19961184 Ver 2_More Info Letter_20110105

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NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
January 5, 2011
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
Mr. David Willis, President
LTY Land Holdings of Blakeney, LLC
620 Briar Patch Terrace
Marvin, North Carolina 28173
DWQ #: EXP 96-1184v2
Mecklenburg County
Subject Property: Kiddie Academy -Blakeney Office Park (Part of Landen Town Center)
REQUEST FOR MORE INFORMATION - Stormwater Management Plan
Dear Mr. Willis:
On January 4, 2011, the Express Review Program of the Division of Water Quality (DWQ) received your
stormwater management plan application dated December 27, 2010 along with supporting information for
the subject project in Mecklenburg County. The DWQ has determined that your application will require
additional information. Please provide the following information so that we may continue to review
your project and prevent return of your application as required by 15A NCAC 2H .0506:
Additional Information Requested
1) Please provide a completed Required Items Checklist along with all the items listed on it. This part
and the Design Summary part makes the Supplement Form complete.
2) Please note that while the Sediment and Sand Filter chambers meet the required minimum individual
surface areas (corresponding to a maximum head of 2.0 feet), the test condition for the sum of the two
areas at that given maximum head is not met. As a result, the device is slightly undersized. You may
increase the maximum head or increase the surface areas.
3) If the Seasonal High Water Table (SHWT) elevation reported on the supplement form is correct, then
the sand filter device cannot be used since the SHWT coincides with the bottom of the sediment
chamber (and top of sand). The 2-foot minimum separation is not met in this case.
4) Please revise and provide adequate information on the supplement form. All items indicating
insufficient information must be addressed.
5) On plan sheet C4.1, the top elevation of the sand bed in the cross section (with underdrain details)
shows 597 feet instead of 597.5 feet.
6) Please make sure ASTM C33 is specified for the sand filter media.
401 OversightlExpress Review Permitting Unit
1650 Mail Service Center, Raleigh, North Carolina 27699-1650
Location: 512 N. Salisbury St., Raleigh, North Carolina 27604 (911 Floor)
Phone: [phone] FAX: [phone]
Internet: http://portal.nodenr.org/web/wq/swp/ws/401
NorthCarolina
;Vaturally
An Equal Opportunity 1 Affirmative Action Employer
Kiddie Academy SMP_holdl
Mecklenburg
Page 2 of 2
January 5, 2011
7) The sand filter should drain within 40 hours. Your supplement form indicates a drainage time of 48
hours. Please ensure that this condition is met, and provide supporting drainage (underdrain sizing)
calculations. Note also that a minimum of 2 underdrains are required and underdrains should have
cleanout pipes.
8) It is recommended that Sand filters are designed as offline stormwater BMPs so that the hydraulic
capacity of the device is not overloaded during larger storms. For such a small drainage area, this
condition can be waived. However, please provide calculations to show that the outlet pipe (6-inch) is
sized adequately so that the performance of the device is not compromised. Even when the outlet pipe
size is found adequate or increased, this office recommends that the overflow structure should be
located in the sediment chamber and the underdrain pipes (in the sand filter bed) should then tie in to
the outlet pipe (from the overflow structure).
Please respond within five (5) days of the date of this letter by sending three (3) copies of the above
information in writing. The Express Review Program is a process that requires all parties to
participate in a timely manner.
This letter only addresses the application review and does not authorize any impacts to wetlands,
waters or protected buffers. Please be aware that any impacts requested within your application are
not authorized (at this time) by the DWQ.
Thank you for your attention to this matter. If you have any questions or wish to discuss these matters
further please do not hesitate to call Joseph Gyamfi at 919-807-6426 or Lia Gilleski 919-807-6446.
Sincerely,
Ian McMillan, Acting Supervisor
401 Oversight/Express Review Program
UM/j9
cc: File copy
Kevin Caldwell, Geoscience Group, Inc., 500 K Clanton Rd., Charlotte, NC 28217
Alan Johnson, MRO