SW8960912_Current Permit_20070202

Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Alan W. Klimek, P.E. Director
Division of Water Quality
February 2, 2007
Ralph H. Griffin, Jr., President
American Auto & Finance Company, Inc.
Post Office Box 205
Wrightsville Beach, NC 28480
Subject: Approved Plan Revision
American Auto & Finance
Stormwater Project No. SW8 960912 Mod.
New Hanover County -
Dear Mr. Griffin:
On November 14, 2006, the Division of Water Quality issued a modified stormwater management
permit to you for the subject project. Unfortunately, the new approved plans did not contain the
necessary orifice size or details as were found on the 1996 approved plans. Your consultant was
contacted and the Division requested that the plans be revised to show the missing orifice information.
The revised plans were submitted on January 30, 2007. The Division is hereby notifying you that Sheet
C4 (Utility, Grading, Drainage & Erosion Control) of the November 14, 2006, approved plan set is to be
discarded and replaced by the enclosed Sheet C5, approved on February 2, 2007. It has been
determined that a formal permit modification is not required for the proposed changes. Please note that
Sheet C5 of the November 14, 2006 plans is the drainage area delineation map, i.e., there will be two
Sheet C5's in the approved plan set.
Please be aware that all terms and conditions of the permit issued on November 14, 2006, remain
in full force and effect. Please also understand that the approval of this revision to the approved
plans for the subject State Stormwater Permit is done on a case -by -case basis. Any other changes
to this project must be approved through this Office prior to construction. The issuance of this plan
revision does not preclude the permittee from complying with all other applicable statutes, rules,
regulations or ordinances which may have jurisdiction over the proposed activity, and obtaining a
permit or approval prior to construction.
If you have any questions concerning this matter, please do not hesitate to call me at [phone].
Sincerely,
'�JrT '�& -
Linda Lewis
Environmental Engineer II
ENB1arl: S:IWQSISTORMWATERIPERMIT1960912MODPR.feb07
cc: Mark Hargrove, P.E., Withers & Ravenel
Beth Wetherill, New Hanover County Engineering
City of Wilmington Development Services
Tony Roberts, New Hanover County Building Inspections
Linda Lewis
Wilmington Regional Office
Central Files
1 roneCarolina
Nawa!!ry
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington, NC 28405 Phonc [phone] Custumer Service
Wilmington Regional Office Internet: www.ncwaterauality.org Fax [phone]
An Equal Opportunity/Affirmative Action Employer— 50% Recycled/10% Post Consumer Paper

Permit No. 15W R% (Al lob
(to be provided by DWQ)
State of North Carolina
Department of Environment and Natural Resources
Division of 11,'zt r Quality
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form may be photocopied for use as an original
DWO 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.
1. PROJECT INFORMATION
Project Name: American Auto & Finance
Contact Person: Mark Hargrove Phone Number: 910-256-9277
For projects with multiple basins, specify which basin this worksheet applies to:
elevations
Basin Bottom Elevation
Permanent Pool Elevation
Temporary Pool Elevation
areas
Permanent Pool Surface Area
Drainage Area
Impervious Area
volumes
Permanent Pool Volume
Temporary Pool Volume
Forebay Volume
other parameters
SA/DA'
Diameter of Orifice
Design Rainfall
Design TSS Removal
Footnotes:
32.0 ft.
(floor of the basin)
36.0 ft.
(elevation of the orifice)
37.3 ft.
(elevation of the discharge structure overflow)
4,429 sq. ft
(water surface area at the orifice elevation)
121 ac.
(on -site and off -site drainage to the basin)
0.76 ac.
(on -site and off -site drainage to the basin)
8,043 cu. ft. (combined volume of main basin and forebay)
6,472 cu. ft. (volume detained above the permanent pool)
2,0R1 cu. ft. (approximately 20% of total volume)
5.32 (surface area to drainage area ratio from, DWQ table)
1.0 in. (2 to 5 day temporary pool draw -down required)
1.5 in.
90 % (minimum 85% required)
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 nonstandard table entries.
In the 20 coastal counties, the requirement for a vegetative filter may be waived if the wet detention basin is designed to
provide 90% TSS removal. The NCDENR BMP manual provides design tables for both 85% TSS removal and 90%
TSS removal.
Form SWU-102 Rev 3.99 Page 1 of 4

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
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.
M N c.
The temporary pool controls runoff from the design storm event.
d.
The temporary pool draws down in 2 to 5 days.
A111A e.
If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations)
N 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.
.N. 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.
Ii'I J� j.
A trash rack or similar device is provided for both the overflow and orifice.
A% k.
A recorded drainage easement is provided for each basin including access to nearest right-of-way.
M1 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.
in. A mechanism is specified which will drain the basin for maintenance or an emergency.
(Pond will be pumped down by mechanical means if required)
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) O does es not incorporate a vegetated filter at the outlet.
This system (check one) 0 does l toes not incorporate pretreatment other than a forebay.
Form SWU-102 Rev 3.99 Page 2 of 4

Maintenance activities shall be performed as follows:
1. 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 the 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.
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 avet
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 3.0 feet in the main pond, the sediment shall be removed.
When the permanent pool depth reads 0.75 feet in the forebay, the sediment shall be removed.
Sediment
Bottom
El. 175
-33. o --
on - �y
FOREBAY
BASIN DIAGRAM
(fill in. the blanks)
Permanent Pool Elevation 36 6
Sediment Removal Elevation 33.0
Bottom Elevation 3a.b
MAIN POND.
75%
25%
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.
7. All components of the wet detention basin system shall be maintained in good working order.
Form SWU-102 Rev 3.99 Page 3 of 4

VI. SUBMITTAL REQUIREMENTS
Only. complete application packages will be accepted and reviewed by the Division of Water Quality (DWQ). A
complete package includes all of the items listed below. The complete application package should be submitted to
the appropriate DWQ Regional Office.
1. Please indicate that you have provided the following required information by initialing in the space provided
next to each item.
Initials
• Original and one copy of the Stormwater Management Permit Application Form /?A7 9
• One copy of the applicable Supplement Form(s) for each BMP MP4--
• Permit application processing fee of (payable to NCDENR)49, W, G a eAtj 1+
• Detailed narrative description of stormwater treatment/management 1p&101}
• Two copies of plans and specifications, including: 01'0 j
- Development/ Project name
- Engineer and firm
- Legend
- North arrow
- Scale
- Revision number & date
- Mean high water line
- Dimensioned property/project boundary
- Location map with named streets or NCSR numbers
- Original contours, proposed contours, spot elevations, finished floor elevations
- Details of roads, drainage features, collection systems, and stormwater control measures
- Wetlands delineated, or a note on plans that none exist
- Existing drainage (including off -site), drainage easements, pipe sizes, runoff calculations
- Drainage areas delineated
- Vegetated buffers (where required)
VIL AGENT AUTHORIZATION
If you wish to designate authority to another individual or firm so that they may provide information on your
behalf, please complete this section.
Designated agent (individual or firm): Withers & Ravenel, Inc.
Mailing Address: _ 7040 Wrightsville Ave, Suite 101
City Wilmington
Phone: ( 910) 256-9277
State: NC
VIII. APPLICANT'S CERTIFICATION
Zip: 28403
Fax: [phone]
I, (print or type name of person listed in General Information, Item 2) Ralph H.Griffin Jr.
certify that the information included on this permit application form is, to the best of my knowledge, correct and
that the project will be constructed in conformance with the approved plans, that the required deed restrictions and
protective covenants will be recorded, and that the proposed project complies with the requirements of 15A
NCAC. 2H.1000.
Date: /0 . Zdv -
Form SWU-101 Version 3.99 Page 4 of 4