665 SAILFISH DR ACC21-0036 BRYCE BROWNING GROUND WATER TABLE AND CALCULATIONS revision 7-7-21_1Comp. By:
Date:
Public Works Department
City of Atlantic Beach
Permit No:RES21-003
Address:665 Sailfish drive
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 = 7,500 ft2
Impervious Area (A) = 2,878 ft2 =38.4%
V = 0.92 x 2,878.0 x 9.3 / 12
V = 2,052 ft3
Provided Storage:
Area 1 - FRONT Area Storage Sideslope:4 :1
(ft)(ft2) (ft
3)
12.5 551 BOTTOM size:X
13.0 1,035 TOB size:X
Area 2 - BACK Area Storage
(ft)(ft2) (ft
3)
0.0 0 BOTTOM size:X
0.0 0 TOB size:X
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) =1035.0 ft2
Depth to ESHWT from BOTTOM (d) =4.5 ft, default is 2.0 ft, verify onsite ESHWT
Pore Factor (pf) = 0.4 default is 0.4
Inground Storage Provided =1863.0 ft3
Required Treatment Volume =2,052 ft3
Supplied Treatment Volume =2,260 ft3
397
0
0
6/30/2021
Retention 380 Seminole Rd_Calcs 6/30/2021
ALPHA SOUTHEAST, INC.
2670 ROSSELLE AVE – SUITE 8
JACKSONVILLE, FL 32204
EVALUATION OF GROUNDWATER TABLE
AT
Atlantic Beach, Florida
The purpose of the exploration was to collect information concerning the subsurface
groundwater conditions near the proposed retention area. The evaluation was performed using a
5ft hand-auger. The hand-auger boring was performed at the location shown in the exhibit below.
The initial boring was completed on Wednesday June 23, 2021 at 9am. The boring was
terminated at 5’ below existing ground. 3” of water was found at the bottom of hole. The boring
was checked on Thursday June 24, 2021 at 09:30am. At time of check 0” of water was found at
bottom of hole.
It is anticipated the Seasonal High Groundwater Elevation in the area will normally be at
4’6” below the existing ground at the boring location .
Respectfully submitted,
ALPHA SOUTHEAST, INC.
FL C.A. 29643
Reynold D. Peterson, P.E.
Sr Project Manager
FL PE NO 84559
Boring Location