SW8050814_HISTORICAL FILE_20070815

STORMWATER DIVISION CODING SHEET
POST-CONSTRUCTION PERMITS
PERMIT NO. SW8
DOC TYPE ❑ CURRENT PERMIT
❑ APPROVED PLANS
XHISTORICAL FILE
❑ COMPLIANCE EVALUATION INSPECTION
DOC DATE 6�, Z7
YYYYMMDD

TRIPP ENGINEERING, P.C.
0 419 Chestnut Street
Wilmington, North Carolina 28401
Phone: [phone] FAX: [phone]
May 31, 2007 JUN n 4 ypp7
NCDENR BY:�-
Division of Water Quality
127 Cardinal Drive
Wilmington, NC 28405-3845
Attn: Ms. Linda Lewis
Re: Duncan Marine
New Hanover County, NC
SW8 050814 Mod.
TE 05087
Dear Linda:
In response to your comments dated May 30, 2007 we offer the following:
I. The outlet structure detail has been corrected to 0.75" instead of 1.00".
2. The site data table has been corrected.
3. The plans have been corrected.
Please review for approval and contact us with any questions or comments. Thank you.
Sincerely,
Tripp Engineering, P.C.
onathan W. Ham E.I.
JWH:jjh
Enc.

�0F \N ATF,q Michael P. Easley,Governor
J
William G.Ross.h.,Secretary
h North Carolina Department of En,nonment and Natural Resources
Alan W.Klimek,P.E. Director
Division of Water Quality
May 30, 2007
Charles Duncan
121 El Ogden Drive
Wilmington, NC 28411
Subject: Request for Additional Information
Stormwater Project No. SW8 050814 Modification
Duncan Marine
New Hanover County
Dear Mr. Duncan:
The Wilmington Regional Office received previously requested information regarding the
modified Stormwater Management Permit Application for Duncan Marine on March 8, 2007. A
preliminary review of that information has determined that the application is not complete. The
following information is needed to continue the stormwater review:
1. The outlet structure detail now indicates that the orifice is proposed to be 1" in
diameter however, no revised calculations were submitted to support this change.
Additionally, as indicated in the Division's letter dated February 9, 2007, a 0.75" fd
orifice will draw down the pond in a shade under 2 days, so a 1" orifice would draw it
down well outside the 2-5 day window. The orifice must be sized such that the pond
will draw down in no less than 2 days and no more than 5 days.
2. Please verify the drainage area. The site data listed on the plans says that the total
project area is 1.2.acres, or 52,272 ftz. However, the application and calculations
use 1.22 acres ol- 53,317 ftz. Which is correct?
3. Please revise the application, supplement and calculations as necessary to reflect all
of the above changes.
Please note that this request for additional information is in response to a preliminary review.
The requested information should be received in this Office prior to June 30, 2007, or the
application will be returned as incomplete. The return of a project will necessitate resubmittal of
all required items, including the application fee.
If you need additional time to submit the information, please mail or fax your request for a time
extension to the Division at the address and fax number at the bottom of this letter. The
request must indicate the date by which you expect to submit the required information. The
Division is allowed 90 days from the receipt of a completed application to issue the permit.
The construction of any impervious surfaces, other than a construction entrance under an
approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject
to enforcement action pursuant to NCGS 143-215.6A.
Please reference the State assigned project number on all correspondence. Any original
documents that need to be revised have been sent to the engineer or agent. All original
documents must be returned or new originals must be provided. Copies are not acceptable. If
you have any questions concerning this matter please feel free to call me at [phone].
No thCarolina
AIUrnlljl
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington,NC 28405 Phone[phone] Customer Service
Wilmington Regional Office Internee www.ncwaterquality.Ora Fax [phone]
An Equal OpportunitylAffirmative Action Employer-50%Recycled110%Post Consumer Paper

Mr. Duncan
May 30, 2007
Stormwater Application No. SW8 050814 Mod.
Sincerely,
Linda Lewis
Environmental Engineer
ENB/arl: S:\WQS\STORMWATERWDDINFO\2007\050814.may07
cc: Jonathan Ham, Tripp Engineering
Linda Lewis
Page 2 of 2

Duncan Marine SW8 050814
Subject: Duncan Marine SW8 050814
From: Linda Lewis <[e-mail]>
Date: Wed, 30 May 2007 15:05:52 -0400
To: Jonathan Ham <[e-mail]>
Jonathan:
Please see the attached request for additional information.
Linda
1050814 may07.doc11 Content Type: application/msword
Content Encoding. base64
I of 1 5/30/2007 3:06 PM

TRIPP ENGINEERING, P.C.
0 419 Chestnut Street
Wilmington, North Carolina 28401
Phone: [phone] FAX: [phone]
March 7, 2007
NCDENR
Division Water Quality
127 Cardinal Drive
Wilmington, NC 28405-3845
Attn: Ms. Linda Lewis
Re: Duncan Marine
Permit No. SW8 050814
TE 05087
Dear Linda:
In response to your comments dated February 9, 2007, we offer the following:
1. Existing contour information has been added.
2. Values on the plans and application now match.
3. Drop inlet No. 1 has been changed to 50.0 rim elevation.
4. The normal pool has been dimensioned.
5. Vicinity map has been updated.
6. The state flood pool is at 47.0, the County flood pool is at 48.9. The plans
now accurately portray this.
7. Outlet structure detail has been corrected.
8. A baffle is proposed to increase travel length to over 108'.
Please review for approval and contact us with any questions, comments or if you
need additional information. Thank you.
Sincerely,
Tripp Engineering, P.C.
R
ECEIVED
Jonathan W. Ham, E.I.
JWH:dcb
Enc.
6r7 )G2 �701,/,t oaf defy-1 0, S o, C2lc5'

Re: SW8 050814 Modification question
Subject: Re: SW8 050814 Modification question
From: Linda Lewis <[e-mail]>
Date: Tue, 06 Mar 2007 11:51:50 -0500
To: "Jonathan W. Ham" <[e-mail]>, Mary Naugle <[e-mail]>,
[e-mail], Rhonda Hall <Rhonda.Hal [e-mail]>, Ed Beck <[e-mail]>,
Cameron Weaver<[e-mail]>
Jonathan:
Yes, baffles are a potential solution but only if you've exhausted every
possibility to manipulate the pond to naturally provide the required 3 :1 L:W ratio.
Baffles make it more difficult to maintain the pond, and far be it from me to make
maintenance more difficult! !
If you must go with baffles, you need to add them to the pond layout detail and
show dimensions for where they are located, how far apart they are, and how far
they extend into the pond. Please also add them to the section detail, making sure
that the top elevation of the baffle is specified at least equal to the temporary
pool elevation or higher.
Linda
Jonathan W. Ham wrote:
Linda,
Would baffle walls be possible in this pond in order to increase the travel
length without changing the pond? The owner's business is placing bulkheads and
sheet pilings, so doing this would not be difficult for him. Please let me know,
so I can return the comment letter to your office by March 9"th Thank you so
much for all your help, and I hope you have a great day!
Thanks!
Jonathan
**Jonathan W. Ham, E.I.**
//Civil Engineering//
**Tripp Engineering, P.C.**
Office: (910) -763-5100
Fax: (910) -763-5631
1 of 1 3/6/2007 11:52 AM

SW8 050814 Mod. Duncan Marine
Subject: SW8 050814 Mod. Duncan Marine
From: Linda Lewis [e-mail]>
Date: Fri, 09 Feb 2007 09:23:02 -0500
To: Jonathan Ham <[e-mail]>
Jonathan:
Attached please find my review comments for this project .
Linda
Content-Encoding: base64
050814.feb07.doc Content-T e: a lication/msword
--.. —1— n
I of 1 2/9/2007 9:23 AM

F W ATF
�O 90 Michael F.Easley,Governor
William G.Ross Jr.,Secretary
r North Carolina Department of Environment and Natural Resources
`C Alan W.Klimek,P.E.Director
Division of Water Quality
February 9, 2007
Charles Duncan
121 El Ogden Drive
Wilmington, NC 28411
Subject: Request for Additional Information
Stormwater Project No. SW8 050814 Modification
Duncan Marine
New Hanover County
Dear Mr. Duncan:
The Wilmington Regional Office received a modified Stormwater Management Permit
Application for Duncan Marine on November 18, 2006. A preliminary review of that information
has determined that the application is not complete. The following information is needed to
continue the stormwater review:
1. Please provide existing contour information.
2. The asphalt and gravel square footages shown on the plans do not match up to
.the values reported on the application.
3. Please lower the Drop Inlet #1 top to 50.0 so that all of the driveway built-upon
area will have the opportunity to be picked up and treated by the pond.
4. Please dimension each line and arc of the permanent pool contour.
5. Please add the nearest intersection of two major roads to the vicinity map. A
major road is any 1 , 2 or 3 digit NC, US or interstate highway. Ideally, the vicinity
map should be geared toward driving to the site from Wilmington.
6. The flood pool elevation shown on the pond section detail is 49.4, however, the
outlet structure detail shows it as 48.9.
7. For small diameter orifices, the Division has found that a larger diameter pipe,
such as 4"-6" with a capped end that has the correct orifice diameter drilled into
it, functions better and reduces the potential for clogging. Additionally, the 0.5"fd
orifice will draw the pond down in a little moer than 4 days. I would rather see a
0.75"fd, which would draw down the pond in a shade under 2 days.
8. Please provide a 3:1 length to width ratio in the pond. The pond's average width
is 36 feet, therefore, it should be a minimum of 108 feet long.
Please note that this request for additional information is in response to a preliminary review.
The requested information should be received in this Office prior to March 9, 2007, or the
application will be returned as incomplete. The return of a project will necessitate resubmittal of
all required items, including the application fee.
N'or hCarolma
Naturally
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington,NC 28405 Phone[phone] Customer Service
Wilmington Regional Office Internet: www.newateraualitvorg Fax [phone]
An Equal OpportunitylAKrmative Action Employer—50%Recycled110%Post Consumer Paper

Mr. Duncan
February 9, 2007
Stormwater Application No. SW8 050814 Mod.
If you need additional time to submit the information, please mail or fax your request for
a time extension to the Division at the address and fax number at the bottom of this
letter. The request must indicate the date by which you expect to submit the required
information. The Division is allowed 90 days from the receipt of a completed application
to issue the permit.
The construction of any impervious surfaces, other than a construction entrance under
an approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and
is subject to enforcement action pursuant to NCGS 143-215.6A.
Please reference the State assigned project number on all correspondence. Any
original documents that need to be revised have been sent to the engineer or agent. All
original documents must be returned or new originals must be provided. Copies are not
acceptable. If you have any questions concerning this matter please feel free to call me
at [phone].
Sincerely,
Linda Lewis
Environmental Engineer
ENB/arl: S:\WQS\STORMWATER\ADDINFO\2007\050814mod.feb07
cc: Jonathan Ham, Tripp Engineering
Linda Lewis
Page 2 of 2

TffipP ENGINEERING, P.C.
0 419 Chestnut Street
Wilmington, North Carolina 28401
Phone: [phone] FAX: [phone] I
November 10, 2006 Sw�
NCDENR
Division Water Quality
127 Cardinal Drive
Wilmington, NC 28405-3845
Attn: Ms. Linda Lewis t,OV
IV 9fl��
Re: Duncan Marine
Permit No. SW8 050814
TE 05087
Dear Linda:
Enclosed please find two (2) sets of plans, one (1) signed original and one (1)
copy of the application form with narrative, one (1) wet detention basin supplement, two
(2) sets of calculations and one check for the review fee. We are requesting a
modification to existing permit SW8 050814.
Please review for approval and contact us with any questions or comments.
Thank you.
Sincerely,
Tripp Engineering, P.C.
Jonathan W. Ham
JWH:dcb
Enc.

11/10/06 TE05087
Stormwater Narrative
Duncan Marine
New Hanover County, NC
Duncan Marine is a 1.224-acre existing vacant tract proposed for a commercial warehouse
complex. The area of disturbance for this project is 1.29 acres including the driveway and outfall
pipe from the detention pond. Impervious areas include 5,600 SF of office and warehouse area,
368 SF of sidewalk, 6,610 SF of asphalt, and 17,248 SF of gravel, creating a total lot impervious
area of 29,826 SF.
The project will be treated by wet detention. The detention pond will be designed to meet the
County's 2-year, 10-year, and 25-year pre-post requirement. Outflow from the pond drains to
Smith Creek, classification C-SW.
RECEIVED
3
NOV 1 2006
DWQ
PROJ# -5l 4-- MCV

I If72006 Duncan Marine 05087
JWH Stormwater Calwlations
Total Dmina a Area
s .ft. acres
53,317 1.22
IrmperviousArea
Land Use sq.ft. acres
buildings 5,600 0.13 %impervious= 0.559
ravel/as halt 23,858 0.55 = 55.9%
sidewalks 368 0.01 say 56.0%
Total 29,826 0.68
Stormwater Calculations:
CPRE= 0.25
Time of Concentration: CPoST= (%imp.)(.95)+(1°/imp.)(.25)
Hydraulic Length(L)= 440 ft. = 0.65
change in Height(H)= 10 ft. Iz= 5.88 in/hr
TO = (L'/H)-/128 Irs= 7.23 m1hr
3.64 min.
Flow for 10 year,6 hour Storm(Qrs):
Flow for 2 year,6 hour Stonn(Q2): QPRE= (CPRE)x(Izs)x(Area)
QPRE_ (CPRE)x(Im)x(Area) = 2.21 cfs
1.80 cfs QPosT= (CPoST)x(1zs)x(Area)
QPOST= (CPoST)x(110)x(Area) = 5.75 cfs
4.68 Of
Soil Stowe Capacity for 10 year Storm.
Soil Storage Ca aci fort year Storm: CN= (98)(%imp.)+(60)(1°/imp.)
CN= (98)(%imp.)+(60)(1-%imp.) = 82
82 P= 4.82 in. for 10 yr,6 hr stone
P= 3.30 in. fo2yr,6 hr storm S= 1000/CN-10
S= 1000/CN-10
2.20 Depth(D)= [P-(0.2)(S)12/[P+(0.8)(S)]
Depth(D)= [P-(0.2)(S)]2/[P+(0.8)(S)] - 2.92 in.
1.62 in.
Time to Peak Flow:
Time to Peak Flow: TP= [(43.5)(D)(Area)]/Qrs POST
TP= [(43.5)(D)(Area)]/Q2.POST = 27.02 min.
18.43 min.
Detention Pond Design: State Surface Area Requirement at normalpool:
Pond side slopes= 3 :1
Pond Size: Depth below N.P.= 7 ft.
Elevation Surface Area SA/DA= 0.0215
(ft. (sq.ft. (Chart for 90%TSS Removal for Wet Detention
Normal Pool 45.00 2.451 Pond without Vegetative Filter
Flootl Pool 47.00 4,181 Required SA= (SA/DA)x(Total Drainage Area)
To of Bank 50.50 7,674 - 1,146 s .ft.
Bottom of Pool 38.00 45
State Volume Required for Storage of first 1"of runoff:
Provided Storage Volume: Rv= .05+.009(%imp)
Vol._ [(Normal pool SA+Flood Pool SA)/21 = 0.553464
x(F.P.elev.-N.P.elev.) V= (Design minfal0(Rv)(Drainage Area)
6.632 w.ft. - 2,459 cu.ftRo
`�I1111111111/���
RECEIVED
ti9`sy
1 =
SEAL
NOV 1% 2006 =y'. 17374 a
< FH
PROJ # �nJBU`- moo GREG0
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05087pond 1 of 2 �•�

I U7/2006 Duncan Marine 05087
JWH Story water Calculations
Pond Volume:
Bottom SA= 45 sq.ft
Normal Pool SA= 2,451 sq.ft.
Vol._ ((N.P.SA+Bottom SA)/2]x(N.P,el.-Bottom el.)
8,736 cu.ft.
Forebaw
Required Volume Provided Volume
Vol.= 20%of storage volume Bottom SA= 64 sq.ft.
1,747 cu.ft. Normal Pool SA= 889 sq.ft.
Vol._ [(N.P.SA+Bottom SA)121 x(N.P.el.-Bottom el.)
= 1,906 cu.ft.
Outlet Structure Design:
Flow for 2-day dmwdown: Flow for 5-day drawtlown:
for 1st 1"of stonnwater, for 1st 1"of stonnwater,
Q= Required Vol.1172,800 sec.(2-days) Q= Required Vol./432,000 sec.(5days)
= 0.014 cis = 0.006 cfs
Required Area of Pipe for 2-day dmwdown: Required Area of Pipe for 5-day drawtlown:
A= Q/[Cdx SQRT(2xgxh)) A= Q/[Cdx SQRT(2xgxh)]
Cd= 0.6 Cd= 0.6
9= 32.2 ft./s' 9= 32.2 ft./s2
h= (F.P.elev.-N.P.elev.)2 h= (F.P.elev.-N.P.elev.)/2
1 ft. = 1 ft.
A= 0.0030 sq,ft. A= 0.0012 sq.ft.
Diameter of Pipe for 2-day drawdown: Diameter of Pipe for 5-day drawtlown:
DIA.= SORT((A x 4)/pi] DIA.= SQRT[(A x 4)/pi]
0,0613 ft. = 0.0388 ft.
0.74 in. - 0.47 in.
'Use:0.5 in diameter pipe
Outlet Structure Check:
Using a 4'x 4'Basin,
Perimeter(L)= 16 ft.
O= CIA
C= (%imp.)(.95)+(1-%imp.)(.25)
0.65
1= 7.23 in.for a 25 yr.Storm
A= 1.22 Acres
5.75 cfs
O= Cwx Lx
H= [Q/(Cw x L)r
Cw= 3
0.24 ft.
Peak elevation= flood pool elevation+H
47,24 ft.
05087pond 2 of 2