20061617 Ver 2_More Info Letter_20080331

~QF W'gTF9Q Michael F. Easley, Governor
`(~ G William G. Ross Jr., Secretary
~ r North Carolina Department of Environment and Natural Resources
p ~ Coleen H. Sullins, Director
Division of Water Quality
March 31, 2008
DWQ EXP No. 06-1617
Wake County
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
Wake County Board of Education
Wake County Public School System
Attn: Mr. Mike Burriss
1429 Rock Quarry Road
Suite 116
Raleigh, NC 27610
Project Name: E-34 (Wendell Elementary School)
REQUEST FOR MORE INFORMATION
On November 1, 2007 the Division of Water Quality (DWQ) issued a 401 Water Quality Certification to
have specified amounts of impacts to state waters and riparian buffers for the purpose of constructing a
Wendell Falls mixed use development, Wendell Falls Parkway and U.S. 64/264 interchange located in
Wake County as described in your application dated September 26, 2006 and May 2, 2007, and all
additional information received by DWQ on October 18, 2006, January 25, 2007, February 9, 2007, June
13, 2007, August 16, 2007, September 5, 2007 and September 12, 2007. In order to meet Conditions 25
and 26 of the 401 Certification for this project, a stormwater management plan was submitted to the
Express Review Program of the DWQ on March 31, 2008. 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 denial of your application as required by 15A NCAC
2H .0506:
Additional Information Requested
Bioretention Cells A & B:
a. Please provide underdrain design calculations to show that the number of underdrain pipes
provided is sufficient. Please also note that, the spacing of collection laterals shall be no
greater than 10 feet center to center. (See Section 5.7 of the NC DWQ Stormwater BMP
Manual).
b. Please specify the following on the construction plans:
i. The slope of the underdrain pipes (0.5% recommended).
ii. The soil mix specifications including the source, composition, permeability and P-
index.
2. Diffuse Flow Provisions:
a. Condition 26 of your 401 Certification states that all stormwater shall be directed at non-
erosive velocities through the protected stream buffers and will not re-concentrate before
discharging into the stream. The outflow velocities of 5.68 ft/s and 6.16 ft/s from the
proposed Bioretentions A and B respectively are considered erosive. The type of energy
dissipation device provided only protects the outlet but will not insure that diffuse flow will
be achieved. Please provide other mechanism to insure that non-erosive velocities are
401 Oversight I Express Review Permitting Unit
1650 Mail Service Center, Raleigh, North Carolina 27699-1650
2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604
Phone: [phone] FAX [phone]nternet: htto://h2o.enr.state.nc.us/ncwetlands
No°e hCarolina
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An Equal OpportunitylAffirmative Action Employer - 50% Recycledl10% Post Consumer Paper

E-34 Wendell Elementary School
Page 2 of 2
March 31, 2008
achieved prior to entering the stream buffers. A vertical circular structure with multiple
outlets and rip-rap apron may be considered.
Please respond within five (5) days of the date of this letter by sending two (2) 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.
Please contact Joseph Gyamfi or Lia Myott at 919-733-1786 if you have any questions regarding, or
would like to set up a meeting to discuss, this matter.
Sincerely,
i
~!1~
Cyndi Karoly, Supervisor
401 Oversight/Express Review Permitting Unit
CBK/jg
cc: James Shern, USACE Raleigh Regulatory Field Office
Lauren Witherspoon, DWQ Raleigh Regional Office
File Copy
Central Files
Pam Kistner, P.E., Dewberry & Davis, Inc., 2301 Rexwood Dr., Suite 200, Raleigh, NC 27607
Larry J. Ragland, RLA, ALSA, McNeely Associates, 5501 McNeely Drive, Raleigh, NC 27622