PW Water Retention WorksheetComp. By: D. Martin
�s
Date: 2/1/2023
Public Works Department
City of Atlantic Beach
Permit No: RES23-0016
Address: 831 Beach Avenue
Re uired Stora a 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 = 17,509 ft'
Impervious Area (A) = 8,857 ftp = 50.6%
V = 0.92 x 8,857.0 x 9.3 /
V = 6,315 ft3
Provided Storage:
Area 1 - Relative Elev. Area
Storage
Sideslope: :1
(ft) (ft)
(ft3)
BOTTOM
size: X
O.t
TOB
size: X
Area 2 - Relative Elev. Area
Storage
ft (ft2)
(ft)
0.0
BOTTOM
size: X
0.C,
TOB
size: X
Area 3 - Relative Elev. Area
Storage
(ft) (fe)
(ft)
0.(
BOTTOM
size: X
0.(
TOB
size: X
Inground Storage: = A*d/pf
Total Storage Area at TOB (A) =
0.0
ftz
Depth to ESHWT from BOTTOM (d) =
2.t�
ft, default is 2.0 ft, verify onsite ESHWT
Pore Factor (pf) =
0.4
default is 0.4
Inground Storage Provided =
0.0
ft3
Required Treatment Volume =
6,315
ft3
Supplied Treatment Volume =
0
ft3
12
Retention W.R. for sending 831 beach ave res23-0016 2/1/2023