20201297 Ver 1_West Duncan Street PCN Cover Letter_20201208

SAGE
ECOLOGICAL
SERVICES
EST ill 2016
December 8, 2020
US Army Corps of Engineers NC Division of Water Resources
Wilmington Regulatory Office Wilmington Regulatory Office
Attn: Ms. Emily Greer Attn: Ms. Joanne Steenhuis
69 Darlington Avenue 127 Cardinal Drive Extension
Wilmington, NC 28403 Wilmington, NC 28405
Re: West Duncan Street Culvert Replacement
Notification to USACE and NCDWR
Sage Project#2020.060
On behalf of The Town of Lillington (applicant and owner) please find attached a complete application and
supplemental information notifying US Army Corps of Engineers (USACE) and North Carolina Division of
Water Resources(NCDWR)that the activities associated with the proposed project described herein qualify
as a non-reporting project under Nationwide Permit 3 (NWP 3) for the reasons described below under
Project Purpose and Detail.
The proposed project qualifies as non-reporting NWP3 because the project is the emergency repair of an
existing transportation facility that was compromised during a recent rain event. The project does not
propose the removal of accumulated sediments and debris outside the existing structure. The culvert
replacement will be used as the previous structure was intended, and minor deviations in the proposed
culvert design from the existing culvert are due to regulatory requirements and current safety standards.
Existing Conditions and Location
The project area is a two-lane road near the intersection of South 13th Street in the Town of Lillington, NC.
The road services single-family residences, an apartment complex, and a wastewater treatment plant for
the Town of Lillington. The existing culvert is a 72" CMP. Land use in the vicinity includes a mixture of
residential properties and undeveloped, forested land. The overall proposed project will be to replace the
existing collapsed culvert under West Duncan Street. The coordinates of 35.4061°N, 78.8224°W generally
correspond to the center of the Site.
The project area contains an existing culvert under West Duncan Street. The pavement above the inlet of
the existing culvert washed out during a recent storm event and exposed the culvert and a perpendicular
utility pipe. The current slope of the existing pipe is approximately 0.68. The rip rap dissipator at the outlet
was blown out and the adjacent banks were scoured causing sever bank failure downstream for
approximately 100 feet and is approximately 50 feet wide. Stream width at the inlet is approximately 5 feet.
Project Purpose and Detail
The project proposes to replace the existing undersized 72" CMP with two adjacent 96" RCPs. The bottom
of both pipes will be set twelve inches below the natural stream bed elevation, and the proposed pipe slope
is approximately 0.26. The design proposes a low flow pipe centered on the primary flow of the stream, and
a high flow pipe positioned in alignment with the floodplain.The low flow pipe will include 4'long and 2' high
concrete baffles on 15' spacing to create a 4'wide low flow channel within the pipe. The high flow pipe will
have a 2'tall concrete sill at the inlet and outlet and will be backfilled with native material to the sill height.
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The proposed slope of the new pipes will be 3.4%. The cast in place headwalls at the inlet and outlet will
be backfilled with rip rap with a minimum diameter of 12" and a minimum thickness of 18". At the inlet, a
flood plain shelf made of 12" rip rap with a top elevation of 133.1 is proposed to act as a flood plain shelf.
A rip rap dissipator is proposed at the outlet using rip rap with a minimum diameter of 24" and minimum
thickness of 36". All rip rap is proposed to be installed so that the top of the rip rap is at proposed grade.All
impacts will occur within the extent of prior stream impacts.
A temporary coffer dam is to be installed on the upstream portion of the stream channel and flow shall be
pumped around the work area during construction. Upon completion, the coffer dam will be removed, and
the stream will be restored to its preconstruction dimensions.
No federally threatened or endangered species are listed to occur on the Site. One elemental occurrence
of Cape Fear shiner is documented within 1 mile of the site according to the NC Natural Heritage Program
(NHP) Database (October 1, 2020). See attached letter from NHP.
This project does not require the maintenance or removal of any bridges. This project does not propose the
construction or installation of wind turbines. The project does not propose the use of blasting or other
percussive activities that would be conducted by machines such as jackhammers, mechanized pile drivers,
etc.
Per the NCSHPO web mapping service, the Site is not designated as a historic property or within a historic
district. Three Surveyed Only properties are listed within 0.5 mile of the Site.
Avoidance and Minimization
All proposed impacts will occur within the existing limits of disturbance as determined during a site meeting
visit with Ms. Joanne Steenhuis of NCDWR, Mr. David Arnold representing the Town of Lillington, and Ms.
Kim Hamlin of Sage Ecological on October 21, 2020. Construction fencing will be used to define the
construction corridor and prevent any accidental additional impacts. Silt fencing will be installed to provide
additional protection from runoff.
Project Impacts
The project does not propose permanent stream impacts. Temporary stream impacts due to dewatering
and a pump around for construction will result in 109 linear feet. All impacts will be performed within the
existing transportation right of way. The Project is not within a drainage with NCDWR regulated riparian
buffers.
Mitigation
No additional permanent stream impacts are proposed for this project and no wetland impacts are
proposed; therefore, no mitigation is proposed.
If you have any questions, please call me at [phone].
Sincerely,
4</ferTriiA
Kim Hamlin
Sage Ecological Services, Inc.
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