U-2579_DocuSign_U-2579Stormwater_Response__L

PAT McCRORY
Governor
NICHOLAS 1. TENNYSON
Secretary
Transportation
November 1, 2016
Mr. Pat Ivey, PE
Division 9 Engineer
Department of Transportation
375 Silas Creek Parkway
Winston Salem, 27127
Subject: Forsyth County; Winston Salem Northern Beltway from US 158 to I-40
Business/US 421; Federal Aid Project No. FSTR HPPNHF-0918(46); WBS
Element 34839.1.1; TIP U-257913: State and Federal Stormwater Compliance
and Stormwater Management Review of Stations -L- Station 520+00 to -L-
Station 530+00, Tabor Pond
Dear Mr. Ivey,
The Hydraulics Unit has reviewed the permits and associated plans for the above referenced project and
confirmed that the stormwater controls and design adhere to both State and Federal post -construction
stormwater requirements as well as the NCDOT Hydraulic Guidelines. The U.S. Army Corps of Engineers
(USACE) Section 404 Individual Permit and the N.C. Division of Water Resources (NCDWR) Section 401
Water Quality Certification for the above referenced project were obtained on June, 17th 2014. In addition,
the project is in accordance with the requirements of the NCDOT National Pollutant Discharge Elimination
System (NPDES) Stormwater Permit, NCS000250 and the National Environmental Policy Act (NEPA).
The development of this project included interactive meetings with resource agencies through planning and
design.
The Hydraulics Unit subsequently reviewed the stormwater controls associated with the area around Tabor
Pond and has confirmed that stormwater management measures have been implemented in accordance with
the NPDES permit and the NCDOT Hydraulics Guidelines. Based on the review of the project in this
location the design implemented the following stormwater management concepts that included:
Planning Stormwater Measures:
Maximizing shoulder section: A significant amount of grass and vegetative shoulders are
implemented with this design. Two -hundred and sixty feet of vegetated right-of-way are
accompanied with 22 feet of grass median.
Assessing and Minimizing the Impacts of Stormwater Runoff to Environmentally
Sensitive Areas: The crossing for Tabor Pond minimized fill into the pond while
providing treatment of stormwater runoff that maximized vegetation conveyance.
Design Stormwater Measures:
Providing adequate ground cover at completion: Proper seeding and establishment of
vegetation has been provided in the design and contract.
Embankments and ditches have been stabilized.
Nothing Compares_
State of North Carolina I Department of Transportation I Hydraulics Unit
1020 Birch Ridge Drive 11590 Mail Service Center I Raleigh, NC 27699-1590
919-707-6700 T

Page 2
November 1, 2016
Forsyth County; Winston Salem Northern Beltway from US 158 to I-40 Business/US 421; Federal Aid Project No. FSTR
HPPNHF-0918(46); WBS Element 34839.1.1; TIP U-2579B: State and Federal Stormwater Compliance and Stormwater
Management Review of Stations -L- Station 520+00 to -L- Station 530+00, Tabor Pond
• Energy Dissipation: Rip Rap has been used to disperse the kinetic energy of the flowing
water at the end of pipes and ditches.
• Natural features and drainage pathways have been used to eliminate direct discharge to
Tabor Pond and provide treatment.
• Diffuse flow was utilized where possible with shoulder sections that promote diffuse flow.
Finally a pre / post analysis was completed for the drainage to Tabor Pond. This analysis identified how
much increase in peak flow would be attributed to the project. The analysis identified that a 6.2% increase
in peak flow would occur. While this is an increase, this increase is not considered substantial since it is
less than 10% and appropriate controls are in place to effectively discharge the peak flow to the receiving
waters.
In closing the Winston Salem Northern Beltway is in accordance with State and Federal post -construction
stormwater management requirements as required by the Department's NPDES permit and as documented
in the issued Section 404 Individual Permit and the N.C. Division of Water Resources (NCDWR) Section
401 Water Quality Certification.
Sincerely,
A�DocuuS'ilg ne/d.'by::
"WNIWW� S .
7A9B8D53FF5D47B...
Matthew S. Lauffer, PE
Hydraulics Unit
Assistant State Hydraulics Engineer
msl
cc:
Mike Randall, NC Division of Environmental Quality
Amy Chapman, NC Division of Environmental Quality