1470 Ocean Blvd RES23-0006 new SFH 4 of 6 stormwater calcsComp. By:
Date:1/13/2023
Public Works Department
City of Atlantic Beach
Permit No:_____________________________
Address:
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 = 6,248 ft2
Impervious Area (A) = 2,670 ft2 =42.7%
V = 0.92 x 2,670.0 x 9.3 /12
V = 1,904 ft3
Provided Storage:
Area 1 - Relative Elev.Area Storage Sideslope:1 :1
(ft)(ft2) (ft
3)
9.3 461 BOTTOM size:6.8 X 67.8
10.9 710 TOB size:10 X 71
Area 2 - Relative Elev.Area Storage
(ft)(ft2) (ft
3)
9.3 192 BOTTOM size:12 X 16
11.3 320 TOB size:16 X 20
Area 3 - Relative Elev.Area Storage
(ft)(ft2) (ft3)
9.3 321 BOTTOM size:15.6 X 20.6
11.5 500 TOB size:20 X 25
Inground Storage: = A*d/pf
Total Storage Area at TOB (A) =1530.0 ft2
Depth to ESHWT from BOTTOM (d) =4.0 ft, default is 2.0 ft, verify onsite ESHWT
Pore Factor (pf) = 0.4 default is 0.4
Inground Storage Provided =2448.0 ft3
Required Treatment Volume =1,904 ft3
Supplied Treatment Volume =4,800 ft3
937
512
903
Retention Saas onsite storage calcs 1/13/2023
RES23-0006
By Jennifer Johnston at 11:31 am, Jan 13, 2023