SWA000079_2020-09-11 SWM Report_20200930

United Rentals
914 Webb Road
Storm Water Management Report
and
Erosion Control Results
Rowan County, North Carolina
Initial Submittal: September 14, 2020
FREELAND and KAUFFMAN, Inc.
Engineers . Landscape Architects
209 West Stone Avenue
Greenville, South Carolina 29609
Tel: [phone]

INDEX
Cover............................................................... i
Index............................................................... ii
I. Executive Summary ......................................................... .
II. Pre -Development Conditions ..................................................
Runoff Curve Number Summary
Time of Concentration Summary
Rainfall Summary
Rate of Runoff Summary
USGS Quadmap
FEMA MAP
Rainfall Data
USDA Soil Survey Map, Legend and Soil Series Information
Pre -Development Drainage Map
TR-55 Pre -Development Calculations
Pre -Developed Area 1: 2, 10, and 100-year Hydrographs
Pre -Developed Area 2: 2, 10, and 100-year Hydrographs
Pre -Developed Area 3: 2, 10, and 100-year Hydrographs
Total Pre -Developed: 2, 10, and 100-year Hydrographs
III. Post -Development Conditions ...............................................
Runoff Curve Number Summary
Time of Concentration Summary
Rainfall Summary
Rate of Runoff Summary
Post -Developed Drainage Map
TR-55 Land -Use Curve Post -Development Calculations
Post -Developed Area 1 A: 2, 10, and 100-year Hydrographs
Post -Developed Area 1 B: 2, 10, and 100-year Hydrographs
Post -Developed Area 2A: 2, 10, and 100-year Hydrographs
Post -Developed Area 213: 2, 10, and 100-year Hydrographs
Post -Developed Area 3: 2, 10, and 100-year Hydrographs
IV. Detention Pond Design and Results ..........................................
Pond 1 Volume Calculations
Pond Report for Pond 1 with Stage/Storage Graph
Pond Report for Pond 1 with Stage/Discharge Graph
Pond 1 Section View
Pond 1 Front View
Pond 1 Routing: 2, 10, and 100-year Storm Event Hydrographs
Total Post -Developed Area 1: 2, 10, and 100-year Storm Event Hydrographs
Pond 2 Volume Calculations
Pond Report for Pond 2 with Stage/Storage Graph
Pond Report for Pond 2 with Stage/Discharge Graph
Pond 2 Section View
Pond 2 Front View
Pond 2 Routing: 2, 10, and 100-year Storm Event Hydrographs
Total Post -Developed Area 2: 2, 10, and 100-year Storm Event Hydrographs

Total Post -Developed: 2, 10, and 100-year Storm Event Hydrographs
V. Pipe Sizing Design and Results ..........................................
Stormdrain Model Report: 10-yr Storm Event
Vd. Erosion and Sediment Control Summary ........................................

Hydrograph Summary Re po r$ydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
SCS Runoff
9.030
2
720
20,716
------
------
------
PRE DEV 1
2
SCS Runoff
4.407
2
720
10,094
------
------
------
PRE DEV 2
3
Combine
13.44
2
720
30,811
1,2
------
------
Total Pre Dev
5
SCS Runoff
8.149
2
716
16,538
------
------
------
Post Dev 1A
6
Reservoir
1.253
2
728
16,886
5
775.60
5,979
Pond 1
7
SCS Runoff
2.920
2
720
6,846
------
------
------
Post Dev I (By -Pass)
8
Combine
4.107
2
720
23,732
6,7
------
------
Total Post Area 1
10
SCS Runoff
3.165
2
716
6,424
------
------
------
Post Dev 2A
11
Reservoir
0.828
2
724
6,419
10
783.31
2,091
Pond 2
12
SCS Runoff
3.295
2
716
6,659
------
------
------
Post Dev 2B (By -Pass)
13
Combine
4.034
2
718
13,078
11,12
------
------
Total Post Area 2
15
Combine
7.978
2
718
36,806
8, 13,
------
------
Total Post Dev
2020-07-17.gpw
Return Period: 2 Year
Tuesday, 07 / 21 / 2020

Hydrograph Summary Repo Oydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cult)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
SCS Runoff
17.57
2
718
40,196
------
------
------
PRE DEV 1
2
SCS Runoff
8.443
2
718
19,314
------
------
------
PRE DEV 2
3
Combine
26.01
2
718
59,510
1,2
------
------
Total Pre Dev
5
SCS Runoff
13.81
2
716
28,577
------
------
------
Post Dev 1A
6
Reservoir
3.350
2
724
28,916
5
776.69
10,499
Pond 1
7
SCS Runoff
6.260
2
720
14,329
------
------
------
Post Dev 1 B (By -Pass)
8
Combine
9.148
2
720
43,241
6,7
------
------
Total Post Area 1
10
SCS Runoff
5.364
2
716
11,101
------
------
------
Post Dev 2A
11
Reservoir
2.453
2
722
11,095
10
783.64
3,458
Pond 2
12
SCS Runoff
5.748
2
716
11,789
------
------
------
Post Dev 2B (By -Pass)
13
Combine
7.286
2
718
22,884
11,12
------
------
Total Post Area 2
15
Combine
15.81
2
720
66,126
8, 13,
------
------
Total Post Dev
2020-07-17.gpw
Return Period: 10 Year
Tuesday, 07 / 21 / 2020

Hydrograph Summary Re po lydraflow Hydrographs Extension for AutodeskO Civil 3DO by Autodesk, Inc. v2021
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
SCS Runoff
32.10
2
718
74,057
------
------
------
PRE DEV 1
2
SCS Runoff
15.23
2
718
35,219
------
------
------
PRE DEV 2
3
Combine
47.33
2
718
109,276
1,2
------
------
Total Pre Dev
5
SCS Runoff
22.66
2
716
48,254
------
------
------
Post Dev 1A
6
Reservoir
6.233
2
724
48,582
5
777.56
17,630
Pond 1
7
SCS Runoff
12.18
2
718
27,895
------
------
------
Post Dev 1 B (By -Pass)
8
Combine
17.85
2
720
76,477
6,7
------
------
Total Post Area 1
10
SCS Runoff
8.803
2
716
18,745
------
------
------
Post Dev 2A
11
Reservoir
5.354
2
722
18,739
10
784.01
4,949
Pond 2
12
SCS Runoff
9.630
2
716
20,276
------
------
------
Post Dev 2B (By -Pass)
13
Combine
14.26
2
718
39,015
11,12
------
------
Total Post Area 2
15
Combine
31.62
2
718
115,492
8, 13,
------
------
Total Post Dev
2020-07-17.gpw
Return Period: 100 Year
Tuesday, 07 / 21 / 2020

I. EXECUTIVE SUMMARY
This report details the storm water management system for the proposed United Rentals Store, located at
914 Webb Road, in Salisbury (Rowan County), North Carolina. The United Rentals site is not a portion of
a larger development, and it will be developed to retain an existing +/- 6,532 square foot building, and will
include all associated parking areas, driveways, utilities, stormwater management system, and landscaping.
Runoff from the parcel currently discharges to both the east and west sides of the property and re-
combines in an un-named tributary of Town Creek before crossing under I-85. A proposed dry -detention
pond, located along the eastern side of the site, and a second dry -detention pond, located on the west
side of the site, will be used in combination to manage water quantity by being designed to fully
attenuating the 2, 10, and 100 year events to less than pre -developed rates while also providing freeboard
above the 100-year event.
Pre -Developed Analysis
Storm Event
Pre -Developed Area 1
Peak Discharge Rate
Pre -Developed Area 2
Peak Discharge Rate
Total Pre -Developed
Peak Discharge Rate
2 year
9.03 cfs
4.41 cfs
13.44 cfs
10 year
17.57 cfs
8.44 cfs
26.01 cfs
100 year
32.10 cfs
15.23 cfs
47.33 cfs
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Total Post-Dev. Area 1
Flow
Storm
Event
Post-Dev. Area
1 A Peak Flow
Post-Dev. Area 1 B
Peak Flow (By -Pass)
Pond 1
Flow
2 year
8.15 cfs
2.92 cfs
1.25 cfs
4.11 cfs
10 year
13.81 cfs
6.26 cfs
3.35 cfs
9.15 cfs
100 year
22.66 cfs
12.18 cfs
6.23 cfs
17.85 cfs
1►..__ ^ n_:_1 _.9 II__1.._:_ na._.._v._._i_.. n__A n_..a:_ _ __-A 31__1.._:_
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Total Post-Dev. Area 2
Flow
Storm
Event
Post-Dev. Area
2A Peak Flow
Post-Dev. Area 2B
Peak Flow (By -Pass)
Pond 2
Flow
2 year
3.17 cfs
3.30 cfs
0.83 cfs
4.03 cfs
10 year
5.36 cfs
5.75 cfs
2.45 cfs
7.29 cfs
100 year
8.93 cfs
9.63 cfs
5.43 cfs
14.36 cfs
Overall Stormwater
Pond
Routing and Analysis
Pre-Dev. Total Post-
Area 2 Dev. Peak
Peak Flow Flow
Post-Dev.
Area 1
Peak Flow
Post-Dev. Total Post -
Area 2 Dev. Flow
Peak
Flow
Storm
Event
Pre-Dev.
Area 1 Peak
Flow
2 year
9.03 cfs
4.41 cfs
13.44 cfs
4.11 cfs
4.03 cfs
7.98 cfs
10 year
17.57 cfs
8.44 cfs
26.01 cfs
9.15 cfs
7.29 cfs
15.81 cfs
100 year
32.10 cfs
15.23 cfs
47.33 cfs
17.85 cfs
14.26 cfs
31.62 cfs

The detention facilities area designed as dry detention ponds where volume is provided to
properly store and release each identified storm event. Staged concrete outlet structures in each
pond will regulate discharge from the facilities. While the ponds are not physically connected or
managed by a common outlet control device, the two facilities will detain runoff for both their
applicable drainage sub -basins and the overall site to less than pre -developed rates. This report
also discusses the erosion control measures planned for the proposed development. The
permanent detention ponds will serve as a temporary sediment basins for the duration of
construction.

II. PRE -DEVELOPMENT CONDITIONS
The proposed development is situated on a +/-18.23 acre tract of land in the northeast quadrant
the intersection of Interstate 85 and Webb road. There are no wetlands (jurisdictional or isolated)
within the development area. The current land use is partially developed for the purposes of
agriculture equipment sales. The property consists of woods, in good condition, grass, gravel and
impervious ground covers.
The total area of analysis can be broken down into two drainage sub -basins (a review of the Pre -
and Post -Development Drainage Maps will help to clarify this Basin setup).
The Predeveloped drainage areas for this project are as follows:
• Pre -Developed Area 1 comprises +/-4.59 acres on the east side of the site. Area 1 drains
via sheet flow, shallow concentrated flow, and channel flow towards an existing open
ended 36" pipe on the eastern side of the site.
• Pre -Developed Area 2 comprises +/-2.13 acres on the west side of the site. Area 2 drains
via sheet flow and shallow concentrated flow towards the drainage ditch along the east
side of I-85.
Runoff Calculations:
TR-55 (Win TR-55, Version 1.00.00): TR-55 is used to calculate only the Runoff Curve Number
and the Time of Concentration for each of the drainage basins in both the pre- and post -
development condition. TR-55 allows for several distinct land -use characteristics and runoff flow
properties to be considered.
Hydraflow Hydrographs (2004, Version 8.0.0.0): Hydraflow Hydrographs, a computer model
based on the SCS Method, is used to generate the pre -developed and post -developed runoff
hydrographs, using the runoff curve number and time of concentration values generated by TR-
55. Hydrographs also models the detention pond, the outlet structure, and provides the routing
for each storm event through the pond system.
A. Runoff Curve Number:
The site is first analyzed to determine all different types of land use. Each land use is assigned a
runoff curve number between 0 and 100. The more impervious a material is, the higher the
runoff curve number. For example, pavement is almost completely impervious, and has a runoff
curve number of 98. Soil type also factors into the curve number for each land use. From review
of the NRCS Web Soil Survey maps, soils on this property are identified as Chewacla loam 0%-2%
(Type B/D), Enon fine sandy loam 2%-8% (Type C), Enon fine sandy loam 8%-15% (Type C),

Sedgefiled fine sandy loam 1 %-6% (Type C/D), Udorthents, loamy (Type C), and Vance sandy clay
loam 2%-8% (Type C) where the majority of the soils on the developed portion of the site being
Type C.
Pre -Developed Area 1
Open space, grass
cover (good
condition): 2.12 Ac
Woods, good
condition: 1.51 Ac.
Gravel: 0.83 Ac.
Impervious: 0.13 Ac.
CN = 74 I CN = 70 I CN = 89 I CN = 98 1
Total Land Area = 4.59 Acres
Weighted Runoff Curve Number = 76
Pre -Developed Area 2
Open space, grass
cover (good
condition): 1.82 Ac
Gravel: 0.14 Ac.
Impervious: 0.17 Ac.
CN = 74 I CN = 89 I CN = 98 I
Total Land Area = 2.13 Acres
Weighted Runoff Curve Number = 77
B. Time of Concentration:
The time of concentration for the existing drainage basin is calculated by determining the path
that runoff takes from the farthest corner of the property to the discharge location. Runoff
assumes three separate flow characteristics when traversing a property, sheet flow, shallow
concentrated flow, and open -channel flow. Sheet flow defines typical overland flow over open
areas. Shallow concentrated flow is used for any overland flow over 100', assuming the flow has
concentrated somewhat. Open -channel flow describes flow through ditches and pipes. TR-55
calculates travel times for each type of flow, given certain parameters. These parameters include
slope, roughness, and velocity. Following are the individual components of the Time of
Concentration:
Pre -Developed Area 1
Sheet Flow
Shallow
Channel flow (85
(100 feet at
Concentrated
feet at 4.00 f/s
4.95% average
flow (155 feet at
slope) short
6.90% average
grass
slope), over
unpaved surface
Tc =6.66 min.
Tc = 0.60 min.
Tc = 0.36 min.

Total Time of Concentration = 7.62 minutes
Pre -Developed A
Sheet Flow
(100 feet at
3.5% average
slope) short
grass
rea 2
Shallow
Concentrated
flow (190 feet at
2.40% average
slope), over
unpaved surface
Tc =7.68 min. I Tc = 1.26 min.
Total Time of Concentration = 8.94 minutes
C. Rainfall
The 24-hour precipitation amounts for the site are per NOAA:
2-year storm event: 3.33 inches
10-year storm event: 4.85 inches
100-year storm event: 7.21 inches
D. Rate of Runoff
The above curve number and time of concentration are parameters used to determine rate of
runoff using the SCS hydrograph method. A hydrograph for the pre -development condition can
be generated showing rate of flow versus time. These hydrographs are included in this section,
Following are the computed rates of runoff for the drainage basin:
Pre -Developed Area 1
Storm Event
Flow Rate, 0 (cfs)
2 year
9.03
10 year
17.57
100 year
32.10
Pre -Developed Area 2
Storm Event
Flow Rate, 0 (cfs)
2 year
4.41
10 year
8.44
100 year
15.23

Total Pre -Developed
Storm Event
Flow Rate, Q (cfs)
2 year
13.44
10 year
26.01
100 year
47.33

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7/9/2020 Precipitation Frequency Data Server
S
NOAA Atlas 14, Volume 2, Version 3
Location name: Salisbury, North Carolina, USA*`
Latitude: 35.6004°, Longitude:-80.5286'
Elevation: 784.42 ft"
source: ESRI Maps vo
M
- 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)'
Average recurrence interval (years)
Duration
1
2 5
16 25 50
������
100
200
500 1000
0.458 0.535
0.588 0.648 0.688
0.724
0.755
0.788 0.810
E-min]F--o.387
(0.357-0.420)
(0.492-0.5810.540-0.637)
(0-0. .423499) )
( ( 0.592-0.701) (0.625-0.745)
(0.654-0.785)
(0.678-0.820)
(0.701-0.858) (0.715-0.884)
0.733 0.856
0.940 1.03 1.10
1.15
1.20
1.25 1.28
[10-min]F-6.619
(0.570-0.671)
(0.676-0.797) (0.788-0.930)
(0.863-1.02) (0.9431.12) (0.996-1.19)
(1.04-1.25)
(1.08-1.30)
(1.11-1.36) (1.13-1.39)
1.45 1.51
1.19 1.31 1.39
1.57 1.60
[15-min1770-.757-3-717­0-9-21-71.08
(0.71 3-0.839)
(0.850-1.00) (0.996-1.18)
(1.09-1.29) (1.20-1.42) (1.26-1.50)
(1.31-1.58) (1.36-1.64)
(1.40-1.71) (1.41-1.75)
1.06
1.27 1.54
1.72 1.94 2.09
2.23 2.35
2.50 2.59
30-min
(0.978-1.15)
(1.17-1.38) (1.42-1.67)
(1.58-1.87) (1.77-2.10) (1.90-2.26)
(2.01-2.41) (2.11-2.55)
(2.22-2.72) (2.29-2.83)
1.32
1.60 1.97
2.24 2.58 2.83
3.07 3.30
3.58 3.79
�-Fi
(1.22-1.43)
(1.47-1.74) (1.82-2.14)
(2.06-2.43) (2.36-2.79) (2.57-3.07)
(2.77-3.33) (2.96-3.58)
(3.19-3.90) (3.34...
F2-hr
1.53
(1.40-1.66)
1.85 2.30
(1.70-2.02) (2.11-2.51)
2.63 3.07 3.39
(2.41-2.87) (2.79-3.34) (3.07-3.69)
3.71 4.02
(3.34 4.04) (3.59 4.39)
4.43 4.73
(3.90 4.84) (4.12-5.18)
1.63
1.96 2.45
2.82 3.32 3.70
4.07 4.45
4.96 5.34
T-hr
1
( .50-1.78)
(1.81-2.15) (2.25-2.68)
(2.58-3.07) (3.01-3.60) (3.34-4.02)
3.66-4.42) (3.96-4.84)
( 4.35-5.41) 4.63-5.84)
(
1.97
2.37 2.96
3.42 4.04 4.52
5.00 5.49
6.16 6.67
6-hr
(1.81-2.15)
(2.19-2.60) (2.72-3.24)
(3.13-3.73) (3.67-4.38) (4.08-4.90)
(4.48-5.43) (4.87-5.97)
(5.39-6.70) (5.76-7.26)
2.80 3.51
4.07 4.84 5.45
6.07 6.72
7.60 8.29
�]F-2.32
(2.14-2.53)
(2.58-3.06) (3.23-3.83)
(3.73-4.43) (4.40-5.25) (4.91-5.90)
(5.43-6.56) (5.94-7.25)
(6.61-8.20) (7.11-8.95)
7.21 E 7.97
8.99 9.80
[�24-hrjL-L,-2.-76-7-3.334.184.855.766.48
58-2.97)
(3.11-3.58) (3.90-4.50)
(4.52-5.21) (5.34-6.18) (6.00-6.95)
(6.66-7.74 J 7.34-8.55)
) (
(8.25-9.66) (8.96-10.5)
3.21
3.87 4.82
5.56 6.56 7.36
8.16 8.99
10.1 11.0
2-day �]F
(3.00-3.44)
(3.61-4.14) (4.50-5.15)
(5.18-5.94) (6.10-7.01) (6.82-7.86)
(7.55-8.72) (8.29-9.61)
(9.28-10.8) (10.0-11.8)
3.42
4.10 5.08
5.86 6.90 7.73
8.57 9.43
00.6 11.5�
F3-day
(3.20_3T65)
(3.84 439) (4.76-5.43)
(5.47-6.25) (6.42-7.37) (7.18-8.26)
(7�94-9.16) (8.71-10.1)
(9.75-11.4) (10.6-12.3)
3.62
434 5.35
6.15 7.24 8.10
8.98 9.88
11.1 12.1
4-day
(3.40-3.86)
(4.08-4.64) (5.01-5.72)
(5.75-6.56) (6.74-7.73) (7.53-8.65)
(8.33-9.60) (9.13-1o.6)
(10.2-11.9) ( 11.1-12.9 )
4.184.98
6.06
6.92 8.09 9.01
9.95 10.9
12.2 13.3
F7-day
(3.94-4.45)
(4.70-5.31) (5.71-6.45)
(6.50-7.36) (7.58 8.60) (8.43-9.58 )
_9.28-10.6) (10.2-11.6)
(
(11.3-13.1 12.2-14.2)
) (
4.77
5.67 6.81
7.70 8.90 9.84
10.8 11.7
13.0 14.0
10-da
(4.51-5.05)
(5.36-6.00) (6.44-7.21)
(7.28-8.15) (8.38-9.41) (9.24-10.4)
(1 0.1-11.4) (11.0-12.4)
(12.1-13.8) (13.0-14.9)
�.dy
6. 0 6174
(7. 05795 8. 9 9.38
9.50-10.5 10.9--12.0 11 9-13.2)
12.i9-14.4 14 04 5.7
1516.4.3
16.5- 8.6)
7.93
9.33 10.8
12.0 13.5 14.7
15.9 17.0
18.5
19.7
30-day
(7.57-8.31)
(8.90-9.76) J L (10.3-11.3) J
L (11.4-12.5) J L (1 2.9-14.2) J L (13.9-15.4) j
1 (15.0-16.6) J L (16.1-17.8) J
L (17.4-19.5) J
L (18.5-20.7)
214
226
-999-­IF-i-1771­-133
14.6 163 17.5
187 19.9
[�i]79
( .58-10A)
(11.2-12.2) (12.8-13.9)
(14.0-15.2) (15.5-16.9) (16.7-18.3)
(17.8-19.5) (18.9-20.8)
(20.3-22.4)
(21.3-23.7)
15-19.4
18.8
60-day
11
13.13-14.4 15 o-16.2)
16.13--1a7.7 18 0--19.5 19 3020.9
2 5122.2 21 6-263.6
I L A232425.3) J
L (2425 6.5
v 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 PIMP 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?lat=35.6004&Ion=-80.5286&data=depth&units=english&series=pds 1/4

7/9/2020 Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
(D Location name: Salisbury, North Carolina, USA*J �P
Latitude: 35.6004°, Longitude:-80.5286' b
Elevation: 784.42 ft**
"source: ESRI Maps V10
- 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/hour)1
Average recurrence interval (years)
Duration
1 2
5 10 25 50 100 200
������
500
1000
5.50
6.42 7.06 7.78 8.26 8.69 9.06
9.46
9.72
[� �]F-4-
.64
(4.28-5.04) (5.08-5.99)
(5.90-6.97) (6.48-7.64) (7.10-8.41) (7.50-8.94) (7.85-9.42) (8814-9.84) 11
(8.41-10.3)
11 (8.58-10.6)
7.66
3.71 4.40
5.14 5.64 6.19 6.58 6.91 7.18
7.48
10-min
(3.42-4.03) (4.06-4.78)
(4.73-5.58) (5.18-6.11) (5.66-6.71) (5.98-7.12) (6.24-7.48) (6.45-7.79)
(6.65-8.14) JL
(6.75-8.35)
3.09 3.68
4.33 4.76 5.24 5.55 5.82 6.04
6.28
6.41
15-min
(2.85-3.36) (3.40-4.01)
I (3.98-4.71) (4.37-5.16) (4.78-5.67) (5.04-6.01) (5.26-6.30) (5.43-6.56)
(5.58-6.83)
(5.65 6.99)
304.18
5.-19
[m]F-2-.1-27F--2.54-�F
-..-
(235277)(2.83-3.34)
.8L1.96230) �.3-45..3.-88..4.45 .4.70.
(316374) (3544�20) (384�(403-4.83)�(422-50)
(444544)�4.575.
.4�.9-9.
66)
3.58
3.79[��-:min
1.32 1.60
1.97 2.24 2.58 2.83 3.07 3.30
(1.22-1.43) (1.47-1.74)
(1.82-2.14) (206-2.43) (2.36 2.79) (2.57-3.07) (2.77-3.33) (2.96-3.58)
(3.19-3.90)
(3.34-4.13)
0.763 0.924
1.15 1.32 1.53 1.70 1.86 2.01
2.21
2.36
- 7
2-hr
]F(0.702-0.832)
( 8848-1.01)
(1.05-1.25) (1.20-1.43) (1.39-1.67) (1.53-1.84) (1.67-2.02) (1.79-2.19)
(1.95-2.42)
(2.06-2.59)
1.65
1.78
0.541 0.654
0.817 0.940 1.10 1.23 1.36 1.48
3-hr
(0.498-0.591) (0.602-0.715)
(0.750-0.892) (0.860-1.02) (1.00-1.20) (1.11-1.34) (1.22-1
(1.45-1.80)
(1.54-1.94)
0.495 0.5717F0.674
0.755
0.836
0.917
1.03
1.11
0.329 0.396
6-hr
(0.303-0.359) (0.365-0.433)
(0.455-0.541) (0.523-0.622) (0.613-0.732)
(0.682-0.819)
(0.749-0.907)
(0.814-0.996)
(0.899-1.12)
(0.962-1.21 )
0.452
0.504
0.558
0.631
0.688
0.291 0.338 0.401
F12F]F-0--19-3-7F-0.232(
(0.178-0.210)0.214-0.254)
(0.268-0.318) (0.310-0.368) (0.365-0.436)
(0.408-0.489)
(0.451-0.545)
(0.493-0.602)
(0.549-0.681)
(0.590-0.743)
0.115 0.139
0.174 0.202 0.240
0.270
0.300
0.332
0.375
0408
24-hr
(0.107-0.124) (0.130-0.149)
(0.163-0.187) (0.188-0.217) (0.223-0.258)
(0.250-0.290)
(0.278-0.322)
(0.306-0.356)
(0.344-0.403)
(0.373-0.439)
0.067 0.081
0.100 0.116 0.137
0.153
0.170
0.187
0.210
0.229
2-day
(0.062-0.072) (0.075-0.086)
(0.094-0.107) (0.108-0.124) (0.127-0.146)
(0.142-0.164)
(082 .157-0.1)
(0.173-0.200)
(0.193-0.225)
(0.209-0.245)
--]F-0.047
0.057
0.071 0.081 0. 996
0.107
0.119
0.131
0.147
0.160
3-da
F
(0.044-0.051) (0053�0.061)
(0.066 075) (0.076-0.087) (0.089-0.102)
(0.100-0.115)
(0.110-Ov127_)
(0.121-0;140)
(OT135-0.158)
(0.147-0.171)
_ 0.045
0.056 0.064 0.075
0.084
0.094
0,103
0.116
0.126
[�-7day]F0.038
(0.035-0.040) (0.042-0.048)
(0.052-0.060) (0^060-0.068) (0.070-0.081)
(0.078-0.090)
(0.087-0.100)
(0.095-0 110)
(0.107-0.124)
(0.115-0.135)
0.025 0.030
0.036 0.041 0.048
0.054
0.059
0.065
0.073
0.079
7-day
(0.023 0.026) (0.028-0.032)
(0.034-0.038) (0.039-0.044) (0.045-0.051)
(0.050-0.057)
(0.055-0.063)
(0.060-0.069)
(0.067-0.078)
(0.073-0.084)
0.020 0.024
0.028 0.032 0.037
O.D41
0.045
0.049
0.054
0.058
F-,_�]0-d
(0.019-0.021) (0.022-0.025)
(0.027-0.030)(0.030-0.034) (0L035-0.039)
(0.039-0.043)
(0.042-0.048)
(0.046-0.052)
(0.051-0.058)
(0.054-0.062)
50
50
20-day
[
0.01 -0---T-0--019-717-0--0-21-�F
014 (0 001 017)
0.018-0 020 0.020 0 022 0.02 -0 025
0.02 028)
(0.027--0 030
50.029 0.033
(0.032--0 036)
0.03 -0 039
0.011 0.013
0.015 0.017 0.019
0.020
0.022
0.024
0.026
0.027
30-day
( 0 011-0 012) (0.012-0.014)
(0.014-0.016) (0.016-0.017) (0.018-0.020)
(0.019-0.021)
(0.021-0.023)
(0.022-0.025)
(0.024-0.027)
(0.026-0.029)
0.009 0.011
0.012 0.014 0.015
0.016
0.017
0.018
0.020
0.021
45-day
(0.009-0.010) (0.010-0.011)
(0.012-0.013) (0.013-0.014) (0.014-0.016)
(0.015-0.017)
(0.016-0.018)
(0.018-0.019)
(0.019-0.021)
(0.020-0.022)
0.013
60-day
(0. 08--0 00. 0 09 9-0 010
0.0 10- 011 0.01100 012 0.0013-0.014)
0.01 30 015
0.01 -0 015
0.01 50 016
0.016-0 018
0.017--0 018
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.htmI?lat=35.6004&Ion=80.5286&data=intensity&units=english&series=pds 1/4

3
35° 36 20" N
Hydrologic Soil Group —Rowan County, North Carolina
Soil Map may not b:- v li z hi cafe.
I
35° 35' 53" N I #'
542600 542700 542900 54M
3
Map Scale: 1:4,130 if printed on A portrait (8.5" x 11") sheet
Meters
N 0 50 100 200 300
A Feet
0 200 400 800 1200
Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 17N WGS84
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
543000
543000 543100
35° 35' 53" N
3
v
S
6/8/2020
Page 1 of 4

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Hydrologic Soil Group —Rowan County, North Carolina
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in A01' Percent of A01
ChA
i Chewacla loam, 0 to 2
B/D 0.9 3.9%
percent slopes,
frequently flooded
EnB
Enon fine sandy loam, 2
C 14.71 64.6%
to 8 percent slopes
EnC
Enon fine sandy loam, 8
C 2.2 ! 9.5%
to 15 percent slopes
---- --
SeB
S fine sandy
C/D 3.4 : 14.7%
I
loa, 1to 6 percent
loam,
slopes
Ud
Udorthents, loamy
C 1.3
VnB2
Vance —a-dyclm
C 0.4 1.7/
o 8percent slopes,
moderately eroded
Totals for Area of Interest 22.81 100.0%"
USDA Natural Resources Web Soil Survey 6/8/2020
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group —Rowan County, North Carolina
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.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff., None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 6/8/2020.
Conservation Service National Cooperative Soil Survey Page 4 of 4

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WinTR-55 Current Data Description
--- Identification Data ---
User: BKS/CRD Date: 7/21/2020
Project: United Rentals Units: English
SubTitle: Salisbury, NC Areal Units: Acres
State: North Carolina
County: Rowan NOAA
Filename: H:\United Rentals\Salisbury NC\Documents\Stormwater\2020-07--16 Pre Dev.w55
--- Sub -Area Data ---
Name Description Reach Area(ac) RCN Tc
------------------------------------------------------------------------------
PRE DEV 1 Outlet 4.59 76 .127
PRE DEV 2 Outlet 2.13 77 .149
Total area: 6.72 (ac)
--- Storm Data --
Rainfall Depth by Rainfall Return Period
2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 1-Yr
(in) (in) (in) (in) (in) (in) (in)
--------------------------------------------------------------------------------
3.33 4.18 4.85 5.76 6.48 7.21 2.76
Storm Data Source: User -provided custom storm data
Rainfall Distribution Type: Type II
Dimensionless Unit Hydrograph: <standard>
WinTR-SS, Version 1.00.10 Page 1 7/21/2020 9:42:15 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Storm Data
Rainfall Depth by Rainfall Return Period
2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 1-Yr
(in) (in) (in) (in) (in) (in) (in)
--------------------------------------------------------------------------------
3.33 4.18 4.85 5.76 6.48 7.21 2.76
Storm Data Source: User -provided custom storm data
Rainfall Distribution Type: Type II
Dimensionless Unit Hydrograph: <standard>
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:42:19 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Sub -Area Summary Table
Sub -Area
Drainage
Time of
Curve
Receiving Sub -Area
Identifier
Area
Concentration
Number
Reach Description
(ac)
(hr)
--------------------------------------------------------------------------------
PRE DEV 1
4.59
0.127
76
Outlet
PRE DEV 2
2.13
0.149
77
Outlet
Total Area: 6.72 (ac)
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:42:24 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Sub -Area Time of Concentration Details
Sub -Area
Flow
Mannings's End
Wetted
Travel
Identifier/
Length
Slope
n Area
Perimeter Velocity
Time
--------------------------------------------------------------------------------
(ft)
(ft/ft)
(sq ft)
(ft) (ft/sec)
(hr)
PRE DEV 1
SHEET
100
0.0495
0.150
0.111
SHALLOW
155
0.0690
0.050
0.010
CHANNEL
85
4.000
0.006
PRE DEV 2
SHEET 100 0.0350 0.150
SHALLOW 190 0.0240 0.050
Time of Concentration .127
0.128
0.021
Time of Concentration .149
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:42:29 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Sub -Area Land Use and Curve Number Details
Sub -Area
Hydrologic
Sub --Area
Curve
Identifier Land Use
Soil
Area
Number
--------------------------------------------------------------------------------
Group
(ac)
PRE DEV 1 Open space; grass cover > 75%
(good)
C
2.12
74
Paved parking lots, roofs, driveways
C
.13
98
Gravel (w/ right-of-way)
C
.83
89
Woods
(good.)
C
1.51
70
Total Area / Weighted Curve Number
4.59
76
PRE DEV 2 Open space; grass cover > 75%
(good)
C
1.82
74
Paved parking lots, roofs, driveways
C
.17
98
Gravel (w/ right-of-way)
C
.14
89
Total Area / Weighted Curve Number
2.13
77
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:42:33 AM

Hydrograph Report
Hydraf low Hydrographs Extension for Autodesk® Civil 3D@ by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 1
PRE DEV 1
Hydrograph type
= SCS Runoff
Peak discharge
= 9.030 cfs
Storm frequency
= 2 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 20,716 cult
Drainage area
= 4.590 ac
Curve number
= 76
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 7.62 min
Total precip.
= 3.33 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 434
PRE DEV 1
Q (cfs)
Hyd. No. 1 -- 2 Year
Q (cfs)
10.00
10.00
8.00
8.00
6.00
6.00
4.00
4.00
2.00
2.00
0.00
0.00
0 2 4 6 8 10 12 14
16 18 20 22
24 26
Time (hrs)
Hyd No. 1

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 121 / 2020
Hyd. No. 1
PRE DEV 1
Hydrograph type
= SCS Runoff
Peak discharge
= 17.57 cfs
Storm frequency
= 10 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 40,196 cuft
Drainage area
= 4.590 ac
Curve number
= 76
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 7.62 min
Total precip.
= 4.85 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
18.00
15.00
12.00
• m
3.00
0.00
0 2 4
Hyd No. 1
PRE DEV 1
Hyd. No. 1 -- 10 Year
6 8 10 12 14
Q (cfs)
18.00
15.00
12.00
M
M
3.00
16 18 20 22 24 26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil MID by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 1
PRE DEV 1
Hydrograph type
= SCS Runoff
Peak discharge
= 32.10 cfs
Storm frequency
= 100 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 74,057 cuft
Drainage area
= 4.590 ac
Curve number
= 76
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 7.62 min
Total precip.
= 7.21 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
PRE DEV 1
Q (cfs)
Hyd. No. 1 -- 100 Year
Q (cfs)
35.00
35.00
30.00
30.00
25.00
25.00
20.00
20.00
15.00
15.00
10.00
10.00
5.00
5.00

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 2
PRE DEV 2
Hydrograph type
= SCS Runoff
Peak discharge
= 4.407 cfs
Storm frequency
= 2 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 10,094 cult
Drainage area
= 2.130 ac
Curve number
= 77
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 8.94 min
Total precip.
= 3.33 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
5.00
4.00
3.00
2.00
1.00
0.00
0 2 4
Hyd No. 2
6 8
PRE DEV 2
Hyd. No. 2 -- 2 Year
Q (cfs)
5.00
4.00
3.00
2.00
1.00
I I I I _ a 0.00
10 12 14 16 18 20 22 24 26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 2
PRE DEV 2
Hydrograph type
= SCS Runoff
Peak discharge
= 8.443 cfs
Storm frequency
= 10 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 19,314 cuft
Drainage area
= 2.130 ac
Curve number
= 77
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 8.94 min
Total precip.
= 4.85 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
10.00
M
4.00
2.00
0.00
0 2 4
Hyd No. 2
PRE DEV 2
Hyd. No. 2 -- 10 Year
6 8 10 12 14
Q (cfs)
10.00
01e,
MI
4.00
2.00
-- 0.00
16 18 20 22 24 26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 2
PRE DEV 2
Hydrograph type
= SCS Runoff
Peak discharge
= 15.23 cfs
Storm frequency
= 100 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 35,219 cuft
Drainage area
= 2.130 ac
Curve number
= 77
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 8.94 min
Total precip.
= 7.21 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
PRE DEV 2
Q (cfs)
Hyd. No. 2 -- 100 Year
Q (cfs)
18.00
18.00
15.00
15.00
12.00
12.00
9.00
9.00
6.00
6.00
3.00
3.00
0.00
0.00
0 2 4 6 8 10 12 14
16 18 20 22
24 26
Time (hrs)
Hyd No. 2

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 3
Total Pre Dev
Hydrograph type
= Combine
Peak discharge
= 13.44 cfs
Storm frequency
= 2 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 30,811 cuft
Inflow hyds.
= 1, 2
Contrib. drain. area
= 6.720 ac
Total Pre Dev

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 3
Total Pre Dev
Hydrograph type
= Combine
Peak discharge
= 26.01 cfs
Storm frequency
= 10 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 59,510 cuft
Inflow hyds.
= 1, 2
Contrib. drain. area
= 6.720 ac
Total Pre Dev

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 3
Total Pre Dev
Hydrograph type
= Combine
Peak discharge
= 47.33 cfs
Storm frequency
= 100 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 109,276 cult
Inflow hyds.
= 1, 2
Contrib. drain. area
= 6.720 ac
Total Pre Dev

M. POST -DEVELOPMENT CONDITIONS:
A dry -detention pond is proposed on the eastern side of the project site and a second dry -
detention pond is proposed on the west side. Outflow from the detention systems will flow into
existing conveyance channels before combining in an un-named tributary of Town Creek before
crossing under I-85.
The total area of analysis can be broken down into four separate drainage basins (a review of the
Pre- and Post -Development Drainage Maps will help to clarify this Basin setup).
• Post Development Area 1 A comprises +/-2.60 acres. Area 1 A drains via sheet flow and
shallow concentrated flow towards pond 1 in the eastern part of the site. From there, run-
off drains to an unnamed tributary of Town Creek which flows under Interstate 85 to
Town Creek.
• Post Development Area 1 B comprises +/-1.97 acres. Area 1 B drains via sheet flow and
shallow concentrated flow that bypasses pond 1. From there, run-off drains to an
unnamed tributary of Town Creek which flows under Interstate 85 to Town Creek.
• Post Development Area 2A comprises +/-4.59 acres. Area 2A drains via sheet flow and
shallow concentrated flow towards pond 2 in the western part of the site. From there,
run-off drains to an unnamed tributary of the Ashley River.
• Post Development Area 2B comprises +/-1.14 acres. Area 2B drains via sheet flow and
shallow concentrated flow towards the detention pond in the northern part of the site.
From there, run-off drains to an unnamed tributary of the Ashley River.
Slopes across the majority of the developed areas range between 1.0% and 6%. Stormwater from
the developed site flows naturally to one of the proposed stormwater ponds or flows off -site
directly.
Runoff Calculations:
Runoff calculations are performed for Post -Development Area.
A. Runoff Curve Number:
Pre -Developed Area 1 A
Open space, grass Gravel: 1.05 Ac. Impervious: 0.54 Ac.
cover (good
condition): 1.01 Ac
CN = 74 I CN = 89 1 CN = 98 1
Total Land Area = 2.60 Acres
Weighted Runoff Curve Number = 85

Pre -Developed Area 1 B
Open space, grass Woods, good
cover (good condition: 1.51 ac.
condition): 0.46 Ac
CN = 74 CN = 70
Total Land Area = 1.97 Acres
Weighted Runoff Curve Number = 71
Pre -Developed Area 2A
Open space, grass Gravel: 0.83 Ac. Impervious: 0.13 Ac.
cover (good
condition): 2.12 Ac
CN = 74 CN = 89 CN = 98
Total Land Area = 4.59 Acres
Weighted Runoff Curve Number = 76
Pre -Developed Area 2B
Open space, grass Gravel: 0.46 Ac. Impervious: 0.15 Ac.
cover (good
condition): 0.53 Ac
CN = 74 CN = 89 CN = 98
Total Land Area = 1.14 Acres
Weighted Runoff Curve Number = 83
B. Time of Concentration:
Post Development Area 1 A
Sheet Flow (57 Shallow concentrated Shallow Concentrated Channel Flow (50'
feet at 1.00% flow for 75' @ 1.00% Flow for 140' @ at average 5 feet
average slope) on paved surface 1.21 % on unpaved per second)
smooth surface surface
Tc = 1.02 min. I Tc = 0.60 min. I Tc = 1.32 min. Tc = 0.18 min.
Total Time of Concentration = 3.12 minutes 4 use 6 minutes

Post Development Area 1 B
Sheet Flow (45 feet at 4.50% Shallow concentrated Channel Flow (220' at
average slope) grass, dense flow for 130' @ 4.50% average 4.5 feet per
on unpaved surface second)
Tc = 5.34 min. Tc = 0.66 min. Tc = 0.84 min.
Total Time of Concentration = 6.84 minutes
Post Development Area 2A
Sheet Flow (100 feet at 2.00% Shallow concentrated Shallow Concentrated
average slope) smooth surface flow for 60' @ 2.00% Flow for 18' @
on paved surface 16.70% on unpaved
surface
Tc = 1.20 min. Tc = 0.36 min. Tc = 0.06 min.
Total Time of Concentration = 1.62 minutes + use 6 minutes
Post Development Area 2B
Sheet Flow (100 feet at 4.60% Shallow concentrated
average slope) smooth surface flow for 30' @ 33.30%
on unpaved surface
Tc = 0.84 min. Tc = 0.06 min.
Total Time of Concentration = 0.90 minutes 4 use 6 minutes
C. Rainfall
The 24-hour precipitation amounts for the site are per NOAA:
2-year storm event: 3.33 inches
10-year storm event: 4.85 inches
100-year storm event: 7.21 inches
D. Rate of Runoff
From this information, a hydrograph can be generated showing rate of flow versus time. Post -
development hydrographs for each storm event are included in this section.
Post Development Area 1 A
Storm Event
Flow Rate, Q (cfs)
2 year
8.15
10 year
13.81
100 year
22.66

Post Development Area 1 B
Storm Event
Flow Rate, Q (cfs)
2 year
2.92
10 year
6.26
100 year
12.18
Post Development Area 2A
Storm Event
Flow Rate, Q (cfs)
2 year
3.17
10 year
5.36
100 year
8.80
Post Development Area 2B
Storm Event
Flow Rate, Q (cfs)
2 year
3.30
10 year
5.75
100 year
9.63

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WinTR-55 Current Data Description
--- Identification Data ---
User: BKS/CRD Date: 7/21/2020
Project: United Rentals Units: English
SubTitle: Salisbury, NC Areal Units: Acres
State: North Carolina
County: Rowan NOAA
Filename: H:\United Rentals\Salisbury NC\Documents\Stormwater\2020-07-20 Post Dev.w55
--- Sub -Area Data ---
Name Description Reach Area(ac) RCN Tc
POST D lA Reach 1 2.6 85 0.1
POST D 1B Reach 1 1.97 71 .114
POST D 2A Reach 2 1.01 86 0.1
POST D 2B Reach 2 1.14 83 0.1
Total area: 6.72 (ac)
--- Storm Data --
Rainfall Depth by Rainfall Return Period
2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 1-Yr
(in) (in) (in) (in) (in) (in) (in)
--------------------------------------------------------------------------------
3.33 4.18 4.85 5.76 6.48 7.21 2.76
Storm Data Source: User -provided custom storm data
Rainfall Distribution Type: Type II
Dimensionless Unit Hydrograph: <standard>
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:41:34 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Storm Data
Rainfall Depth by Rainfall Return Period
2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 1-Yr
(in) (in) (in) (in) (in) (in) (in)
----------------------------------------------------------------------------------
3.33 4.18 4.85 5.76 6.48 7.21 2.76
Storm Data Source: User -provided custom storm data
Rainfall Distribution Type: Type II
Dimensionless Unit Hydrograph: <standard>
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:41:38 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Sub -Area Summary Table
Sub -Area
Drainage
Time of
Curve
Receiving Sub -Area
Identifier
Area
Concentration
Number
Reach Description
(ac)
(hr)
---------------------------------------------------------------------------------
POST D lA
2.60
0.100
85
Reach 1
POST D 1B
1.97
0.114
71
Reach 1
POST D 2A
1.01
0.100
86
Reach 2
POST D 2B
1.14
0.100
83
Reach 2
Total Area: 6.72 (ac)
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:41:46 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Sub -Area Time of Concentration Details
Sub -Area
Flow
Mannings's End Wetted
Travel
Identifier/
Length
Slope
n Area Perimeter
Velocity
Time
(ft)
(ft/ft)
(sq ft) (ft)
(ft/sec)
(hr)
--------------------------------------------------------------------------------
POST D lA
SHEET
57
0.0100
0.011
0.017
SHALLOW
75
0.0100
0.025
0.010
SHALLOW
140
0.0121
0.050
0.022
CHANNEL
50
5.000
0.003
Time of Concentration 0.1
POST D 1B
SHEET
45
0.0450
0.240
0.089
SHALLOW
130
0.0450
0.050
0.011
CHANNEL
220
4.500 0.014
Time of Concentration .114
POST D 2A
SHEET
100
0.0200
0.011
0.020
SHALLOW
60
0.0200
0.025
0.006
SHALLOW
18
0.1670
0.050
0.001
Time of Concentration 0.1
POST D 2B
SHEET 100 0.0116 0.011 0.025
SHALLOW 40 0.1000 0.050 0.002
Time of Concentration 0.1
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:41:53 AM

BKS/CRD United Rentals
Salisbury, NC
Rowan NOAA County, North Carolina
Sub -Area Land Use and Curve Number Details
Sub -Area
Hydrologic
Sub -Area
Curve
Identifier
Land Use
Soil
Area
Number
--------------------------------------------------------------------------------
Group
(ac)
POST D lA
Open space;
grass cover > 75%
(good)
C
1.01
74
Paved parking
lots, roofs, driveways
C
.54
98
Gravel (w/
right-of-way)
C
1.05
89
Total Area
/ Weighted Curve Number
2.6
85
POST D 1B
Open space;
grass cover > 75%
(good)
C
.46
74
Woods
(good)
C
1.51
70
Total Area
/ Weighted Curve Number
1.97
71
POST D 2A
Open space;
grass cover > 75%
(good)
C
.3
74
Paved parking
lots, roofs, driveways
C
.11
98
Gravel (w/
right-of-way)
C
.6
89
Total Area
/ Weighted Curve Number
1.01
86
POST D 2B
Open space;
grass cover > 75%
(good)
C
.53
74
Paved parking
lots, roofs, driveways
C
.15
98
Gravel (w/
right-of-way)
C
.46
89
Total Area
/ Weighted Curve Number
1.14
83
WinTR-55, Version 1.00.10 Page 1 7/21/2020 9:41:58 AM

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk0 Civil 31DO by Autodesk, Inc. v2021 Tuesday, 07 / 21 / 2020
Hyd. No. 5
Post Dev 1 A
Hydrograph type
= SCS Runoff
Peak discharge
= 8.149 cfs
Storm frequency
= 2 yrs
Time to peak
= 11.93 hrs
Time interval
= 2 min
Hyd. volume
= 16,538 cuft
Drainage area
= 2.600 ac
Curve number
= 85
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 6.00 min
Total precip.
= 3.33 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
10.00
M
. M
4.00
2.00
0.00 -
0 2 4
Hyd No. 5
Post Dev 1 A
Hyd. No. 5 -- 2 Year
6 8 10 12 14 16
Q (cfs)
10.00
M
4.00
2.00
0.00
18 20 22 24
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for AutodeskO Civil 3D0 by Autodesk, Inc. v2021
Hyd. No. 5
Post Dev 1 A
Hydrograph type
= SCS Runoff
Storm frequency
= 10 yrs
Time interval
= 2 min
Drainage area
= 2.600 ac
Basin Slope
= 0.0 %
Tc method
= User
Total precip.
= 4.85 in
Storm duration
= 24 hrs
Post Dev 1 A
Tuesday, 07 / 21 / 2020
Peak discharge
= 13.81 cfs
Time to peak
= 11.93 hrs
Hyd. volume
= 28,577 cuft
Curve number
= 85
Hydraulic length
= 0 ft
Time of cons. (Tc)
= 6.00 min
Distribution
= Type II
Shape factor
= 484

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk@ Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 5
Post Dev 1 A
Hydrograph type =
SCS Runoff
Peak discharge
= 22.66 cfs
Storm frequency =
100 yrs
Time to peak
= 11.93 hrs
Time interval =
2 min
Hyd. volume
= 48,254 cuft
Drainage area =
2.600 ac
Curve number
= 85
Basin Slope =
0.0 %
Hydraulic length
= 0 ft
Tc method =
User
Time of conc. (Tc)
= 6.00 min
Total precip. =
7.21 in
Distribution
= Type II
Storm duration =
24 hrs
Shape factor
= 484
Post Dev 1 A
Q (cfs)
Hyd. No. 5 -- 100 Year
Q (cfs)
24.00
24.00
20.00
20.00
16.00
16.00
12.00
12.00
8.00
8.00
4.00
4.00
0.00
0.00
0.0 2.0 4.0
6.0 8.0 10.0
12.0 14.0 16.0
18.0 20.0
Time
(hrs)
Hyd No. 5

Hydrograph Report
Hydraflow Hydrographs Extension forAutodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 7
Post Dev 1 B (By -Pass)
Hydrograph type
= SCS Runoff
Storm frequency
= 2 yrs
Time interval
= 2 min
Drainage area
= 1.970 ac
Basin Slope
= 0.0 %
Tc method
= User
Total precip.
= 3.33 in
Storm duration
= 24 hrs
Q (cfs)
3.00
M
W111l
0.00
0 2 4
Hyd No. 7
Tuesday, 07 / 21 / 2020
Peak discharge
= 2.920 cfs
Time to peak
= 12.00 hrs
Hyd. volume
= 6,846 cuft
Curve number
= 71
Hydraulic length
= 0 ft
Time of conc. (Tc)
= 6.80 min
Distribution
= Type II
Shape factor
= 484
Post Dev 1 B (By -Pass)
Hyd. No. 7 -- 2 Year
6 8 10 12 14 16 18 20 22 24
Q (cfs)
3.00
2.00
1.00
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 7
Post Dev 1 B (By -Pass)
Hydrograph type
= SCS Runoff
Peak discharge
= 6.260 cfs
Storm frequency
= 10 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 14,329 cuft
Drainage area
= 1.970 ac
Curve number
= 71
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 6.80 min
Total precip.
= 4.85 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
7.00
. M
5.00
4.00
3.00
411111
1.00
0.00
0 2 4
Hyd No. 7
6 8
Post Dev 1 B (By -Pass)
Hyd. No. 7 -- 10 Year
Q (cfs)
7.00
M
5.00
4.00
IM1111
2.00
1.00
- I I I I __._. 0.00
10 12 14 16 18 20 22 24 26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Tuesday, 07 121 / 2020
Hyd. No. 7
Post Dev 1 B (By -Pass)
Hydrograph type
= SCS Runoff
Peak discharge
= 12.18 cfs
Storm frequency
= 100 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 27,895 cult
Drainage area
= 1.970 ac
Curve number
= 71
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 6.80 min
Total precip.
= 7.21 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
14.00
12.00
10.00
F-MINE
AM
4.00
0.00
0 2 4
Hyd No. 7
6 8
Post Dev 1 B (By -Pass)
Hyd. No. 7 -- 100 Year
Q (cfs)
14.00
12.00
10.00
ee
4.00
2.00
'--- 0.00
10 12 14 16 18 20 22 24 26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk@ Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 10
Post Dev 2A
Hydrograph type
= SCS Runoff
Storm frequency
= 2 yrs
Time interval
= 2 min
Drainage area
= 1.010 ac
Basin Slope
= 0.0 %
Tc method
= User
Total precip.
= 3.33 in
Storm duration
= 24 hrs
Q (cfs)
4.00
3.00
2.00
U1iI1l
0.00
0 2 4
Hyd No. 10
Tuesday, 07 / 21 / 2020
Peak discharge
= 3.165 cfs
Time to peak
= 11.93 hrs
Hyd. volume
= 6,424 cuft
Curve number
= 85
Hydraulic length
= 0 ft
Time of conc. (Tc)
= 6.00 min
Distribution
= Type II
Shape factor
= 484
Post Dev 2A
Hyd. No. 10 -- 2 Year
6 8 10 12 14 16 18 20 22
Q (cfs)
4.00
3.00
2.00
1.00
0.00
24
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 10
Post Dev 2A
Hydrograph type
= SCS Runoff
Peak discharge =
5.364 cfs
Storm frequency
= 10 yrs
Time to peak =
11.93 hrs
Time interval
= 2 min
Hyd. volume =
11,101 cuft
Drainage area
= 1.010 ac
Curve number =
85
Basin Slope
= 0.0 %
Hydraulic length =
0 ft
Tc method
= User
Time of conc. (Tc) =
6.00 min
Total precip.
= 4.85 in
Distribution =
Type II
Storm duration
= 24 hrs
Shape factor =
484
Post Dev 2A
Q (cfs)
Hyd. No. 10 -- 10 Year
Q (cfs)
6.00
6.00
5.00
5.00
4.00
4.00
3.00
3.00
2.00
2.00
1.00
1.00
0.00
0.00
0.0 2.0 4.0
6.0 8.0 10.0 12.0
14.0 16.0 18.0
20.0 22.0
Time
(hrs)
Hyd No. 10

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 10
Post Dev 2A
Hydrograph type
= SCS Runoff
Peak discharge
= 8.803 cfs
Storm frequency
= 100 yrs
Time to peak
= 11.93 hrs
Time interval
= 2 min
Hyd. volume
= 18,745 cuft
Drainage area
= 1.010 ac
Curve number
= 85
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 6.00 min
Total precip.
= 7.21 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Post Dev 2A
Q (cfs)
Hyd.
No. 10 -- 100 Year
Q (cfs)
10.00
10.00
8.00
8.00
6.00
6.00
4.00
4.00
2.00
2.00
0.00
0.00
0.0 2.0 4.0
6.0 8.0
10.0 12.0 14.0 16.0
18.0 20.0
Hyd No. 10
Time
(hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 12
Post Dev 2B (By -Pass)
Hydrograph type
= SCS Runoff
Storm frequency
= 2 yrs
Time interval
= 2 min
Drainage area
= 1.140 ac
Basin Slope
= 0.0 %
Tc method
= User
Total precip.
= 3.33 in
Storm duration
= 24 hrs
Q (cfs)
4.00
3.00
2.00
1.00
0.00
0 2 4
Hyd No. 12
Tuesday, 07 / 21 / 2020
Peak discharge
= 3.295 cfs
Time to peak
= 11.93 hrs
Hyd. volume
= 6,659 cuft
Curve number
= 83
Hydraulic length
= 0 ft
Time of conc. (Tc)
= 6.00 min
Distribution
= Type II
Shape factor
= 484
Post Dev 2B (By -Pass)
Hyd. No. 12 -- 2 Year
6 8 10 12 14 16 18 20 22
Q (cfs)
4.00
3.00
2.00
1.00
0.00
24
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension forAutodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 12
Post Dev 2B (By -Pass)
Hydrograph type
= SCS Runoff
Peak discharge =
5.748 cfs
Storm frequency
= 10 yrs
Time to peak =
11.93 hrs
Time interval
= 2 min
Hyd. volume =
11,789 cuft
Drainage area
= 1.140 ac
Curve number =
83
Basin Slope
= 0.0 %
Hydraulic length =
0 ft
Tc method
= User
Time of conc. (Tc) =
6.00 min
Total precip.
= 4.85 in
Distribution =
Type II
Storm duration
= 24 hrs
Shape factor =
484
Post Dev 2B (By -Pass)
Q (cfs)
Hyd. No. 12 -- 10 Year
Q (cfs)
6.00
6.00
5.00
5.00
4.00
4.00
3.00
3.00
2.00
2.00
1.00
1.00
0.00
0.00
0.0 2.0 4.0
6.0 8.0 10.0 12.0
14.0 16.0 18.0
20.0 22.0
Time
(hrs)
Hyd No. 12

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 12
Post Dev 2B (By -Pass)
Hydrograph type
= SCS Runoff
Storm frequency
= 100 yrs
Time interval
= 2 min
Drainage area
= 1.140 ac
Basin Slope
= 0.0 %
Tc method
= User
Total precip.
= 7.21 in
Storm duration
= 24 hrs
Tuesday, 07 / 21 / 2020
Peak discharge
= 9.630 cfs
Time to peak
= 11.93 hrs
Hyd. volume
= 20,276 cuft
Curve number
= 83
Hydraulic length
= 0 ft
Time of conc. (Tc)
= 6.00 min
Distribution
= Type II
Shape factor
= 484

IV. DETENTION POND DESIGN AND RESULTS
Following are the results of the drainage study for this project. The overall post -development
discharge rate is represented by the outflow from the combined dry -detention ponds.
The stormwater management ponds for the site are designed to store and release all storm events
up to, and including, the 100-year storm. The ponds have been designed to ensure the 2, 10, and
100-year storm events have been fully attenuated to less than their pre -development flow rates.
Freeboard has been provided from the top of the 100-year storm event and the top of each pond,
as can be seen in the Flow Rate Summary Tables below. The top of the pond 1 is 32.25', and the
100-year storm event reaches an elevation of 31.38'. The top of the pond 2 is 32.25" and the
100-year storm event reaches an elevation of 31.38'.Water quality is not required for this site.
Dry -detention pond 1, as can be seen outlined on the grading plan, will have a bottom elevation at
773.60' and a top elevation of 780.00. The outlet structure will send the first 16,886 cf (2-year
runoff) through a 6" orifice set at 773.60'. The riser has a 0.50' weir set at elevation 775.65,
(right above the 2-year storm elevation) to control the outflow in the riser structure along with the
top of the riser structure set at elevation 777.60'. See calculations below.
Dry -detention pond 2, as can be seen outlined on the grading plan, will have a bottom elevation at
782.30' and a top elevation of 785.00'. The outlet structure will send the first 6,424 cf (2-year
runoff) through a 6" orifice set at 782.30'. The riser has a 2.75' weir set at elevation 783.35,
(right above the 2-year storm elevation) to control the outflow in the riser structure along with the
top of the riser structure set at elevation 785.00'. See calculations below.
Each stormwater pond's discharge will be regulated by a 5-foot x 5-foot square concrete riser.
The top of the concrete riser will serve as the primary spillway.
The staged outlet structure is designed using the pond modeling software Hydraflow Hydrographs
2004 (included in this section). Hydrographs are generated showing the actual routing of the
design storm events through the detention pond. These hydrographs are included in this section.
The detention ponds routing and analysis are summarized as follows:

Stormwater Ponds Routing and Analysis
Pre -Developed Analysis
Storm Event
Pre -Developed Area 1
Peak Discharge Rate
Pre -Developed Area 2
Peak Discharge Rate
Total Pre -Developed
Peak Discharge Rate
2 year
9.03 cfs
4.41 cfs
13.44 cfs
10 year
17.57 cfs
8.44 cfs
26.01 cfs
100 year
32.10 cfs
15.23 cfs
47.33 cfs
nIwo f Villa
VI n11Q lyala Ja1,01
Ill"O K'il f a/llai Iwuan#y
QIMY n1lNiyala
Total Post-Dev. Area 1
Flow
Storm
Event
Post-Dev. Area
1 A Peak Flow
Post-Dev. Area 1 B
Peak Flow (By -Pass)
Pond 1
Flow
2 year
8.15 cfs
2.92 cfs
1.25 cfs
4.11 cfs
10 year
13.81 cfs
6.26 cfs
3.35 cfs
9.15 cfs
100 year
22.66 cfs
12.18 cfs
6.23 cfs
17.85 cfs
nI WU & r villa
vl nnalyala .aavunrVaacl
f WINU nvuaIny
auaa nuaIyala
Total Post-Dev. Area 2
Flow
Storm
Event
Post-Dev. Area
2A Peak Flow
Post-Dev. Area 2B
Peak Flow (By -Pass)
Pond 2
Flow
2 year
3.17 cfs
3.30 cfs
0.83 cfs
4.03 cfs
10 year
5.36 cfs
5.75 cfs
2.45 cfs
7.29 cfs
100 year
8.93 cfs
9.63 cfs
5.43 cfs
14.36 cfs
Overall Stormwater
Pond
Routing and
Analysis
Total Post-
Dev. Peak
Flow
Post-Dev.
Area 1
Peak Flow
Post-Dev. Total Post -
Area 2 Dev. Flow
Peak
Flow
Storm
Event
Pre-Dev.
Area 1 Peak
Flow
Pre-Dev.
Area 2
Peak Flow
2 year
9.03 cfs
4.41 cfs
13.44 cfs
4.1 1 cfs
4.03 cfs
7.98 cfs
10 year
17.57 cfs
8.44 cfs
26.01 cfs
9.15 cfs
7.29 cfs
15.81 cfs
100 year
32.10 cfs
15.23 cfs
47.33 cfs
17.85 cfs
14.26 cfs
31.62 cfs
As demonstrated in the above table, the combined discharges of the Bypass Area and Ponds are
both detained to less than the pre -developed rates in the 2, 10, and 100 year events are passed
through the riser structures without overtopping the ponds. Hydrograph discharge tables are
provided in this section, with each table displaying time vs flow rate for each pond.

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 6
Pond 1
Hydrograph type
= Reservoir
Peak discharge
= 1.253 cfs
Storm frequency
= 2 yrs
Time to peak
= 12.13 hrs
Time interval
= 2 min
Hyd. volume
= 16,886 cult
Inflow hyd. No.
= 5 - Post Dev 1A
Max. Elevation
= 775.60 ft
Reservoir name
= Pond 1
Max. Storage
= 5,979 cuft
Storage Indication method used
k

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 6
Pond 1
Hydrograph type
= Reservoir
Peak discharge
= 3.350 cfs
Storm frequency
= 10 yrs
Time to peak
= 12.07 hrs
Time interval
= 2 min
Hyd. volume
= 28,916 cuft
Inflow hyd. No.
= 5 - Post Dev 1A
Max. Elevation
= 776.69 ft
Reservoir name
= Pond 1
Max. Storage
= 10,499 cuft
Storage Indication method used.
Pond 1

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 6
Pond 1
Hydrograph type
= Reservoir
Storm frequency
= 100 yrs
Time interval
= 2 min
Inflow hyd. No.
= 5 - Post Dev 1A
Reservoir name
= Pond 1
Storage Indication method used.
Q (cfs)
24.00
16.00
12.00
W
4.00
0.00
0 2 4
Hyd No. 6
Peak discharge
Time to peak
Hyd. volume
Max. Elevation
Max. Storage
Pond 1
Hyd. No. 6 -- 100 Year
Tuesday, 07 / 21 / 2020
= 6.233 cfs
= 12.07 hrs
= 48,582 cult
= 777.56 ft
= 17,630 cuft
6 8 10 12 14 16 18 20 22 24
Hyd No. 5 1 i 1 1 Total storage used = 17,630 cuft
Q (cfs)
24.00
20.00
16.00
12.00
4.00
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 8
Total Post Area 1
Hydrograph type
= Combine
Peak discharge
= 4.107 cfs
Storm frequency
= 2 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 23,732 cuft
Inflow hyds.
= 6, 7
Contrib. drain. area
= 1.970 ac
Total Post Area 1

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk@ Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 8
Total Post Area 1
Hydrograph type
= Combine
Peak discharge
= 9.148 cfs
Storm frequency
= 10 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 43,241 cuft
Inflow hyds.
= 6, 7
Contrib. drain. area
= 1.970 ac
Total Post Area 1

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 8
Total Post Area 1
Hydrograph type
= Combine
Peak discharge
= 17.85 cfs
Storm frequency
= 100 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 76,477 cuft
Inflow hyds.
= 6, 7
Contrib. drain. area
= 1.970 ac
Q (cfs)
18.00
15.00
12.00
RIM
Alfa
3.00
0.00
0 2 4
Hyd No. 8
Total Post Area 1
Hyd. No. 8 -- 100 Year
Q (cfs)
18.00
15.00
swill]
• e$
m
3.00
� - 0.00
8 10 12 14 16 18 20 22 24 26
Time (hrs)
Hyd No. 6 Hyd No. 7

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 11
Pond 2
Hydrograph type
= Reservoir
Storm frequency
= 2 yrs
Time interval
= 2 min
Inflow hyd. No.
= 10 - Post Dev 2A
Reservoir name
= Pond 2
Storage Indication method used.
Q (cfs)
4.00
3.00
2.00
1.00
0.00
0 2 4
Hyd No. 11
Peak discharge
Time to peak
Hyd. volume
Max. Elevation
Max. Storage
Pond 2
Hyd. No. 11 -- 2 Year
Tuesday, 07 / 21 / 2020
= 0.828 cfs
= 12.07 hrs
= 6,419 cult
= 783.31 ft
= 2,091 cuft
6 8 10 12 14 16 18 20 22 24
Hyd No. 10 I I 1 1 i I Total storage used = 2,091 CA
Q (cfs)
4.00
3.00
2.00
MRiZ17
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk0 Civil 31DO by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 11
Pond 2
Hydrograph type
= Reservoir
Peak discharge
= 2.453 cfs
Storm frequency
= 10 yrs
Time to peak
= 12.03 hrs
Time interval
= 2 min
Hyd. volume
= 11,095 cuft
Inflow hyd. No.
= 10 - Post Dev 2A
Max. Elevation
= 783.64 ft
Reservoir name
= Pond 2
Max. Storage
= 3,458 cuft
Storage Indication method used

Hydrograph Report
Hydraflow Hydrographs Extension forAutodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 11
Pond 2
Hydrograph type
= Reservoir
Storm frequency
= 100 yrs
Time interval
= 2 min
Inflow hyd. No.
= 10 -Post Dev 2A
Reservoir name
= Pond 2
Storage Indication method used.
Q (cfs)
10.00
: 1O
AM
"I
2.00
0.00
0 2 4
Hyd No. 11
Peak discharge
Time to peak
Hyd. volume
Max. Elevation
Max. Storage
Pond 2
Hyd. No. 11 -- 100 Year
6 8 10
Hyd No. 10
Tuesday, 07 / 21 12020
= 5.354 cfs
= 12.03 hrs
= 18,739 cuft
= 784.01 ft
= 4,949 cuft
12 14 16 18 20 22 24
! i I I I 1 Total storage used = 4,949 cuft
Q (cfs)
10.00
4.00
2.00
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 13
Total Post Area 2
Hydrograph type
= Combine
Storm frequency
= 2 yrs
Time interval
= 2 min
Inflow hyds.
= 11, 12
Tuesday, 07 / 21 12020
Peak discharge
= 4.034 cfs
Time to peak
= 11.97 hrs
Hyd. volume
= 13,078 cuft
Contrib. drain. area
= 1.140 ac
Total Post Area 2

Hydrograph Report
Hydraflow Hydrographs Extension for AutodeskO Civil 3D0 by Autodesk, Inc. v2021
Hyd. No. 13
Total Post Area 2
Hydrograph type
= Combine
Storm frequency
= 10 yrs
Time interval
= 2 min
Inflow hyds.
= 11, 12
Q (cfs)
8.00
We
4.00
2.00
Tuesday, 07 / 21 / 2020
Peak discharge
= 7.286 cfs
Time to peak
= 11.97 hrs
Hyd. volume
= 22,884 cuft
Contrib. drain. area
= 1.140 ac
Total Post Area 2
Hyd. No. 13 -- 10 Year
0.00 -'' ----`-zm 1 r
0 2 4 6 8 10 12 14 16
Hyd No. 13 Hyd No. 11 Hyd No. 12
18 20 22 24
Q (cfs)
8.00
4.00
2.00
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Hyd. No. 13
Total Post Area 2
Hydrograph type
= Combine
Storm frequency
= 100 yrs
Time interval
= 2 min
Inflow hyds.
= 11, 12
Tuesday, 07 / 21 / 2020
Peak discharge
= 14.26 cfs
Time to peak
= 11.97 hrs
Hyd. volume
= 39,015 cuft
Contrib, drain. area
= 1.140 ac
Total Post Area 2

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 15
Total Post Dev
Hydrograph type
= Combine
Peak discharge
= 7.978 cfs
Storm frequency
= 2 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 36,806 cuft
Inflow hyds.
= 8, 13
Contrib. drain. area
= 0.000 ac
Q (cfs)
8.00
RIM
4.00
2.00
Total Post Dev
Hyd. No. 15 -- 2 Year
0.00
0 2 4 6 8 10 12 14 16
Hyd No. 15 Hyd No. 8 Hyd No. 13
18 20 22 24
Q (cfs)
8.00
4.00
will]
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 15
Total Post Dev
Hydrograph type
= Combine
Peak discharge
= 15.81 cfs
Storm frequency
= 10 yrs
Time to peak
= 12.00 hrs
Time interval
= 2 min
Hyd. volume
= 66,126 cuft
Inflow hyds.
= 8, 13
Contrib. drain. area
= 0.000 ac
Q (cfs)
18.00
15.00
MiI1l
• es
RIM
3.00
0.00
0 2 4
Hyd No. 15
0
Total Post Dev
Hyd. No. 15 -- 10 Year
Q (cfs)
18.00
15.00
12.00
M
3.00
- , 0.00
8 10 12 14 16 18 20 22 24 26
Hyd No. 8 Hyd No. 13 Time (hrs)

Hydr®graph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021
Tuesday, 07 / 21 / 2020
Hyd. No. 15
Total Post Dev
Hydrograph type
= Combine
Peak discharge
= 31.62 cfs
Storm frequency
= 100 yrs
Time to peak
= 11.97 hrs
Time interval
= 2 min
Hyd. volume
= 115,492 cuft
Inflow hyds.
= 8, 13
Contrib. drain. area
= 0.000 ac
Total Post Dev

V. Pipe Sizing Design and Results
Included in this report are the pipe sizing calculations for the on -site pipes and catch basins.
These are generated by the rational method and are based on the 10-year intensity for all storm
drain structures flowing to the pond. These calculations show the total flow for each pipe section,
velocity, hydraulic grade elevations, and spreads at each inlet. The flow, velocity, percent full, and
hydraulic grades have also been placed on the storm drain profile drawings.
It is noted that for certain pipes, these calculations show the "Total Flow (cfs)" exceeding the
listed "Capacity Full (cfs)." The Hydraflow Storm Sewers program calculates the "Capacity Full"
using the Manning's pipe equation for full flow. This equation assumes the slope of the Energy
Grade Line (EGL) to be equal to the slope of the pipe, and a flow depth equal to the diameter of
the pipe. For this project, the pipe sizes are minimized so that certain pipes are allowed to flow
under a surcharged condition. Surcharging a pipe places the Hydraulic Grade Line above the
crown of the pipe, builds up head on the flow through the pipes, and puts the pipes under
pressure. The HGL becomes steeper than the pipe inverts, and a flow greater than the full flow
capacity is observed. The Hydraflow Storm Sewers Version 8.0 User Manual explains this
phenomenon as a common and expected occurrence.

0
m
c
J
N
O
N
R
V
N
N
M
W
W
O
CO
C)dM'
N
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VII. EROSION and SEDIMENT CONTROL
The following is a narrative of the sediment and erosion control devices to be used on the
proposed development to be constructed at 914 Webb Road. During land disturbance activities,
there will be approximately +/- 5.30 acres of total disturbance. Erosion and sedimentation
control for this project will be accomplished with a series of Best Management Practices (BMP's)
which are broken down into two construction phases.
During land disturbing activities on the subject site, the runoff will be controlled via a series of
sediment basins, inlet protection, check dams, silt fence, and stone construction entrance. The
sediment basins will be dewatered using Faircloth skimmers. The sediment basins will be
discharged with a reinforced concrete riser structure and will be converted to a permanent
stormwater pond. These items will be implemented per the NCDEQ erosion and sediment control
handbook and Rowan County requirements and maintained on a regular basis to insure their
proper operation.
Temporary seeding should be used throughout construction as needed, and all disturbed areas
should either receive stone base (for pavements) or permanent seeding as soon as each area is
complete. Permanent stabilization activities should not be delayed for the end of the project. Inlet
protection will be installed at storm drain inlets during all phases of construction, and check dams
will be employed as needed. Maintenance of the best management practices will continue until
final site stabilization can be achieved.
The SWPPP Plans and Details, which include a generalized sequence of construction, maintenance
notes, etc., can be found in the Site Development Plans, prepared by Freeland and Kauffman, Inc.