SW6210503_Design Calculations (Required Volume)_20211110

Townsend Estates Required Storm Volume
Pond #1
Drainage Area:
16.89 acres 735,826 sf
Impervious Area: 344,472 sf (7.91 ac)
Impervious: 46.8%
1 inch Storm Event:
Rv = 0.05+0.009 1
Rv = runoff coefficient
1= percent impervious
Rv=0.05+0.009*46.8%
= 0.4712
For volume that must be controlled:
Volume=3,630*Rd*Rv*A
Volume required = 3,630*(1 inch)*(0.4712)*16.89 acres = 28,890 cf
1yr Storm retained volume: 28,898 cf
Total volume provided = 40,789 cf
Main pond vol = 40,789 cf
Forebay vol = 7,878cf (19% of main pond)
SA/DA ratio is 1.6229 for a depth of 3.3 feet
Required surface area = 16.89ac * (0.016229) = 0.2741ac or 11,940 sf
Surface area provided = 12,244 sf
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