SW8050441_COMPLIANCE_20050915

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE
r�%F97 J ORl`i
WYYMMDD

STORMWATER DIVISION CODING SHEET
NCG PERMITS
PERMIT NO.
/v
DOC TYPE
❑ HISTORICAL FILE
❑ MONITORING REPORTS
DOC DATE
❑
YYYYMMDD

WET DETENTION POND ANALYSIS
FILE NAME
PROJECT #: SW8 050441.sep05
PROJECT NAME: Bobby Morton Project
S:IWQSIPOND1050441.sep05.WK1
REVIEWER: L. Lewis
DATE: 15-Sep-05
Receiving Stream: UT f � ue Creek Class: SC NSW
Drainage Basin: White Oak Index No. WOK02 19-8
Site Area 9.95 acres
Drainage Area 2r.925300 square feet Area in Acres 6.41
IMPERVIOUS AREAS
Rational C
Buildings
66800.00
square feet
Parking
136932.00
square feet
SW
-1435,00
square feet
Other
121.00
square feet
Future
5000.00
square feet
square feet
square feet
TOTAL1;�t�3t3
00„
square feet Rational Cc= 0.05
SURFACE AREA CALCULATION
% IMPERVIOUS 7h.30�V
Des. Depth 6
TSS: 90
SAIDA Ratio 4.27%
Req. SA 11928 sf
Prov. SA 2003sf
VOLUME CALCULATION * place a "1" in the box if Rational is used
Rational ?*
Des. Storm '' 1lJO' inches
Rv= 0.728
Bottom 11 msl
Perm. Pool ;' 1 r:LO'' msl
Design Pool '18.37 msl
Storage met @elev 18.29 msl
Req. Volume " 1'fi 3t5 cf
Vol. Prov. at DP �' J'!.,.18029`�I cf
ORIFICE CALCULATION
FOREBAY
Perm. Pool Volume= 34909
Req. Forebay Volume= 6981.8
Provided Volume= 6834.00
Percent=
Elevation Area
17.00 12003.00
18.37 14317.00
Inc. Vol.
18029.20
Ace. Vol.
0.00
18029.20
Avg. Head = s
0.64 ft
Q2 Area = 3,65
sq. inches
Flow Q2, cfs
0.098 cfs
Q5 Area = 1.46
sq. inches
Flow Q5, cfs
0.039 cfs
Orifice Area 3.14
sq. inches
No. of Orifices
,.
Q= 0.084
cfs
Diameter, inches
I'' ..i 2'':C?(�.='.I
weir H x W
u , in x
.'
in
Drawdown =
_ 2'3''f
days
Surface Area @DP =
14317 sq. ft.
Falling Head Drawdown =
3.4 days
C: 3.312888889
L= -0.129
COMMENTS
Surface Area , Volume and Orifice are within Design Guidelines

RECEIVED
JUL 12 2005
DWQ
t0i # �0 05044• �
1. PROJECT DESCRIPTION
µ CA
Design Calculations ; =o .• �E5' !29
Stormwater Treatment Facilities 9�
for S AL
Bobby Morton Development 148
located in
Qnslow County ;� / •c�No
(Revised April 20, 2005) K. N
`tlti0l��,
The Project consists of proposed townhomes/businesses on a 7.35 acre tract and associated sitework.
2. COMPUTE POND AREA REQUIRED
a. Compute Percent Impervious:
Impervious Areas:
On -Site Buildings
On -Site Streets
On -Site Parking
On -Site Sidewalks
Other on -site
Off -site
Sub -Total
FUTURE
FUTURE(reserved)
Tota I
Total Area Drainage to Pond:
Percent Impervious =
b. Compute Pond Surface Area
0 205,288
...................................................
0 5,000
0 210,288
0.753 or 75.3 %
Total
66,800 SF
0 SF
136,932 SF
1,435 SF
121
0
205,288 SF
0
5,000 SF
210,288 SF
279,253 SF
Using Surface Area to Drainage Area Ratio Chart for 90% TSS Removal (copy attached) and
assuming foot pond depth:
SAIDA = ;~3' % (interpolated)
Therefore:
Surface Area = SAIDA x Drainage Area
11,928 SF say;:;€>l=? SF

c. Compute Minimum Pond Dimensions
Assume rectangular shape with 3:1 Length (L) to Width (W) Ratio:
Length = 189.74 feet
Width = 63.25 feet
Site conditions, however, dictate irregular shaped pond:
Hydr. Length = J'feet
so, Hydr. Width 46.5 feet (avg)
Actual LIW = 4.9 (irregular shape)
3. DETERMINE VOLUME TO BE CONTROLLED FROM 1" STORM
Using Schuler "Simple Method":
Rv = 0.05 + 0.009(l) where I = percent impervious
Rv = 0.728 inlin
Control Volume = Design Rainfall x Rv x Drainage Area
Control Volume = 16,935 CF
4. DETERMINE REQUIRED STORAGE DEPTH
Assume: 3:1 side slopes
solving for depth (d) by trial & error:
d = 1.51
5. DETERMINE ORIFICE SIZE
say €)( CF
Control Volume must be drawn down over a 2 day - 5 day period.
Using orifice equation, solve for Diameter (D) that results in 3-112 day period:
D = (Q 1 0,026 (h) 5)"
Where: Q = (Control Volume 1 3.5 days x 86,400 sec/day)
0.060 cfs
h=d12
= 0.76

Solving for D:
D = 1.62 Use<= € `" pipe
Actual Drawdown with actual drawdown pipe diameter (using orifice equation):
Q= 0.090 cfs
Draw Down Period = 2.31 days OK, < 5.0
6. SELECT OUTLET STRUCTURE DIAMETER
Size outlet structure such that depth of 010 flow <1.0 feet:
Using Rational Formula (Q=CIA) where:
...........................
Cimper
CperyMEW
Ccum
...........................
11 D = «<v<sT7 in/hr
A _ ::.:.:....:.::6.41 ac
Q10 = 29.96 cfs
Assuming 1/2 circumference is used as weir and using
Francis Formula (Q=3.33LH"5) to solve for L such that H = 1.0:
L = 9.00 Feet
Min 60 inch diameter outlet structure
Use 60 inch diameter outlet structure
7. DETERMINE Q10 STAGE
Q10 = 29.96 cfs
Using Francis Formula (Q=3.33LH'-5) solve for H:
H10 = 1.09 feet
8. DETERMINE Q100 STAGE (ELEV. OF EMERGENCY SPILLWAY)
Using Rational Formula (Q=CIA) where:
Ccum = 0.65
..........................
...........................
1100 = <` in/hr
Q100 = 35.52
Using Francis Formula (Q=3.33LH1'5) solve for H:

H 100 = 1.23 feet
9. DETERMINE Q100 STAGE OVER EMERGENCY SPILLWAY (TOP BERM ELEV.)
Assume primary spillway blocked (i.e., emergency spillway to accommodate Q100)
Emergency spillway shall be a broad crested earthern weir designed to pass 100 year storm.
Using broad crested weir equation H = (QICw x L)213
where: Q = Q100 35.52 cfs
Cw = 3.0
Length = €<'rCffeet
H = 0.44 feet
10. FOREBAY SIZING
Compute Actual Pond Volumes (using average end method):
Avg
Incr.
Incr.
Cum.
Main Bay Volume
Elevation
Area SF
Area S
Depth (FTC
Vol CF
Vol CF
Pond Bottom
41 E30
2:168
Bottom Veg Shelf
15 33
5;03
3,600
4.33
15,588
15,588
Normal Pond
17 G0:
:9 923;
7,478
1.67
12,487
28,075
Main Bay Volume = 28,075 CF
Forebay Volume Elevation Area SF Area SF Depth (FT i Vol CF Vol CF
Pond Bottom 11.00 ...::.:.:::: �— .0
Normal Pond 17.00r;;:;:>::;2 178D': 1,139 6.00 6,834 6,834
Forebay Volume = 6,834 CF
Total Pond Volume = 34,909 CF
Forebay Volume equates to 19.6 % of Total Volume
Temp. Storage VolumeElevation A F Area (SF Depth (FT l VolCF Vol CF
Normal Pond 17.00 12,003
Temp. Pond Level 1$ 37 1�#'$17 13,160 1.37 18,029 18,029
Temp. Pool Volume = 18,029 CF
1.0 Yr Storage Volume : Elevation Area SF Area SF Depth (ET_l Vol (CE Vol CF
Temp Pond Level 18.37 14,317
Temp. Pond Level 194fi i618f' 15,249 1.09 16,695 16,695

Temp. Pool Volume =
00 Yr Storage VqjUme
Temp Pond Level
Temp. Pond Level
Temp. Pool Volume
11. SUMMARY
Pond Elevations:
Top Berm (minimum)
100-Yr. Flood
10-Yr. Flood
1-inch Storage
16,695 CF
vatio Area (SF Area SF t T VolC Vol (CF)
18.37 14,317
19 6t3: 1;6404'. 15,361 1.23 18,837 18,837
18,837 CF
e a b Actual
9.04 20.04
M= 0.44
8.60 19.60 (emerg. weir elev)
H100 = 1.23
8.46 19.46
H10 = 1.09
storage depth = 1.37
Permanent Pool
pond depth = 6
Pond Bottom
12. WET DETENTION BASIN SUPPLEMENT
Basin Bottom Elevation
11.00
Perm. Pool Elevation
17.00
Temp. Pool Elevation
18.37
Perm Pool Surface Area
12,003 SF
Drainage Area
6.41 AC
Impervious Area
4.83 AC
Perm. Pool Volume
34,909 CF
Temp Pool Volume
18,029 CF
Forebay Volume
6,834 CF
SAIDA
4.2713
Diameter of Orifice
2.00
Design Rainfall
1"
7.37 18.37 (primary weir elev)
6.00 17.00 (invert out elev)

Stormwater Treatment &
Erosion Control Narrative
(Revised April 20, 2005)
Bobby Morton Project
Bobby R. Morton proposes to construct a commercial (retail/storage) development on a 9.95 acre lot located
on NC 241US 258 (Richlands Hwy), just past Hickory Road, in the Jacksonville Township, Onslow County.
The site is currently undeveloped.
The project site is located approximately 0.11 miles from an UT of Blue Creek (SC;NSW) in the White Oak
Basin. The proposed development activities are high density (percent impervious > 25 %); therefore,
stormwater treatment facilities are required. The attached Stormwater Plan includes a 12,003 sf wet detention
basin at the eastern side of the site.
The pond is sized to accommodate 210,288 square feet of impervious area allocated as follows:
Buildings
Streets
Parking
Sidewalks
Other (Dump. Pad)
Reserve for Future
Total
Site
Offsite
Total
66,800 sf
-0-
66,800 sf
-0-
-0-
-0-
136,932 sf
-0-
136,932 sf
1,435 sf
-0-
1,435 sf
121 sf
-0-
121 sf
5 000 sf
-0-
5,000 sf
210,288 sf -0-
210,288 sf
The proposed pond is sized for 90% TSS removal. The pond does not incorporate pretreatment, other than
the forebay. The pond does not include a vegetated filter at the outlet.
All stormwater emanating from new impervious surfaces that is generated on -site shall be collected and
directed to the eastern side of the site by a system of sheet drainage, grassed swales and storm drainage
pipes.
The treatment system will require periodic maintenance. Maintenance frequency shall be dictated by pond
depths. Pond depths shall be checked by the owner on a quarterly basis. When measured depths are less
than 4.50' (for the main pond as well as the forebay), the pond shall be manually dewatered (pump) and
accumulated sediment removed and properly disposed of.
Site topography is gently sloping (0 — 5%) with the lowest elevations towards the southeasterly boundary of
the tract. Soils are loamy sand/sandy loam.
The entire area designated within "Clearing Limits" will be disturbed during initial construction, and will include
grading for parking, swales and storm drainage.

CHARLES F. RIGGS & ASSOCIATES, INC.
202 WARLICK STREET
P.O. BOX 1570
JACKSONVILLE, NORTH CAROLINA 28541
Telephone [phone]
Facsimile: [phone]
[e-mail]
�C9TVEI]
June 2, 2005 JUN 0 3 2005
Ms. Linda Lewis BY:
Environmental Engineer
Division of Water Quality
Wilmington Regional Office
State of North Carolina Department of Environment and Natural Resources
129 Cardinal Drive Extension
Wilmington, North Carolina 28405
Re: Stormwater Application for Bobby R. Morton
Jacksonville Township, Onslow County, North Carolina
Stormwater Permit No. SW9050441
Dear Ms. Lewis:
On behalf of Mr. Bobby R. Morton, Charles F. Riggs & Associates, and David K. Newsom, P.E.
Crystal Coast Engineering, P.A., have enclosed the following for your review; (2) two copies
"Drainage Area Supplement, (2) two sets of the of the Stormwater Management Permit
Application Forms, with (1) one copy Wet Detention Basin Supplement, (2) two sets Design
Calculations, (1) one copy Stormwater Treatment Narrative, (3) three sets of plans, and check #
2065 in the amount of $420.00,
Respectfully,