SW8990730_Historical File_20040308

DETENTION POND ANALYSIS FILE NAME: S:1WQSIPOND1990730.WK1
PROJECT#: SW8 990730 REVIEWER: arl
PROJECT NAME: Jones/Byrd Condominiums DATE: 18-Dec-03
Receiving Stream: Calabash Creek Class: SA
Drainage Basin: Lumber Index No. 15=25=5
Site Area acres
Drainage Area 3314916.00 square feet needs to be verified
Area in Acres 76.10 acres
IMPERVIOUS AREA
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Champions Condos 36154'8.00 square feet
Offsite Lots Discovery Lake 182020.00 square feet 25 @7000, 1 @7020
Offsite ex. clubhouse & parking 165528.00 square feet 1475 550
Offsite roads 30492.00 square feet 13O50O
Offsite Cartpaths 37026.00 square feet 37050
Future Conference Center 87120.00 square feet
TOTAL 863734.00 Cc= 0.15
% IMPERVIOUS 26.06% Pond Depth: 6.0 TSS: 90
SURFACE AREA CALCULATION
Rational ? If Rational is used put a
SA/DA 1.44% "1" in box E26. If not, leave it blank.
Req. SA 47809 square feet
Prov. SA 206940 square feet [From plan Contours]
VOLUME CALCULATION Perm. Pool Volume= 150783
Req. Forebay Volume= 30156.6
Bottom 19.00 MSL Provided Volume=
Perm. Pool 25.00 MSL Percent= 0
Design Pool 25.50 MSL
Design SA 211230 square feet Des. Storm 1.00 inches
Req. Volume 78592 cubic feet Rv= 0.28450386
Prov. Volume 104543 cubic feet SA @ =
Elevation= _
ORIFICE CALCULATION
Avg. Head = 0;1.25 ft
Flow Q2, cfs 0.455 Area, sq. in. 38.47
Flow Q5, cfs 0.182 Area, sq. in. 15.39
No. of Orifices <:>:::.:<:t ::r:::..rr::>.;v <::::.<::r:::.>:.:.:. =:<:Y<>.:::.;::<:::; #�=>'[::< Diameter, in. ' > fi ;>:<<:<> <:: :.:
.. ... .. >` ... . .:.' Area - 28.274 sq. in.
Q, cfs = 0.334 Drawdown V;:k.311:112741 days
COMMENTS
Surface Area, Volume and Orifice are within Design Guidelines.

Sea Trail Plantation
Master Stormwater Plan •
Stormwater Permit No. SW8 940226
SUPPLEMENTAL CALCULATIONS
AND
SUPPORTING MATERIAL
FOR
EXISTING STORMWATER PONDS
SERVING
CHAMPIONS CONDOMINIUM/DISCOVERY LAKE EASTWOOD PARK PHASES 1 &2
O KWOOD PARK PHASE 1
OC7( R4003 RECEIVE D
„..,,,it• -, OCT 14 2003 s
/' r '" swe DW4vz2G,
ta 01 {6 2 . . PROD#
S.`��:� •s ,i'f. F�'%I��JJrr 730
i, D�;cc.ecoccce cc,,,i ,-
Prepared by:
...Ai
ips
T •
East Coast
Engineering Company, P.A.
Consulting Engineers
Shallotte,North Carolina 28459
Post Office Box 2469 4918 Main Street
Office: 910.754.8029

•
Sea Trail East Coast Engineering Company, PA
Champions Condos ACL
Wet Detention Basin Calculations
Champions Condominiums @ Sea Trail
Existing Stormwater Pond
Hey/ Drainage Area (DA) = 3,314,916 sf or 76.10 ac
New Impervious Area (IA)= 863795 sf 19.83 ac
Percent Impervious(I) IA/DA 0.26 or 26%
SA/DA;90% TSS Pond Depth= 6 0.0144 or 1.44%
(no vegetative filter req'd)
Min. req'd SA @ PP (SA/DA)x(DA) 47,734.79 sf
Min. req'd storage volume Rv=0.05+(0.009 x I)= 0.285
Volume= 1 in x(1 ft/12 in)x Rv x DA 78,596.78 cf
SA provided @ PP Pond Elev= 25 206,940 sf
Enough SA provided? YES
Min. storage depth req'd Min. storage volume/SA provided @ PP 0.38 ft
Storage depth set at 0.5 ft
Elevation of temporary pool 25.5 ft
SA @ Temporary pool 211,230 sf
Storage volume provided Average of SA @ temp. pool& PP x storage depth 104,542.50 cf OK
Outlet Sizing
Q-2 day drawdown time Min. req'd storage volume x(1 in.12 days) 0.455 cfs
Q-5 day drawdown time Min. req'd storage volume x(1 in./5 days) 0.182 cfs
Height h (1/2 Min. Storage Depth) 0.25 ft
Co Constant 0.6
Required Area for Q-2 A=Q/(C x(2gh)1/2) 27.21 in2
Required Area for Q-5 A=Q/(C x(2gh)1/2) 10.88 in2
Orifice Choosen 6.00 in
CHECK
Area Provided by Orifice Choosen A=nr2 28.28 in2
Area Provided by Orifice Choosen 0.196 ft2
The Average head h= 1/2(Temporary Pool depth-1/2(orifice diameter)) 1.5 in
The Average head 0.125 ft
Q provided Q=Ca(2gh)1r2 0.334 cfs OK
.30 �d.
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Revision Date:10/10/03

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