SW6230705_Design Calculations_20230831 (4)

4D Site Solutions, Inc.
DESIGN REQUIREMENTS:
A. Pass the storm event
SCM 12 Pre-Development Runoff-100-yr
Drainage Area,(DA)= 10.33 acres
Intensity,(I)= 7.57 inches/hr
Composite Runoff Coefficient,(C)=> 0.30
Maximum Release Rate,(Qloo)=> 23.46 cfs
SCM 12 Post-Development Runoff-100-yr
Drainage Area,(DA)= 10.33 acres
Intensity,(I)= 9.52 inches/hr
Composite Runoff Coefficient,(C)=> 0.58
Peak Release Rate,(Qloo)=> 57.04 cfs
Detention Pond Stage-Storage Function
Contour Contour Incr. Accum. Stage
Elev. Area Storage Storage(S) (Z)
(ft) (sf) (cf) (cf) (ft) ln(S) ln(Z) Z est
312.5 12,511 - - -
313.0 13,945 6,614 6,614 0.50 8.80 -0.69 0.55
313.5 14,683 7,157 13,771 1.00 9.53 r 0.00 1.03
314.0 15,437 7,530 21,301 1.50 9.97 0.41 1.50
315.0 16,986 16,212 37,513 2.50 10.53 0.92 2.44
316.0 18,591 17,789 55,301 3.50 10.92 1.25 3.41
317.0 20,253 19,422 74,723 4.50 11.22 1.50 4.42
318.0 21,970 21,112 95,835 5.50 11.47 1.70 5.48
319.0 23,744 22,857 118,692 6.50 11.68 1.87 6.59
320.0 25,575 24,660 143,351 7.50 11.87 2.01 7.75
Regression Output:
b= 1.16 (X Variable Coeff)
Ks= 13,325 (eY-b`tercept)
Stage-Storage Equation is of the form:S=(Ks)(Z)b
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4D Site Solutions, Inc.
Primary Spillway
Barrel
Number of Barrels= 1
Dia.of Barrel= 24 inches
Area of Barrel,(Ab)= 3.14 sf
Pipe Length,(L)= 80 feet
Friction Coeff.,(Kp)= 0.01058
Inv.of Barrel= 307.29 feet
Riser
Elev.of Riser Crest= 318.00 feet
Rectangular
Length Weir= 36 inches Width Weir= 48 inches
Total Weir Length= 14.00 feet
Area of Riser= 12.00 sq.ft.
Orifice in Riser
Dia.of Orifice= 2.40 inches
Number of Orifices= 1
Area of Orifice,(Ab)= 0.03 sf
Orifice Coefficient(CO= 0.60
Inv.of Orifice= 312.50 feet
Length of weir 1.90 feet
Top of weir= 313.72 feet
Weir Coefficient(Cw)= 3.00
Emergency Spillway
Width of Spillway(Approx.)= 25 feet
Weir Coefficient= 3.3
Crest Elevation= 319.00 feet
Summary of Results
Maximum Release Rate,(Qloo)= 23.46 cfs
Release Rate,(Q1oo)= 35.18 cfs
Normal Water Surface Elev.= 312.50 feet
Water Surface Elev.@ Outlet(Q100)= 317.06 feet
printed: 7/7/2023 12.59 PM Page 2 of 3

4D Site Solutions, Inc.
Inflow Hydrograph-100-yr
Peak Inflow,(Qp)_> 57.04 cfs
Time to Peak Calculation: CN= 70 P= 7.91 in. S= 4.29 in.
Q*= 4.39 in. (depth of runoff)
Vol= 164,505 cf (vol.of runoff)
Time to Peak,(Tp)=> 34.6 minutes
(SCS TR-55)
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