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1753 E PARK TER RES20-0114 revision 7-16-20 Park Terrace East 1753 Water Retaintion calcs 8 of 8Retention 1753 E PARK TER RES20-0114 revision 7-16-20 Park Terrace East 1753 Water Retaintion calcs 8 of 8 7/20/2020 Comp. By: Date:7/20/2020 Public Works Department City of Atlantic Beach Permit No:RES 20-0114 Address:1753 Park Terrace East Required Storage Volume Criteria: Section 24-66 of the City of Atlantic Beach's Zoning, Subdivsion, and Land Development Regulations requires that stormwater runoff from impervious areas be stored onsite. Volume to be retained is as follows: V = CAR/12 which is the Modified Rational Method for estimating stormwater runoff Where:V = Volume of Runoff to be stored (cubic feet) C = Runoff Coefficient, 0.92, the difference between impervious area (C=1.0) and undeveloped conditions (C=0.08). A = Impervious Area (square feet) R= 25-yr / 24-hr rainfall depth (9.3 inches for Atlantic Beach) Onsite Storage Volume Required for Impervious Area: Lot Area = 13,650 ft2 Impervious Area (A) = 5,806 ft2 =42.5% V = 0.92 x 5,806.0 x 9.3 /12 V = 4,140 ft3 Provided Storage: Area 1 - Relative Elev.Area Storage Sideslope:2 :1 (ft)(ft2)(ft3) 0.0 225 BOTTOM size:15 X 15 1.5 441 TOB size:21 X 21 Area 2 - Relative Elev.Area Storage (ft)(ft2)(ft3) 0.0 72 BOTTOM size:18 X 41.5 240 TOB size:24 X 10 Area 3 - Relative Elev.Area Storage (ft)(ft2)(ft3) 0.0 126 BOTTOM size:14 X 9 1.5 300 TOB size:20 X 15 Area 4 - Relative Elev.Area Storage (ft)(ft2)(ft3) 0.0 1,440 BOTTOM size:90 X 16 1.5 2,112 TOB size:96 X 22 Area 5 - Relative Elev.Area Storage (ft)(ft2)(ft3) 0.0 646 BOTTOM size:34 X 19 1.5 1,000 TOB size:40 X 25 Area 6 - Relative Elev.Area Storage 1,235 Fabio Fasanelli 500 234 320 2,664 Retention 1753 E PARK TER RES20-0114 revision 7-16-20 Park Terrace East 1753 Water Retaintion calcs 8 of 8 7/20/2020 Comp. By: Date:7/20/2020 Public Works Department City of Atlantic Beach Permit No:RES 20-0114 Address:1753 Park Terrace East Fabio Fasanelli (ft)(ft2)(ft3) 0.0 456 BOTTOM size:24 X 191.5 750 TOB size:30 X 25 Inground Storage:= A*d/pf Total Storage Area at TOB (A) =3902.0 ft2 Depth to ESHWT from BOTTOM (d) =2.0 ft, default is 2.0 ft, verify onsite ESHWT Pore Factor (pf) =0.4 default is 0.4 Inground Storage Provided =3121.6 ft3 Required Treatment Volume =4,140 ft3 Supplied Treatment Volume =4,175 ft3 905