20061214 Ver 2_More Info Received_20070705

Environmental Consultants, PA
:Road Raleigh, North Carolina 27614 Phone: [phone] Fax: [phone]
Division of Water Quality
Attn: Cyndi Karoly /Ian McMillan
2321 Crabtree Boulevard
Suite 250
Raleigh, NC 27604
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Re: Reply to the Division of Water Quality's 05/02/07 Request for Additional
Information
Recreation Tract for Woodcreek (formerly Wild Acres) Stormwater Management
Plan
Wake County, North Carolina
Dear Ms. Karoly and Mr. McMillan:
This letter is in response to your letter dated May 2, 2007 which requested additional
information for the Recreation Tract for Woodcreek (formerly Wild Acres) Stormwater
Management Plan. The following restates your questions/comments and is then followed
by our response.
Additional Information Requested
1. The acreage of the impervious surfaces and open space reported on
the enhanced aerial photograph do not match the acreages reported in
the Extended Detention Worksheet, Please explain the discrepancy.
The discrepancy in the impervious surfaces and open space has been corrected. Please
see the attached revised Stormwater Management Report.
2. Please provide an overall site plan that shows lot layouts and the
footprints of the impervious surfaces. The site plan. must show that all
of the Stormwater from the site will be routed to the extended detention
wetland.
Charlotte Office:
236 LePhillip Court, Suite C
Concord, NC 28025
Phone: [phone]
Fax: [phone]
Greensboro Office:
3817-E Lawndale Drive
Greensboro, NC 27455
Phone: [phone]
Fax: [phone]
July 5, 2007
S&EC Project # 9615.W1
DWQ No. # 06-1214, Ver 2.

An overall site plan that shows the lot layouts and the footprints of the impervious
surfaces has been included. The stormwater conveyance system is shown on the exhibit
map in the attached revised Stormwater Management Report.
3. The roadside drainage from the proposed new street may not be
directed to a level spreader without first being treated by an allowable
BMP for Nutrient Sensitive Waters (NSW) as described in General
Certification 3631.
Per discussion with DWQ representatives and the 401 Water Quality Certification and
Authorization Certificate addition conditions issued on January 31, 2007, the roadside
drainage does not require treatment as described in General Certification 3631 since it is
not in Tract D, Tract F, Tract J or the Recreation Tract (a.k.a. Amenity Center Phase).
The approval states that constructed wetland or bio-retention ponds must be used to treat
stormwater for the above Tracts due to their proposed percent imperviousness. The
roadside drainage is not located in one of the above Tracts and therefore, the discharge is
diffused with a level spreader.
4. Please revise the drainage system to the extended detention wetland so
that all of the stormwater is routed to the fore bay at the north end of
the constructed wetland. The fore bay that is currently proposed in the
center of the wetland will reduce the treatment capability of the
wetland and likely result inshort-circuiting.
The drainage system has been revised so that all of the stormwater is routed to the fore
bay at the north end of the constructed wetland. Please see the attached revised
Stormwater Management Report.
S. Please provide all of the information under listed [sic] in the
"Required Item Checklist" in the DWQ Extended Detention
Worksheet. Some of the omitted items include a planting plan, a
delineation of the drainage area, and the plan details for the inlet and
outlet structures.
The above mentioned information form the "Required Item Checklist" has been included.
The planting plan and inlet and outlet details are included on the constructed wetland
detail sheet (22" X 34") that is included in the appendix. The delineation of the drainage
area is shown on the project exhibit map (11"X17"). The signed and notarized site
specific operation and maintenance agreement was included with the previous submittal;
it was not re-submitted with this submittal.
6. The outflow from the extended detention wetland may not be directed
to a scour hole in the currently proposed location. A scour hole is only

allowable in areas where the down slope is less than or equal to two
percent. (See the Level Spreader BMP Manual Chapter at:
http: //h2o. enr.state. nc. us/ncwetlands/documents/LevelspreadersBMPMan
ualchapter.doc). Please replace the scour hole with a properly designed
level spreader. In your re-submittal, please include level spreader plans,
calculations and a DWQ level spreader worksheet so that DWQ staff can
evaluate the design of the level spreader.
A ditch has been designed to carry the outflow from the extended detention wetland
through the buffer, directly into the receiving stream. The ditch is shown on the
construction drawing which is included in the Appendix of the attached Stormwater
Management Report.
The estimated 10-year velocity in the ditch is 3.Oft/s. As a result rip rap was only used at
the pipe outlet; the remainder of the ditch will be grass. Also, the ditch grade ties to the
receiving stream's invert. With the slow ditch velocities and the backwater influences
from the receiving stream, it is not anticipated that erosion will be a problem at the ditch
outlet.
Please feel free to call me if you require any further explanation.
Sincerely,
~ `~ /
icole J. Tho on
Regulatory Specialist
Attachments: 5 copies of Response letter
5 copies of Revised Stormwater Management Report
CC: Mr. Jamie Shern (USAGE)
Mr. Mike Horan, DWQ Raleigh Regional Office
Mr. Tim Smith, 100 Weston Estates Way, Cary, NC 27513