93 GARDEN CT RES22-0253 PW_Water Retention Calcs_REVISION 11-1-22Comp. By:
Date:########
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 = 6,777 ft2
Impervious Area (A) = 3,049 ft2 =45.0%
V = 0.92 x 3,049.0 x 9.3 /12
V = 2,174 ft3
Provided Storage:
Area 1 - Relative Elev.Area Storage Sideslope:2 :1
(ft)(ft2) (ft
3)
0.0 0 BOTTOM size:0 X 0
0.0 1,121 TOB size:X
Area 2 - Relative Elev.Area Storage
(ft)(ft2) (ft
3)
0.0 0 BOTTOM size:0 X 0
0.0 167 TOB size:0 X 0
Area 3 - Relative Elev.Area Storage
(ft)(ft2) (ft
3)
0.0 0 BOTTOM size:0 X 0
0.0 317 TOB size:0 X 0
Inground Storage: = A*d/pf
Total Storage Area at TOB (A) =1605.0 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 =2247.0 ft3
Required Treatment Volume =2,174 ft3
Supplied Treatment Volume =2,247 ft3
0
0
0
Retention Water Retention_Atlantic Beach 10/28/2022
By Toni Gindlesperger at 5:03 pm, Nov 01, 2022