SW6210506_Design Calculations Pond 1_20210528

DESIGN REQUIREMIENTS:
A. Contain the I inch storm
Drainage Area, (DA) - 13.59 acres
Intensity, (1) - 0.13 inches/hr
Composite Runoff Coefficient, (C) 0.30
Maximum Release Rate, (Qj) => 0.53 efs
Drainage Area, (DA) - 13.59 acres
Intensity, (1) - 0.13 inches/hr
Composite Runoff Coefficient, (C) 0.60
Peak Release Rate, (Qj) - 1.06 efs
Contour
Contour
Iner.
Accum.
Stage
Elev.
Area
Storage
Storage (S)
(Z)
00
(sf)
(cf)
(cf)
00
In (S)
In (Z)
Z est
289.5
-
-
-
-
-
290.0
12,366
3,092
3,092
0.50
8.04
-0.69
0.46
290.5
13,060
6,357
9,448
1.00
.......................
9.15
................. ........
0.00
1.06
291.0
13,768
6,707
16,155
1.50
9.69
0.41
1.58
291.5
14,489
7,064
23,219
2.00
10.05
0.69
2.06
292.0
15,226
7,429
30,648
2.50
10.33
0.92
2.53
292.5
15,976
7,801
38,449
3.00
10.56
1.10
2.99
293.0
16,740
8,179
46,628
3.50
10.75
1.25
3.45
293.5
17,519
8,565
55,192
4.00
10.92
1.39
3.91
294.0
18,311
8,958
64,150
4.50
11.07
1.50
4.36
Regression Output:
b- 1.35 (X Variable Coeff)
Ks- 8,735 (e Y-iriter-pt )
Stage - Storage Equation is of the form: S - (Ks)(Z) b
printed: 5/20/2021 8 44 AM Page 1 of 3

Barrel
Number of Barrels —
Dia. of Barrel —
Area of Barrel, (Ab) —
Pipe Length, (L) —
Friction Coeff., (Kp) —
Inv. of Barrel —
Riser
Elev. of Riser Crest
Rectangul
Length Weir— 36 inches
Total Weir Length
Area of Riser —
Orifice in Riser
Dia. of Orifice —
Number of Orifices —
Area of Orifice, (Ab) —
Orifice Coefficient (Cd) —
Inv. of Orifice —
Length of weir —
Top of weir —
Weir Coefficient (Cw)—
Width of Spillway (Approx.) —
Weir Coefficient —
Crest Elevation —
Maximum Release Rate, (Qj) —
Release Rate, (Qj) —
Normal Water Surface Elev. —
1
36 inches
7.07 sf
50 feet
0.00616
289.50 feet
292.15 feet
Width Weir— 48 inches
14.00 feet
12.00 sq. ft.
2.75 inches
1
0.04 sf
0.60
289.50 feet
0.00 feet
292.15 feet
3.00
20 feet
3.3
293.00 feet
0.53 efs
0.31 efs
289.50 feet
Water Surface Elev. @ Outlet (Qj) — 292.09 feet
printed: 5/20/2021 8 44 AM
Page 2 of 3

Peak Inflow, (Qp) =>
Time to Peak Calculation: CN
Q*—
vol—
Time to Peak, (Tp)
(SCS TR-55)
1.06 efs
79 p— 2.96 in.
1.16 in. (depth of runoff)
57,191 ef (vol. of runoff)
646.9 minutes
S— 2.66 in.
printed: 5/20/2021 8 44 AM
Page 3 of 3

Cotswold
Pond 41
Antiflotation Calculation
Input Data
Safety Factor:
1.50
Top Width of Riser (ft)
3.00
Top Length of Riser (ft)
4.00
Thickness of Riser (ft)
0.50
Thickness of Bottom of Riser (ft)
0.50
Top of Riser (ft)
292.15
Invert of Riser (ft)
289.50
Volume of Riser (cf)
21.90
Unit Weight Of Concrete (lb/cf)
150.00
Unit Weight of Water (lb/cf)
62.40
Block Height (ft)
0.00
Block Width (ft)
0.00
Block Length (ft),
0.00
Output
Fw (Uplift Force, lb)
1984.32
Fc (Weight of Concrete,lb)
3285.00
Design Volume (cf),
21.90
Design Safety Factorl
Volume OK
1728-POND I Antiflotation.xls 5/20/2021

Cotswold Pond #1
Drawdown Time
Temporary storage volume —
Orifice #I diameter=
Area of orifice
Orifice #2 diameter
Area of orifice
Orifice Coefficient (Cd)
Orifice elevation --
Water elevation ---
Driving head (H) =
Discharge (Q) —
Drawdown time =
31,705 cf
2.75 in
1
0.0413 sf
0 in
0
0.0000 sf
0.60
289.50 ft
292.09 ft
0.86 ft
0.1846 cfs
171789 s
47.7 hr
2.0 days
1728-Drawdown.xlsx Printed 5/20/2021

Cotswold Pond Hl
Storm Water Control
SCS curve number
Hydraulic Soil Group: B
Area
SCS CN
Building (sf)
134,100
98
Driveways (sf)
14,136
98
Pavement (sf)
124,469
98
291,016
Pond (sf)
18,311
98
Open space (sf)
253,239
61
Offsite -open space (sf)
47,709
61
Offsite -impervious (sf)
0
98
Total (sf)
591964
79
Total (ac)
13.59
Rational Coefficient
Predevelopme
Postdevelopme
Area
C
Area
C
Impervious (sf)
0
0.95
Building (sf)
134,100
0.95
Open space (sf)
579,018
0.30
Driveways (sf)
14,136
0.95
Pavement (sf)
124,469
0.95
Pond (sf)
18,311
0.30
Open space (sf)
253,239
0.30
Offsite -open space (sf)
47,709
0.3
Offsite -impervious (sf)
0
0.95
Total (ac)
579018
0.30
Total (ac)
591964
0.60
Total (ac)
13.29
Total (ac)
13.59
1728-Runoff coefficient calcs.xls Printed 5/20/2021

Dsite
Cotswold Pond #1 Required Storm Volume solutions
4kciivvi� engineering [ land surveying
Wet Pond
Drainage Area:
13.59 acres
Impervious Area: 291,016 sf (6.68 ac)
% Impervious: 49.2%
1 inch Storm Event:
Rv = 0.05+0.009 1
Rv = runoff coefficient
I= percent impervious
Rv=0.05+0.009*49.2%
For volume that must be controlled:
Volume=3,630*Rd*Rv*A
Volume = 3,630*(l inch)*(0.4928)*13.59 acres = 24,310 cf
Temporary volume stored = 31,705 cf
SA/DA ratio is 1.79 for a depth of 3.0 feet
Required surface area = 13.59 ac * (0.0179) = 0.2433 ac or 10,598 sf
Surface area provided (main permanent pool) = 11,021 sf
409 Chicago Drive, Suite 112, Fayetteville, NC 28306
office 1910-426-6777 fax [phone] license number I C-2354
On time, every time. I www.4Dsitesolutions.com