SW8051220_COMPLIANCE_20060227

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE
YYYYMMDD

WET DETENTION POND ANALYSIS
FILE NAME: S:1WQSIPOND1051220.WK1
PROJECT #: SW8 051220 REVIEWER: R. Hall
PROJECT NAME: Medical Office Building Memorial Dr. DATE: 27-Feb-06
Receiving Stream: Scales Creek Class: SC;HQW; NSW
Drainage Basin: White Oak Index No. 19-16-4
Site Area 1.40 acres
Drainage Area 609730i, square feet Area in Acres 1.40
IMPERVIOUS AREAS
Buildings
Parking
SW
TOTAL
SURFACE AREA CALCULATION
8237.00 square feet
23318.00 square feet
1350.00 square feet
square feet
square feet
square feet
square feet
3290 Of}'„ square feet
Rational C
Rational Cc= 0.09
% IMPERVIOUS
53.97%
SAIDA Ratio
3.82%
Des. Depth
5
Req. SA
2328 sf
TSS:
90
Prov. SA
2941;': sf
VOLUME CALCULATION
Req. Volume ;2722< cf
Vol. Prov. at DP 30 cf
ORIFICE CALCULATION
* place a "1" in the box if Rational is used
FOREBAY
Perm. Pool Volume= 4922
Req, Forebay Volume= 984.4
Provided Volume= 980.00
Percent=
Elevation
Area Inc. Vol.
32.00
2941.00
32.92
3698.00 3053.94
Avg.'Head =
0.44 ft
Q2 Area =
0.71
sq. inches
Flow Q2, cfs
0.016 cfs
Q5 Area =
0.28
sq. inches
Flow Q5, cfs
0.006 cfs
Orifice Area
0.44
sq. inches
No. of Orifices
:<.;:<.1<:>
Q=
0.010
cfs
COMMENTS
Surface Area , Volume and Orifice are within Design Guidelines
Acc. Vol.
0.00
3053.94

Stormwater Treatment &
Erosion Control Narrative
Medical Office Building Memorial Drive
Dr. Adesola Awomolo and husband, Abayomi Osunkoya propose to construct a commercial (medical office)
development on a 1.40 acre lot located on Memorial Drive next to Onslow Memorial Hospital in the
Jacksonville Township, Onslow County. The site is currently undeveloped.
The project site is located immediately adjacent to an UT of Scales Creek (SC;HQW,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 2,941 sf wet detention
basin at the western side of the site.
The pond is sized to accommodate 32,905 square feet of impervious area allocated as follows:
Site
Offsite
Total
Buildings
8,237 sf
-0-
8,237 sf
Streets
-0-
-0-
-0-
Parking (exist. + prop.)
23,318 sf
-0-
23,318 sf
Sidewalks
1,350 sf
-0-
1,350 sf
Other
-0-
-0-
-0-
Reserve for Future
-0-
-0-
-0-
32,905 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 impervious surfaces that is generated on -site shall be collected and directed to
the rear western portion 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 3.75' in the main pond (3..00' in the forebay), the pond shall be manually dewatered (pump) and
accumulated sediment removed and properly disposed of.
Site topography is gently sloping (0 — 5%), generally draining towards the westerly boundary of the tract. Soils
are loamy sandlsandy loam.
The entire area designated within "Clearing Limits" will be disturbed during initial construction, and will include
grading for parking, swales and storm drainage.
During construction, all runoff will be diverted by a series of temporary diversion ditches and/or storm drain
pipes to the Treatment Pond. The treatment pond is of adequate size and volume to contain sediment from
the entire disturbed area during construction. The pond will be dewatered and accumulated sediment
removed when the site is adequately stabilized.

55151yy1,11,
= BtiiSi
Design Calculations = Iv3s
Stormwater Treatment Facilities b'
for -,;�/ •5:•,'\;
Medical Office Building - Adesola Awomolo & Abayomi Osunkoya - ....... '
located in 111 2-3fal-
Onslow County
1. PROJECT DESCRIPTION
The Project consists of proposed business on a 1.40 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)
Total
Total Area Drainage to Pond:
Percent Impervious =
b. Compute Pond Surface Area
248 32,657
0 0
248 32,657
0.540 or 54.0 %
Total
8,237 SF
248 SF
23,070 SF
1,350 SF
0
0
32,905 SF
0
0 SF
32,905 SF
Using Surface Area to Drainage Area Ratio Chart for 90% TSS Removal (copy attached) and
assuming foot pond depth:
Therefore:
Surface Area = SAIDA x Drainage Area
2,376 SF say SF

c. Compute Minimum Pond Dimensions
Assume rectangular shape with 3:1 Length (L) to Width (W) Ratio:
Length = 93.93 feet
Width = 31.31 feet
Site conditions, however, dictate irregular shaped pond:
Hydr. Length = feet
so, Hydr. Width 32.7 feet (avg)
Actual LAN = 2.8 (irregular shape)
3. DETERMINE VOLUME TO BE CONTROLLED FROM 1" STORM
Using Schuler "Simple Method":
Rv = 0.05 + 0.009(I) where I = percent impervious
Rv = 0.536 in/in
Control Volume = Design Rainfall x Rv x Drainage Area
Control Volume = 2,722 CF say CF
4. DETERMINE REQUIRED STORAGE DEPTH
Assume: 3:1 side slopes
solving for depth (d) by trial & error:
d = 0.92
5. DETERMINE ORIFICE SIZE
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 10.026 (h)-$)-5
Where: Q = (Control Volume 1 3.5 days x 86,400 sectday)
= 0.010 cfs
h=dl2
= 0.46
Solving for D:

Actual Drawdown with actual drawdown pipe diameter (using orifice equation):
Q= 0.010 cfs
Draw Down Period = 3.50 days OK, < 5.0
6. SELECT OUTLET STRUCTURE DIAMETER
Size outlet structure such that depth of Q10 flow <1.0 feet:
Using Rational Formula (Q=CIA) where:
Cimper =
Cpery =
Ccum = 0.52
110 = inlhr
A = 1.40 ac
010 = 5.23 cfs
Assuming 112 circumference is used as weir and using
Francis Formula (Q=3.33LH"5) to solve for L such that H = 1.0:
L = 1.57 Feet
Min 24 inch diameter outlet structure
Use 36 inch diameter outlet structure
7. DETERMINE Q10 STAGE
Q10 = 5.23 cfs
Using Francis Formula (Q=3.33LH") solve for H:
H 10 = 0.48 feet
8. DETERMINE Q100 STAGE (ELEV. OF EMERGENCY SPILLWAY)
Using Rational Formula (Q=CIA) where:
Ccum = 0.52
1100 = in/hr
A = 1.40 ac
Q100 = 6.20
Using Francis Formula (Q=3.331<1-11'5) solve for H:
H 100 = 0.54 feet
9. DETERMINE 0100 STAGE OVER EMERGENCY SPILLWAY (TOP BERM ELEV.)

r
Assume primary spillway blocked (i.e., emergency spillway to accommodate Q100)
Emergency spillway shall be a broad crested earthem weir designed to pass 100 year storm.
Using broad crested weir equation H = (Q]Cw x L)2f3
where: Q = Q100 6.20 cfs
Cw = 3.0
Length = : feet
H = 0.27 feet
10. FOREBAY SIZING
Compute Actual Pond Volumes (using average end method):
Main Bay Volume:
Pond Bottom
Bottom Veg Shelf
Normal Pond
Main Bay Volume =
Forebay olume
Pond Bottom
Normal Pond
Forebay Volume =
Total Pond Volume =
Forebay Volume equates to
Avg Incr. Incr. Cum.
Elevation Area SF Area SF Depth (FT) Vol (CF) Vol CF
S27 Odra58�q -
at�30'33�717 388 3.33 1,290 1,290
32 01) k 2 4g 1,588 1.67 2,651 3,942
3,942 C F
Elevation Area SF Area SF Depth (FT) Vol CF Vol CF
28.00 i`" 7
32.00 ys483 245 4.00 980 980
980 CF
4,922 CF
19.9 % of Total Volume
Temp. Storage Volume: Elevation Area SF Area SF Depth (FT) Vol (CF) Vol CF
Normal Pond 32.00 2,941
Temp. Pond Level 3698; 3,320 0.92 3,054 3,054
Temp. Pool Volume = 3,054 CF
10 Yr Storage Volume: Elevation Area SF Area SF Depth (FT) Vol CF Vol CF
Temp Pond Level 32.92 3,698
Temp. Pond Level ,'33 403984 3,841 0.48 1,$47 1,847
Temp. Pool Volume = 1,847 CF
100 Yr Storage Volume: Elevation Area SF Area SF Depth FT Vol (CF) Vol CF
Temp Pond Level 32.92 3,698
Temp. Pond Level n a 'a33 46NF ,, 4'031 3,865 0.54 2,081 2,081

Temp. Pool Volume = 2,081 CF
11. SUMMARY
Pond Elevations:
Top Berm (minimum)
H= 0.27
100-Yr. Flood
H100 = 0.54
10-Yr. Flood
ht10 = 0.48
1-inch Storage
storage depth = 0.92
Permanent Pool
pond depth = 5
Pond Bottom
12. WET DETENTION BASIN SUPPLEMENT
Basin Bottom Elevation
27.00
Perm, Pool Elevation
32.00
Temp. Pool Elevation
32.92
Perm Pool Surface Area
2,941 SF
Drainage Area
1.40 AC
Impervious Area
0.76 AC
Perm. Pool Volume
4,922 CF
Temp Pool Volume
3,054 CF
Forebay Volume
980 CF
SAIDA
3.8967
Diameter of Orifice
0.75
Design Rainfall
1"
Design TSS Removal
90%
Relative
Actual
6.73
33.73
6.46
33.46 (emerg. weir elev)
6.40
33.40
5.92
32.92 (primary weir elev)
5.00
32.00 (invert out elev)
0

WHITE OAK RIVER BASIN
Name of Stream
Subbasin
Stream Index Number
Map Number
Class
Queen Creek
WOK01
19-41-16
I30NW1
SA;HQW
Rawson Creek
WOK05
21-35-7-35
133NW4
SA;ORW
Rocky Run
WOK02
19-16-2-2
I29NE2
C;NSW
Rogers Bay
WOK02
19-39-1
J29NW2
SA;HQW
Roosevelt Natural Area Swamp
WOK03
20-36-9.5-(1)
131NE4
C;Sw,ORW
Roosevelt Natural Area Swamp
WOK03
20-36-9.5-(2}
131NE4
SA;Sw,ORW
Russell Creek
WOK03
21-26
H32SW9
SA;HQW
Salliers Bay
WOK02
19-41-3
1295E5
SA;HQW
Salters Creek
NEU14
21-35-7-10-2
H33NW9
Sc
Salters Creek
WOK04
21-35-7-10-2
H33NW9
SC
Sanders Creek
WOK03
20-36-4-1
130NE3
SA;HQW
Sanders Creek
WOK03
20-36-6
I31NW4
SA;ORW
Sandy Branch
WOK03
20-36-7-1-1-1
I31NW1
SA;HQW
Sandy Branch
WOK03
21-13
H31SES
C
Sandy Run Branch
WOK02
19-10-1
H29SW9
SC;NSW
Saunders Creek
WOK01
19-41-12
I30SW2
SA;HQW
Scales Creek
WOK02
19-16-4
H29SW9
SC;HQW,NSW
School House Branch
WOK03
21-8
H31SE7
C
Schoolhouse Branch
WOK01
20-23-1
H30SE7
SA;HQW
Shacklefoot Channel
WOK01
19-41-9
I30SW2
SA;HQW
Sheep Pen Creek
WOK05
21-35-7-6
H33SE4
SA;HQW
Sheep Pen Creek
WOK05
21-35-7-32
I33NW4
SA;ORW
Shoe Branch
WOK03
21-6
H31SW6
C
Sikes Branch
WOK03
20-36-6-1-1
I31NW4
SA;HQW
Sleepy Creek
WOK04
21-35-1-12-1
I32NE3
SA;HQW
Smiths Swamp
WOK03
21-9
H31SW9
C
Smiths Swamp Branch
WOK03
21-10
H31SE7
C
Smyrna Creek
WOK04
21-35-7-22-1
H33SW4
SA;HQW
Sneads Creek
WOK02
19-33-1
I29SW3
SA;HQW
Snows Swamp Branch
WOK03
21-12
H31SE7
C
Socoe Creek
WOK02
19-9-2
H29SWB
SC;NSW
South Fork white Oak River
WOK01
20-3
H29NE7
C
South Leopard Creek
WOK04
21-35-1-7-3
H32SEB
SA;HQW
Southwest Creek
WOK02
19-17-(0,5)
H28SE4
C;NSW
Southwest Creek
WOK02
19-17-(6.5)
I29NW5
C;HQW,NSW
Southwest Prong Newport River
WOK03
21-3
H31SW0
C
Spit Bay
WOK04
21-35-7-21
H33SW7
SA;HQW
Spooner Creek
WOK03
20-36-10
I31NE2
SA;HQW
Spring Branch
WOKO1
20-14
H30SW7
C
Squires Run
WOK02
19-3
H26NE5
C;NSW
Starkey Creek
WOK01
20-29-2
130NE1
SA;HQW
Starkeys Creek
WOKD1
20-10
H29SE3
C
Steep Hill Branch
WOK01
20-23-2
H30SE7
SA;HQW
Stevens Creek
WOK01
20-28
I30NE4
SA;HQW
Stick Creek
WOK02
19-15
I29NW2
SC;HQW,NSW
Stones Bay
WOK02
19-30
I29SW2
SA;HQW
Stones Creek
WOK02
19-30-3
I29SW4
SA;HQW
Strawhorn Creek
WOK02
19-13-1
I29NW2
SC;HQW,NSW
Styron Bay
WOK04
21-35-7-3
H33SEI
SA;ORW
Styron Creek
WOK04
21-35-7-3-3
H33SW3
SA;HQW
Tank Creek
WOK02
19-17-5
129NW1
C;NSW
Tar Landing Bay
WOK03
20-36-15
I32NW5
SA;HQW
Taylor Bay
WOK03
20-36-3
130NEG
SA;ORW
Taylor Creek
WOKO1
20-20
H30SW9
C
Taylor Creek
WOK03
21-34
I32NE4
SC
Taylor Creek
WOK04
21-34
I32NE4
SC
The Ditch
WOK05
21-35-6-1
I32NE9
SA;ORW
The Straits
WOK04
21-35-1-12
I32NE2
SA;HQW
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