SW8060604_COMPLIANCE_20060712

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

WET DETENTION POND ANALYSIS
FILE NAME: S.\VVQS\POy4D\060604junO6.VVK1
vcew
PROJECT NAME: Rocky Point DATE: 12Jul-06
River Class: :S
Drainage Basin: . pi Index No.
Site Area
Drainage Area square feet Area in Acres 5.00
Receiving Stream: N
IMPERVIOUS AREAS
Buildings
Parking
GVV
Future
TOTAL
SURFACE AREA CALCULATION
96IMPERVIOUS 80.006
Des. Depth
TSS.85VrBO:
VOLUME CALCULATION
Rational ?°
Oem.Stomn
linches
Rv=
0,770
Bottomnns|
Perm. Pool
mns|
Design Pool
nlS|
Storage met @e|ev 34.26 rns|
Req. Volume
139EL5jcf
Vol. Prov. at OP
17169 jcf
ORIFICE CALCULATION
Avg. Heed=
0.81
ft
Flow Q2. ofm
0.081
ofs
Flow O5. nfa
0.082
ofs
No. nfOrifices
Diameter, inches
weir HxVV
C' 3.314242424
COMMENTS .
Rational
square feet
square feet
square feet
square feet
square feet
square feet
square feet
square feet
8A/DA Ratio 5.30%
Req.SA 11317 of
* place a "l " in the box if Rational is used
Pomn. Pool Vu|unne=
on Area
on Area
Inc. Vol.
Acc. Vol.
0.00
0.00
17169]0
17188.10
Q2Area = 3.10 sq. inches
C\5 Area = 1.24 sq. inches
Orifice Area 3.14 sq.inohau
[�= 0.082 ofs
iO x in
Surface Area @[)P= 14485sq. ff.
Falling Head Drovvdovvn= 3.3 days
L= -O.122

Permit No. U
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.
I. PROJECT INFORMATION
Project Name: The Pavilion at Rocky Point
Contact Person: J. Phillip Norris, P.E. Prone Number: [phone]
For projects with multiple basins, specify which basin this worksheet applies to:
elevations
Basin Bottom Elevation
27.70
ft.
(floor of the basin)
Permanent Pool Elevation
33.20
ft.
(elevation of the orifices)
Temporary Pool Elevation
34.50
ft.
(elevation of the discharge structure overflow)
areas
Permanent Pool Surface Area
11,929
sq. ft.
(water surface area at the orifrce elevation)
Drainage Area
4.99
ac.
(on -site and off -site drainage to the basin)
Impervious Area
3.99
ac.
(on -site and of -site drainage to the basin)
volumes
Permanent Pool Volume 25,385 cu. ft. (combined volume of main basin and forebay)
Temporary Pool Volume 15,235 cu. ft. (volume detained above the permanent pool)
Forebay Volume 5,053 cu. ft. (approximately 20% of total volume)
Other parameters
SAIDA' 0.052
Diameter of Orifice 2.0 in.
Design Rainfall 1.0 in.
Design TSS Removal 2 90 %
Form SWU-102 Version 3.99
(surface area to drainage area ratio from DWQ table)
(2 to 5 day temporary pool draw -down required)
(minimum 85% required)
Page 1 of 4

Footnotes:
1. When using the Division SA/DA 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 fitter may be waived if the wet detention basin is designed to provide
90% TSS removal. The NCDLTIR 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.
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.
the temporary pool controls runoff from the design storm event.
d. The temporary pool draws down in 2 to 5 days.
e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow
calcmlations_
The basin length to width ratio is greater than 3:1.
The basin side slopes above the permanent pool are no steeper than 3:1.
A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail).
Vegetative cover above the permanent pool elevation is specified.
A trash rack or similar device is provided for both the overflow and orifice.
A recorded drainage easement is provided for each basin including access to nearest right-
of-way.
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.
A mechanism is specified which will drain the basin for maintenance or an emergency.
III. 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) ❑ does
Form SWU-102 Version 3.99
® does not incorporate a vegetated filter at the outlet.
® does not incorporate pretreatment other than a forebay.
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
When the permanent pool depth reads
Sediment Re oval H. 29.08 75
Bottom EI vation 27 70 --
FOREBAY
4.12 feet in the main pond, the sediment shall be removed.
4.12 feet in the forebay, the sediment shall be removed.
BASIN DIAGRAM
(fill in the blanks)
Permanent Pool Elevation 33.20
Sediment Removal Elevation 29.08 75%
------------------------------------- -----
Bottom Elevation 27.70 125%
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

7. 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: Steve Saieed
Title: Manaaer
Address: 1135 Milita Cutoff Road, Suite 201 Wilmington, NC 28405
Phone: [phone]
Signature:
Date: ^ �A4Qa
Note: The legally responsible party should not 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 ofi)r` �Q, �(�
__
County of �Nf L�(L�()VQ , do hereby certify that _ �`I )i Q `S (L i � L8
Personally appeared before me this 4-� day of M and acknowledge the due
Ij
Execution of the foregoing wet detention basin maintenance requirements. Witness my hand and official seal.
0ti�u���+n+ar+ryrr
TA
G
uiffe 10t ��� I SEAL
Signature S
My commission expires
Form SWU-102 Version 3.99 Page 4 of 4