the flood / SU6650675 LL
providedeasystem pywi eves sye
_______ Channel,Culvert,or Storm Sewer hazard and risk information for this area to reflect are encouraged
of the levee system.To mitigate flood risk in o60 0624 06440654U664067b^n484 JOHNSTON COUNTY
residual risk areas,property owners and residents are encouraged to consider flood insurance and floodproofing
=Accredited Or Provisionally Accredited or other protective measures.For more information on flood insurance,interested parties should visit the FEMA
Website at http://www.Tema.gov/businesslnfip/index.shtm. 968 0602 0622 0642 0662 0682 1602 CU
GENERAL Levee,Dike,or Floodwall LEEcouNTY
LIMIT OF MODERATE WAVE ACTION NOTES TO USERS:For some coastal flooding zones the AE Zone
STRUCTURES t,t,t„t,t r t t Non-accredited Levee,Dike,or Floodwall category has been divided bye Limit of Moderate Wave Action(UMWA).The LIMWA represents the approximate 9680 0600 0620 0640 0660 0680 1600 1820 O
landward limit of the 1 5-foot breaking wave.The effects of wave hazards between the VE Zone and the LiMWA
BM5510X North Carolina Geodetic Survey bench mark (or between the shoreline and the LiMWA for areas where VE Zones are not identified)will be similar to,but less }�
Pere than those in the VE Zone. 0569059915091519 �.s�
BM55100 National Geodetic Survey bench mark severe 9548 sse noes osee osae 0548 0568 1 8 C V
Limit of Moderate Wave Action(LiMWA) 05880598 5081518
BK15510,, Contractor Est.NCFMP Survey bench mark 05879597 1 111M11
Z
COASTAL BARRIER RESOURCES SYSTEM(CBRS)NOTE 46 9566 9586 0506 0526 0546 0566 — 1506 1546
01 tel Cross Sections with 1%Annual Chance 9536 OW0536 1 3
Water Surface Elevation(BFE) g 595459555 This map may include approximate boundaries of the CBRS for informational purposes only.Flood insurance is not
E) available within CBRS areas for structures that are newly built or substantially improved on Or atter the date(s) -‘ 9564 9584 0504 0524 0544„"0564'�0584__1504 1524 —•-s
Indicated on the map.For more information see http:/Avww.fws.govlabilatconservagon/coastaLberner.html,the g.,,34g54. 54
8 Coastal Transact FIS Report,or call the U.S.Fish and Wildlife Service Customer Service Center at 1-800-344-WILD.
9553 9583959,,db0405l.3 t5230533
Coastal Transect Baseline \ 1 CBRS Area r,'-:',.1 Otherwise Protected Area 01'\--.., -'9562-1958•
'Nov,'
—-— Profile Baseline j CUMBERLAND COUNTY SAMPSON COUNTY ...ors,
�._�
Hydrographic Feature xoKEcouNrr 2 �� 01527MAP NUMBER
5 37201527001
OTHER Limit of Study '•t (,
FEATURES Jurisdiction Boundary ( 1 � .' MAP REVISED
01/05/07

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i L et1. `V..' „_,A ••• ' ^`ems 4 Fr"'C@G@
570000 FEET y . ......' - ' _ v - •. r* •1 °,, ' - 570000 FEET
78°33'30"W 78°33'0"W 78"3730'W 78°32'0"W
2130000 FEET 2140000 FEET
!1' I nn1Sr :,lint:Ii-.lipa:,l til:llr
This digital Flood Insurance Rate Map(FIRM)was produced through a unique
cooperative partnership between the Stale of North Carolina and the Federal
Emergency Management Agency(FEMA). The State of North Carolina has
implemented a long term approach to floodplain management to decrease the
costs associated with flooding.This Is demonstrated by the State's commitment
to map flood hazard areas at the local level.Asa part of this effort,the State of
North Carolina has joined in a Cooperating Technical State agreement with
FEMA to produce and maintain this digital FIRM.
FLOOD HAZARD INFORMATION NOTES TO USERS SCALE
`
NORTH CAROLINA FLOODPLAIN MAPPING PROGRAM
SEE FIS REPORT FOR ZONE DESCRIPTIONS AND INDEX MAP For information and questions about this map,available products associated with this FIRM Including Map Projection:' E NATIONAL FLOOD INSURANCE PROGRAM
historic versions of this FIRM,how to order products or the National Flood Insurance Program in general, ) ( 3200) FLOOD INSURANCE RATE MAP
THE INFORMATION DEPICTED ON THIS MAP AND SUPPORTING e North Carolina State Plane Projection Feet Zone
please call the FEMA Map Information eXchangeal 1-877-FEMA-MAP(1-677-338-2827)or visit the FEMA Map Datum:NAD 1983Sta(Horizontal),lroj NAVDeet(one2l) Cti
DOCUMENTATION ARE ALSO AVAILABLE IN DIGITAL FORMAT AT Service Centerwebsiteathtlp://mac.lama.gov.An accompanying Flood Insurance Study report,Letter of Map11
// / Revision(CONK)or Latter of Map Amendment(LOMA)revising porboce of this panel,and digital versions of this corn to NORTH CAROLINA 09.
HTTP: FRIS.NC.GOV FRIS FIRM may be available.Visit the North Carolina Floodplain Mapping Program websile at hi //www.nclloodma iAs1
or contact the FEMA Map Service Center. 1 inch=500 feet 1:6,000 O Without Base Flood Elevation(BFE) Communities annexing land on adjacent FIRM panels must obtain a current copy of the adjacent panel as well as Lq 7ollc'A.l/,A9;I the current FIRM Index-These may be ordered directly from the Map Service Center at the number listed above. D 25O 5OO 1,000 PANEL 1537 With BFE or Depth z,e AE,AO,AH,VE AR Feet o s�
For community and countywide map dates refer to the Rood Insurance Study report for this jurisdiction. Meters
SPECIAL FLOOD ,. y; To determine if insurance is available in the community,contact Insurance agentor call the National I C V !�.
HAZARD AREAS r"i !' Regulatory tyrre,rnear ce0 75 150 300 I T^,
Flood Insurance Program at 1-800-6386620.
• IN 0.2%Annual Chance Flood Hazard,Areas Base reap informalionshown on this FIRM was provided in digital format by the North Carolina Floodplain PANEL LOCATOR =
Mapping Program(NCFMP).The source of this information can be determined from the metadate available in the /�� =-.r."---,tains:
of 1%Annual Chance Flood with Average digital FLOOD database and in the Technical Support Data Notebook(TSDN). \V
Depth Less Than One Foot or With Drainage ACCREDITED LEVEE NOTES TO USERS:If an accredited levee note appears on this panel check with your local 5 • COMMUNITY CID PANEL SUFFIX
Areas of Less Than One Square Mile zone x community to obtain more information,such as the estimated level of protection provided(which may exceed the i
1-percent-annual-chance level)and Emergency Action Plan,on the levee system(s)shown as providing protection. / - ARNETT COUNTY 3703281 1537 L
— Future Conditions 1%Annual To mitigate flood risk in residual risk areas,property owners and residents are encouraged to consider flood /✓ Cl)N JOHNSTON COUNTY 370138 1537 L
insurance and ibodproofing or other protective measures.For more information on flood insurance,interested = SAMPSON COUNTY 370220 1537 L
Chance Flood Hazard Zone X panes should Volt the FEMA Website at http://www.fema.gov/business/nfip/index.shlm. CHATHAM COUNTY %
)THERAREASOF Area with Reduced Flood Risk due to Levee PROVISIONALLY ACCREDITED LEVEE NOTES TO USERS:If a Provisionally Accredited Levee(PAL)note % WANE COUNTY i
MD
FLOOD HAZARD appears on this panel,check with your local community to obtain more information,such as the estimated level of -
See Notes zone x protection provided(which may exceed the 1-percent-annual-chance level)and Emergency Action Plan,on the
OTHER levee system(s)shown as providing protection.To maintain accreditation,the levee owner or community is �l1 -.ofiz6 — j 0
Areas Determined to be Outside the required to submit the data and documentation necessary to comply with Section 65.10 of the NFIP regulations. t /'.. 0646 0
AREAS If community w owner does not provide the necessary data and documentation w 8 the data and documentation j -/
0.2%Annual Chance Floodplain zone x 0645065506650675
provided indicates the levee system does not comply with Section 65.10 requirements,FEMA will revise the flood f '-0sad Oslo \ mad / LL
hazard and risk information for this area to reflect de-accreditation of the levee system To mitigate flood risk in 0644e6,,06640fi73''.. JOHNSTON COUNTY
Channel,Culvert,or Storm Sewer
residual risk areas,propeuy owners and residents are encouraged to consider flood insurance and floodproofing / ,
Accredited or Provisionally Accredited or other protective measures.For more information on flood insurance,interested parties should visit the FEMA
Websiie at hltplivevw.fema.gov/business/nfip7index.shtrn. 9682,/ 0602 0622 0642 0662 0682 1111602
Levee,Dike,or Floodwall LEE COUNTY ,
0.5
GENERAL LIMIT OF MODERATE WAVE ACTION NOTES TO USERS:For some coastal flooding zones the AE Zone +
STRUCTURES 1 r 1 r 1 r r 1 r t t 11 Non-accredited Levee,Dike,or Floodwall category has been divided by a Limit of Moderate Wave Action(LiMWA).The LiMWA represents the approximate '9680 0600 0620 aaso 0660 0680 1600x 1620 O
landward limit of the 15-foot breaking wave.The effects of wave hazards between the VE Zone and the LiMWA
96i0 �
BM5510x North Carolina Geodetic Survey bench mark (or between the shoreline and the LiMWA for areas where VE Zones are not identified)will be similar to,but less / }+
severe than dlose in the VE Zone. 5 0589 0599 15091519 1I
BM5510® National Geodetic Survey bench mark sa i 9548 /9568 9588 0508 0528 0548 0568 0588059E 15081518 152` CES
BM5510® Contractor Est.NCFMP Survey bench mark Limit of Moderate Wave Action(LiMWA) L 1!
O58]0597 1527 Z
COASTAL BARRIER RESOURCES SYSTEM CBRS NOTE 45a6 9566 9586 osofi oszfi 0546 0566 1506 1546
01 18.2 Cross Sections with 1%Annual Chance (CBRS) 9536 0586,0596 152 53W'
Water Surface Elevation(BFE) 9$3
This map may include approximate boundaries of the CBRS for informational purposes only.Flood Insurance is not
available within CBRS areas for structures that are newly built or substantially improved on or after the date(s) 5954595559564 9584 0504 0524 0544.,"g5fi4"•"�0584 1504 1 1524
indicated on the map.For more information see hcp:/Avww.fws.gov/habilenter 1.500/coastal_barrier.himl,the 953d 9544,9554
as Coastal Transect FIS Report,or call the U.S.Fish and Wildlife Service Customs Service Center at i 8]0 344-WILD. j J'
9.553 95839593050Sk?A523f0533 f
Coastal Transect Baseline 1 CBRS Area r,-:°;' Otherwise Protected Area - ,4562 C'
l��- M1 958]
Profile Baseline ,1 CUMBERIANDCOUNTY )S SAMPSON COUNTY 5`A'F>
e)
Hydrographic Feature HOKECOUNTY r t MAP NUMBER
OTHER Limit of Study 1 '`' 3720153700E
FEATURES Jurisdiction Boundary — .„..„,,,,,,, 01/05107

PRE-DEVELOPMENT
HYDROLOGIC CALCULATIONS
Dunn Operations Center& Mobile Substation Storage
DKE-22052

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Summary of Results 6/20/2023
HYDROLOGY INPUT SUMMARY Mr -III
Onsite Area[acres] Offsite Area[acres] Total Area
Sub-basin ID Impervious Open Wooded Pond Row CropTotal Impervious Open Wooded Pond Row CropTotal SCS CN Tc[min]
P P P P [acres]
1 0.00 0.21 0.77 0.00 9.06 10.04 0.00 0.00 0.00 0.00 0.00 0.00 10.04 64 30.64
2 0.00 1.48 6.10 0.15 4.08 11.81 0.14 1.56 0.02 0.00 0.00 1.71 13.53 67 33.37
3 0.00 0.26 0.00 0.00 8.66 8.92 0.00 0.00 0.00 0.00 0.00 0.00 8.92 66 23.39
4 0.00 0.37 0.00 0.00 3.18 3.56 0.16 1.13 0.37 0.00 0.00 1.66 5.21 57 24.85
Totals= 0.00 2.33 6.87 0.15 24.98 34.32 0.29 2.69 0.39 0.00 0.00 3.37 37.69

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 1 6/20/2023
I.SCS CURVE NUMBE•-
Soils from WebSoilSurvey are only inclusive of indirectly connected areas
HSG I Impervious Open 1 Wooded Row Crops(SR)
A 98 39 30 67
B 98 61 55 78
C 98 74 70 85
D 98 80 77 89
Assume: HSG'A'= 100.0%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 0.0%
Cover Condition I SCS CN I Comments
Impervious 98 -
Open 39 Assume good condition
Wooded 30 Assume good condition
Row Crops(SR) 67 Assume good condition
II. PRE-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 0 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals I 0 I 0.00
B. Watershed Land Use Breakdown
Contributing Area I SCS CN I Area[sfl I Area[acres] I Comments
Onsite impervious 98 0 0.00 -
Onsite open 39 9,301 0.21 Assume good condition
Onsite wooded 30 33,448 0.77 Assume good condition
Onsite pond 100 0 0.00 -
Onsite row crops(SR) 67 394,528 9.06 Assume good condition
Offsite impervious 98 0 0.00 -
Offsite open 39 0 0.00 Assume good condition
Offsite wooded 30 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite row crops(SR) 67 0 0.00 Assume good condition
Total area= 10.04 acres
437,277 sf
Composite SCS CN= 64
%Impervious= 0.0%

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 1 6/20/2023
III.TIME OF CONCENTRATION INFORMATION Il
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 932 ft
Top Elev= 230.50 ft Top Elev= 230.25 ft
Bot Elev= 230.25 ft Bot Elev= 215.00 ft
Height= 0.25 ft Height= 15 ft
Slope= 0.0025 ft/ft Slope= 0.0164 ft/ft
Manning's n= 0.17 >20%Residue Cover Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 2.06 ft/sec
Segment Time= 23.11 minutes Segment Time= 7.53 minutes
Time of Concentration= 30.64 minutes
SCS Lag Time= 18.38 minutes(SCS Lag=0.6*Tc)
Time Increment= 5.33 minutes(=0.29*SCS Lag)

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 2 6/20/2023
I.SCS CURVE NUMBE•-
Soils from WebSoilSurvey are only inclusive of indirectly connected areas
HSG I Impervious Open 1 Wooded Row Crops(SR)
A 98 39 30 67
B 98 61 55 78
C 98 74 70 85
D 98 80 77 89
Assume: HSG'A'= 40.5%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 59.5%
Cover Condition I SCS CN I Comments
Impervious 98 -
Open 63 Assume good condition
Wooded 58 Assume good condition
Row Crops(SR) 80 Assume good condition
II. PRE-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 209 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals I 209 I 0.00
B. Watershed Land Use Breakdown
Contributing Area I SCS CN I Area[sfl I Area[acres] I Comments
Onsite impervious 98 209 0.00 -
Onsite open 63 64,656 1.48 Assume good condition
Onsite wooded 58 265,547 6.10 Assume good condition
Onsite pond 100 6,449 0.15 -
Onsite row crop 80 177,677 4.08 Assume good condition
Offsite impervious 98 5,961 0.14 -
Offsite open 63 67,777 1.56 Assume good condition
Offsite wooded 58 916 0.02 Assume good condition
Offsite pond 100 0 0.00 -
Offsite row crop 80 0 0.00 Assume good condition
Total IC area= 13.53 acres
589,192 sf
Composite SCS CN= 67
%Impervious= 1.0%

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 2 6/20/2023
III.TIME OF CONCENTRATION INFORMATION Il
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 467 ft
Top Elev= 236.00 ft Top Elev= 235.50 ft
Bot Elev= 235.50 ft Bot Elev= 227.00 ft
Height= 0.5 ft Height= 9 ft
Slope= 0.0050 ft/ft Slope= 0.0182 ft/ft
Manning's n= 0.24 dense grass Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 2.18 ft/sec
Segment Time= 23.08 minutes Segment Time= 3.58 minutes
Segment 3:Channel Flow
Length= 588 ft
Top Elev= 227.00 ft
Bot Elev= 226.00 ft
Height= 1 ft
Slope= 0.0017 ft/ft
Manning's n= 0.045 natural channel
Flow Area= 10.50 sf(assume 3.5'w x 3'h channel)
Wetted Perimeter= 9.50 If(assume 3.5'x 3'channel)
Channel Velocity= 1.46 ft/sec
Segment Time= 6.71 minutes
Time of Concentration= 33.37 minutes
SCS Lag Time= 20.02 minutes(SCS Lag=0.6*Tc)
Time Increment= 5.81 minutes(=0.29*SCS Lag)

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 3 6/20/2023
I.SCS CURVE NUMBE•-
Soils from WebSoilSurvey are only inclusive of indirectly connected areas
HSG I Impervious Open Wooded Row Crops(SR)
A 98 39 30 67
B 98 61 55 78
C 98 74 70 85
D 98 80 77 89
Assume: HSG'A'= 100.0%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 0.0%
Cover Condition I SCS CN I Comments
Impervious 98 -
Open 39 Assume good condition
Wooded 30 Assume good condition
Row Crops(SR) 67 Assume good condition
II. PRE-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 0 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals I 0 I 0.00
B. Watershed Land Use Breakdown
Contributing Area I SCS CN I Area[sfl I Area[acres] I Comments
Onsite impervious 98 0 0.00 -
Onsite open 39 11,249 0.26 Assume good condition
Onsite wooded 30 0 0.00 Assume good condition
Onsite pond 100 0 0.00 -
Onsite row crop 67 377,107 8.66 Assume good condition
Offsite impervious 98 0 0.00 -
Offsite open 39 0 0.00 Assume good condition
Offsite wooded 30 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite row crop 67 0 0.00 Assume good condition
Total IC area= 8.92 acres
388,356 sf
Composite SCS CN= 66
%Impervious= 0.0%

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 3 6/20/2023
III.TIME OF CONCENTRATION INFORMATION Il
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 1090 ft
Top Elev= 232.50 ft Top Elev= 231.50 ft
Bot Elev= 231.50 ft Bot Elev= 218.00 ft
Height= 1 ft Height= 14 ft
Slope= 0.0100 ft/ft Slope= 0.0124 ft/ft
Manning's n= 0.17 >20%Residue Cover Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 1.80 ft/sec
Segment Time= 13.27 minutes Segment Time= 10.12 minutes
Time of Concentration= 23.39 minutes
SCS Lag Time= 14.03 minutes(SCS Lag=0.6*Tc)
Time Increment= 4.07 minutes(=0.29*SCS Lag)

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 4 6/20/2023
I.SCS CURVE NUMBE•-
Soils from WebSoilSurvey are only inclusive of indirectly connected areas
HSG I Impervious Open Wooded Row Crops(SR)
A 98 39 30 67
B 98 61 55 78
C 98 74 70 85
D 98 80 77 89
Assume: HSG'A'= 100.0%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 0.0%
Cover Condition I SCS CN I Comments
Impervious 98 -
Open 39 Assume good condition
Wooded 30 Assume good condition
Row Crops(SR) 67 Assume good condition
II. PRE-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 0 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals I 0 I 0.00
B. Watershed Land Use Breakdown
Contributing Area I SCS CN I Area[sfl I Area[acres] I Comments
Onsite impervious 98 0 0.00 -
Onsite open 39 16,201 0.37 Assume good condition
Onsite wooded 30 103 0.00 Assume good condition
Onsite pond 100 0 0.00 -
Onsite row crop 67 138,642 3.18 Assume good condition
Offsite impervious 98 6,840 0.16 -
Offsite open 39 49,237 1.13 Assume good condition
Offsite wooded 30 16,083 0.37 Assume good condition
Offsite pond 100 0 0.00 -
Offsite row crop 67 0 0.00 Assume good condition
Total IC area= 5.21 acres
227,106 sf
Composite SCS CN= 57
%Impervious= 3.0%

DUNN OPERATIONS CENTER MOBILE SUBSTATION STORAGE PRE-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 4 6/20/2023
III.TIME OF CONCENTRATION INFORMATION Il
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 770 ft
Top Elev= 235.00 ft Top Elev= 234.00 ft
Bot Elev= 234.00 ft Bot Elev= 225.00 ft
Height= 1 ft Height= 9 ft
Slope= 0.0100 ft/ft Slope= 0.0117 ft/ft
Manning's n= 0.24 dense grasses Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 1.74 ft/sec
Segment Time= 17.49 minutes Segment Time= 7.36 minutes
Time of Concentration= 24.85 minutes
SCS Lag Time= 14.91 minutes(SCS Lag=0.6*Tc)
Time Increment= 4.32 minutes(=0.29*SCS Lag)

MCADAMS
Scenario: Pre-
Development
POA 2
A
Sul-4
APOA 4
•
APOA3
POA 1
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 6/20/2023

�J MCADAMS
FlexTable: Catchment
Table (DKE-22052
PondPack.ppc)
Current Time: 0.00 min
Label Area SCS CN Time of Notes
(ft2) Concentration
(min)
Sub-1 437,277 64 30.64 Pre
Sub-2 I 589,192 67 33.37 Pre
Sub-3 388,356 66 23.39 Pre
Sub-4 227,106 57 24.85 Pre
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 6/20/2023

�J MCADAMS
Subsection: Master Network Summary
Catchments Summary
Label Scenario Return Hydrograph Time to Peak Peak Flow
Event Volume (min) (ft3/s)
(years) (ac-ft)
Sub-1 Pre-Dev 1-Year 1 0.411 744.00 2.74
Sub-1 Pre-Dev 10-Year 10 1.647 740.00 13.22
Sub-1 Pre-Dev 25-Year 25 2.365 739.00 18.44
Sub-2 Pre-Dev 1-Year 1 0.688 744.00 4.89
Sub-2 Pre-Dev 10-Year 10 2.500 743.00 19.55
Sub-2 Pre-Dev 25-Year 25 3.522 739.00 26.50
Sub-3 Pre-Dev 1-Year 1 0.423 736.00 3.57
Sub-3 Pre-Dev 10-Year 10 1.585 733.00 14.97
Sub-3 Pre-Dev 25-Year 25 2.247 733.00 20.42
Sub-4 Pre-Dev 1-Year 1 0.114 755.00 0.58
Sub-4 Pre-Dev 10-Year 10 0.620 736.00 5.06
Sub-4 Pre-Dev 25-Year 25 0.939 736.00 7.72
Node Summary
Label Scenario Return Hydrograph Time to Peak Peak Flow
Event Volume (min) (ft3/s)
(years) (ac-ft)
POA 1 Pre-Dev 1-Year 1 0.411 744.00 2.74
POA 1 Pre-Dev 10-Year 10 1.647 740.00 13.22
POA 1 Pre-Dev 25-Year 25 2.365 739.00 18.44
POA 2 Pre-Dev 1-Year 1 0.688 744.00 4.89
POA 2 Pre-Dev 10-Year 10 2.500 743.00 19.55
POA 2 Pre-Dev 25-Year 25 3.522 739.00 26.50
POA 3 Pre-Dev 1-Year 1 0.423 736.00 3.57
POA 3 Pre-Dev 10-Year 10 1.585 733.00 14.97
POA 3 Pre-Dev 25-Year 25 2.247 733.00 20.42
POA 4 Pre-Dev 1-Year 1 0.114 755.00 0.58
POA 4 Pre-Dev 10-Year 10 0.620 736.00 5.06
POA 4 Pre-Dev 25-Year 25 0.939 736.00 7.72
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 6/20/2023

1 2 3 4 5 6 7 8 9 1
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/ / / \ \\ re.,i'` --, , / / MAILING ADDRESS:
/ // // \\ \ ` 1Th 7 _ ` �/ I MARK B.FRANKLIN
JLL-DUKE ENERGY ACCOUNT
/ // /� \\ \\ - ,',,' / _ _ ' � 410 S.WILMINGTON STREET
\ / , I RALEIGH,NORTH CAROLINA 27602
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\ SUB 3 0 AREA 5.21 AC ; w�Z ���,,;
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_ -----------------_I I ��czp• ,/' ` ( i _-����11' �,I�i'li � /, J*� � -�_/� -'l_,� I ---� PROJECT NO: DKE-22052
I I \, ,' J/ r, /�q1) I- �'�a A��'.i `� i\ I I / DRAWING NUMBER
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E I '\,\ I ' , ELECTRONIC FILE
DRAWN BY: $CF
A I`�' J \` \\ 06/06/2023
\ \ • , , • '''',
Si
/ - � +, \ /t I / ,� , E-MAIL: [e-mail]
' 1 ___---�1---- - - ��y�'�'� r hy„ \X 1 i 'lTHIS DESIGN DRAWING IS THE EXCLUSIVE PROPERTY OF DUKE ENERGY
- - - _ y -I --- __� ;\ I I \, C\' n 1 oaA�°rlo°COPIED, poNL.aeU:eP ORTHE se�FCeaaeCr
`�, \ / / I SHEET TITLE:
I )' \ / , / I
At PRE-DEVELOPMENT
A 1 I J p' / \ \ // / 1 A HYDROLOGY MAP
\ I I 1// _--J ` / \ \ \ / / I
/ / i' L • '_—> / \ ,/ / I
/ /// / I /�� I \ \ \ \\ // / II P GRAPHIC SCALE SHEET NO.
/ \ \ I / I \ / \ \ \ / / 1 1 �IIIIII1 �I
_ 21nh-2DDn PRE—DA
i // \ \ II!// I — — — — — y \ 1 \\\ // —/ �\ NOT RELEASED FOR CONSTRUCTION
1 2 3 4 5 6 7 8 9
El SIZE DWG:PLOT SIZE(30x42)

POST-DEVELOPMENT
HYDROLOGIC CALCULATIONS
Dunn Operations Center& Mobile Substation Storage
DKE-22052

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Summary of Results 10/10/2023
HYDROLOGY INPUT SUMMARY
Onsite Area[acres] Offsite Area[acres] Total Area
Sub-basin ID Impervious Open Wooded Pond Gravel Total Impervious I Open Wooded I Pond Total [acres] SCS CN Tc[min]
1 to SCM A 4.70 2.46 0.00 0.71 14.15 22.01 0.00 0.00 0.00 0.00 0.00 22.01 78 5.00
1 Bypass 0.00 0.80 0.09 0.00 0.00 0.90 0.00 0.00 0.00 0.00 0.00 0.90 38 5.00
2 to SCM B 0.11 1.30 1 0.00 0.63 1 2.37 4.41 1.72 0.00 0.00 0.00 1.72 6.12 85 5.00
2 Bypass 0.00 1.96 1.76 0.15 0.00 3.87 0.00 0.00 0.00 0.00 0.00 3.87 74 11.84
3 0.19 1.83 1 0.00 0.00 0.00 2.02 1 0.00 0.00 0.00 0.00 0.00 2.02 45 18.71
4 0.23 0.89 0.00 0.00 0.00 1.12 0.16 1.12 0.37 0.00 1.65 2.77 52 21.82
Totals= 5.23 9.25 1.85 1.48 16.52 34.32 1.88 1.12 0.37 0.00 3.37 37.69

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin Ito SCM A 10/10/2023
HSG Impervious Open Wooded Gravel
A 98 39 30 76
B 98 61 55 85
C 98 74 70 89
D 98 80 77 91
Assume: HSG'A'= 92.9%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 7.1%
Cover Condition SCS CN Comments
_ Impervious 98 -
Open 42 Assume good condition
_ Wooded 33 Assume good condition
Gravel 77 Assume good condition
II. POST-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 34,947 0.80
Roof 99,008 2.27
Sidewalk/Patio 70,702 1.62
Other 0 0.00
Totals 204,657 4.70
B. Watershed Land Use Breakdown
Contributing Area SCS CN Area[sf] ' Area[acres] Comments
Onsite impervious 98 204,657 4.70 -
Onsite open 42 107,086 2.46 Assume good condition
Onsite wooded 33 0 0.00 Assume good condition
Onsite pond 100 30,777 0.71 -
Onsite gravel 77 616,160 14.15 Assume good condition
Offsite impervious 98 68 0.00 -
Offsite open 42 0 0.00 Assume good condition
Offsite wooded 77 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite gravel 77 0 0.00 Assume good condiiton
Total area= 22.01 acres
958,748 sf
Composite SCS CN= 78
%Impervious= 85.6%
C. Time of Concentration Information
Time of concentration is assumed to be 5 minutes.
Time of Concentration= 5.00 minutes
SCS Lag Time= 3.00 minutes(SCS Lag=0.6*Tc)
Time Increment= 0.87 minutes(=0.29*SCS Lag)

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 1 Bypass 10/10/2023
HSG I Impervious I Open Wooded I Gravel
A 98 39 30 76
B 98 61 55 85
C 98 74 70 89
D 98 80 77 91
Assume: HSG'A'= 100.0%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 0.0%
Cover Condition I SCS CN I Comments
Impervious 98 -
Open 39 Assume good condition
Wooded 30 Assume good condition
Gravel 76 Assume good condition
II. POST-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 0 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals 1 0 1 0.00
B. Watershed Land Use Breakdown
Contributing Area I SCS CN I Area[sf] Area[acres] I Comments
Onsite impervious 98 0 0.00 -
Onsite open 39 35,065 0.80 Assume good condition
Onsite wooded 30 3,970 0.09 Assume good condition
Onsite pond 100 0 0.00 -
Onsite gravel 76 0 0.00 Assume good condition
Offsite impervious 98 0 0.00 -
Offsite open 39 0 0.00 Assume good condition
Offsite wooded 76 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite gravel 76 0 0.00 Assume good condiiton
Total area= 0.90 acres
39,035 sf
Composite SCS CN= 38
%Impervious= 0.0%
C. Time
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Time of Concentration= 5.00 minutes
SCS Lag Time= 3.00 minutes(SCS Lag=0.6*Tc)
Time Increment= 0.87 minutes(=0.29*SCS Lag)

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 2 to SCM 8 10/10/2023
HSG Impervious Open Wooded Gravel
A 98 39 30 76
B 98 61 55 85
C 98 74 70 89
D 98 80 77 91
Assume: HSG'A'= 49.1%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 50.9%
Cover Condition SCS CN Comments
_ Impervious 98 -
Open 60 Assume good condition
_ Wooded 54 Assume good condition
Gravel 84 Assume good condition
II. POST-DEVELOPMENT ill
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 2,609 0.06
Sidewalk/Patio 2,000 0.05
Other 0 0.00
Totals 4,609 0.11
B. Watershed Land Use Breakdown
Contributing Area SCS CN I Area[sf] ' Area[acres] Comments
Onsite impervious 98 4,609 0.11 -
Onsite open 60 56,799 1.30 Assume good condition
Onsite wooded 54 0 0.00 Assume good condition
Onsite pond 100 27,258 0.63 -
Onsite gravel 84 103,235 2.37 Assume good condition
Offsite impervious 98 74,822 1.72 -
Offsite open 60 0 0.00 Assume good condition
Offsite wooded 54 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite gravel 84 0 0.00 Assume good condition
Total area= 6.12 acres
266,723 sf
Composite SCS CN= 85
Impervious= 68.5%
C. Time of Concentration Information
Time of concentration is assumed to be 5 minutes.
Time of Concentration= 5.00 minutes
SCS Lag Time= 3.00 minutes(SCS Lag=0.6*Tc)
Time Increment= 0.87 minutes(=0.29*SCS Lag)

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 2 Bypass 10/10/2023
HSG Impervious Open Wooded Gravel
A 98 39 30 76
B 98 61 55 85
C 98 74 70 89
D 98 80 77 91
Assume: HSG'A'= 12.5%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 87.5%
Cover Condition SCS CN Comments
_ Impervious 98 -
Open 75 Assume good condition
_ Wooded 71 Assume good condition
Gravel 89 Assume good condition
II. POST-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 0 0.00
Roof 0 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals 0 0.00
B. Watershed Land Use Breakdown
Contributing Area SCS CN Area[sf] Area[acres] Comments
Onsite impervious 98 0 0.00 -
Onsite open 75 85,376 1.96 Assume good condition
Onsite wooded 71 76,539 1.76 Assume good condition
Onsite pond 100 6,448 0.15 -
Onsite gravel 89 0 0.00 Assume good condition
Offsite impervious 98 0 0.00 -
Offsite open 75 0 0.00 Assume good condition
Offsite wooded 71 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite gravel 89 0 0.00 Assume good condition
Total area= 3.87 acres
168,363 sf
Composite SCS CN= 74
Impervious= 0.0%

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 2 Bypass 10/10/2023
C. Time of Concentration Information
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 60 ft
Top Elev= 233.00 ft Top Elev= 229.50 ft
Bot Elev= 229.50 ft Bot Elev= 226.00 ft
Height= 3.5 ft Height= 4 ft
Slope= 0.0350 ft/ft Slope= 0.0583 ft/ft
Manning's n= 0.24 dense grasses Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 3.90 ft/sec
Segment Time= 10.61 minutes Segment Time= 0.26 minutes
Segment 3:Channel Flow
Length= 146 ft
Top Elev= 226.00 ft
Bot Elev= 225.28 ft
Height= 0.72 ft
Slope= 0.0049 ft/ft
Manning's n= 0.045 natural channel
Flow Area= 10.50 sf(assume 3.5'w x 3'h channel)
Wetted Perimeter= 9.50 If(assume 3.5'x 3'channel)
Channel Velocity= 2.49 ft/sec
Segment Time= 0.98 minutes
Time of Concentration= 11.84 minutes
SCS Lag Time= 7.11 minutes(SCS Lag=0.6*Tc)
Time Increment= 2.06 minutes(=0.29*SCS Lag)

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 3 10/10/2023
HSG I Impervious I Open I Wooded I Gravel
A 98 39 30 76
B 98 61 55 85
C 98 74 70 89
D 98 80 77 91
Assume: HSG'A'= 100.0%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 0.0%
Cover Condition I SCS CN I Comments
Impervious 98 -
Open 39 Assume good condition
Wooded 30 Assume good condition
Gravel 76 Assume good condition
II. POST-DEVELOPMENT
A. Onsite Impervious Breakdown
Contributing Area I Area[sf] I Area[ac]
Roadway Area 0 0.00
Driveway/Parking Lot 7,838 0.18
Roof 0 0.00
Sidewalk/Patio 534 0.01
Other 0 0.00
Totals 1 8,372 10.19
B. Watershed Land Use Breakdown
Contributing Area I SCS CN I Area[sf] I Area[acres] I Comments
Onsite impervious 98 8,372 0.19 -
Onsite open 39 79,601 1.83 Assume good condition
Onsite wooded 30 0 0.00 Assume good condition
Onsite pond 100 0 0.00 -
Onsite gravel 76 191 0.00 Assume good condition
Offsite impervious 98 0 0.00•
-
Offsite open 39 0 0.00 Assume good condition
Offsite wooded 76 0 0.00 Assume good condition
Offsite pond 100 0 0.00 -
Offsite gravel 76 0 0.00 Assume good condiiton
Total area= 2.02 acres
88,164 sf
Composite SCS CN= 45
%Impervious= 9.7%

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 3 10/10/2023
C. Time of Concentration Informs
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 203 ft
Top Elev= 225.00 ft Top Elev= 224.00 ft
Bot Elev= 224.00 ft Bot Elev= 218.00 ft
Height= 1 ft Height= 6 ft
Slope= 0.0100 ft/ft Slope= 0.0296 ft/ft
Manning's n= 0.24 dense grasses Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 2.77 ft/sec
Segment Time= 17.49 minutes Segment Time= 1.22 minutes
Time of Concentration= 18.71 minutes
SCS Lag Time= 11.23 minutes(SCS Lag=0.6*Tc)
Time Increment= 3.26 minutes(=0.29*SCS Lag)

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 4 10/10/2023
HSG Impervious Open Wooded Gravel
A 98 39 30 76
B 98 61 55 85
C 98 74 70 89
D 98 80 77 91
Assume: HSG'A'= 100.0%
HSG'B'= 0.0%
HSG'C'= 0.0%
HSG'D'= 0.0%
Cover Condition SCS CN Comments
Impervious 98 -
Open 39 Assume good condition
Wooded 30 Assume good condition
Gravel 76 Assume good condition
A. Onsite Impervious Breakdown
Contributing Area Area[sf] Area lac]
Roadway Area 0 0.00
Driveway/Parking Lot 10,174 0.23
Roof 0 0.00
Sidewalk/Patio 0 0.00
Other 0 0.00
Totals 10,174 0.23
B. Watershed Land Use Breakdown
Contributing Area SCS CN Area[sf] Area[acres] Comments
Onsite impervious 98 10,174 0.23 -
Onsite open 39 38,798 0.89 Assume good condition
Onsite wooded 30 0 0.00 Assume good condition
Onsite pond 100 0 0.00 -
Onsite gravel 76 0 0.00 Assume good condition
Offsite impervious 98 6,840 0.16 -
Offsite open 39 48,979 1.12 Assume good condition
Offsite wooded 76 16,083 0.37 Assume good condition
Offsite pond 100 0 0.00 -
Offsite gravel 76 I 0 0.00 Assume good condiiton
Total area= 2.77 acres
120,874 sf
Composite SCS CN= 52
%Impervious= 14.1%

Dunn Operations Center Mobile Substation Storage POST-DEVELOPMENT HYDROLOGY S.FERRITER,El
DKE-22052 Subbasin 4 10/10/2023
C. Time of Concent
Time of concentration is calculated using the SCS Segmental Approach(TR-55).
Segment 1:Overland Flow Segment 2:Concentrated Flow
Length= 100 ft Length= 563 ft
Top Elev= 235.00 ft Top Elev= 234.00 ft
Bot Elev= 234.00 ft Bot Elev= 222.00 ft
Height= 1 ft Height= 12 ft
Slope= 0.0100 ft/ft Slope= 0.0213 ft/ft
Manning's n= 0.24 dense grasses Paved?= No
P(2-year/24-hour)= 3.7 inches(Dunn,NC) Velocity= 2.36 ft/sec
Segment Time= 17.49 minutes Segment Time= 3.98 minutes
Segment 3:Pipe Flow
Length= 129 ft
Top Elev= 221.06 ft
Bot Elev= 220.10 ft
Height= 0.96 ft
Slope= 0.0074 ft/ft
Manning's n= 0.013 concrete pipe
Pipe Diameter= 2.00 ft
Flow Area= 3.14 sf
Wetted Perimeter= 6.28 If(2 ft ID pipe)
Channel Velocity= 6.23 ft/sec
Segment Time= 0.35 minutes
Time of Concentration= 21.82 minutes
SCS Lag Time= 13.09 minutes(SCS Lag=0.6*Tc)
Time Increment= 3.80 minutes(=0.29*SCS Lag)

LII MCADAMS
Scenario: Post-
Development
POA 2
.u• 2 to SC B
:ss
4
lJb P•Ct
Sue • A
POA 4
la
0 b- /Afr
t
� ��•- POA 3
0,411°
POA 1
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 6/20/2023

�J MCADAMS
FlexTable: Catchment
Table (DKE-22052
PondPack.ppc)
Current Time: 0.00 min
Label Outflow Node Area SCS CN Time of Notes
(ft2) Concentration
(min)
Sub-1 Bypass POA 1 39,035 38 5.00 Post
Sub-1 to SCM A SCM A 958,748 78 5.00 Post
Sub-2 to SCM B SCM B 266,723 85 5.00 Post
Sub-2 Bypass POA 2 168,363 74 11.84 Post
Sub-3 Post POA 3 88,164 45 18.71 Post
Sub-4 Post POA 4 120,874 52 21.82 Post
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/9/2023

�J MCADAMS
Subsection: Master Network Summary
Catchments Summary
Label Scenario Return Hydrograph Time to Peak Peak Flow
Event Volume (min) (ft3/s)
(years) (ac-ft)
Sub-1 to SCM A Post-Dev 1-Year 1 2.136 722.00 45.10
Sub-1 to SCM A Post-Dev 10-Year 10 5.889 721.00 106.86
Sub-1 to SCM A Post-Dev 25-Year 25 7.826 721.00 130.81
Sub-1 Bypass Post-Dev 1-Year 1 0.000 0.00 0.00
Sub-1 Bypass Post-Dev 10-Year 10 0.022 751.00 0.11
Sub-1 Bypass Post-Dev 25-Year 25 0.046 750.00 0.27
Sub-2 to SCM B Post-Dev 1-Year 1 0.832 721.00 18.16
Sub-2 to SCM B Post-Dev 10-Year 10 1.994 721.00 35.87
Sub-2 to SCM B Post-Dev 25-Year 25 2.568 721.00 42.20
Sub-2 Bypass Post-Dev 1-Year 1 0.303 727.00 4.55
Sub-2 Bypass Post-Dev 10-Year 10 0.913 726.00 12.50
Sub-2 Bypass Post-Dev 25-Year 25 1.238 726.00 15.75
Sub-3 Post Post-Dev 1-Year 1 0.005 1,080.00 0.01
Sub-3 Post Post-Dev 10-Year 10 0.108 753.00 0.60
Sub-3 Post Post-Dev 25-Year 25 0.191 734.00 1.33
Sub-4 Post Post-Dev 1-Year 1 0.032 759.00 0.12
Sub-4 Post Post-Dev 10-Year 10 0.249 736.00 1.90
Sub-4 Post Post-Dev 25-Year 25 0.396 734.00 3.22
Node Summary
Label Scenario Return Hydrograph Time to Peak Peak Flow
Event Volume (min) (ft3/s)
(years) (ac-ft)
POA 1 Post-Dev 1-Year 1 1.556 902.00 1.56
POA 1 Post-Dev 10-Year 10 5.299 757.00 10.57
POA 1 Post-Dev 25-Year 25 7.255 755.00 17.13
POA 2 Post-Dev 1-Year 1 0.812 727.00 4.67
POA 2 Post-Dev 10-Year 10 2.241 726.00 12.85
POA 2 Post-Dev 25-Year 25 2.879 726.00 16.20
POA 3 Post-Dev 1-Year 1 0.005 1,080.00 0.01
POA 3 Post-Dev 10-Year 10 0.108 753.00 0.60
POA 3 Post-Dev 25-Year 25 0.191 734.00 1.33
POA 4 Post-Dev 1-Year 1 0.032 759.00 0.12
POA 4 Post-Dev 10-Year 10 0.249 736.00 1.90
POA 4 Post-Dev 25-Year 25 0.396 734.00 3.22
Pond Summary
Label Scenario Return Hydrograph Time to Peak Peak Flow Maximum Maximum
Event Volume (min) (ft3/s) Water Pond Storage
(years) (ac-ft) Surface (ac-ft)
Elevation
(ft)
SCM A(IN) Post-Dev 1- 1 2.136 722.00 45.10 (N/A) (N/A)
Year
SCM A Post-Dev 1- 1 1.556 902.00 1.56 217.27 1.324
(OUT) Year
SCM A(IN) Post-Dev 10- 10 5.889 721.00 106.86 (N/A) (N/A)
Year
SCM A Post-Dev 10- 10 5.278 758.00 10.52 219.33 3.072
(OUT) Year
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/9/2023

�J MCADAMS
Subsection: Master Network Summary
Pond Summary
Label Scenario Return Hydrograph Time to Peak Peak Flow Maximum Maximum
Event Volume (min) (ft3/s) Water Pond Storage
(years) (ac-ft) Surface (ac-ft)
Elevation
(ft)
SCM A(IN) Post-Dev 25- 25 7.826 721.00 130.81 (N/A) (N/A)
Year
SCM A Post-Dev 25- 25 7.208 756.00 16.99 220.35 4.022
(OUT) Year
SCM B(IN) Post-Dev 1- 1 0.832 721.00 18.16 (N/A) (N/A)
Year
SCM B Post-Dev 1- 1 0.509 1,084.00 0.24 227.97 0.633
(OUT) Year
SCM B(IN) Post-Dev 10- 10 1.994 721.00 35.87 (N/A) (N/A)
Year
SCM B Post-Dev 10- 10 1.328 1,084.00 0.54 229.20 1.505
(OUT) Year
SCM B(IN) Post-Dev 25- 25 2.568 721.00 42.20 (N/A) (N/A)
Year
SCM B Post-Dev 25- 25 1.642 1,085.00 0.64 229.82 1.973
(OUT) Year
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/9/2023

1 2 3 4 5 6 7 8 9
/ / //� /7 // I i L, I /I- --_-__, -__---___/ DRAWING NO.
' �\ 1 I 1 --- l I 1
/ ,' J ,'_ _ _ —�� DUKE
j / f J
_ , ' ENERGY®
1, /,
/ / / �� \ s�'�- �� I MAILING ADDRESS:
/ / // \ \\ y ,�' ` I , MARK B.FRANKLIN
fi �\ I JLL-DUKE ENERGY ACCOUNT
/ i i _
/ /r / / ^ \ —%' • I 470 S.WILMINGTON STREET
/ / / / \ RALEIGH,NORTH CAROLINA 27602
, /i
�
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Safety Expectations:, /
/ / // 1 � / \ \ is/
/� y \\ • r '_� > / �QILLNESS��Reduce Risk
-_-' r o ,-- l I ZERO Remove Exposures to Hazards
, / \ A. �, = ®®m'm/? , 1v/ �� / INJURY
/ / r`_,\�,- ;_. �^ ' / I --\ op�Ov Reinforce Safe Behavior
/ \ SUB 2 BYPASS r I,; . , ,, aT G
/ v AREA = 3.87 AC ; __�_ �,, 6 a , _ �` .. ��` / / 1
/ / 168 363 sf 'WFr/,--/,--J,----, i ) ,,,, o --
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/ / v POA 2 4,� ,,/� iq � /' d SUB 2 TO SCM B ;*.® ®
EXISTING WETLAND .,7t� ,,_ 7 o� ��il i SCM B I i •
AREA = 6.12 AC �° -y 1
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` T �ti� T • ������� ' if �1�1r t The JohnR McAdams Company.Inc.
/ / �� -�` �� , O ® / / / '� 2905 Meridian Parkway
\ / \ ��i _•`i•_•_•w ` 1 1 ® O y \ , / 1 Durham.NC 27713
g ♦ / / - - b456, \ .4,47:048)�i Y .— ,.� ...,/-„. - Jam•'-- , I Phone 9.361. sao0
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J / I POST-DEVELOPMENT
A I �� \ L__�;_-T / A HYDROLOGY MAP
G / \ 200
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El SIZE DWG:PLOT SIZE(30x42)

STORMWATER CONTROL MEASURE
DESIGN CALCULATIONS 'A'
Dunn Operations Center& Mobile Substation Storage
DKE-22052

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Above NP 10/10/2023
MOBILE SUBSTATION STORAGE
FTAGE-STORAGE FUNCTION-ABOVE NORMAL POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
215.50 0.00 30,777
218.00 2.50 36,218 33498 83744 83744 2.52
219.00 3.50 38,493 37356 37356 121099 3.48
220.00 4.50 40,825 39659 39659 160758 4.47
221.00 5.50 43,213 42019 42019 202777 5.48
222.50 7.00 46,902 45058 67586 270364 7.06
Storage vs.Stage
300000 -
250000 — y=29306x1.137
R2=0.9996
200000 —
ii
m 150000 —
`o
"' 100000 —
50000 —
0 , I I I I I I I
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Stage(feet)
Ks= 29306
b= 1.1370

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Road Crossing 10/10/2023
MOBILE SUBSTATION STORAGE
STAGE-STORAGE FUNCTION-ABOVE NORMAL POOL ii
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
209.00 0.00 65
210.00 1.00 297 181 181 181 1.12
211.00 2.00 1,164 731 731 912 1.79
212.00 3.00 4,436 2800 2800 3712 2.70
213.00 4.00 14,121 9279 9279 12990 3.89
214.00 5.00 31,278 22700 22700 35690 5.22
215.00 6.00 54,482 42880 42880 78570 6.57
Storage vs.Stage
90000
80000 - •
70000 -
60000 -
o y=123.75x3.4274
En 50000 R'=0.9901
12 40000
o •
30000
20000 -
10000 -
0 , • 1 1 1 1
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00
Stage(feet)
KS= 124
b= 3.4274

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Main Pool 10/10/2023
MOBILE SUBSTATION STORAGE
STAGE-STORAGE FUNCTION-MAIN POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
210.00 -0.50 13,937
210.50 0.00 14,434 Sediment Storage
212.00 1.50 16,501 15468 23201 23201 1.50
214.00 3.50 18,933 17717 35434 58635 3.47
215.00 4.50 20,188 19561 19561 78196 4.49
215.50 5.00 22,906 21547 10774 88969 5.04
*surface area and volume used for avg.depth calculation
Storage vs.Stage
100000 -
90000
80000 y=14735x11111
R2=0.9996
70000 —
o 60000 —
rn 50000 —
R
O 40000 —
• 30000 —
20000 —
10000 —
0
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Stage(feet)
KS= 14735
b= 1.1111

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Forebay 10/10/2023
MOBILE SUBSTATION STORAGE
FTAGE-STORAGE FUNCTION-FOREBAY
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
210.00 -0.50 1,330
210.50 0.00 1,596 Sediment Storage
212.00 1.50 2,681 2139 3208 3208 1.51
214.00 3.50 4,171 3426 6852 10060 3.42
215.00 4.50 5,024 4598 4598 14657 4.48
215.50 5.00 6,760 5892 2946 17603 5.10
Storage vs.Stage
20000 -
18000 —
16000 — y=1801.2x1.3985
14000 R2=0.9974
Li
0 12000 —
a) 10000 —
2
.2 8000 —
rn
6000 —
4000 —
2000 —
0 1 1 1 1I
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Stage(feet)
Ks= 1801.2
b= 1.3985

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Volume Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
(TOTAL VOLUME OF FACILITY
Volume of Main Pool below Normal Pool= 88,969 cf
Volume of Forebay below Normal Pool= 17,603 cf
Total Volume Below Normal Pool= 106,573 cf
Total Volume Above Normal Pool= 270,364 cf
Total Volume of Facility= 376,936 cf
FOREBAY PERCENTAGE OF PERMANENT POOL VOLUME -111
Per NCDEQ Minimum Design Criteria,the forebay volume should equal
approximately 15-20%of the main pool volume.
Total Main Pool Volume= 88,969 cf
Provided Forebay Volume= 17,603 cf
Provided Forebay Volume%= 20%
AVERAGE DEPTH OF MAIN POOL
Main Pool Volume at Normal Pool= 88,969 cf
Main Pool Area at Normal Pool= 22,906 sf
Average Depth= 3.88 ft

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Surface Area Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
WET DETENTION BASIN SUMMARY
Enter the drainage area characteristics==>
Total drainage area to pond= 22.01 acres
Total impervious area to pond= 18.84 acres
Note The basin must be sized to treat all impervious surface runoff draining into the pond,not just the impervious
surface from on-site development.
Drainage area= 22.01 acres @ 85.6% impervious
Estimate the surface area required at pond normal pool elevation==>
Wet Detention Basins are based on an minimum average depth of = 3.88 feet(Calculated)
3.0 3.88 4.0
Lower Boundary=> 80.0 2.92 2.41
Site%impervious=> 85.6 3.11 2.60 2.54
Upper Boundary=> 90.0 3.25 2.64
Therefore,SA/DA required= 2.60
Surface area required for main pool at normal pool= 24,973 ft2
= 0.57 acres
Surface area provided for main pool at normal pool= 30,777 ft2

DKE22052 STORMWATER CONTROL MEASURE O.INGALLS,El
DUNN OPERATIONS CENTER AND WQV Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
ERMINATION OF WATER QUALITY VOLUME
WQ v=(PI(R v)(AI/12
where,
WQv=water quality volume(in acre-ft)
Rv=0.05+0.009(1)where I is percent impervious cover
A=area in acres
P=rainfall(in inches)
Input data:
Total area,A= 22.01 acres
Impervious area= 18.84 acres
Percent impervious cover,I= 85.6 %
Rainfall,P= 1.00 inches
Calculated values:
Rv= 0.82
WQv= 1.50 acre-ft
= 65556 cf.
ASSOCIATED DEPTH IN POND
WQv= 65556 cf.
Stage/Storage Data:
Ks= 29306
b= 1.137
Zo= 215.50
Volume in 1"rainfall= 65556 cf.
Calculated values:
Depth of WQv in Basin= 2.03 ft
= 24.36 inches
Elevation= 217.53 ft

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND WQV Drawdown Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
[bRAWDOWN ORIFICE DESIGN
Per NCDEQ"Storm water Design Manual"Part B.Stormwater Calculations
Orifice Equation for WQv Flow:
Q=CdA(2gHa)o.s
Cd orifice= 0.60
D orifice= 3.50 inch
#orifices= 1
Area orifice= 0.067 sf
g= 32.2 ft/s`
Orifice Invert= 215.50 ft
WSEL @ 1"Runoff Volume= 217.53 ft
Ho= 0.628 ft*
*Average head over the orifice(assuming average head is 1/3 the total depth)
Q= 0.2550 cfs
Drawdown Time=Volume/Flowrate/86400(sec/day)
Volume in 1"rainfall= 65,556 cf
Drawdown Time= 2.98 days

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Temp Pool Drawdown Calc 10/10/2023
MOBILE SUBSTATION STORAGE
gRAW DOWN ORIFICE DESIGII
Per NCDEQ"Storm water Design Manual"Part B.Stormwater Calculations
Orifice Equation for WQv Flow:
Q=Cd A(2gHa)os
Cd orifice= 0.60
D orifice= 3.50 inch
#orifices= 1
Area orifice= 0.067 sf
g= 32.2 ft/s`
Orifice Invert= 215.50 ft
Temp Pool Elevation= 217.75 ft
Ho= 0.701 ft*
*Average head over the orifice(assuming average head is 1/3 the total depth)
Q= 0.2694 cfs
Drawdown Time=Volume/Flowrate/86400(sec/day)
Temp Pool Volume= 73,687 cf
Drawdown Time= 3.17 days

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Surface Area Calculation 6/20/2023
MOBILE SUBSTATION STORAGE
WET DETENTION BASIN SUMMARY
Enter the drainage area characteristics==>
Total drainage area to pond= 22.01 acres
Total impervious area to pond= 18.84 acres
Note The basin must be sized to treat all impervious surface runoff draining into the pond,not just the impervious
surface from on-site development.
Drainage area= 22.01 acres @ 85.6% impervious
Estimate the surface area required at pond normal pool elevation==>
Wet Detention Basins are based on an minimum average depth of = 3.88 feet(Calculated)
3.0 3.88 4.0
Lower Boundary=> 80.0 2.92 2.41
Site%impervious=> 85.6 3.11 2.60 2.54
Upper Boundary=> 90.0 3.25 2.64
Therefore,SA/DA required= 2.60
Surface area required for main pool at normal pool= 24,973 ft2
= 0.57 acres
Surface area provided for main pool at normal pool= 30,777 ft2

DKE22052 STORMWATER CONTROL MEASURE O.INGALLS,El
DUNN OPERATIONS CENTER AND WQV Calculation 6/20/2023
MOBILE SUBSTATION STORAGE
ERMINATION OF WATER QUALITY VOLUME
WQ v=(PI(R v)(AI/12
where,
WQv=water quality volume(in acre-ft)
Rv=0.05+0.009(1)where I is percent impervious cover
A=area in acres
P=rainfall(in inches)
Input data:
Total area,A= 22.01 acres
Impervious area= 18.84 acres
Percent impervious cover,I= 85.6 %
Rainfall,P= 1.00 inches
Calculated values:
Rv= 0.82
WQv= 1.50 acre-ft
= 65556 cf.
ASSOCIATED DEPTH IN POND
WQv= 65556 cf.
Stage/Storage Data:
Ks= 29306
b= 1.137
Zo= 215.50
Volume in 1"rainfall= 65556 cf.
Calculated values:
Depth of WQv in Basin= 2.03 ft
= 24.36 inches
Elevation= 217.53 ft

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND WQV Drawdown Calculation 6/20/2023
MOBILE SUBSTATION STORAGE
IDRAWDOWN ORIFICE DESIGN
D orifice= 3.5 inch
#orifices= 1
Ks= 29306
b= 1.1370
Cd orifice= 0.60
Normal Pool Elevation= 215.50 feet
Volume @ Normal Pool= 0 cf
Orifice Invert= 215.50 feet
WSEL @ 1"Runoff Volume= 217.53 feet
WSEL Vol.Stored Orifice Flow Avg.Flow Incr.Vol. Incr.Time
(feet) (cf) (cfs) (cfs) (cf) (sec)
217.53 65556 0.441
217.35 59126 0.420 0.430 6431 14943
217.18 52778 0.398 0.409 6347 15532
217.00 46522 0.374 0.386 6256 16219
216.83 40365 0.349 0.361 6156 17035
216.65 34321 0.322 0.335 6045 18030
216.47 28402 0.292 0.307 5919 19286
216.30 22629 0.259 0.276 5773 20947
216.12 17029 0.221 0.240 5599 23313
215.94 11647 0.175 0.198 5383 27139
215.77 6556 0.108 0.142 5091 35881
Drawdown Time= 2.41 days
By comparison,if calculated by the average head over the orifice
(assuming average head is one-third the total depth),the result would be:
Average driving head on orifice= 0.628 feet
Orifice composite loss coefficient= 0.600
Cross-sectional area of siphon= 0.067 sf
Q= 0.2550 cfs
Drawdown Time=Volume/Flowrate/86400(sec/day)
Drawdown Time= 2.98 days

�J MCADAMS
Subsection: Elevation-Area Volume Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Elevation Planimeter Area Al+A2+sqr Volume Volume(Total)
(ft) (ft2) (ft2) (A1*A2) (ac-ft) (ac-ft)
(ft2)
215.50 0.0 30,777 0 0.000 0.000
218.00 0.0 36,218 100,382 1.920 1.920
219.00 0.0 38,493 112,049 0.857 2.778
220.00 0.0 40,825 118,960 0.910 3.688
221.00 0.0 43,213 126,040 0.964 4.653
222.50 0.0 46,902 135,135 1.551 6.204
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Requested Pond Water Surface Elevations
Minimum (Headwater) 215.50 ft
Increment(Headwater) 0.10 ft
Maximum (Headwater) 222.50 ft
Outlet Connectivity
Structure Type Outlet ID Direction Outfall El E2
(ft) (ft)
Rectangular Weir Weir for Forward Culvert- 1 217.00 217.50
Orifice-2
Orifice-Area Orifice-2 Forward Culvert- 1 217.50 222.50
Rectangular Weir Weir- 1 Forward Culvert- 1 219.60 222.50
Inlet Box Riser- 1 Forward Culvert- 1 220.50 222.50
Orifice-Circular WQ Orifice Forward Culvert- 1 215.50 222.50
Culvert-Circular Culvert- 1 Forward TW 215.50 222.50
Tailwater Settings Tailwater (N/A) (N/A)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Structure ID: Culvert 1
Structure Type: Culvert-Circular
Number of Barrels 1
Diameter 24.00 in
Length 49.00 ft
Length (Computed Barrel) 49.00 ft
Slope(Computed) 0.010 ft/ft
Outlet Control Data
Manning's n 0.013
Ke 1
Kb 0
Kr 1
Convergence Tolerance 0.00 ft
Inlet Control Data
Equation Form Form 1
K 0.0098
M 2.0000
C 0.0398
Y 0.6700
T1 ratio(HW/D) 1
T2 ratio(HW/D) 1
Slope Correction Factor -1
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 &T2...
T1 Elevation 217.81 ft T1 Flow 15.55 ft3/s
T2 Elevation 218.10 ft T2 Flow 17.77 ft3/s
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Structure ID: Riser- 1
Structure Type: Inlet Box
Number of Openings 1
Elevation 220.50 ft
Orifice Area 16.0 ft2
Orifice Coefficient 1
Weir Length 13.00 ft
Weir Coefficient 3.00(ft^0.5)/s
K Reverse 1
Manning's n 0
Key, Charged Riser 0
Weir Submergence False
Orifice H to crest False
Structure ID: WQ Orifice
Structure Type: Orifice-Circular
Number of Openings 1
Elevation 215.50 ft
Orifice Diameter 3.50 in
Orifice Coefficient 1
Structure ID: Orifice-2
Structure Type: Orifice-Area
Number of Openings 1
Elevation 217.00 ft
Orifice Area 1.5 ft2
Top Elevation 217.50 ft
Datum Elevation 217.25 ft
Orifice Coefficient 1
Structure ID: Weir- 1
Structure Type: Rectangular Weir
Number of Openings 1
Elevation 219.60 ft
Weir Length 3.00 ft
Weir Coefficient 3.00(ft^0.5)/s
Structure ID: Weir for Orifice-2
Structure Type: Rectangular Weir
Number of Openings 1
Elevation 217.00 ft
Weir Length 3.00 ft
Weir Coefficient 3.00(ft^0.5)/s
Structure ID: TW
Structure Type: TW Setup, DS Channel
Tailwater Type Free Outfall
Convergence Tolerances
111lF_99(1c9 F nnnnnnn PP

�J MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Convergence Tolerances
Maximum Iterations 30
Tailwater Tolerance 0.01 ft
(Minimum)
Tailwater Tolerance 0.50 ft
(Maximum)
Headwater Tolerance 0.01 ft
(Minimum)
Headwater Tolerance 0.50 ft
(Maximum)
Flow Tolerance(Minimum) 0.001 ft3/s
Flow Tolerance(Maximum) 10.000 ft3/s
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
215.50 0.00 (N/A) 0.00 (no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1,WQ Orifice,Culvert- 1)
215.60 0.01 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
215.70 0.04 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
215.80 0.11 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
215.90 0.15 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.00 0.17 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.10 0.20 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.20 0.22 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.30 0.24 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.40 0.26 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.50 0.27 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.60 0.29 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.70 0.31 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
216.80 0.32 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,0rifice-2,Weir- 1,Riser
- 1)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
216.90 0.34 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,Orifice-2,Weir- 1,Riser
- 1)
217.00 0.35 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-
2,Orifice-2,Weir- 1,Riser
- 1)
217.10 0.63 (N/A) 0.00 Weir for Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Orifice-2,Weir- 1,Riser-
1)
217.20 1.14 (N/A) 0.00 Weir for Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Orifice-2,Weir- 1,Riser-
1)
217.30 1.79 (N/A) 0.00 Weir for Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Orifice-2,Weir- 1,Riser-
1)
217.40 2.54 (N/A) 0.00 Weir for Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Orifice-2,Weir- 1,Riser-
1)
217.50 3.92 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
217.60 4.58 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
217.70 5.16 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
217.80 5.68 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
217.90 6.15 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.00 6.58 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.10 6.99 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
218.20 7.38 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.30 7.75 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.40 8.11 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.50 8.44 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.60 8.76 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.70 9.08 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.80 9.37 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
218.90 9.60 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.00 9.82 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.10 10.03 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.20 10.25 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.30 10.46 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.40 10.66 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
219.50 10.87 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.60 11.08 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Weir-
1,Riser- 1)
219.70 11.49 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
219.80 12.10 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
219.90 12.83 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.00 13.63 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.10 14.51 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.20 15.44 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.30 16.44 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.40 17.49 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.50 18.58 (N/A) 0.00 Orifice-2,Weir- 1,WQ
Orifice,Culvert- 1 (no Q:
Weir for Orifice-2,Riser-
1)
220.60 20.49 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
220.70 23.04 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
220.80 25.83 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
220.90 28.16 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
221.00 29.93 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
221.10 31.36 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
221.20 32.46 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
221.30 33.20 (N/A) 0.00 Orifice-2,Weir- 1,Riser-
1,WQ Orifice,Culvert- 1
(no Q: Weir for Orifice-2)
221.40 33.66 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
221.50 34.03 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
221.60 34.39 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
221.70 34.75 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
221.80 35.11 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
221.90 35.46 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
222.00 35.80 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
222.10 36.15 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
222.20 36.49 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
222.30 36.83 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM A Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
222.40 37.16 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
222.50 37.50 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Weir for Orifice-
2,Orifice-2,Weir- 1,WQ
Orifice)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 1 years
Label: SCM A (IN) Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 215.50 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 45.10 ft3/s Time to Peak(Flow, In) 722.00 min
Flow(Peak Outlet) 1.56 ft3/s Time to Peak(Flow, Outlet) 902.00 min
Elevation (Water Surface, 217.27 ft
Peak)
Volume(Peak) 1.324 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 2.136 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 1.557 ac-ft
Outflow)
Volume(Retained) 0.579 ac-ft
Volume(Unrouted) 0.000 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 10 years
Label: SCM A (IN) Storm Event: 10-Year
Scenario: Post-Dev 10-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 215.50 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 106.86 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 10.52 ft3/s Time to Peak(Flow, Outlet) 758.00 min
Elevation (Water Surface, 219.33 ft
Peak)
Volume(Peak) 3.073 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 5.889 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 5.278 ac-ft
Outflow)
Volume(Retained) 0.610 ac-ft
Volume(Unrouted) 0.000 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 25 years
Label: SCM A (IN) Storm Event: 25-Year
Scenario: Post-Dev 25-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 215.50 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 130.81 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 16.99 ft3/s Time to Peak(Flow, Outlet) 756.00 min
Elevation (Water Surface, 220.35 ft
Peak)
Volume(Peak) 4.022 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 7.826 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 7.209 ac-ft
Outflow)
Volume(Retained) 0.617 ac-ft
Volume(Unrouted) 0.000 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 100 years
Label: SCM A (IN) Storm Event: 100-Year
Scenario: Post-Dev 100-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 215.50 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 165.72 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 34.01 ft3/s Time to Peak(Flow, Outlet) 754.00 min
Elevation (Water Surface, 221.49 ft
Peak)
Volume(Peak) 5.148 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 11.235 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 10.613 ac-ft
Outflow)
Volume(Retained) 0.622 ac-ft
Volume(Unrouted) 0.000 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

DUNN OPERATIONS CENTER STORMWATER CONTROL MEASURE'A' S.FERRITER,El
DKE-22052 Anti-Flotation Block Calculations 6/23/2023
RISER ANTI-FLOTATION CALCULATION •
Input Data==>
Safety Factor:
Safety factor to use= 1.15 (recommend 1.15 or higher)
Concrete:
Concrete unit weight= 142.0 PCF Note: NC Products lists unit wt.of
manhole concrete at 142 PCF.
Riser:
Inside height of Riser= 5.00 feet
Inside length of riser= 4.00 feet
Inside width of riser= 4.00 feet
Wall thickness of riser= 6.00 inches
Base thickness of riser= 6.00 inches
Base length of riser= 5.00 feet
Base width of riser= 5.00 feet
Openings:
Total Orifice Area = 1.567 SF
OD of barrel exiting manhole= 37.00 inches
Size of drain pipe(if present)= 6.0 inches
Trash Rack:
Bottom Length= 7.00 feet
Bottom Width= 7.00 feet
Top Length= 1.00 feet
Top Width= 1.00 feet
Height= 2.00 feet
Trash Rack water displacement= 38.00 CF
Concrete Present in Riser Structure==>
Total amount of concrete:
Base of Riser= 12.50 CF
Riser Walls= 45.00 CF
Adjust for openings:
Opening for Orifices= 0.78 CF
Opening for barrel= 3.73 CF
Opening for drain pipe= 0.10 CF
Total Concrete present,adjusted for openings= 52.885 CF
Weight of concrete present= 7,510 lbs

DUNN OPERATIONS CENTER STORMWATER CONTROL MEASURE'A' S.FERRITER,El
DKE-22052 Anti-Flotation Block Calculations 6/23/2023
Amount of water displaced by Riser Structure==>
Displacement by concrete= 52.89 CF
Displacement by open air in riser= 80.00 CF
Displacement by trash rack= 38.00 CF
Total water displaced by riser/barrel structure= 170.89 CF
Weight of water displaced= 10,663 lbs
Calculate size of base for riser assembly==>
Length= 8.00 feet
Width= 8.00 feet
Thickness= 12 inches
Concrete Present= 64.00 CF
Check validity of base as designed==>
Total Water Displaced= 222.39 CF
Total Concrete Present= 116.89 CF
Total Water Displaced= 13,877 lbs
Total Concrete Present= 16,598 lbs
Actual safety factor= 1.20 OK
Results of design==>
Base length= 8.00 feet
Base width= 8.00 feet
Base Thickness= 12.00 inches
CY of concrete total in base= 2.37 CY
Concrete unit weight in added base>= 142.0 PCF

DUNN OPERATIONS CENTER STORMWATER CONTROL MEASURE'A' S.FERRITER,El
DKE-22052 Anti-Flotation Block Calculations 6/23/2023
II. CALCULATION FOR RISER ANTI-FLOTATION STEEL
Input Data==>
Anti-Floatation Block Length= 8.0 feet
Anti-Floatation Block Width= 8.0 feet
Anti-Floatation Block Thickness= 12 inches
Asteei to Aconcrete Ratio= 0.0020 (recommend 0.0018 or higher)
Cross-Section Calculations==>
Cross-Section Area*= 8.00 SF
Minimum Steel Area Required= 0.016 SF
2.30 SI
*Note: Assumes a"square"x-sec(L and W same)
Rebar Calculations==>
Bar Size 4 5 6 7 I 8
Diameter(inches) 0.500 0.625 0.750 0.875 1.000
X-Sec Area(SI) 0.196 0.307 0.442 0.601 0.785
Minimum Number of Bars 12 8 6 4 3

DESIGN OF RIPRAP OUTLET PROTECTION WORKSHEET
Project DUNN OPERATIONS CENTER MOBILE SUBSTATION ST Date 10/12/2023
Project No. DKE-22052 Designer SCF
Outlet ID SCM A
Flow,Qlo_yr 9.3 cfs
Slope,S 1.02 %
Pipe Diameter, Do 30 inches
Pipe Diameter, Do 2.5 feet
Number of pipes 1
Pipe separation 0 feet
Manning's n 0.013
Figure 8.06.b.1
25
20 Zone 6 Zone�J
15
Zone 5
;, 10
Zone 4
5 Zone
Zone 1
0
0 1 2 3 4 5 6 7 8 9 10
Pipe diameter(ft)
Zone from graph above= 2
Outlet pipe diameter 30 in. Length= 15.0 ft.
Outlet flowrate 9.3 cfs Width= 7.5 ft.
Outlet velocity 6.8 ft/sec Stone diameter= 6 in.
Material= Class B Thickness= 22 in.
Zone Material Diameter Thickness Length Width
1 Class A 3 9 4 x D(o) 3 x D(o)
2 Class B 6 22 6 x D(o) 3 x D(o)
3 Class I 13 22 8 x D(o) 3 x D(o)
4 Class I 13 22 8 x D(o) 3 x D(o)
5 Class II 23 27 10 x D(o) 3 x D(o)
6 Class II 23 27 10 x D(o) 3 x D(o)
7 Special study required
1.Calculations based on NY DOT method-Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual
2.Outlet velocity based on full-flow velocity
SCM -Rip Rap Outlet Protection Design.xlsml0/12/2023

STORMWATER CONTROL MEASURE
DESIGN CALCULATIONS 'B'
Dunn Operations Center& Mobile Substation Storage
DKE-22052

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Above NP 10/10/2023
MOBILE SUBSTATION STORAGE
FTAGE-STORAGE FUNCTION-ABOVE NORMAL POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
227.00 0.00 27,235
228.00 1.00 29,514 28375 28375 28375 1.01
229.00 2.00 31,804 30659 30659 59034 1.98
230.00 3.00 34,156 32980 32980 92014 2.97
231.00 4.00 36,589 35373 35373 127387 4.00
232.00 5.00 39,114 37852 37852 165239 5.07
Storage vs.Stage
180000
160000 —
y=28049x10925
140000 — R2=0.9995
-- 120000 —u_
U
100000
rn
9.
80000 —
' 60000 —
40000 —
20000 —
0 , I I I I I
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Stage(feet)
Ks= 28049
b= 1.0925

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Main Pool 10/10/2023
MOBILE SUBSTATION STORAGE
FTAGE-STORAGE FUNCTION-MAIN POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
221.00 -1.00 11,022
222.00 0.00 11,985 Sediment Storage
223.00 1.00 12,981 12483 12483 12483 1.01
224.00 2.00 14,011 13496 13496 25979 1.97
225.00 3.00 15,074 14543 14543 40522 2.95
226.00 4.00 16,179 15627 15627 56148 3.96
227.00 5.00 20,722 18450 18450 74598 5.13
*surface area and volume used for avg.depth calculation
Storage vs.Stage
80000 -
70000 - 11035
y= 12282x
60000 — R2=0.9984
U 50000 -
s 40000 -
R
r n 30000 -
20000 -
10000 -
0 1 1 1 1 1
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Stage(feet)
KS= 12282
b= 1.1035

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND SSFxn Forebay 10/10/2023
MOBILE SUBSTATION STORAGE
FTAGE-STORAGE FUNCTION-FOREBAY
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (feet)
222.00 -1.00 1,732
223.00 0.00 2,165 Sediment Storage
224.00 1.00 2,653 2409 2409 2409 1.02
225.00 2.00 3,185 2919 2919 5328 1.94
226.00 3.00 3,758 3472 3472 8799 2.91
227.00 4.00 5,945 4852 4852 13651 4.16
Storage vs.Stage
16000 -
14000 — •
12000 y=2347.1 x1 2359
R2=0.9944
U 10000 —
co 8000 —
E
(02 6000 —
4000 —
2000 —
0 1 I I I I
0.00 1.00 2.00 3.00 4.00 5.00
Stage(feet)
K5= 2347.1
b= 1.2359

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Volume Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
(TOTAL VOLUME OF FACILITY
Volume of Main Pool below Normal Pool= 74,598 cf
Volume of Forebay below Normal Pool= 13,651 cf
Total Volume Below Normal Pool= 88,249 cf
Total Volume Above Normal Pool= 165,239 cf
Total Volume of Facility= 253,488 cf
FOREBAY PERCENTAGE OF PERMANENT POOL VOLUME —111
Per NCDEQ Minimum Design Criteria,the forebay volume should equal
approximately 15-20%of the main pool volume.
Total Main Pool Volume= 74,598 cf
Provided Forebay Volume= 13,651 cf
Provided Forebay Volume%= 18%
AVERAGE DEPTH OF MAIN POOL
Main Pool Volume at Normal Pool= 74,598 cf
Main Pool Area at Normal Pool= 20,722 sf
Average Depth= 3.60 ft

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Surface Area Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
WET DETENTION BASIN SUMMARY
Enter the drainage area characteristics==>
Total drainage area to pond= 6.12 acres
Total impervious area to pond= 4.19 acres
Note The basin must be sized to treat all impervious surface runoff draining into the pond,not just the impervious
surface from on-site development.
Drainage area= 6.12 acres @ 68.5% impervious
Estimate the surface area required at pond normal pool elevation==>
Wet Detention Basins are based on an minimum average depth of = 3.60 feet(Calculated)
3.0 3.60 4.0
Lower Boundary=> 60.0 2.09 1.77
Site%impervious=> 68.5 2.45 2.20 2.04
Upper Boundary=> 70.0 2.51 2.09
Therefore,SA/DA required= 2.20
Surface area required for main pool at normal pool= 5,877 ft2
= 0.13 acres
Surface area provided for main pool at normal pool= 20,722 ft2

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND WQV Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
ERMINATION OF WATER QUALITY VOLUME
WQ v=(PI(R v)(AI/12
where,
WQv=water quality volume(in acre-ft)
Rv=0.05+0.009(1)where I is percent impervious cover
A=area in acres
P=rainfall(in inches)
Input data:
Total area,A= 6.12 acres
Impervious area= 4.19 acres
Percent impervious cover,I= 68.5 %
Rainfall,P= 1.00 inches
Calculated values:
Rv= 0.67
WQv= 0.34 acre-ft
= 14811 cf.
ASSOCIATED DEPTH IN POND
WQv= 14811 cf.
Stage/Storage Data:
Ks= 28049
b= 1.093
Zo= 227.00
Volume in 1"rainfall= 14811 cf.
Calculated values:
Depth of WQv in Basin= 0.56 ft
= 6.69 inches
Elevation= 227.56 ft

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND WQV Drawdown Calculation 10/10/2023
MOBILE SUBSTATION STORAGE
[bRAWDOWN ORIFICE DESIGN
Per NCDEQ"Storm water Design Manual"Part B.Stormwater Calculations
Orifice Equation for WQv Flow:
Q=CdA(2gHa)o.s
Cd orifice= 0.60
D orifice= 2.75 inch
#orifices= 1
Area orifice= 0.041 sf
g= 32.2 ft/s`
Orifice Invert= 227.00 ft
WSEL @ 1"Runoff Volume= 227.56 ft
Ho= 0.148 ft*
*Average head over the orifice(assuming average head is 1/3 the total depth)
Q= 0.0763 cfs
Drawdown Time=Volume/Flowrate/86400(sec/day)
Volume in 1"rainfall= 14,811 cf
Drawdown Time= 2.25 days

DKE22052 STORMWATER CONTROL MEASURE 0.INGALLS,El
DUNN OPERATIONS CENTER AND Temp Pool Drawdown Calc 10/10/2023
MOBILE SUBSTATION STORAGE
gRAW DOWN ORIFICE DESIGII
Per NCDEQ"Storm water Design Manual"Part B.Stormwater Calculations
Orifice Equation for WQv Flow:
Q=Cd A(2gHa)os
Cd orifice= 0.60
D orifice= 2.75 inch
#orifices= 1
Area orifice= 0.041 sf
g= 32.2 ft/s`
Orifice Invert= 227.00 ft
Temp Pool Elevation= 227.75 ft
Ho= 0.212 ft*
*Average head over the orifice(assuming average head is 1/3 the total depth)
Q= 0.0914 cfs
Drawdown Time=Volume/Flowrate/86400(sec/day)
Temp Pool Volume= 20,485 cf
Drawdown Time= 2.59 days

�J MCADAMS
Subsection: Elevation-Area Volume Curve Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Elevation Planimeter Area Al+A2+sqr Volume Volume(Total)
(ft) (ftz) (ftz) (A1*A2) (ac-ft) (ac-ft)
(ft2)
227.00 0.0 27,235 0 0.000 0.000
228.00 0.0 29,514 85,101 0.651 0.651
229.00 0.0 31,804 91,956 0.704 1.355
230.00 0.0 34,156 98,919 0.757 2.112
231.00 0.0 36,589 106,097 0.812 2.924
232.00 0.0 39,114 113,533 0.869 3.793
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Requested Pond Water Surface Elevations
Minimum (Headwater) 227.00 ft
Increment(Headwater) 0.10 ft
Maximum (Headwater) 232.00 ft
Outlet Connectivity
Structure Type Outlet ID Direction Outfall El E2
(ft) (ft)
Orifice-Circular Orifice-2 Forward Culvert- 1 227.75 232.00
Inlet Box Riser- 1 Forward Culvert- 1 231.00 232.00
Orifice-Circular WQ Orifice Forward Culvert- 1 227.00 232.00
Culvert-Circular Culvert- 1 Forward TW 227.00 232.00
Tailwater Settings Tailwater (N/A) (N/A)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Structure ID: Culvert 1
Structure Type: Culvert-Circular
Number of Barrels 1
Diameter 24.00 in
Length 144.00 ft
Length (Computed Barrel) 144.00 ft
Slope(Computed) 0.007 ft/ft
Outlet Control Data
Manning's n 0.013
Ke 1
Kb 0
Kr 1
Convergence Tolerance 0.00 ft
Inlet Control Data
Equation Form Form 1
K 0.0098
M 2.0000
C 0.0398
Y 0.6700
T1 ratio(HW/D) 1
T2 ratio(HW/D) 1
Slope Correction Factor -1
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 &T2...
T1 Elevation 229.31 ft T1 Flow 15.55 ft3/s
T2 Elevation 229.61 ft T2 Flow 17.77 ft3/s
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Outlet Input Data Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Structure ID: Riser- 1
Structure Type: Inlet Box
Number of Openings 1
Elevation 231.00 ft
Orifice Area 16.0 ft2
Orifice Coefficient 1
Weir Length 16.00 ft
Weir Coefficient 3.00(ft^0.5)/s
K Reverse 1
Manning's n 0
Key, Charged Riser 0
Weir Submergence False
Orifice H to crest False
Structure ID: WQ Orifice
Structure Type: Orifice-Circular
Number of Openings 1
Elevation 227.00 ft
Orifice Diameter 2.75 in
Orifice Coefficient 1
Structure ID: Orifice-2
Structure Type: Orifice-Circular
Number of Openings 1
Elevation 227.75 ft
Orifice Diameter 3.00 in
Orifice Coefficient 1
Structure ID: TW
Structure Type: TW Setup, DS Channel
Tailwater Type Free Outfall
Convergence Tolerances
Maximum Iterations 30
Tailwater Tolerance 0.01 ft
(Minimum)
Tailwater Tolerance 0.50 ft
(Maximum)
Headwater Tolerance 0.01 ft
(Minimum)
Headwater Tolerance 0.50 ft
(Maximum)
Flow Tolerance(Minimum) 0.001 ft3/s
Flow Tolerance(Maximum) 10.000 ft3/s
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
227.00 0.00 (N/A) 0.00 (no Q: Orifice-2,Riser-
1,WQ Orifice,Culvert- 1)
227.10 0.01 (N/A) 0.00 WQ Orifice,Culvert- 1
I (no Q: Orifice-2,Riser-
1)
227.20 0.05 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.30 0.08 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.40 0.10 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.50 0.11 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.60 0.13 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.70 0.14 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.75 0.15 (N/A) 0.00 WQ Orifice,Culvert- 1
(no Q: Orifice-2,Riser-
1)
227.80 0.16 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
227.90 0.20 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.00 0.25 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.10 0.29 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.20 0.32 (N/A) 0.00 Orifice-2,WQ
I Orifice,Culvert- 1 (no Q:
Riser- 1)
228.30 0.35 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.40 0.38 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.50 0.40 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.60 0.42 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
228.70 0.45 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.80 0.47 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
228.90 0.49 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.00 0.50 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.10 0.52 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.20 0.54 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.30 0.56 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.40 0.57 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.50 0.59 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.60 0.60 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.70 0.62 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.80 0.63 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
229.90 0.65 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.00 0.66 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.10 0.68 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.20 0.69 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.30 0.70 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.40 0.72 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Composite Rating Curve Return Event: 1 years
Label: SCM B Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Composite Outflow Summary
Water Surface Flow Tailwater Elevation Convergence Error Contributing Structures
Elevation (ft3/s) (ft) (ft)
(ft)
230.50 0.73 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.60 0.74 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.70 0.75 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.80 0.77 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
230.90 0.78 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
231.00 0.79 (N/A) 0.00 Orifice-2,WQ
Orifice,Culvert- 1 (no Q:
Riser- 1)
231.10 2.30 (N/A) 0.00 Orifice-2,Riser- 1,WQ
Orifice,Culvert- 1
231.20 5.04 (N/A) 0.00 Orifice-2,Riser- 1,WQ
Orifice,Culvert- 1
231.30 8.59 (N/A) 0.00 Orifice-2,Riser- 1,WQ
Orifice,Culvert- 1
231.40 12.79 (N/A) 0.00 Orifice-2,Riser- 1,WQ
Orifice,Culvert- 1
231.50 17.57 (N/A) 0.00 Orifice-2,Riser- 1,WQ
Orifice,Culvert- 1
231.60 22.75 (N/A) 0.00 Orifice-2,Riser- 1,WQ
Orifice,Culvert- 1
231.70 27.04 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Orifice-2,WQ Orifice)
231.80 27.39 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Orifice-2,WQ Orifice)
231.90 27.73 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Orifice-2,WQ Orifice)
232.00 28.06 (N/A) 0.00 Riser- 1,Culvert- 1 (no
Q: Orifice-2,WQ Orifice)
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 1 years
Label: SCM B (IN) Storm Event: 1-Year
Scenario: Post-Dev 1-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 227,00 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 18.16 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 0.24 ft3/s Time to Peak(Flow, Outlet) 1,084.00 min
Elevation (Water Surface, 227 97 ft
Peak)
Volume(Peak) 0.633 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 0.832 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 0.509 ac-ft
Outflow)
Volume(Retained) 0.323 ac-ft
Volume(Unrouted) 0.000 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 10 years
Label: SCM B (IN) Storm Event: 10-Year
Scenario: Post-Dev 10-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 227,00 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 35.87 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 0.54 ft3/s Time to Peak(Flow, Outlet) 1,084.00 min
Elevation (Water Surface, 229 20 ft
Peak)
Volume(Peak) 1.506 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 1.994 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 1.327 ac-ft
Outflow)
Volume(Retained) 0.666 ac-ft
Volume(Unrouted) 0.000 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 25 years
Label: SCM B (IN) Storm Event: 25-Year
Scenario: Post-Dev 25-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 227,00 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 42.20 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 0.64 ft3/s Time to Peak(Flow, Outlet) 1,085.00 min
Elevation (Water Surface, 229 82 ft
Peak)
Volume(Peak) 1.972 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 2.568 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 1.642 ac-ft
Outflow)
Volume(Retained) 0.926 ac-ft
Volume(Unrouted) -0.001 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

�J MCADAMS
Subsection: Level Pool Pond Routing Summary Return Event: 100 years
Label: SCM B (IN) Storm Event: 100-Year
Scenario: Post-Dev 100-Year
Infiltration
Infiltration Method No Infiltration
(Computed)
Initial Conditions
Elevation (Water Surface, 227,00 ft
Initial)
Volume(Initial) 0.000 ac-ft
Flow(Initial Outlet) 0.00 ft3/s
Flow(Initial Infiltration) 0.00 ft3/s
Flow(Initial,Total) 0.00 ft3/s
Time Increment 1.00 min
Inflow/Outflow Hydrograph Summary
Flow(Peak In) 51.24 ft3/s Time to Peak(Flow, In) 721.00 min
Flow(Peak Outlet) 0.78 ft3/s Time to Peak(Flow, Outlet) 1,085.00 min
Elevation (Water Surface, 230.88 ft
Peak)
Volume(Peak) 2.825 ac-ft
Mass Balance(ac-ft)
Volume(Initial) 0.000 ac-ft
Volume(Total Inflow) 3.560 ac-ft
Volume(Total Infiltration) 0.000 ac-ft
Volume(Total Outlet 2.087 ac-ft
Outflow)
Volume(Retained) 1.472 ac-ft
Volume(Unrouted) -0.001 ac-ft
Error(Mass Balance) 0.0
DKE-22052 E.Magoon,PE
DKE-22052 PondPack.ppc 10/12/2023

DUNN OPERATIONS CENTER STORMWATER CONTROL MEASURE'B' S.FERRITER,El
DKE-22052 Anti-Flotation Block Calculations 10/10/2023
RISER ANTI-FLOTATION CALCULATION
Input Data==>
Safety Factor:
Safety factor to use= 1.15 (recommend 1.15 or higher)
Concrete:
Concrete unit weight= 142.0 PCF Note: NC Products lists unit wt.of
manhole concrete at 142 PCF.
Riser:
Inside height of Riser= 5.00 feet
Inside length of riser= 4.00 feet
Inside width of riser= 4.00 feet
Wall thickness of riser= 6.00 inches
Base thickness of riser= 6.00 inches
Base length of riser= 5.00 feet
Base width of riser= 5.00 feet
Openings:
Total Orifice Area = 0.267 SF
OD of barrel exiting manhole= 30.00 inches
Size of drain pipe(if present)= 6.0 inches
Trash Rack:
Bottom Length= 7.00 feet
Bottom Width= 7.00 feet
Top Length= 1.00 feet
Top Width= 1.00 feet
Height= 2.00 feet
Trash Rack water displacement= 38.00 CF
Concrete Present in Riser Structure==>
Total amount of concrete:
Base of Riser= 12.50 CF
Riser Walls= 45.00 CF
Adjust for openings:
Opening for Orifices= 0.13 CF
Opening for barrel= 2.45 CF
Opening for drain pipe= 0.10 CF
Total Concrete present,adjusted for openings= 54.814 CF
Weight of concrete present= 7,784 lbs

DUNN OPERATIONS CENTER STORMWATER CONTROL MEASURE'B' S.FERRITER,El
DKE-22052 Anti-Flotation Block Calculations 10/10/2023
Amount of water displaced by Riser Structure==>
Displacement by concrete= 54.81 CF
Displacement by open air in riser= 80.00 CF
Displacement by trash rack= 38.00 CF
Total water displaced by riser/barrel structure= 172.81 CF
Weight of water displaced= 10,784 lbs
Calculate size of base for riser assembly==>
Length= 8.00 feet
Width= 8.00 feet
Thickness= 12 inches
Concrete Present= 64.00 CF
Check validity of base as designed==>
Total Water Displaced= 224.31 CF
Total Concrete Present= 118.81 CF
Total Water Displaced= 13,997 lbs
Total Concrete Present= 16,872 lbs
Actual safety factor= 1.21 OK
Results of design==>
Base length= 8.00 feet
Base width= 8.00 feet
Base Thickness= 12.00 inches
CY of concrete total in base= 2.37 CY
Concrete unit weight in added base>= 142.0 PCF

DUNN OPERATIONS CENTER STORMWATER CONTROL MEASURE'B' S.FERRITER,El
DKE-22052 Anti-Flotation Block Calculations 10/10/2023
II. CALCULATION FOR RISER ANTI-FLOTATION STEEL
Input Data==>
Anti-Floatation Block Length= 8.0 feet
Anti-Floatation Block Width= 8.0 feet
Anti-Floatation Block Thickness= 12 inches
Asteel to Aconcrete Ratio= 0.0020 (recommend 0.0018 or higher)
Cross-Section Calculations==>
Cross-Section Area*= 8.00 SF
Minimum Steel Area Required= 0.016 SF
2.30 SI
*Note: Assumes a"square"x-sec(L and W same)
Rebar Calculations==>
1 Bar Size 4 5 6 7 8
Diameter(inches) 0.500 0.625 0.750 0.875 1.000
X-Sec Area(SI) 0.196 0.307 0.442 0.601 0.785
Minimum Number of Bars 12 8 6 4 3

DESIGN OF RIPRAP OUTLET PROTECTION WORKSHEET
Project DUNN OPERATIONS CENTER MOBILE SUBSTATION ST Date 10/12/2023
Project No. DKE-22052 Designer SCF
Outlet ID SCM B
Flow,Qlo_yr 0.5 cfs
Slope,S 0.69 %
Pipe Diameter, Do 24 inches
Pipe Diameter, Do 2.0 feet
Number of pipes 1
Pipe separation 0 feet
Manning's n 0.013
Figure 8.06.b.1
25
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Pipe diameter(ft)
Zone from graph above= 1
Outlet pipe diameter 24 in. Length= 8.0 ft.
Outlet flowrate 0.5 cfs Width= 6.0 ft.
Outlet velocity 2.6 ft/sec Stone diameter= 3 in.
Material= Class A Thickness= 9 in.
Zone Material Diameter Thickness Length Width
1 Class A 3 9 4 x D(o) 3 x D(o)
2 Class B 6 22 6 x D(o) 3 x D(o)
3 Class I 13 22 8 x D(o) 3 x D(o)
4 Class I 13 22 8 x D(o) 3 x D(o)
5 Class II 23 27 10 x D(o) 3 x D(o)
6 Class II 23 27 10 x D(o) 3 x D(o)
7 Special study required
1.Calculations based on NY DOT method-Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual
2.Outlet velocity based on full-flow velocity
SCM -Rip Rap Outlet Protection Design.xlsml0/12/2023

Dunn Ops & Mobile
Substation Storage
DUNN, NORTH CAROLINA
EROSION CONTROL CALCULATIONS
PROJECT NUMBER: DKE-22052
DESIGNED BY: CLAUDIA PRADO, PE
DATE: OCTOBER 2023 ,,,,,,,,,,,,1,,,,,
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MCADAMS
621 HILLSBOROUGH ST, SUITE 500
RALEIGH, NORTH CAROLINA 27603
NC LIC. # C-0293

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Date:
Designed By: 10/11/2023
Checked By:
Company:
Project Name: Dunn Ops Center
Project No.: DKE22052
Site Location(City/Town) Dunn,NC
Endwall ID. FES-100
Total Drainage Area(acres) 13.86
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.
Outlet pipe diameter,Do(in.) 48
Tailwater depth(in.) 0
Minimum/Maximum tailwater? Min TW(Fig.8.06a)
Discharge(cfs) 70.46
Velocity(ft./s) 7.00
Step 2. Based on the tailwater conditions determined in step 1.enter Figure
8.06a or Figure 8.06b.and determine dso riprap size and minimum apron length
(L.). The d5 size is the median stone size in a well-graded nprap 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.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap dso,(ft.) 0.9
Minimum apron length,La(ft.) 36
Apron width at pipe outlet(ft.) 12
Apron shape Trap
Apron width at outlet end(ft.) 40
Step 4. Determine the maximum stone diameter:
d =1.5xd,s
Minimum TW Maximum TW
Max Stone Diameter,dmax(ft.) 1.35
Step 5. Determine the apron thickness:
Apron thickness=1.5 x d ,
Minimum TW Maximum TW
Apron Thickness(ft.) 2.025
Step 6. Fit the riprap apron to the site by making it level for the minimum
length,L., 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.
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.

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Date:
Designed By: 10/11/2023
Checked By:
Company:
Project Name: Dunn Ops Center
Project No.: DKE22052
Site Location(City/Town) Dunn,NC
Endwall ID. FES-200
Total Drainage Area(acres)
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.
Outlet pipe diameter,Do(in.) 48
Tailwater depth(in.) 0
Minimum/Maximum tailwater? Min TW(Fig.8.06a)
Discharge(cfs) 42.08
Velocity(ft./s) 5.20
Step 2. Based on the tailwater conditions determined in step 1.enter Figure
8.06a or Figure 8.06b.and determine dso riprap size and minimum apron length
(L.). The d5 size is the median stone size in a well-graded nprap 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.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap dso,(ft.) 0.9
Minimum apron length,La(ft.) 36
Apron width at pipe outlet(ft.) 12
Apron shape Trap
Apron width at outlet end(ft.) 40
Step 4. Determine the maximum stone diameter:
d =1.5xd,s
Minimum TW Maximum TW
Max Stone Diameter,dmax(ft.) 1.35
Step 5. Determine the apron thickness:
Apron thickness=1.5 x d ,
Minimum TW Maximum TW
Apron Thickness(ft.) 2.025
Step 6. Fit the riprap apron to the site by making it level for the minimum
length,L., 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.
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.

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Date:
Designed By: 10/11/2023
Checked By:
Company:
Project Name: Dunn Ops Center
Project No.: DKE22052
Site Location(City/Town) Dunn,NC
Endwall ID. FES-300
Total Drainage Area(acres) 7.33
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.
Outlet pipe diameter,Do(in.) 36
Tailwater depth(in.) 0
Minimum/Maximum tailwater? Min TW(Fig.8.06a)
Discharge(cfs) 30.66
Velocity(ft./s) 6.24
Step 2. Based on the tailwater conditions determined in step 1.enter Figure
8.06a or Figure 8.06b.and determine dso riprap size and minimum apron length
(L.). The d5 size is the median stone size in a well-graded nprap 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.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap dso,(ft.) 0.8
Minimum apron length,La(ft.) 20
Apron width at pipe outlet(ft.) 9
Apron shape Trap
Apron width at outlet end(ft.) 23
Step 4. Determine the maximum stone diameter:
d =1.5xd,s
Minimum TW Maximum TW
Max Stone Diameter,dmax(ft.) 1.2
Step 5. Determine the apron thickness:
Apron thickness=1.5 x d,,,,,
Minimum TW Maximum TW
Apron Thickness(ft.) 1.8
Step 6. Fit the riprap apron to the site by making it level for the minimum
length,L., 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.
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.