SW8061117_Current Permit_20071227

Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Coleen H. Sullins Director
Division of Water Quality
December 27, 2007
Glenn Richardson, Member
Smithville Crossing, LLC
1327 Live Oak Parkway
Wilmington, NC 28403
Subject: Approved Plan Revision
Smithville Crossing
Stormwater Project No. SW8 061117
Brunswick County
Dear Mr. Richardson:
On September 27, 2007, the Wilmington Regional Office received a plan revision for
Stormwater Management Permit Number SW8 061117. The revisions include the removal of
the middle portion of the building and the installation of a courtyard between the remaining two
buildings. It has been determined that a formal permit modification is not required for the
proposed changes. We are forwarding you an approved copy of the revised plans for your
files. Please add the attached plans to the previously approved plan sheets.
Please be aware that all terms and conditions of the permit issued on February 9, 2007,
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 submitted to and approved through the
Division of Water Quality 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 (910)
796-7215.
Sincerely, o
Rhonda Hall
Environmental Engineer
ENB1arl: S:IWQSISTORMWATERIPERMIT1061117PR.dec07
cc: Denise L. Freund, P.E., WK Dickson
Brunswick County Building inspections
Rhonda Hall
Wilmington Regional Office
Central Files
Non, CaC0ural1 a
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington, NC 28405 Phone [phone] Customer Service
Wilmington Regional Office Internet: www.ncwaterguality.org Fax [phone] I-877-623-6748
An Equal Opportunity/Affirmative Action Employer— 50% Recycled/10% Post Consumer Paper

Permit No. S t% o (- 111 "7
(to be provided by DWQ)
State of North Carolina
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.
1. PROJECT INFORMATION
Project Name: Smithville Crossing
Contact Person: Denise Freund, P.E. Phone Number: [phone]
For projects with multiple basins, specify which basin this worksheet applies to: Wet Detention Basin #1
elevations
Basin Bottom Elevation 19.5
ft.
(floor of the basin)
Permanent Pool Elevation 22.5
ft.
(elevation of the orifice)
Temporary Pool Elevation 23.15
ft.
(elevation of the discharge structure overflow)
areas
Permanent Pool Surface Area 12,929
sq. ft.
(water surface area at the orifice elevation)
Drainage Area 1.1 R
ac.
(on -site and off -site drainage to the basin)
Impervious Area 2.43
ac.
(on -site and off site drainage to the basin)
volumes
Permanent Pool Volume 21,978
cu. ft.
(combined volume of main basin and forebay)
Temporary Pool Volume 8,790
cu. ft.
(volume detained above the permanent pool)
Forebay Volume 4,244
cu. ft.
(approximately 20% of total volume)
other parameters
SA/DA' 8.88
(surface area to drainage area ratio from, DWQ table)
Diameter of Orifice 1 5
in.
(2 to 5 day temporary pool draw -down required)
Design Rainfall 1 _o
M.
Design TSS Removae 90
%
(minimum 85%required)
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 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 SW-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.
1 c. The temporary pool controls runoff from the design storm event.
d. The temporary pool draws down in 2 to 5 days.
!zC-7'C- —zo- "�KZ52L-�' e"idz� Is_-
e. If required, a 30-foot vegetative filter is provided at the outlet (include non -erosive flow calculations)
�l 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.
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. — ►�,U W��-r - �'A
m. A mechanism is specified which will drain the basi�i o�r miain'x'tenance or an e ge cy.
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) O does V does not incorporate a vegetated filter at the outlet.
This system (check one) O does does not incorporate pretreatment other than a forebay.
Form SW-102 Rev 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 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 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 1: '5 feet in the main pond, the sediment shall be removed.
When the permanent pool depth reads I J'�> feet in the forebay, the sediment shall be removed.
BASIN DIAGRAM
(fill in the blanks)
Permanent Pool Elevation 2Z .S
Sediment Reshoval El. M 75
rr Sediment removal Elevation �.ZS 7596
BottomEle ation �� 2- % ------------------------------------------ ----
FOREBAY
Bottom Elevation `_L %a 25%
MAINPOND.
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.
G. 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

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 parry.
Print name: Glenn Richardson
Title: Member
Address: 1327 Live Oak Parkway Wilmington, NC 28403
Phone: [phone]
Date:
Signa
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.
I; -� �• Q rre/� a Notary Public for the State of N 0'�' Ca I n a
County of Neq)-kanoyl° r do hereby certify that l -n rI I .' ChO-r SSYl
personally appeared before me this X"'Iday of 3(-n uar and acknowledge the due
execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal,
HA
�r
PueV
.,�"",,',,INA��,����.
SEAL
My commission expires au
Form SWU-102 Rev 3.99 Page 4 of 4

State Stormwr ,r Management Systems
Permit No. SW8 061117
JSmithville Crossing LJ 01
Stormwater Permit No. SW8 061117
Brunswick Countv 1 �"
Designer's Certification
1, V�St_ , as a duly registered
in the State of North Carolina, having been authorized to observe (periodically/ weekly/
full time) the construction of the project,
CSS�Azs�
(Project)
for (Project Owner) hereby state that, to the
best of my abilities, due care and diligence was used in the observation of the project
construction such that the construction was observed to be built within substantial
compliance and intent of the approved plans and specifications.
The checklist of items on page 2 of this form is included in the Certification.
Noted deviations from approved plans and specification:
Signature
Registration Number.
Date'C�
SEAL
�Y1 CAR
408y7
INS "
'
I�P+P/P11 rll},
Page 7 of 8

State. Stormv -.r Management Systems
Permit No. SW8 061117
Certification Requirements:
✓ 1. The drainage area to the system contains approximately the permitted
acreage.
_ 2. The drainage area to the system contains no more than the permitted
amount of built -upon area.
✓ 3. All the built -upon area associated with the project is graded such that the
runoff drains to the system.
4. All roof drains are located such that the runoff is directed into the system.
✓ 5. The outlet/bypass structure elevations are per the approved plan.
✓ 6. The outlet structure is located per the approved plans.
✓ 7. Trash rack is provided on the outlet/bypass structure.
✓ 8. All slopes are grassed with permanent vegetation..
9: Vegetated slopes are no steeper than 3:1.
10. The inlets are. located per the approved plans and do not cause short-
circuiting of the system.
✓ -11. The permitted amounts of surface area and/or volume have been
provided.
12. Required drawdown devices are correctly sized per the approved plans.
✓ 13. All required design depths are provided.
14. All required parts of the system are provided, such as a vegetated shelf,
and a oirebay.
15. The required system dimensions are provided per the approved plans.
cc: NCDENR-DWQ Regional Office
Brunswick County Building Inspections
Page 8 of 8