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1753 E. Park Terr RES20-0114 3 of 15 retention calcs_1Comp. By: Date: Public Works Department City of Atlantic Beach Permit No: Address:1604 Coquina Place Required Storage Volume Criteria: Section 24-66 of the City of Atlantic Beach's Zoning, Subdivsion, and Land Development Regulations requires that the difference between the pre- and postdevelopment volume of stormwawter runoff be stored on site. Volume of Runoff is defined as follows: V = CAR/12 Where:V = Volume of Runoff C = Coefficient of Runoff A = Area of lot in square feet R= 25-yr / 24-hr rainfall depth (9.3-inches for Atlantic Beach) Predevelopment Runoff Volume: Lot Area (A) = 13,712 ft2 Runoff Coefficient Area Lot Area Description (ft2)(ft2)"C"Wtd "C" Impervious 6,001 13,712 1.00 0.44 Pervious 7,711 13,712 0.20 0.11 Runoff Coefficient (C) =0.55 Runoff Volume V = 0.55 x 13,712 x 9.3 /12 V = 5,846 ft3 Postdevelopment Runoff Volume: Lot Area (A) = 13,712 ft2 Runoff Coefficient Area Lot Area Description (ft2)(ft2)"C"Wtd "C" Impervious 5,806 13,712 1.00 0.42 Pervious 7,906 13,712 0.20 0.12 Runoff Coefficient (C) =0.54 Runoff Volume V = 0.54 x 13,712 x 9.3 /12 V = 5,725 ft3 Required Storage Volume DV = Postdevelopment Runoff Volume - Predevelopment Runoff Volume DV = 5,725 -5,846 DV = -121 ft3 Retention Retention Calcs 4-13-20 5/6/2020 Comp. By: Date: Public Works Department City of Atlantic Beach Permit No: Address:1604 Coquina Place Provided Storage: Elevation Area Storage (ft)(ft2)(ft3) 10.0 0 0 BOTTOM 10.7 0 0 10.7 0 0 TOB Required Treatment Volume =-121 ft3 Supplied Treatment Volume =0 ft3 Retention Retention Calcs 4-13-20 5/6/2020