SW8050304_COMPLIANCE_20050305

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW t`JI�Ii�IDLI
DOC TYPE
El CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE
YYYYMMDD

DETENTION POND ANALYSIS FILE NAME: 050304-1
PROJECT#: SW8 050304 REVIEWER: P.Bartlett
PROJECT NAME: Racine Dr. Comm. SD
DATE: 03-Mar-05
Receiving Stream: Spring Branch Class: C; SW
Drainage Basin: Cape Fear Index No. 18-74-63-1
Site Area V1 5.2 2 acres
Drainage Area
.9$4 . square feet Area = 15.22 acres
IMPERVIOUS AREAS
TOTAL
SURFACE AREA CALCULATION
% IMPERVIOUS 76,41%
Des. Depth 5
TSS: 90
VOLUME CALCULATION
Rational ?*
Des. Storm
inches
Rv=
0.74
Bottom
30 msl,,
Perm. Pool
msl
Design Pool
35.9 rnsl ✓
Desig,) SA
55553 sf
Req. Volume
'0-7-5.8: cf
7 1
Prov. Volume
cf
ORIFICE CALCULATION
Avg. Head =
Flow Q2, cfs
Flow Q5, cfs
No. of Orifices
Diameter, inches
Drawdown =
0.38 ft
0.236 cfs
0.094 cfs
77771 v1
weir H x W
days -'
square feet
square feet
square feet
square feet
square feet
square feet
square feet
SA/DA Ratio
Req. SA
Prov. SA
Rational C
Rational Cc= 0.05
5.45%
36125 sf
5.05.72Isf
* place a "'I " in the box if Rational is used
FOREBAY
Perm. Pool Volume=
Req. Forebay Volume=
Provided Volume=
Percent=
SA @
Elevation=
Q2 Area =
Q5 Area =
Orifice Area
in
COMMENTS
Surface Area , Volume and Orifice are within Design Guideline,-:
169307
33861.4
32598.00 ✓
11.49
sq. in.
4.59
sq. in.
9.62
sq. in.
0.198
cfs
x
in

NKT #(Al 15
Permit No.
State of North Carolina (to be provided by DWQ)
Department of Environment and Natural Resources
Division of Water Quality
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form may be photocopied for use as an original
DWQ Stormwater Management Plan Review_
A complete stormwater management plan submittal includes an application form, a wet detention basin
supplement for each basin, design calculations, and plans and specifications showing all basin and outlet
structure details.
L PROJECT INFORMATION
Project Name:
Racine Drive Commercial Subdivision
Contact Person: John A. Kuske, III, P.E. Phone Number:
For projects with multiple basins, specify which basin this worksheet applies to:
[phone]
1
elevations
Basin Bottom Elevation 30.00 ft. (floor of the basin)
Permanent Pool Elevation 35.00 ft. (elevation of the orifices)
Temporary Pool Elevation 35.90 ft. (elevation of the discharge structure overflow)
areas
Permanent Pool Surface Area 50,572 sq. ft. (water surface area at the orifice elevation)
Drainage Area 15.22 ac. (on -site and off -site drainage to the basin)
Impervious Area 11.63 ac. (on -site and off -site drainage to the basin)
Lot No. 1-6 @ 90% Impervious Coverage
volumes
Permanent Pool Volume
Temporary Pool Volume
Forebay Volume
Other parameters
SAIDA'
Diameter of Orifice
Design Rainfall
Design TSS Removal z
169,307 cu. ft.
44,824 Required
47,757 Provided cu. ft.
32,598 (19.25%) cu. ft.
(combined volume of main basin and forebay)
(volume detained above the permanent pool)
(approximately 20% of total volume)
0.0545 (surface area to drainage area ratio from DWQ table)
3.50 in. (2 to 5 day temporary pool draw -down required)
1 in.
90 % (minimum 85% required)
Form SWU-102 Version 3.99 Page 1 of 4

Footnotes:
When using the Division SAIDA tables, the correct SAIDA ratio for permanent pool sizing should be computed based upon the
actual impervious % and permanent pool depth. Linear interpolation should be employed to determine the correct value for non-
standard table entries.
2. In the 20 coastal counties, the requirement for a vegetative filter may be waived if the wet detention basin is designed to provide
901/o TSS removal. The NCDENR BMP manual provides design tables for both 85%TSS removal and 90% TSS removal.
H. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices Manual
(N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Code
Section: 15 A NCAC 2H .1008.
Initial in the space provided to indicate the following design requirements have been met and supporting
documentation is attached. If the applicant has designated an agent in the Stormwater Management Permit
Application Form, the agent may initial below. If a requirement has not been met, attach justification.
Applicants Initials
MIQ a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet).
b. The forebay volume is approximately equal to 20% of the basin volume.
c. The temporary pool controls runoff from the design storm event.
d. The temporary pool draws down in 2 to 5 days
^M!!6 664& e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow
calculations.
f. The basin length to width ratio is greater than 3:1.
g. The basin side slopes above the permanent pool are no steeper than 3:1.
h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail).
i. Vegetative cover above the permanent pool elevation is specified.
j. A trash rack or similar device is provided for both the overflow and orifice.
k. A recorded drainage easement is provided for each basin including access to nearest right-
of-way.
d 1. If the basin is used for sediment and erosion control during construction, clean out of the
basin is specified prior to use as a wet detention basin.
m. A mechanism is specified which will drain the basin for maintenance or an emergency.
A portable pump can be provided.
M. WET DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT
The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the
vegetated filter if one is provided.
This system (check one) ❑ does
This system (check one) 0 does
® does not incorporate a vegetated filter at the outlet.
® does not incorporate pretreatment other than a forebay.
Form SWU-102 Version 3.99 Page 2 of 4

Maintenance activities shall be performed as follows:
After every significant runoff producing rainfall event and at least monthly:
a. Inspect the wet detention basin system for sediment accumulation, erosion, trash accumulation,
vegetated cover, and general condition.
b. Check and clear the orifice of any obstructions such that drawdown of temporary pool occurs
within 2 to 5 days as designed.
2. Repair eroded areas immediately, re -seed as necessary to maintain good vegetative cover, mow vegetative
cover to maintain a maximum height of six inches, and remove trash as needed.
3. Inspect and repair the collection system (i.e. catch basins, piping, swales, riprap, etc.) quarterly to
maintain proper functioning.
4. Remove accumulated sediment from the wet detention basin system semi-annually or when depth is
reduced to 75% of the original design depth (see diagram below). Removed sediment shall be disposed of
in an appropriate manner and shall be handled in a manner that will not adversely impact water quality (i.e.
stockpiling near a wet detention basin or stream, etc.)
The measuring device used to determine the sediment elevation shall be such that it will give an accurate
depth reading and not readily penetrate into accumulated sediments.
When the permanent pool depth reads 3.75 feet in the main pond, the sediment shall be removed.
When the permanent pool depth reads 3 feet in the forebay, the sediment shall be removed.
BASIN DIAGRAM
(fill in the blanks)
Permanent Pool Elevation 35.00
Sediment Re?ioval El. 32.00 j 7
Vvation
Sediment Removal Elevation 31.25 75%
BottomE------------------------------------- -----
Bottom Elevation 30.00 25%/
FOREBAY MAIN POND
5. Remove cattails and other indigenous wetland plants when they cover 50% of the basin surface. These
plants shall be encouraged to grow along the vegetated shelf and forebay berm.
6. If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through
the emergency drain shall be minimized to the maximum extent practical.
Form SWU-102 Version 3.99 Page 3 of 4

0
All components of the wet detention basin system shall be maintained in good working order.
I acknowledge and agree by my signature below that I am responsible for the performance of the seven
maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any
changes to the system or responsible party.
Print name: Henry E. Miller, III
Title: ....President
President
..........
Address: 1111 Military Cutoff Rd., Suite 151 Wilmington, NC 28405
Phone: [phone]
Signature:
Date: S 1 so k 0
Note: The legally responsible party should riot be a homeowners association unless more than 50% of the lots have been sold and
a resident of the subdivision has been named the president.
a Notary Public for the State of bs 0
County of , do hereby certify that [` ;
Personally appeared before me this day of T, and acknowledge the due
Execution of the foregoing wet detention basin maintenance requirements. Witness my hand and official seal.
+��Hunllrar.
y 5-.—NO
�OTARr
gNOVER.,.��'''
SEAL
Signature v
--L
My commission expires 6 _b j �p—
Form SWU-102 Version 3.99 Page 4 of 4