SW6090303_HISTORICAL FILE_20090328

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

:r
NC®ENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
March 28, 2009
Mr. Merrick Dugal, III, PE
Wilbur Smith Associates
421 Fayetteville Street, Suite I303" "
Raleigh, North Carolina 27601
Subject: Request for additional Information
Phase II Post -Construction Stormwater Permit Application
Stormwater Project No. SW6090303
Sandhills Community College
Hoke County
Dear Mr. Dugal:
The Division of Water Quality received your Stormwater Management Permit Application for the subject
project on March 19, 2009. A preliminary review of that information has determined that the application is not
complete. The following information is needed to continue the stormwater review:
Impervious surface numbers reported on the supplement, Section I11-9, do not agree. In the Basin
Information table you reported a proposed impervious area of 78,844 sf. In the Impervious
Surface table you reported 81,020 sf where the numbers add up to only 78,844. The numbers
should agree. Please resubmit pages 2 of 4 and 3 of 4 with the corrected numbers.
2. Please provide data on how the rainfall intensity was determined. It appears low given the slope
and length of flow.
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to May 1, 2009, or the application will be returned
as incomplete. The return of a project will necessitate resubmittal of all required items, including the application
fee. If you need additional time to submit the information, please mail or fax your request for a time extension to
the Division at the address and fax number at the bottom of this letter. The request must indicate the date by
which you expect to submit the required information. The Division is allowed 90 days from the receipt of a
completed application to issue the permit. Please reference the State assigned project number S W6090303 on all
correspondence. All original documents must be returned or new originals trust be provided.
Wetlands and Stormwater Branch
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604
Phone: [phone] \ FAX: [phone] \ Customer Service: 1-877-623-6748
Internet: www.ncwaterquality.org
An Equal Opportunity \ Affirmative Action Employer
North Carolina
naturally

The construction of any impervious surfaces, other than a construction entrance under an
approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject to
enforcement action pursuant to NCGS 143-215.6A.
All original documents must be returned or new originals must be provided. Copies are not
acceptable. If you have any questions concerning this matter please feel free to contact me at (919) 807-
6374 or [e-mail].
Sincerely,
Mike Randall
Environmental Engineer
Stormwater Permitting Unit
cc: Fayetteville Regional Office
Stornwater Permitting Unit Files

1�
�m NODEN R
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins
Governor Director
February 16, 2009 �^
Mr. Richard J Gough
Vice President of Business and Administrative Services
Sandhills Community College ® 1Y7�
3935 Airport Road
Souther Pines, North Carolina 28374
Subject: Phase II Post -Construction Stormwater Permit Application Return
Sandhills Community College
Hoke County
Dear Mr. Gough:
Dee Freeman
Secretary
To obtain a permit to construct a wet detention basin in North Carolina, the wet detention basin
must meet all of the regulation -based Major Design Elements listed the State BMP Manual. North
Carolina rules require that a wet detention basin must be designed by a licensed professional. Further, the
designer must subsequently certify that he inspected the facility during construction, that the BMP was
built in accordance with the approved plans, and that the system complies with the requirements of the
rules. The Division of Water Quality received your Stormwater Management Permit Application for the
subject project on February 12, 2009. A preliminary review of that information has determined that the
application is not complete and is being returned along with the application check. The following
information is needed to continue the stormwater review:
1. The numbers reported on the supplement, the numbers used in the calculations and what is drawn
or detailed on the plans is inconsistent. The supplement form indicates a 10-foot wide vegetated
shelf and a trash rack, but none on the plans.
2. The orifice drawdown calculation provided does not use the correct head. The average head to
use in the orifice equation is approximately 1/3 of the distance between the PPE and the elevation
of the next available outlet above the PPE.The plans indicate a 3" orifice and the supplement
form indicates a 1" orifice. The calculations indicate a 3 foot head but the depth of the temporary
pool as shown on the drawing is only 2 feet and to the drop inlet the depth is only 3.25 feet.
Calculations for the temporary, pool volume draw -down time are provided in Section 3.4 of the
North Carolina BMP Manual.
3. A minimum 10-foot wide vegetated shelf shall be installed around the perimeter. The inside edge
of the shelf shall be 6" below the permanent pool elevation; the outside edge of the shelf shall be
6" above the permanent pool elevation.
Wetlands and Stormwater Branch
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604 One North
1
Phone: [phone] \ FAX: [phone] \ Customer Service: 1-877-623-6748 1 ne CaCO11IIa
Internet: www.ncwatergualitveAct N%timal�y
An Equal Opportunity\ ANirmative Action Employer K L!4

4. Failure to provide a detailed landscaping plan for vegetated shelf and the slopes of the wet pond.
The planting plan must be prepared by a qualified design professional licensed in North Carolina.
The landscaping plan should provide specifications for the selection of vegetation, its installation,
and the post -installation care.
5. The orifice configuration provided does not provide for adequate maintenance access. With the
"tee" type configuration, the small orifice opening should be provided at the bottom of the "tee"
underwater so that a rod may be used to unclog it.
6. Please delineate all wetlands on site, or provide a note on the plans stating there are no wetlands
on site.
7. DWQ requires wet detention basin discharges to be evenly distributed across a minimum 30 feet
long vegetative filter strip unless it is designed to remove 90% TSS.
8. Plans do not delineate offsite drainage area— there appears to be possible offsite drainage being
directed to the swales at both the east and west end. Sizing must take into account all runoff at
ultimate build -out, including off -site drainage.
9. Supplement Form indicates an average depth of 2.5 feet. DWQ requires an average depth of 3.0
feet.
10. Information on the seasonal high water table (SHWT) was not provided. If the SHWT is below
the permanent pool elevation (PPE), then a liner will need to be provided in order to maintain the
permanent pool. If a clay liner is proposed, then a minimum 4-inch layer of topsoil shall be
provided on the vegetated shelf for planting.
11. The average depth calculation does not include the 1-foot of sediment depth at the bottom of the
pond. A minimum 1-foot of additional depth must be provided for sediment.
12. Please show all roof leaders for the proposed building, or provide a note on the plans that all roof
leaders must be directed to the wet pond.
Wet detention basins are typically part of the initial site clearing and grading activities and are
often used as sediment basins during construction. The NCDENR Erosion and Sediment Control
Planning and Design Manual contains design requirements for sediment basins required during
construction. A sediment basin typically does not include all the engineering features of a wet detention
basin, and the design engineer must insure that the wet detention basin includes all the features identified
in this section, including the full sizing as a wet detention basin. If the wet detention basin is used as a
sediment trap during construction, all sediment deposited during construction must be removed, erosion
features must be repaired, and the vegetated shelf must be restored, before operation as a stormwater
BMP begins.
Emergency overflow spillways must be designed with hardened materials at the points where
extreme conditions might compromise the integrity of the structure. North Carolina rules require a
vegetative filter strip on the discharge from a wet detention basin, along with a level spreader or other
engineered device to ensure even, non -erosive distribution of the flow. Wet detention ponds designed for
85% TSS removal are required to discharge through a 30 foot vegetated filter to minimize erosion and to
provide additional pollutant removal. There may be projects where it is difficult to construct a functional
vegetated filter, and the outflow must discharge to the watercourse. In these instances, additional storage
shall be provided to compensate for the lack of a filter and the pond must be designed to remove 90%
TSS instead of 85%. Chapter 13 Filter Strip contains information on the design elements of the vegetative
filter strip. Chapter 8 Level Spreader contains information on the design elements of a level spreader.

The return will necessitate resubmittal of all required items, including the application fee. The
original plans submitted with the application are being kept in the Stormwater Permitting Unit file.
The construction of any impervious surfaces, other than a construction entrance under an
approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject to
enforcement action pursuant to NCGS 143-215.6A.
All original documents must be returned or new originals must be provided. Copies are not
acceptable. If you have any questions concerning this matter please feel free to contact me at (919) 807-
6374 or [e-mail].
Sincerely,
Mike Randall
Environmental Engineer
Stormwater Permitting Unit
cc: Merrick Dugal 111, PE Wilbur Smith Associates
Fay_etteyille Regional Office
Stormwater Permitting Unit Files