20100647 Ver 1_More Info Letter_20110221

NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
February 21, 2011
DWQ Project # 10-0647
Wake County
Arthur and Janet Begun
104 Aberson Court
Cary, NC 27519
Subject Property: 104 Aberson Court
UT to Crabtree Creek [030402, 27-33-(10), C, NSW]
REQUEST FOR MORE INFORMATION: STORMWATER MANAGEMENT PLAN
Dear Mr. and Mrs. Begun:
On September 23, 2010, the Division of Water Quality (DWQ) issued a Neuse Riparian Buffer
Protection Rules Minor Variance to impact approximately 242 square feet of Zone 2 of the protected
buffers to construct a sunroom on the above named property.
Condition Number 4 of the minor variance requires that you submit a final, written stormwater
management plan to the DWQ, which must be approved in writing before the impacts specified in the
variance may occur. On January 12, 2011, the DWQ received a stormwater management plan (dated
January 11, 2011) from your consultant, Mr. Andrew Rodak, P.E. of Duncklee & Dunham. The
DWQ has determined that the stormwater management plan was incomplete as discussed below.
Additional Information Requested:
1. Please provide a minimum of two underdrain pipes in parallel.
2. Please re-design the forebay so that it is not at a lower elevation than the main treatment area
of the bioretention cell. This is likely to cause short-circuiting.
3. The soils report provided does not document the actual elevation in feet mean sea level of the
seasonal high water table. Please ask the soil scientist to provide this information. Also,
please insure that the proposed design complies with the BMP Manual's requirements
regarding the seasonal high water table.
4. In order to use an Internal Water Storage Zone (IWS), the media depth above the gravel layer
must be at least three feet - the depth specified in the current design is inadequate. Piedmont
installations of IWS also run the risk of collecting stagnated water if the soils do not have
enough permeability to drain between storms. The DWQ recommends using a traditional
grassed bioretention cell design at this location. If you decide to pursue an IWS design, then
please provide the appropriate media depth.
Nor
E ployer
104 Aberson Court
Page 2 of 2
February 21, 2011
5. Please provide specifications for the following:
a. The precise species of sod that will be used.
b. Sod installation.
c. The procedure for establishing the sod on the bioretention cell, including watering
and a one-time fertilizer application.
The DWQ will require the above additional information to finalize review of the stormwater
management plan for the subject property. Please provide this information within 30 calendar days.
If you have any questions, please telephone me at [phone].
Sincerely,
anvx?&-
l
Annette M. Lucas, P.E.
Wetlands, Buffers and Stormwater Compliance and
Permitting Unit
AMLIaml
cc: Lauren Witherspoon, DWQ Raleigh Regional Office
DLR Raleigh Regional Office
File Copy
Filename: 100647AbersonCourt104(Wake)_SW Hold.doc