SWA000140_Design Calculations_20220406

STORMWATER MANAGEMENT REPORT
West Edge
Forsyth County, NC
SAPA Project # 19-057CD
Owner:
ADAMS PROPERTY GROUP
2298 MT. PLEASANT STREET
CHARLESTON, SC 29403
SEAL '
i 14985
a 3/17/22 a
WA
March 17, 2022
Designed By:
--0#40stimmel 601 N. TRADE STREET, SUITE 200
WINSTON-SALEM, NC 27101
www.stimmelpa.com 336.723.1067
LANDSCAPE ARCHITECTURE CIVIL ENGINEERING LAND PLANNING

WET DETENTION POND
CALCULATIONS

SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
PROJECT INFORMATION
1 Project Name
West Edge
2 Project Area ac
25.9
3 Coastal Wetland Area ac
0
4 Surface Water Area ac
0
5
Is this project High or Low Density?
High
6
Does this protect use an off -site SCM?
No
COMPLIANCE WITH 02H .1003(4)
7
Width of vegetated setbacks provided feet
30
8
Will the vegetated setback remain vegetated?
Yes
9
If BUA is proposed in the setback, does it meet NCAC 02H.1003 4 c-d ?
I N/A
10
1 Is streambank stabilization proposed on this project?
No
NUMBER AND TYPE OF SCMs:
11
Infiltration S stem
12
Bioretention Cell
13
Wet Pond
1
14
Stormwater Wetland
15
Permeable Pavement
16
Sand Filter
17
Rainwater Harvesting RWH
18
Green Roof
19
Level Spreader -Filter Strip LS-FS
20
Disconnected Impervious Surface DIS
21
Treatment Swale
22
Dry Pond
23
StormFilter
24
Silva Cell
113ayfilter
IFilterra
25
26
FORMS LOADED
DESIGNER CERTIFICATION
27 IName and Title:
Street address:
City, State, Zip:
Phone number(
Email:
J. Neal Tucker, P.E Director of Civil Enginee
Stimmel Associates, PA
601 N. Trade St. Suite 200
Winston-Salem, NC 27101
336-723-1067
ntucker(a)stimmelpa.com
Certification Statement:
I certify, under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or supervision; that
the information provided in the form is, to the best of my knowledge and belief, true, accurate, and complete; and that the engineering plans,
specifications, operation and maintenance agreements and other supporting information are consistent with the information provided here.
N CARo
'a SEAL
14985
�! .FNG I
Seal
Signature f PCsigner
Date
3/17/22

DRAINAGE AREAS
1
Is this a high density project?
Yes
2
If so, number of drainage areas/SCMs
1
3
Does this roiect have low densit areas?
Yes
4
F5
If so, number of low densitydrainage areas
2
Is all/part of this project subject to previous rule
versions?
No
FORMS LOADED
DRAINAGE AREA INFORMATION
Entire Site
1
LD 1
LD 2
4
T pe of SCM
Wet Pond
N/A
N/A
5
Total drainage area (sq ft
1235874
1101765
57728
76381
6
Onsite drainage area (sq ft
757944
757944
0
0
7
Offsite draina a area (sq ft
0
0
0
0
8
Total BUA in project (sq ft)
757944
757944 sf
sf
sf
9
New BUA on subdivided lots (subject to
ermitting) (sq ft
N/A
N/A
N/A
N/A
10
New BUA not on subdivided lots (subject to
ermittin s
11
Offsite BUA (sq ft
N/A
N/A
N/A
N/A
12
Breakdown of new BUA not on subdivided lots:
- Parking (sq ft
- Sidewalk (sq ft
- Roof (sq ft
- Roadway s ft
- Future (sq ft
- Other, please specify in the comment box
below (sq ft)
13
New infiltrating permeable pavement on
subdivided lots (sq ft
N/A
N/A
N/A
N/A
14
New infiltrating permeable pavement not on
subdivided lots (sq ft)
N/A
N/A
N/A
N/A
15
Existing BUA that will remain (not subject to
ermitting) (sq ft
N/A
N/A
N/A
N/A
16
Existing BUA that is already ermitted (sq ft
N/A
N/A
N/A
N/A
17
Existing BUA that will be removed (sq ft
26612 sf
26612 sf
N/A
N/A
18
Percent BUA
19
Design storm inches
1.0 in
1.0 in
N/A
N/A
20
Design volume of SCM cu ft
61438 cf
21
Calculation method for design volume
Simple Method
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
22 drainage area(s):

WET POND
Drainage area number
ERAL MDC FROM 02H .1050
3
Is the SCM sized to treat the SW from all surfaces at build -out?
Yes
4
Is the SCM located away from contaminated soils?
Yes
5
What are the side slopes of the SCM (H:V)?
3:1
6
Does the SCM have retaining walls, gabion walls or other
engineered side slopes?
No
7
Are the inlets, outlets, and receiving stream protected from erosion
(10-year storm)?
Yes
8
Is there an overflow or bypass for inflow volume in excess of the
desi n volume?
Yes
9
What is the method for dewatering the SCM for maintenance?
Drawdown Orifice
10
If applicable, will the SCM be cleaned out after construction?
Yes
11
Does the maintenance access comply with General MDC (8)?
Yes
12
Does the drainage easement comply with General MDC (9)?
Yes
13
If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?
N/A
14
Is there an O&M Agreement that complies with General MDC (11)?
Yes
151
Is there an O&M Plan that complies with General MDC (12)?
Yes
161
Does the SCM follow the device specific MDC?
Yes
17
Was the SCM designed by an NC licensedprofessional?
Yes
WET POND
MDC FROM 02H .1053
18
Sizing method used
SA/DA
19
Has a stage/storage table been provided in the calculations?
Yes
20
Elevation of the excavated main pool depth (bottom of sediment
removal) (fmsl
833.50
21
Elevation of the main pool bottom (top of sediment removal) (fmsl)
834.00
221
Elevation of the bottom of the vegetated shelf (fmsl)
840.50
23
Elevation of the permanent pool (fmsl)
841.00
24
Elevation of the top of the vegetated shelf (fmsl)
841.50
25
Elevation of the temporary pool (fmsl)
846.25
26
Surface area of the main permanent pool (square feet)
22243
27
Volume of the main permanent pool (cubic feet)
96118 cf
28
Average depth of the main pool (feet)
5.09 ft
29
Average depth equation used
Equation 3
30
If using equation 3, main pool perimeter (feet)
672.0 ft
31
If using equation 3, width of submerged veg. shelf (feet)
5.0 ft
32
Volume of the forebay (cubic feet)
16008 cf
33
Is this 15-20% of the volume in the main pool?
Yes
34
Clean -out depth for forebay (inches)
6 in
35
Design volume of SCM (cu ft)
61438 cf
361
Is the outlet an orifice or a weir?
Orifice
37
If orifice, orifice diameter (inches)
3 in
38
If weir, weir height (inches)
39
If weir, weir length (inches)
40
Drawdown time for the temporary pool (days)
3.6
41
Are the inlet(s) and outlet located in a manner that avoids short-
circuiting?
Yes
42
Are berms or baffles provided to improve the flow path?
Yes
43
Depth of forebay at entrance (inches)
60 in
44
Depth of forebay at exit (inches)
40 in
45
Does water flow out of the forebay in a non -erosive manner?
Yes
46
Width of the vegetated shelf (feet)
loft
47
Slope of vegetated shelf (H:V)
10:1
48
Does the orifice drawdown from below the top surface of the
permanentpool?
Yes
49
Does the pond minimize impacts to the receiving channel from the 1-
r, 24-hr storm?
Yes
50
Are fountains proposed? (If Y, please provide documentation that
MDC(9) is met.
No
51
Is a trash rack or other device provided to protect the outlet system?
Yes
52
Are the dam and embankment planted in non -clumping turf grass?
Yes
53
Species of turf that will be used on the dam and embankment
Fescue
54
Hasa planting plan been provided for the vegetated shelf?
Yes
ADDITIONAL
INFORMATION
55
Please use this space to provide any additional information about
the wet pond(s):
Wet Pond 1 4:34 PM 3/14/2022

Project: West Edge Sheet: 1 of 4
Project No.: 19-057CD
Designed By: BMH
Checked By: JNT Date: 11.16.2021
Revised:
WATER QUALITY POND DESIGN
Wet Pond 1
rE DATA
WATERSHED INFORMATION
On -Site Drainage Area to Pond =
25.30 acres
Watershed = Yadkin River
On -Site Proposed Impervious Area =
17.40 acres
Classification = Site not located in classified /
On -Site Future Impervious Area =
0.00 acres
regulated watershed
Total On -Site Impervious Area =
17.40 acres
OFFSITE DATA
Offsite Drainage Area to Pond =
0.00 acres
Offsite Impervious Area =
0.00 acres
Offsite Future Impervious Area =
0.00 acres
Total Offsite Impervious Area =
0.00 acres
Total Drainage Area = 25.30 acres
Total Impervious Area = 17.40 acres
Total Impervious % = 68.8%
DETERMINE DESIGN VOLUME (DV)
SIMPLE METHOD
Runoff Coefficient (Rv) = 0.05 + 0.9 x IA
IA = Impervious Fraction (Impervious Area/Drainage Area)
Design Volume (DV) = 3630 x Rp x Rv x A, (Cubic Feet)
Rp = Design Storm Depth (in)
A = Drainage Area (ac)
Design Storm Depth (in) = 1.00
IA = 0.688
Rv = 0.669
DV= 61,438 Cubic Feet
601 N. Trade Street, Suite 200 PHONE: [phone]
Stimmel Associates, P.A. Winston-Salem, NC 27101 FAX: [phone]

Project: West Edge Sheet: 2 of 4
Project No.: 19-057CD
Designed By: BMH
Checked By: JNT Date: 11.16.2021
Revised:
WATER QUALITY POND DESIGN
Wet Pond 1
POND SIZING CALCULATIONS
Stage -Storage Data
Stage
(Feet)
Elevation
(Feet)
Forebay Area
(SF)
Forebay
Volume
(CF)
Cumulative
Forebay
Volume
CF
Main Pool
Area
(SF)
Main Pool
Volume
(SF)
Cumulative
Main Pool
Volume
CF
Cumulative
Combined
Volume
CF
0.0
834.00
0
0
0
8582
0
0
0
2.0
836.00
1291
1291
1291
11130
19712
19712
21003
4.0
838.00
2458
3749
5040
14116
25246
44958
49998
6.0
840.00
3920
6378
11418
17706
31822
76780
88198
6.5
840.50
4324
2061
13479
18702
9102
85882
99361
7.0
841.00
5792
2529
16008
22243
10236
96118
112126
7.5
841.50
31266
13377
109496
125504
8.0
842.00
32265
15882.75
125378.25
141386
10.0
844.00
36405
68670
194048.25
210056
12.0
846.00
40772
77177
271225.25
287233
14.0
848.00
45364
86136
357361.25
373369.25
15.0
849.00
47745
46554.5
403915.75
419923.75
Stage at Permanent Pool = 7
Elevation = 841.00
Forebay Volume = 16,008.00
Main Pool Volume = 96,118.25
lForebay volume shall be 15-20% of Main Pool Volume : 16.65% Forebay Size OK
601 N. Trade Street, Suite 200 PHONE: [phone]
Stimmel Associates, P.A. Winston-Salem, NC 27101 FAX: [phone]

Project: West Edge
Project No.: 19-057CD
Designed By: BMH
Checked By: JNT
Sheet: 3 of 4
Date: 11.16.2021
Revised:
I WATER QUALITY POND DESIGN I
depth when shelf is submerged:
Depth (Davg) = (VPP - Vshelf)/Abottomofshelf
D,g = Average depth in feet
VPP = Total volume of permanent pool (CF)
Vshelf = Volume over shelf only (CF)
Abottomofshelf = Area of wet pond at the bottom of the shelf (SF)
shelf = 0.5 X Depthmaxovershelf X Perlmete rpermpool X Wldthsubmergedshelf
Depthmaxovershelf = Depth of water at the deep side of the shelf (FT)
Pe ri mete rpermanentpool = Perimeter of permanent pool at bottom of shelf (FT)
Widthsubmergedshelf= Width from deep side of shelf to dry side (FT)
Depthmaxovershelf =
Pe ri mete rpermanentpool =
Wldthsubmergedshelf =
Vshelf =
Stage at Bottom of Shelf =
Elevation =
Abottomofshelf =
VPP =
D,,,g =
0.50 FT
672.00 FT
5.00 FT
840 Cubic Feet
6.50
840.50
18,702.00
96,118.25 Cubic Feet
5.09 FT
Table 1: Piedmont and Mountain SA/DA Table (Adapted from Driscoll, 1986
Percent
Impervious
Permanent Pool Average Depth (ft)
3.0
4.0
5.0
6.0
7.0
8.0
10%
0.51
0.43
0.37
0.30
0.27
0.25
20%
0.84
0.69
0.61
0.51
0.44
0.40
30%
1.17
0.94
0.84
0.72
0.61
0.56
40%
1.51
1.24
1.09
0.91
0.78
0.71
50%
1.79
1.51
1.31
1.13
0.95
0.87
60%
2.09
1.77
1.49
1.31
1.12
1.03
70%
2.51
2.09
1.80
1.56
1.34
1.17
80%
2.92
2.41
2.07
1.82
1.62
1.40
90%
3.25
2.64
2.31
2.04
1.84
1.59
100%
3.55
2.79
2.52
2.34
2.04
1.75
68.8%
2.46
2.05
1.76
1.53
1.31
1.15
Required SA/DA ratio =
Required surface area =
Provided surface area =
1.74
19,176.20 SF
22,243.00 SF Provided Surface Area OK
16.0% Larger than required surface area
601 N. Trade Street, Suite 200 PHONE: [phone]
Stimmel Associates, P.A. Winston-Salem, NC 27101 FAX: [phone]

Project: West Edge
Project No.: 19-057CD
Designed By: BMH
Checked By: JNT
Sheet: 4 of 4
Date: 11.16.2021 I
Revised:
I WATER QUALITY POND DESIGN I
DETERMINE DESIGN VOLUME STORAGE ELEVATION & DESIGN ORIFICE DIAMETER
Design Volume Storage Elevation
DV =
61,438 Cubic Feet
Permanent Pool Elevation =
841.00
Volume =
112,126 Cubic Feet
Contour Above Permanent Pool =
842.00
Volume =
141,386 Cubic Feet
Head Difference =
1.00
0 =
29,260 Cubic Feet
Min. DV Elevation =
843.10
Design Orifice Diameter
Orifice Equation: Q = Cd x A x (2gH)0.5
Cd = Coefficient of Discharge
A = Area of Orifice Opening, Based on Diameter of Orifice
g = gravity
H = Driving Head, Use H/3 for Drawdown Calculations
Q = Orifice Discharge
Cd = 0.6
Diameter of Orifice = 3.00
in
A = 0.04909
SF
g = 32.2
H = 2.10
FT
H/3 = 0.70
FT
Q = 0.19774
CFS
Determine Drawdown Time
Drawdown Time = DV/Q
Target Drawdown Time = 2 - 5 Days
DV= 61,438
Cubic Feet
Drawdown Time = 86.31
Hrs
3.60
Days
601 N. Trade Street, Suite 200 PHONE: [phone]
Stimmel Associates, P.A. Winston-Salem, NC 27101 FAX: [phone]

Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Pond No. 1 - WetPond
Pond Data
Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 834.00 ft
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sgft) Incr. Storage (cult) Total storage (cult)
0.00
834.00
8,582
0
0
2.00
836.00
12,421
20,883
20,883
4.00
838.00
16,574
28,892
49,775
6.00
840.00
21,626
38,084
87,860
7.00
841.00
28,035
24,759
112,619
7.50
841.50
31,266
14,816
127,435
8.00
842.00
32,265
15,881
143,316
10.00
844.00
36,405
68,622
211,937
12.00
846.00
40,772
77,128
289,065
14.00
848.00
45,364
86,087
375,152
15.00
849.00
47,745
46,545
421,696
Monday, 03 / 14 / 2022
Culvert / Orifice Structures
Weir Structures
[A]
[B]
[C]
[PrfRsr]
[A]
[B]
[C]
[D]
Rise (in)
= 30.00
3.00
6.00
0.00
Crest Len (ft)
= 24.00
20.00
Inactive
0.00
Span (in)
= 30.00
3.00
6.00
0.00
Crest El. (ft)
= 846.25
847.00
0.00
0.00
No. Barrels
= 1
1
1
0
Weir Coeff.
= 3.33
2.60
3.33
3.33
Invert El. (ft)
= 833.50
841.00
844.75
0.00
Weir Type
= 1
Broad
Broad
---
Length (ft)
= 122.00
0.00
0.00
0.00
Multi -Stage
= Yes
No
No
No
Slope (%)
= 3.04
0.00
0.00
n/a
N-Value
= .013
.013
.013
n/a
Orifice Coeff.
= 0.60
0.60
0.60
0.60
Exfil.(in/hr)
= 0.000 (by
Contour)
Multi -Stage
= n/a
Yes
Yes
No
TW Elev. (ft)
= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage /
Storage / Discharge Table
Stage
Storage
Elevation
Clv A
Clv B
Clv C
PrfRsr
Wr A
Wr B
Wr C
Wr D
Exfil
User
Total
ft
cuft
ft
cfs
cfs
cfs
cfs
cfs
cfs
cfs
cfs
cfs
cfs
cfs
0.00
0
834.00
0.00
0.00
0.00
---
0.00
0.00
---
---
---
---
0.000
2.00
20,883
836.00
1.76 is
0.00
0.00
---
0.00
0.00
---
---
---
---
0.000
4.00
49,775
838.00
1.76 is
0.00
0.00
---
0.00
0.00
---
---
---
---
0.000
6.00
87,860
840.00
1.76 is
0.00
0.00
---
0.00
0.00
---
---
---
---
0.000
7.00
112,619
841.00
1.76 is
0.00
0.00
---
0.00
0.00
---
---
---
---
0.000
7.50
127,435
841.50
1.76 is
0.14 is
0.00
---
0.00
0.00
---
---
---
---
0.145
8.00
143,316
842.00
1.76 is
0.22 is
0.00
---
0.00
0.00
---
---
---
---
0.221
10.00
211,937
844.00
1.76 is
0.40 is
0.00
---
0.00
0.00
---
---
---
---
0.401
12.00
289,065
846.00
1.76 is
0.52 is
0.95 is
---
0.00
0.00
---
---
---
---
1.467
14.00
375,152
848.00
85.51 is
0.09 is
0.38 is
---
85.03 s
52.00
---
---
---
---
137.50
15.00
421,696
849.00
89.06 is
0.05 is
0.20 is
---
88.74 s
147.08
---
---
---
---
236.08

Project:
West Edge
Project No.:
19-057CD
Sheet:
1
Designed By:
BMH
Date:
3/17/2022
Checked By:
JNT
Structure Location / Identifier:
Wet Pond
RECTANGULAR PRECAST CONCRETE STRUCTURE
FLOATATION CALCULATIONS
UNIT WEIGHT OF WATER =
62.4 PCF
UNIT WEIGHT OF CONCRETE (In Air) =
150.0 PCF
ANTI-BOUYANCY FACTOR OF SAFETY =
1.25
UNIT WEIGHT OF PIPE MATERIAL =
389 # / LF
30" class IV
RCP
RECTANGULAR STRUCTURE
OUTSIDE OUTSIDE WALL
WALL BASE
LEN FT WID FT THK IN
HT FT THK IN
WALLS: 7.00 7.00 6.00
13.92
BASE: 0.00 0.00
0.00
DISPLACED VOLUME / WEIGHT ADDS: (Collar)
HT (FT) WID (FT) THK (IN)
#
DISPL.
BOUYANT
ADD 1: 5 7 12
1
VOLUME
WEIGHT
FORCE
ADD 2: 0 0 0
0
(CF)
(LBS)
(LBS)
WALLS
682.08
27,144
42,562
WEIGHT DEDUCTS:
BASE
0.00
0
-
CORES: DIA (IN) THK (IN) #
STRUCTURE:
682.08
27,144
42,562
CORE 1: 3.58 18 1
CORE 2: 6 6 2
BARREL
82.13
4,279
5,125
CORE 3: 0 0 0
COLLAR 1
35.00
5250
2,184
NOTCH: WID (IN) HT (IN) #
COLLAR 2
0.00
0
0
NOTCH 1 0 0 0
NOTCH 1
-N/A-
0
-N/A-
NOTCH 2 0 0 0
NOTCH 2
-N/A-
0
-N/A-
CORE 1
-N/A-
-16
-N/A-
EXPOSED BARREL
CORE 2
-N/A-
-29
-N/A-
LEN (FT) DIA (IN)
CORE 3
-N/A-
0
-N/A-
11.00 37.00
INSTALLED TOTALS
799.21
36,628
49,871
BOUYANT FORCE = 49,871
LBS ACTING UPWARD
STRUCTURE WEIGHT = 36,628
LBS ACTING DOWNWARD
NET FORCE = 13,243
LBS ACTING UPWARD
BALLAST REQUIREMENTS: 25,711
LBS BALLAST REQUIRED FOR FACTOR OF SAFETY OF 1.25
293.50
CUBIC FEET OF CONCRETE
FACTOR
LENGTH
WIDTH THICKNESS
VOLUME
WEIGHT
OF
ACTUAL BALLAST: (FT)
(FT) (FT)
(CF)
(LBS)
SAFETY
Ballast Pad: 10
10 2.5
250.0
21,900
1.17
Invert Pour: 6
6 0.5
18.0
2,700
24,600
1.23
BASE SECTION WEIGHT:
BASE HEIGHT (FT) =
0
GROSS BASE WEIGHT (LBS) =
0
BASE SECTION BLOCK OUTS:
DIA # OF
WEIGHT
(SHIPPING CONDITION)
(IN) BLOCK OUTS
(LBS)
1
0
NET BASE
SECTION
2
0
SHIPPING WEIGHT:
3
0
0 LBS.

sapa PROJECT: West Edge
PROD. NO.: 19-057CD SHEET: of
DESIGNED BY: BMH DATE: 03/17/22
CHECKED BY: .JNT DATE:
Stimmel Associates, PA LOCATION / DESCRIPTION:
Pond Primary Spillway Discharge Channel at Barrel Outlet
OPEN CHANNEL FLOW CALCULATIONS
DESIGN FLOW RATE 'Q1oo' = 85.50 CFS
CHANNEL GEOMETRY:
CHANNEL SLOPE =
0.50
%
LEFT SIDE SLOPE =
3.00
:1
RIGHT SIDE SLOPE =
3.00
:1
BOTTOM WIDTH =
10.00
FT. Condition At Barrell Outlet
JJI:IIIkiI;IeZel:FilkiIki1N11s1•]I;IQ11111[•P►E
MANNING'S'n' =
FLOW DEPTH =
FT
FLOW RATE 'Q' =
#DIV/0!
CFS
FLOW AREA =
0.00
SF
WETTED PERIMETER =
10.00
LF
HYDRAULIC RADIUS =
0.00
FT
FLOW VELOCITY =
#DIV/0!
FT/SEC
VELOCITY * HYD RAD =
#DIV/0!
SF/SEC
MAX SHEAR STRESS =
0.00
LBS/SF
TOP WIDTH OF FLOW =
10.00
FT
LINED CHANNEL CONDITION:
MANNING'S'n' =
FLOW DEPTH =
FLOW RATE 'Q' =
FLOW AREA =
WETTED PERIMETER =
HYDRAULIC RADIUS =
FLOW VELOCITY =
VELOCITY * HYD RAD =
MAX SHEAR STRESS =
TOP WIDTH OF FLOW =
0.071 10" Rip -Rap @ 24" Thickness (Class 1)
2.41 FT
85.50 CFS
41.48 SF
25.23 LF
1.64 FT
2.06 FT/SEC
3.39 SF/SEC
0.75 LBS/SF
24.45 FT
COMMENTS:
Liner is stable. Max shear stress for Class 2 rip rap is 3.8 psf.
601 N. Trade Street, Suite 200 PHONE: [phone]
Stimmel Associates, P.A. Winston-Salem, NC 27101 FAX: [phone]

sapa PROJECT: West Edge
PROD. NO.: 19-057CD SHEET: of
DESIGNED BY: BMH DATE: 03/17/22
CHECKED BY: .JNT DATE:
Stimmel Associates, PA LOCATION / DESCRIPTION:
Pond Primary Spillway Discharge Channel at end of Channel
OPEN CHANNEL FLOW CALCULATIONS
DESIGN FLOW RATE 'Q1oo' = 85.50 CFS
CHANNEL GEOMETRY:
CHANNEL SLOPE =
0.50
%
LEFT SIDE SLOPE =
3.00
:1
RIGHT SIDE SLOPE =
3.00
:1
BOTTOM WIDTH =
20.00
FT. Condition at Full Width Channel
JJI:IIIkiI;IeZel:FilkiIki1N11s1•]I;IQ11111[•P►E
MANNING'S'n' =
FLOW DEPTH =
FT
FLOW RATE 'Q' =
#DIV/0!
CFS
FLOW AREA =
0.00
SF
WETTED PERIMETER =
20.00
LF
HYDRAULIC RADIUS =
0.00
FT
FLOW VELOCITY =
#DIV/0!
FT/SEC
VELOCITY * HYD RAD =
#DIV/0!
SF/SEC
MAX SHEAR STRESS =
0.00
LBS/SF
TOP WIDTH OF FLOW =
20.00
FT
LINED CHANNEL CONDITION:
MANNING'S'n' =
FLOW DEPTH =
FLOW RATE 'Q' =
FLOW AREA =
WETTED PERIMETER =
HYDRAULIC RADIUS =
FLOW VELOCITY =
VELOCITY * HYD RAD =
MAX SHEAR STRESS =
TOP WIDTH OF FLOW =
0.070 10" Rip -Rap @ 24" Thickness (Class 1)
1.77 FT
85.50 CFS
44.76 SF
31.19 LF
1.44 FT
1.91 FT/SEC
2.74 SF/SEC
0.55 LBS/SF
30.61 FT
COMMENTS:
Liner is stable. Max shear stress for Class 1 rip rap is 3.8 psf.
601 N. Trade Street, Suite 200 PHONE: [phone]
Stimmel Associates, P.A. Winston-Salem, NC 27101 FAX: [phone]

t.'i stimmel 601 SN. TON-S LEM,NC2710E200 DATE: 2-2-2022 JOB#: 19-057CD
WINSTON-SALEM, NC 27101
www.stimmelpa.com 336.723.1067 e West Edge
g
LANDSCAPE ARCHITECTURE CIVIL ENGINEERING LAND PLANNING
OUTLET PROTECTION BMH
CALCULATION SHEET BY:
Wet Pond
Do=30 in
La=16 ft
WI=3DD=8 ft
W2=Do+La=24 ft
20
10
n
Outlet IW = Do + La
PIPe i
diameter (Do)
La —•1
ry T ilwater_< 0.5Do
60
50 '
Discharge
L.J 0
1000
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).

HYDROGRAPH CALCULATIONS

Watershed Model Schematic Hydraflow Hydrographs Extension forAutodesk® Civil 3D® by Autodesk, Inc. v2020
1
2*
3
UD
6
4
ED
8
9
CD
10
Legend
Hvd. Origin Description
1 SCS Runoff West -Pre
2 SCS Runoff South -Pre
3 SCS Runoff North -Pre
4 Combine Total -Pre
6 SCS Runoff Pond -Post
7 Reservoir Post Thru SCM
8 SCS Runoff West-ByPass
9 SCS Runoff South-ByPass
10 Combine TOTAL -POST
Project: WetPond_1.gpw
Sunday, 08 / 29 / 2021

Hydrograph Return Period Recap
Hy raflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Hyd.
Hydrograph
Inflow
Peak Outflow (cfs)
Hydrograph
No.
type
hyd(s)
Description
(origin)
1-yr
2-yr
3-yr
5-yr
10-yr
25-yr
50-yr
100-yr
1
SCS Runoff
------
0.682
2.694
-------
-------
12.62
20.63
27.66
35.45
West -Pre
2
SCS Runoff
------
0.839
3.505
-------
-------
16.24
26.28
35.03
44.69
South -Pre
3
SCS Runoff
------
1.165
2.145
-------
-------
5.295
7.449
9.250
11.18
North -Pre
4
Combine
1, 2, 3
1.719
6.601
-------
-------
30.22
49.10
65.57
83.80
Total -Pre
6
SCS Runoff
------
70.75
93.43
-------
-------
154.36
191.29
220.60
250.99
Pond -Post
7
Reservoir
6
0.447
1.079
-------
-------
10.83
49.02
95.44
128.33
Post Thru SCM
8
SCS Runoff
------
0.496
1.113
-------
-------
3.242
4.752
6.034
7.424
West-ByPass
9
SCS Runoff
------
0.638
1.431
-------
-------
4.168
6.110
7.757
9.545
South-ByPass
10
Combine
7, 8, 9
1.442
2.899
-------
-------
11.52
52.39
102.51
138.71
TOTAL -POST
Proj. file: WetPond_1.gpw
Monday, 03 / 14 / 2022

Hydrograph Summary Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
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
0.682
1
736
8,092
------
------
------
West -Pre
2
SCS Runoff
0.839
1
728
8,671
------
------
------
South -Pre
3
SCS Runoff
1.165
1
719
2,837
------
------
------
North -Pre
4
Combine
1.719
1
730
19,600
1, 2, 3
------
------
Total -Pre
6
SCS Runoff
70.75
1
718
143,694
------
------
------
Pond -Post
7
Reservoir
0.447
1
1443
54,470
6
844.66
241,983
Post Thru SCM
8
SCS Runoff
0.496
1
720
1,508
------
------
------
West-ByPass
9
SCS Runoff
0.638
1
720
1,939
------
------
------
South-ByPass
10
Combine
1.442
1
720
57,917
7, 8, 9
------
------
TOTAL -POST
WetPond_1.gpw
Return Period: 1 Year
Monday, 03 / 14 / 2022

Hydrograph Summary Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
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
2.694
1
729
16,404
------
------
------
West -Pre
2
SCS Runoff
3.505
1
725
17,579
------
------
------
South -Pre
3
SCS Runoff
2.145
1
718
4,681
------
------
------
North -Pre
4
Combine
6.601
1
726
38,664
1, 2, 3
------
------
Total -Pre
6
SCS Runoff
93.43
1
718
191,965
------
------
------
Pond -Post
7
Reservoir
1.079
1
1186
86,074
6
845.39
270,222
Post Thru SCM
8
SCS Runoff
1.113
1
719
2,675
------
------
------
West-ByPass
9
SCS Runoff
1.431
1
719
3,439
------
------
------
South-ByPass
10
Combine
2.899
1
719
92,187
7, 8, 9
------
------
TOTAL -POST
WetPond_1.gpw
Return Period: 2 Year
Monday, 03 / 14 / 2022

Hydrograph Summary Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
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
12.62
1
727
47,589
------
------
------
West -Pre
2
SCS Runoff
16.24
1
723
50,999
------
------
------
South -Pre
3
SCS Runoff
5.295
1
718
10,719
------
------
------
North -Pre
4
Combine
30.22
1
723
109,307
1, 2, 3
------
------
Total -Pre
6
SCS Runoff
154.36
1
717
324,694
------
------
------
Pond -Post
7
Reservoir
10.83
1
753
208,393
6
846.48
314,136
Post Thru SCM
8
SCS Runoff
3.242
1
718
6,697
------
------
------
West-ByPass
9
SCS Runoff
4.168
1
718
8,611
------
------
------
South-ByPass
10
Combine
11.52
1
752
223,700
7, 8, 9
------
------
TOTAL -POST
WetPond_1.gpw
Return Period: 10 Year
Monday, 03 / 14 / 2022

Hydrograph Summary Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
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
20.63
1
726
71,393
------
------
------
West -Pre
2
SCS Runoff
26.28
1
723
76,509
------
------
------
South -Pre
3
SCS Runoff
7.449
1
718
14,967
------
------
------
North -Pre
4
Combine
49.10
1
723
162,869
1, 2, 3
------
------
Total -Pre
6
SCS Runoff
191.29
1
717
407,558
------
------
------
Pond -Post
7
Reservoir
49.02
1
725
290,808
6
846.95
334,576
Post Thru SCM
8
SCS Runoff
4.752
1
718
9,620
------
------
------
West-ByPass
9
SCS Runoff
6.110
1
718
12,369
------
------
------
South-ByPass
10
Combine
52.39
1
725
312,797
7, 8, 9
------
------
TOTAL -POST
WetPond_1.gpw
Return Period: 25 Year
Monday, 03 / 14 / 2022

Hydrograph Summary Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
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
27.66
1
726
92,344
------
------
------
West -Pre
2
SCS Runoff
35.03
1
723
98,960
------
------
------
South -Pre
3
SCS Runoff
9.250
1
718
18,575
------
------
------
North -Pre
4
Combine
65.57
1
723
209,880
1, 2, 3
------
------
Total -Pre
6
SCS Runoff
220.60
1
717
474,361
------
------
------
Pond -Post
7
Reservoir
95.44
1
723
357,510
6
847.40
353,946
Post Thru SCM
8
SCS Runoff
6.034
1
718
12,139
------
------
------
West-ByPass
9
SCS Runoff
7.757
1
718
15,608
------
------
------
South-ByPass
10
Combine
102.51
1
723
385,257
7, 8, 9
------
------
TOTAL -POST
WetPond_1.gpw
Return Period: 50 Year
Monday, 03 / 14 / 2022

Hydrograph Summary Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
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
35.45
1
726
115,699
------
------
------
West -Pre
2
SCS Runoff
44.69
1
723
123,989
------
------
------
South -Pre
3
SCS Runoff
11.18
1
718
22,499
------
------
------
North -Pre
4
Combine
83.80
1
723
262,187
1, 2, 3
------
------
Total -Pre
6
SCS Runoff
250.99
1
717
544,459
------
------
------
Pond -Post
7
Reservoir
128.33
1
723
427,515
6
847.88
374,712
Post Thru SCM
8
SCS Runoff
7.424
1
718
14,907
------
------
------
West-ByPass
9
SCS Runoff
9.545
1
718
19,166
------
------
------
South-ByPass
10
Combine
138.71
1
722
461,589
7, 8, 9
------
------
TOTAL -POST
WetPond_1.gpw
Return Period: 100 Year
Monday, 03 / 14 / 2022

-YR / 24 HOUR HYDROGRAPHS

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 1
West -Pre
Hydrograph type
= SCS Runoff
Peak discharge
= 0.682 cfs
Storm frequency
= 1 yrs
Time to peak
= 736 min
Time interval
= 1 min
Hyd. volume
= 8,092 cuft
Drainage area
= 12.840 ac
Curve number
= 56
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= TR55
Time of conc. (Tc)
= 19.90 min
Total precip.
= 2.83 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
West -Pre
Hyd. No. 1 -- 1 Year
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
1 1 1 .I I I I I I 1. 1 0.00
120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 1 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 2
South -Pre
Hydrograph type
= SCS Runoff
Peak discharge
= 0.839 cfs
Storm frequency
= 1 yrs
Time to peak
= 728 min
Time interval
= 1 min
Hyd. volume
= 8,671 cuft
Drainage area
= 13.760 ac
Curve number
= 56
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= TR55
Time of conc. (Tc)
= 14.70 min
Total precip.
= 2.83 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
South -Pre
Hyd. No. 2 -- 1 Year
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
1 1 1 .I I I I I I I. 1 0.00
120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 2 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Hyd. No. 3
North -Pre
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Time interval
= 1 min
Drainage area
= 1.760 ac
Basin Slope
= 0.0 %
Tc method
= User
Total precip.
= 2.83 in
Storm duration
= 24 hrs
Q (cfs)
2.00
1.00
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
North -Pre
Hyd. No. 3 -- 1 Year
120 240 360 480 600 720 840 960
Hyd No. 3
Monday, 03 / 14 / 2022
= 1.165 cfs
= 719 min
= 2,837 cuft
= 65
= 0 ft
= 6.00 min
= Type II
= 484
Q (cfs)
2.00
1.00
0.00
1080 1200 1320 1440 1560
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 4
Total -Pre
Hydrograph type
= Combine
Peak discharge
= 1.719 cfs
Storm frequency
= 1 yrs
Time to peak
= 730 min
Time interval
= 1 min
Hyd. volume
= 19,600 cuft
Inflow hyds.
= 1, 2, 3
Contrib. drain. area
= 28.360 ac
Q (cfs)
2.00
1.00
Total -Pre
Hyd. No. 4 -- 1 Year
120 240 360 480 600 720 840 960
Hyd No. 4 Hyd No. 1 Hyd No. 2
Q (cfs)
2.00
1.00
0.00
1080 1200 1320 1440 1560
Time (min)
Hyd No. 3

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Hyd. No. 6
Pond -Post
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Time interval
= 1 min
Drainage area
= 25.290 ac
Basin Slope
= 0.0 %
Tc method
= TR55
Total precip.
= 2.83 in
Storm duration
= 24 hrs
Q (cfs)
80.00
70.00
50.00
40.00
30.00
10.00
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Pond -Post
Hyd. No. 6 -- 1 Year
Monday, 03 / 14 / 2022
= 70.75 cfs
= 718 min
= 143,694 cuft
= 86
= 0 ft
= 6.50 min
= Type II
= 484
Q (cfs)
80.00
70.00
50.00
40.00
30.00
20.00
10.00
0.00 1 1 1 1 1 1 1 1 10.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440
— Hyd No. 6 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 7
Post Thru SCM
Hydrograph type
= Reservoir
Peak discharge
= 0.447 cfs
Storm frequency
= 1 yrs
Time to peak
= 1443 min
Time interval
= 1 min
Hyd. volume
= 54,470 cuft
Inflow hyd. No.
= 6 - Pond -Post
Max. Elevation
= 844.66 ft
Reservoir name
= WetPond
Max. Storage
= 237,379 cuft
Storage Indication method used. Wet pond routing start elevation = 841.00 ft
Q (cfs)
80.00
70.00
•1 11
50.00
40.00
30.00
r1 11
10.00
Post Thru SCM
Hyd. No. 7 -- 1 Year
Q (cfs)
80.00
70.00
•1 11
50.00
40.00
30.00
20.00
10.00
0.00 0.00
0 300 600 900 1200 1500 1800 2100 2400 2700 3000
Time (min)
— Hyd No. 7 Hyd No. 6 Total storage used = 237,379 cuft

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 8
West-ByPass
Hydrograph type
= SCS Runoff
Peak discharge
= 0.496 cfs
Storm frequency
= 1 yrs
Time to peak
= 720 min
Time interval
= 1 min
Hyd. volume
= 1,508 cuft
Drainage area
= 1.330 ac
Curve number
= 61
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 6.00 min
Total precip.
= 2.83 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
West-ByPass
Hyd. No. 8 -- 1 Year
Q (cfs)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 8 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 9
South-ByPass
Hydrograph type
= SCS Runoff
Peak discharge
= 0.638 cfs
Storm frequency
= 1 yrs
Time to peak
= 720 min
Time interval
= 1 min
Hyd. volume
= 1,939 cuft
Drainage area
= 1.710 ac
Curve number
= 61
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 6.00 min
Total precip.
= 2.83 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
South-ByPass
Hyd. No. 9 -- 1 Year
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
1 1 1 11 I I I I 1 i. 1 0.00
120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 9 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020.4
Monday, 03 / 14 / 2022
Hyd. No. 10
TOTAL -POST
Hydrograph type
= Combine
Peak discharge
= 1.442 cfs
Storm frequency
= 1 yrs
Time to peak
= 720 min
Time interval
= 1 min
Hyd. volume
= 57,917 cuft
Inflow hyds.
= 7, 8, 9
Contrib. drain. area
= 3.040 ac
Q (Cfs)
2.00
1.00
TOTAL -POST
Hyd. No. 10 -- 1 Year
Q (cfs)
2.00
1.00
0.00
300 600 900 1200 1500 1800 2100 2400 2700 3000
Time (min)
Hyd No. 10 Hyd No. 7 Hyd No. 8 Hyd No. 9

WATERSHED CHARACTERISTICS

Project : West Edge Sheet : 1
Project No.: 19-057CD Date : 8/29/2021
Designed by: BMH
Checked by: JNT
SCS RUNOFF CURVE NUMBERS
West- Existing Conditions
BASIN LAND USE
SOIL
NAME
HYDROL.
GROUP
AREA
(SF.)
AREA
(AC.)
AREA
(%)
CURVE NO
(CN)
CN x
AREA
Undisturbed Area - Wooded
Ci/Na
B
433,558
9.95
77.51 %
55
547
Open Space - Good
Ci/Na
B
124,351
2.85
22.23%
61
174
Disturbed Area - Impervious
Ci/Na
B
1,455
0.03
0.26%
98
3
TOTALS 559,364 12.84 100.0% 725
WEIGHTED CN (PRE -DEVELOPED) = 56
South- Existing Conditions
BASIN LAND USE
SOIL
NAME
HYDROL.
GROUP
AREA
(SF.)
AREA
(AC.)
AREA
(%)
CURVE NO
(CN)
CN x
AREA
Undisturbed Area - Wooded
Ci/Na
B
555,547
12.75
92.66%
55
701
Open Space - Good
Ci/Na
B
32,286
0.74
5.39%
61
45
Disturbed Area - Impervious
Ci/Na
B
11,707
0.27
1.95%
98
26
TOTALS 599,540 13.76 100.0% 773
WEIGHTED CN (PRE -DEVELOPED) = 56
North - Existing Conditions
BASIN LAND USE
SOIL
NAME
HYDROL.
GROUP
AREA
(SF.)
AREA
(AC.)
AREA
(%)
CURVE NO
(CN)
CN x
AREA
Undisturbed Area - Wooded
Ci/Na
B
29,600
0.68
38.57%
55
37
Open Space - Good
Ci/Na
B
33,684
0.77
43.90%
61
47
Disturbed Area - Impervious
Ci/Na
B
13,450
0.31
17.53%
98
30
TOTALS 76,734 1.76 100.0% 115
WEIGHTED CN (PRE -DEVELOPED) = 65

Project: West Edge
Project No.: 19-057CD
Designed by: BMH
Checked by: JNT
Sheet:
Date :
1
8/29/2021
SCS RUNOFF CURVE NUMBERS
West- SCM
Drainage Area
BASIN LAND USE
SOIL
NAME
HYDROL.
GROUP
AREA
(SF.)
AREA
(AC.)
AREA
(%)
CURVE NO
(CN)
CN x
AREA
Undistrubed Area - Wooded
Ci/Na
B
0
0.00
0.00%
55
0
Disturbed Area - Open Space
Ci/Na
B
343,821
7.89
31.21 %
61
481
Disturbed Area - Impervious
757,944
17.40
68.79%
98
1705
TOTALS 1,101,765 25.29 100.0%
2187
WEIGHTED CN (POST -DEVELOPED) =
86
West- Bypass Area
BASIN LAND USE
SOIL
NAME
HYDROL.
GROUP
AREA
(SF.)
AREA
(AC.)
AREA
(%)
CURVE NO
(CN)
CN x
AREA
Disturbed Area - Open Space
Ci/Na
B
57,728
1.33
100.00%
61
81
Undisturbed Area - Wooded
Ci/Na
B
0
0.00
0.00%
55
0
TOTALS 57,728 1.33 100.0% 81
WEIGHTED CN (POST -DEVELOPED) = 61
South- Bypass Area
BASIN LAND USE
SOIL
NAME
HYDROL.
GROUP
AREA
(SF.)
AREA
(AC.)
AREA
(%)
CURVE NO
(CN)
CN x
AREA
Disturbed Area - Open Space
Ci/Na
B
76,381
1.75
100.00%
61
107
Undisturbed Area - Wooded
Ci/Na
B
0
0.00
0.00%
55
0
TOTALS 76,381 1.75 100.0% 107
WEIGHTED CN (POST -DEVELOPED) = 61

Chapter 2 Estimating Runoff Technical Release 55
Urban Hydrology for Small Watersheds
Table 2-2a Runoff curve numbers for urban areas I/
Curve numbers for
----------- Cover description ------------------
-----hydrologic
soil group ------
Average percent
Cover type and hydrologic condition impervious area v
A
B
C
D
Fully developed urban areas (vegetation established)
Open space (lawns, parks, golf courses, cemeteries, etc.) a/:
Poor condition (grass cover < 50%)..........................................
68
79
86
89
Fair condition (grass cover 50% to 75%)..................................
Good condition (grass cover > 75%).........................................
49
39
61
79
74
84
80
Impervious areas:
Paved parking lots, roofs, driveways, etc.
(excluding right-of-way).............................................................
98
98
98
98
Streets and roads:
Paved; curbs and storm sewers (excluding
right-of-way)................................................................................
98
98
98
98
Paved; open ditches (including right-of-way) ..........................
83
89
92
93
Gravel (including right -of -way) .................................................
76
85
89
91
Dirt (including right -of -way) ......................................................
72
82
87
89
Western desert urban areas:
Natural desert landscaping (pervious areas only) / .....................
63
77
85
88
Artificial desert landscaping (impervious weed barrier,
desert shrub with 1- to 2-inch sand or gravel mulch
and basin borders)......................................................................
96
96
96
96
Urban districts:
Commercial and business.................................................................
85
89
92
94
95
Industrial.............................................................................................
72
81
88
91
93
Residential districts by average lot size:
1/8 acre or less (town houses)..........................................................
65
77
85
90
92
1/4 acre................................................................................................
38
61
75
83
87
1/3 acre................................................................................................
30
57
72
81
86
1/2 acre................................................................................................
25
54
70
80
85
1 acre...................................................................................................
20
51
68
79
84
2 acres..................................................................................................
12
46
65
77
82
Developing urban areas
Newly graded areas
(pervious areas only, no vegetation) 5/ ................................................................ 77 86 91 94
Idle lands (CN's are determined using cover types
similar to those in table 2-2c).
1 Average runoff condition, and Ia = 0.2S.
2 The average percent impervious area shown was used to develop the composite CN's. Other assumptions are as follows: impervious areas are
directly connected to the drainage system, impervious areas have a CN of 98, and pervious areas are considered equivalent to open space in
good hydrologic condition. CN's for other combinations of conditions may be computed using figure 2-3 or 2-4.
3 CN's shown are equivalent to those of pasture. Composite CN's may be computed for other combinations of open space
cover type.
4 Composite CN's for natural desert landscaping should be computed using figures 2-3 or 2-4 based on the impervious area percentage
(CN = 98) and the pervious area CN. The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition.
5 Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 24
based on the degree of development (impervious area percentage) and the CN's for the newly graded pervious areas.
(210-VI-TR-55, Second Ed., June 1986) 2-5

Chapter 2 Estimating Runoff Technical Release 55
Urban Hydrology for Small Watersheds
Table 2-2c Runoff curve numbers for other agricultural lands I/
Curve numbers for
----------------------- Cover description ----------------------
-------
hydrologic soil group -------
Hydrologic
Cover type
condition
A
B
C
D
Pasture, grassland, or range —continuous
Poor
68
79
86
89
forage for grazing.,
Fair
49
69
79
84
Good
39
61
74
80
Meadow —continuous grass, protected from
—
30
58
71
78
grazing and generally mowed for hay.
Brush —brush -weed -grass mixture with brush
Poor
48
67
77
83
the major element. 3/
Fair
35
56
70
77
Good
30
48
65
73
Woods —grass combination (orchard
Poor
57
73
82
86
or tree farm).
Fair
43
65
76
82
Good
32
58
72
79
Woods. s6J
Poor
45
66
77
83
Fair
36
73
79
Good
30 V
55
70
77
Farmsteads —buildings, lanes, driveways,
—
59
74
82
86
and surrounding lots.
1 Average runoff condition, and Ia = 0.25.
2 Poor. <50%) ground cover or heavily grazed with no mulch.
Fair: 50 to 75% ground cover and not heavily grazed.
Good: > 75% ground cover and lightly or only occasionally grazed.
3 Poor. <50%ground cover.
Fair: 50 to 75% ground cover.
Good: >759/oground cover.
4 Actual curve number is less than 30; use CN = 30 for runoff computations.
5 CN's shown were computed for areas with 50%woods and 50%grass (pasture) cover. Other combinations of conditions may be computed
from the CN's for woods and pasture.
6 Poor: Forest litter, small trees, and brush are destroyed by heavy grazing or regular burning.
Fair: Woods are grazed but not burned, and some forest litter covers the soil.
Good: Woods are protected from grazing, and litter and brush adequately cover the soil.
(210-VI-TR-55, Second Ed., June 1986) 2-7

TR55 Tc Worksheet
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020
Hyd. No. 1
West -Pre
Description
A
B
C
Totals
Sheet Flow
Manning's n-value
= 0.400
0.011
0.011
Flow length (ft)
= 123.0
0.0
0.0
Two-year 24-hr precip. (in)
= 3.42
0.00
0.00
Land slope (%)
= 5.40
0.00
0.00
Travel Time (min)
= 16.48 +
0.00 +
0.00 =
16.48
Shallow Concentrated Flow
Flow length (ft)
= 850.00
0.00
0.00
Watercourse slope (%)
= 6.60
0.00
0.00
Surface description
= Unpaved
Paved
Paved
Average velocity (ft/s)
=4.15
0.00
0.00
Travel Time (min)
= 3.42 +
0.00 +
0.00 =
3.42
Channel Flow
X sectional flow area (sqft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope (%)
= 0.00
0.00
0.00
Manning's n-value
= 0.015
0.015
0.015
Velocity (ft/s)
=0.00
0.00
0.00
Flow length (ft)
({0})0.0
0.0
0.0
Travel Time (min)
= 0.00 +
0.00 +
0.00 =
0.00
Total Travel Time, Tc..............................................................................
19.90 min

TR55 Tc Worksheet
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020
Hyd. No. 2
South -Pre
Description
A
B
C
Totals
Sheet Flow
Manning's n-value
= 0.240
0.011
0.011
Flow length (ft)
= 150.0
0.0
0.0
Two-year 24-hr precip. (in)
= 3.42
0.00
0.00
Land slope (%)
= 6.00
0.00
0.00
Travel Time (min)
= 12.30 +
0.00 +
0.00 =
12.30
Shallow Concentrated Flow
Flow length (ft)
= 601.00
0.00
0.00
Watercourse slope (%)
= 6.65
0.00
0.00
Surface description
= Unpaved
Paved
Paved
Average velocity (ft/s)
=4.16
0.00
0.00
Travel Time (min)
= 2.41 +
0.00 +
0.00 =
2.41
Channel Flow
X sectional flow area (sqft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope (%)
= 0.00
0.00
0.00
Manning's n-value
= 0.015
0.015
0.015
Velocity (ft/s)
=0.00
0.00
0.00
Flow length (ft)
({0})0.0
0.0
0.0
Travel Time (min)
= 0.00 +
0.00 +
0.00 =
0.00
Total Travel Time, Tc..............................................................................
14.70 min

TR55 Tc Worksheet
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020
Hyd. No. 6
Pond -Post
Description
A
B
C
Totals
Sheet Flow
Manning's n-value
= 0.410
0.011
0.011
Flow length (ft)
= 15.0
0.0
0.0
Two-year 24-hr precip. (in)
= 3.42
0.00
0.00
Land slope (%)
= 5.00
0.00
0.00
Travel Time (min)
= 3.22 +
0.00 +
0.00 =
3.22
Shallow Concentrated Flow
Flow length (ft)
= 74.00
0.00
0.00
Watercourse slope (%)
= 3.00
0.00
0.00
Surface description
= Paved
Paved
Paved
Average velocity (ft/s)
=3.52
0.00
0.00
Travel Time (min)
= 0.35 +
0.00 +
0.00 =
0.35
Channel Flow
X sectional flow area (sqft)
= 15.90
0.00
0.00
Wetted perimeter (ft)
= 14.00
0.00
0.00
Channel slope (%)
= 1.00
0.00
0.00
Manning's n-value
= 0.015
0.015
0.015
Velocity (ft/s)
=10.82
0.00
0.00
Flow length (ft)
({0})1900.0
0.0
0.0
Travel Time (min)
= 2.93 +
0.00 +
0.00 =
2.93
Total Travel Time, Tc..............................................................................
6.50 min