49 Dudley St RES20-0172 9 of 17 impervious surface calcs_1Comp. By:
Date:
Public Works Department
City of Atlantic Beach
Permit No:_____________________________
Address:49 Dudley Street
Required Storage Volume
Criteria:
Section 24-66 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 = 9,421 ft2
Impervious Area (A) = 1,889 ft2 =20.1%
V = 0.92 x 1,889.0 x 9.3 /12
V = 1,347 ft3
Provided Storage:
Area 1 - Relative Elev.Area Storage Sideslope:4 :1
(ft)(ft2) (ft
3)
8.0 282 BOTTOM size:23.5 X 12
9.0 630 TOB size:31.5 X 20
Area 2 - Relative Elev.Area Storage
(ft)(ft2) (ft
3)
8.0 68 BOTTOM size:13.5 X 5
9.0 280 TOB size:21.5 X 13
Area 3 - Relative Elev.Area Storage
(ft)(ft2) (ft
3)
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) =909.5 ft2
Depth to ESHWT from BOTTOM (d) =2.5 ft, default is 2.0 ft, verify onsite ESHWT
Pore Factor (pf) = 0.4 default is 0.4
Inground Storage Provided =909.5 ft3
Required Treatment Volume =1,347 ft3
Supplied Treatment Volume =1,539 ft3
Reynold D. Peterson, P.E.
456
174
0
5/19/2020
Retention COAB_STORAGE CALCS_49 DUDLEY Street 5/19/2020