SW8000824_HISTORICAL FILE_20061208

STORMWATER DIVISION CODING SHEET
POST-CONSTRUCTION PERMITS
PERMIT NO. SW8
DOC TYPE ❑ CURRENT PERMIT
❑ APPROVED PLANS
HISTORICAL FILE
❑ COMPLIANCE EVALUATION INSPECTION
DOC DATE
YYYYM M D D

_,...... 3ob No. 04,07 Z
Date:
0
TRIPP ENGINEERING, P.C:
419 Chestnut Street, Wilmington, NC 28401
Phone: [phone] • FAX: [phone]
Email: [e-mail]
RECEIVED
LETTER OF TRANSMITTAL DEC 0 0 7006
To: NenEuR BY:
Attention: L I NDA Lew le,
Subject: 146•2041TAGE PAQ1L WAREFIORSE EXP• IV
FAX TRANSMITTAL: NUMBER OF PAGES INCLUDES COVER
I am sending you: ( ►/fATT'ACHED ( ) UNDER SEPARATE COVER
( ) Prints ( ) Tracings ( ) Copy of letter ( ) Specifications ( ) Other
Copies Item No Description
I CI NiGNyc-mro SirE PLAN
These are transmitted as checked below:
( ) For Approval ( ✓rFor Your Use ( ) Sign & Return ( ) Review
Remarks: —r14)Q1JK5 l
cc:
Signed:

TRII'P ENGINEERING, P.C.
0 419 Chestnut Street
Wilmington, North Carolina 28401
Phone: [phone] • FAX: [phone] Ov
September 19, 2006 Q o
NCDENR
Division Water Quality
127 Cardinal Drive
Wilmington, NC 28405-3845
Attn: Ms. Linda Lewis
Re: Hermitage Park Warehouse Expansion IV
New Hanover County, NC
TE 06072
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 application fee.
Please review for approval and contact us with any questions or comments.
Thank you.
Sincerely,
Tripp Engineering, P.C.
Jonathan W. Ham, E.I.
JWH:dcb
Enc. SEP 191006
RECEIVED
SEP 1 9 2006
BY:__-----

September 15, 2006 TE 06072
Stormwater Narrative
Hermitage Park Warehouse Expansion IV
New Hanover County, NC
Hermitage Park Warehouse Expansion IV is a pre-existing commercial site of 13.7 acres.
This project is a modification of the existing stormwater permit, number SW8 000824.
The tract is zoned industrial. Three structures currently exist on site, three warehouse
buildings along with gravel parking and access. The existing impervious area is 2.71
acres. The proposed expansion includes a 24,000 sf building , 21,912 sf of gravel access,
and 144,938 sf of future area brings the total impervious area to 304,169 sf.
The existing stormwater pond is sized to treat the existing impervious area and in addition
is sized to handle more than the proposed additional impervious area. Outflow will
discharge through existing ditches to an unknown tributary to Prince George Creek,
classification C-SW.
RECEIVED
SEP 19 2006
DWQ
PROJ # SA)-9000 8Z�-Mbc(

9/152006 Heritage Park Warehouse Expansion IV 06072
JWH Storwater Calculations
Total Drainage Area
ft. I acres
596,772 1 13.70
Impervious Area
Land Use sq.ft acres
Future Impervious 144,938 3.33
Buildings 98,040 2.25
Gravel 60.569 1.39 %impervious= 0.510
Concrete 621 0.01 = 51.0%
Total 304,169 6.98 say 51.0%
Storwater Calculations:
Time of Concentration:
Hydraulic Length(L)= 1,300 R
change in Height(H)= 7.3 ft.
Tc = (L'/H)-/128
14.36 min. Cr E= 0.25
CPo T= (%imp.)(.95)+(1-%imp.)(.25)
Flow for 10 year,6 hour Storm(Q10): - 0.61
Arse= (QrsE)x(110)x(Area) 110= 6.30 in/hr
= 21.58 cis Ix= 7.13 in/hr
QPoST- (CFWr)X(110)X(Area)
52.65 cfs Flow for 25 year,6 hour Storm(Qz ):
Qr _ (CrsE)x(1�)x(Area)
Soil Stores a Capacity for 10 year Storm: = 24.42 cts
CN= (98)(%imp.)+(60)(1-%imp.) Q�T= (CST)x(6)x(Area)
= 80 - 59.59 cfs
P= 4.82 in. furl Oyr,6 hr storm
S= 1000/CN-10 Soil Stoma a Capacity for 25 year Storm:
= 2.50 CN= (98)(%imp.)+(60)(1-%imp.)
Depth(D)= [P-(0.2)(S)12/]P+(0.8)(S)1 = 80
2,74 in. P= 5.71 in. for 25 yr,6 hr storm
S= 1000/CN-10
Time to Peak Flow = 2.50
Tr= [(43.5)(D)(Area)]/Oz.Posr Depth(D)= [P-(0.2)(S)]`/[P+(0.8)(S)1
30.97 min. - 3.52 in.
Detention Pond Design Time to Peak Flow:
Tr= I(43.5)(D)(Area)1/01o.PosT
Pond Size: - 35.21 min.
Elevation Surface Area
ft. .ft.
Normal Pool 24.20 36.772 State Surface Area Requirement at normal 0o1:
Flood Pool 26.20 42,262 Pond side slopes= 3 :1
Top of Bank 30.00 53,316 Depth below N.P.= 6 ft.
Bottom of Pool 18.20 9,182 SA/DA= 0.0277
(Chart for 90%TSS Removal for Wet Detention
Provided Storage Volume: Pond without Vegetative Filler
Vol._ [(Normal pool SA+Flood Pool SA)/2] Required SA= (SAIDA)x(Total Drainage Area)
x(F.P.elev.-N.P.elev.) - 16,531 sq.ft-
79.034 cu.ft.
State Volume Required for Storage of first 1"of runoff.
\ Vol._ [(1/12)x(DA)x(%imp-)l+
.\-•(N FARO �� 1(1/12)x(DA)x(1-%imp)xC]
!� C= g.2
RECEIVED ��� " � = 30,224 cu ft.
C 9(
SEAL
a 17374
SEP 19 20M =y `�
�i���jA%�;GINE�:
DWQ GREGORy
SIy1 � �ZQ MGIJ `
CXx �.,/�
PROJ # •CPO
06072pond 1 of 2

9I15I2006 Hermitage Park Warehouse Expansion IV
06072
JWH Stormvrater Calculations
Pond Volume:
Bottom SA= 9,182 sq.ft.
Normal Pool SA= 36,772 sq.R
Vol._ [(N.P.SA+Bottom SA)!21 x(N.P.el.-Bottom el.)
126,374 cu.ft.
O F
Required Volume Provided Volume
Vol.= 20%of total permenant storage volume Bottom SA= 5,917 sq.ft.
= 25,275 ou.ft. Normal Pool SA= 9,367 sq.ft.
Vol._ [(N.P.SA+Bottom SA)/21 x(N.P.el.-Bottom el.)
22,926 w,ft.
de th= 3 ft
Outlet Structure Design:
Flow for 2-day dmwdown: Flow for 5-day drawdown:
for 1 st 1"of storowater, for 1 st 1"of stomowater,
Q= Required Vol./172,800 sec.(2-days) Q= Required Vol./432,000 sec.(5days)
0.175 cfs = 0.070 CIS
Required Area of Pipe for 2-day drawdown: Required Area of Pipe for 5-day dmwdown:
A= Q/[Cd x SQRT(2 x g x h)] A= Q/[Cd x SQRT(2 x g x h)]
Cd= 0.6 Cd= 0.6
9= 32.2 ft./s' 9= 32.2 ft./s'
h= (F.P_elev.-N.P.elev.)/2 h= (F.P.elev.-N.P.elev.)/2
= 1ft. = tft.
A= 0-0363 sq.ft. A= 0.0145 s .R
Diameter of Pipe for 2-day drawdown: Diameter of Pipe for 5-day drawdown:
DIA.= SQRT[(A x 4)/pi]
= 0,2151 ft. = 0.1360 ft.
2.58 in.
'Use:2 in diameter pipe
Outlet Structure Check:
Using a 4'x 4'Basin,
Perimeter L = 16 ft.
Q= CIA
C= I%imp.)(.95)+(1-%imp_)(.25)
= 0.61
1= 7.13 in.for a 25 yr.Storm
A= 13.70 Acres
59.59 cis
Q= CwxLxH-
H= [Q/(Cw x L)]°
Cw= 3
1.16 ft.
Peak elevation= flood pool elevation+H
27.36 ft.
06072pond 2 of 2