WR spreadhseet PPI24-0001 331 2nd St.Comp. By:
Date:3/26/2024
Public Works Department
City of Atlantic Beach
Permit No:PPI24-0001
Address:331 2nd Street
Required Storage Volume
Criteria:
Section 24-68 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 = 7,000 ft2
Impervious Area (A) = 2,765 ft2 =40%
V = 0.92 x 2,765.0 x 9.3 /12
V = 1,971 ft3
Provided Storage:
Area 1 - Relative Elev.Area Storage Sideslope:2 :1
(ft)(ft2)(ft3)
8.5 544 BOTTOM size:-2 X -2
9.0 979 TOB size:0 X 0
Area 2 - Relative Elev.Area Storage
(ft)(ft2)(ft3)
8.5 24 BOTTOM size:-2 X -2
9.0 216 TOB size:0 X 0
Area 3 - Relative Elev.Area Storage
(ft)(ft2)(ft3)
0.0 0 BOTTOM size:0 X 0
0.0 0 TOB size:0 X 0
Inground Storage:= A*d/pf
Total Storage Area at TOB (A) =1195.0 ft2
Depth to ESHWT from BOTTOM (d) =3.5 ft, default is 2.0 ft, verify onsite ESHWT
Pore Factor (pf) =0.4 default is 0.4
Inground Storage Provided =1673.0 ft3
Required Treatment Volume =1,971 ft3
Supplied Treatment Volume =2,114 ft3
D. Martin
381
60
0
Retention WR Worksheet PPI24-0001 331 2nd St. 3/26/2024