SW8050807_COMPLIANCE_20060817

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE
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August 17, 2006
Mr. W. Christopher Stephens, President
Southwood Developers, Inc.
5022 Wrightsville Avenue
Wilmington, NC 28403
Subject: Revised page 3 of Stormwater Permit
Bridgeport Townhomes
Stormwater Project No. SW8 050807
Brunswick County
Dear Mr. Stephens:
Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Alan W. Klimek, P.E. Drector
Division of Water Quality
On August 9, 2006, the Division of Water Quality issued a Stormwater Management Permit to
you for Bridgeport Townhomes. Section 1.7 0) on page 3 of that permit contains a
typographical error. It currently reads that the permitted orifice size for the on -site wet pond is
2"0. This should read as 1.5"0.
Attached please find a revised page 3 of the permit with the corrected information. Please
replace the incorrect page 3 with this corrected page 3. All other terms and conditions of the
permit issued to you on August 9, 2006, remain in full force and effect.
If you have any questions, please do not hesitate to call me at [phone]
Sincerely,
Linda Lewis
Environmental Engineer II
ENBlarl: S:IWQSISTORMWATERIREVISION1050807.aug06
cc: Comer Lyons, P.E., Cape Fear Engineering
Delaney Aycock
Linda Lewis
Wilmington Regional Office
Central Files
North Carolina
,Vatura!!y
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington, NC 28405 I'hone [phone] Customer Service
Wilmington Regional Office Internet: www,ncw•atcraoalin'.orFax [phone] 1-877-623-6748
An Equal OpportunitylAffirmative Action Employer — 50% Recycled110% Post Consumer Paper

State Stormwater Management Systems
Permit No. SW8 050807
6. Pond No. 3 of Stormwater Permit Number SW8 041041 is designed to receive the
runoff from 152,333 ft2 of impervious area generated by this project. As of the date
of this permit, Pond #3 is permitted to and maintained by Southwood Developers,
nc.
7. The following design criteria have been provided in the "Onsite" wet detention pond
and must be maintained at design condition:
a. Drainage Area, Rcres:
Onsite, ft :
Offsite, ft2:
b. Total Impervious Surfaces, ft2:
C. Design Storm, inches:
d. Pond Depth, feet:
e. TSS removal efficiency:
f. Permanent Pool Elevation, FMSL:
g. Permanent Pool Surface Arei, ft
h. Permitted Storage Volume, ft :
i. Temporary Storage Elevation, FMSL:
j. Controlling Orifice:
k. Permitted Forebay Volume, ft3:
I. Receiving Stream/River Basin:
M. Stream Index Number:
n. Classification of Water Body:
4.5
196,020
0
104,446
1
7.0
90%
68.0
11,840
8,824
68.7
1.5 "O pipe
2,416
Banton Branch 1 Cape Fear
18-77-1-1-2
"C Sw"
8. The following design criteria have been provided in the "Offsite" wet detention pond
No. 3 permitted under SW8 041041 and must be maintained at design condition:
a. Drainage Area, Acres:
Onsite, ft :
Offsite, ft2:
b. Total Impervious Surfaces, ft2:
Lot BUA, ft
Roads/Parking, ft2:
Offsite, ft2 (SW8 050807):
C. Design Storm, inches:
d. Pond Depth, feet:
e. TSS removal efficiency:
f. Permanent Pool Elevation, FMSL :
g. Permanent Pool Surface Areq, ft
h. Permitted Storage Volume, ft :
i. Temporary Storage Elevation, FMSL
j. Controlling Orifice:
k. Permitted Forebay Volume, ft3:
I. Receiving Stream/River Basin:
M. Stream Index Number:
n. Classification of Water Body:
II. SCHEDULE OF COMPLIANCE
17.71
512,701
257,440
332,671
126,324
54,014
152,333
7.0
90%
62.0
14,444
28,906
63.8
2 "0 pipe
9,240
Banton Branch 1 Cape Fear
18-77-1-1-2
"C Sw"
The stormwater management system shall be constructed in its entirety, vegetated
and operational for its intended use prior to the construction of any built -upon
surface.
2. During construction, erosion shall be kept to a minimum and any eroded areas of
the system will be repaired immediately.
Page 3 of 8

WET DETENTION POND ANALYSIS
FILE NAME:
PROJECT #: SW8 050807
PROJECT NAME: Bridgeport Townhomes
SAWQSIPOND1050807.WK1
REVIEWER: L. Lewis
DATE: 09-Aug-06
Receiving Stream: Banton Branch Class: CSw
Drainage Basin: Gape Fear Index No, CPF17 18-77-1-1-2
Site Area 14,31 acres
Drainage Area 196020.00 square feet Area in Acres 4.50
IMPERVIOUS AREAS
Buildings
Street
SW (road)
Contingency
TOTAL
SURFACE AREA CALCULATION
52698.00 square feet
41802.00 square feet
9946.00 square feet
square feet
square feet
square feet
square feet
104446.00 square feet
% IMPERVIOUS 53,28% SAIDA Ratio
Des. Depth 7 Req. SA
TSS: 90 Prov. SA
VOLUME CALCULATION
Rational ?*
Des. Storm
1 .00d
inches
Rv=
0.530
Bottom
61 msl
Perm. Pool
68.00 msl
Design Pool
68.7 msl
Storage met @elev 68.69 msl
Req. Volume
8650
cf
Vol. Prov. at DP
8824
cf
ORIFICE CALCULATION
Avg. Head =
Flow Q2, cfs
Flow Q5, cfs
No. of Orifices
Diameter, inches
Drawdown =
0.3188 ft
0.0501 cfs
0.0200 cfs
1
1.50 weir H x W
3.0 days
C: 3.288214286
Rational C
Rational Cc= 0.09
2.06%
4046 sf
11840 sf
" place a "1" in the box if Rational is used
FOREBAY
Perm. Pool Volume= 33166
Req. Forebay Volume= 6633.2
Provided Volume= 6684.00
Percent= 20.2%
Elevation Area Inc. Vol. Acc. Vol.
68.00 11840.00
69.00 13370.00 12605.00 12605.00
Q2 Area = 2.65
Q5 Area = 1.06
Orifice Area 1.77
Q= 0.033
in x
Surface Area @DP =
Falling Head Drawdown =
L= -0, 064
COMMENTS
Surface Area & Volume are within Design Guidelines.
Orifice is too large , forebay is too small.
sq. inches
sq. inches
sq. inches
cfs
in
12911 sq. ft.
4.1 days

CAPE FEAR
Engineering, Inc.
May 16, 2006
Linda Lew6
Environmental Engineer
NC DENR-DWO
127 Cardinal Drive EXtCn51on
Wilmington, NC 26405-3845
Re: Bridgeport Townhome5
5tormwater Project No. 5W8 050607
Request for Additional Information: 5/ 1 5/06
Dear Ms. Lewis:
RECEIVED
.MAY 10 2006
i]WQ
pa,03 0
The pond's forebay and orifice size have been updated 35 you requested. The forebay has been re5lzed
to include 20% of the total pond's volume and now provlde5 GG54 cubic feet of volume. The orifice has
been updated to have a correct draw down time between 2 and 5 days, and is now 1 .5 inches it
diameter.
Enclosed: please find the updated 5tormwater and Erosion Control Plan, Page I of the Wet Detention
Bann Supplement for the current onsite pond, and the updated West Pond Calculations for Bridcjeport
Townhome5.
Thanks acjain for your quick reviews and help with gcttincj this project approved. Please let our office
know if any further information +5 required for approval of this 5tormwater design.
Sincerely,
oe Boyd
cc : File (235-02)
Enclosures
151 Poole Road, Suite 100 • 6elvifle, NC25451 • TEL: [phone] • FAX: [phone]
www.capefearengineering.com
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Bridgeport Townhomes SW8 050807
Subject: Bridgeport Townhomes SW8 050807
From: Linda Lewis <[e-mail]>
Date: Mon, 15 May 2006 16:57:29 -0400
To: Joe Boyd<[e-mail]>
CC: Chris Stephens <WCHRIS [e-mail]>
Joe:
The orifice and forebay volume are still not correct.
The forebay is supposed to be 20% of the permanent pool volume (33,166 cubic feet)
which is 6,633 cubic feet. You have provided only 2,416 cubic feet. Please revise
the forebay volume to provide a minimum of 6,000 cubic feet up to a maximum of
7,300 cubic feet at: the permanent pool elevation.
The calculated flowrate through a 2" orifice under head is .0583 cfs, but that rate
is faster than the allowable maximum of .05 cfs. The 2" orifice is too big and now
draws down the pond in less than 2 days. If you translate those 2 and 5 day
flowrates into orifice areas, then diameters, you will find that the acceptable
range of orifice diameters is somewhere near 1.17" to 1.85". Please resize the
orifice such that the orifice provides a flowrate that draws the pond down between
2 and 5 days and revise the calculations.
Thanks,
Linda
l of 1 5/15/2006 5:00 PM

z. J.
CAPE FEAR
Engineering, Inc.
August 9. 2000
Linda Lewis
Environmental Engineer
NC DENK-DWO
127 Cardinal Drive Extension
Wilmington, NC 28405-3545
Re: Bridgeport Townhomes
5tormwater Project No. 5W8 050807
Request for Additional Information. 8191OG
Dear Ms. Lewis:
The on5ite pond's detail on the plan has been updated to correctly show the 1 .5" diameter orifice as you
requested.
Enclosed, please find two copies of the updated 5tormwater and Erasion Control Plan.
Thanks again for your quick reviews and heo with getting this project approved. Please let our office
know If any further information 15 required for approval of this 5tormwater design.
Sincerely,
Joe Boyd
cc : File (235-02)
Enclosures
RE EI V ED
AUG 0 9 2006
151 Poole Road, Suite 100 , Belville, NG28451 • rEt: [phone] - FAX: [phone]
www.ca pefearengincering.com
I';V7+0 lij 0 i'\'I ol'; RIIIM Vi QVI-[md:d—i<k-U.4md—

Bridgeport Townhomes SW8 050807
Subject: Bridgeport Townhomes SWS 050807
From: Linda Lewis <[e-mail]>
Date: Wed, 09 Aug 2006 10:35:14 -0400
To: Joe Boyd<[e-mail]>
Joe:
The pond section detail on the revised plans I received on May 16, 2006, indicate
that the orifice is I" diameter, however, the calculations and supplement were
revised to a 1.5" diameter. Please revise the detail and submit 2 revised plan
sheets with the correct orifice size.
Thanks,
Linda
1 of 1 8/9/2006 10:40 AM