20150503 Ver 1_Other Documents_20150514 (161)

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Project Narrative
CAMA Major Permit Application
TIP# U-5534B
Walkway Under Heide Trask Drawbridge
Wilmington, New Hanover County
RE: TIP# U=5534B — Walkway Under Heide Trask Drauiibrialge
GAMA Mejor Permit Application Project Narrative
Project Description
The. Cify of Wilmington proposes to construct an 8' wide pedestrian walkway under the Heide Trask
Drawbridge in Wilmington, North Carolina. The Heide Trask D�awbridge carries US 74176
(Wrightsville Avenue) over the Atlantic Intracoastal Waterway (AIVVVV) and connects the City of
Wilmington to the Town of Wrightsville Beach. The proposed walkway project will be constructed
entirely within the North Carolina Department of Transportation (NCDOT) righf-of-way associafed with
US 74/76, and the walkway will cross beneath the Heide Trask Drawbridge between the second and
tliird support bents (the second span of the bridge). The eastern end of the project area begins
waterward of the mean high water line (MHW) of the AIWW, including two small coastal marsh
wetlands, and extends landward of MHW to the sandy slopes leading up to the road elevation of US
74/76, ending at the existing sidewalk on either side of US 74/76.
Proposed Work
The proposed walkway beneath the Heide Trask Drawbridge will provide safe, dedicated pedestrian
connectivity across US 74/76 (Wrightsville Avenue) connecting to the Cross City Trail, a multi-use trail
providing bicycle and pedestrian access across Wilmington. Separating bicycle and pedestrian traffic
from this busy thoroughfare will provide significant public benefit due to increased safety for
pedestrians and decreased danger and delays for vehicular iraffic in the area. The proposed walkway
will also provide additional public benefit through increased recreational opportunities and improved
watertront access with minimal environmental impacts, and the proposed walKway will meet
Americans with Disability Acts (ADA) requirements.
The proposed walkway will begin on the north side of US 74176, tying into the existing sidewalk and
consisting of an 8' wide asphalt path outside of the 75' Area of Environmental Concem (AEC) buffer.
The paved path will continue into the AEC buffer to the 30' impervious area setback where fhe path
wifl transition to an elevated 8'-wide boardwalk constructed of drip-through Trex composite decking
and 8" timber support piles. The eleVated boardwalk is proposed at 8' wide instead of the 6' wide
maximum allowed by the NC Division of Coastal Management (NCDCM) rules since the 8' width is
necessary for safe public utility as 8' is the narrowest width that allows two-way pedestrian or bicycle
traffc. The 8' width will enhance the overall public utility of this project, and will ensure the project
provides safe travel for pedestrians.
Parfially within the 30' impervious area setback, the City of Wilmington proposes to construct a
covered octagonal landing to provide a rest location for Cross City Trail pedestrians and cyclists, and
to provide a public viewing deck to facilitate the enjoyment of the coastal ecosy��i�o ��l�l�j
DCM WILMINGTON, NC
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f�om the proposed walkway. The octagonal landing extend from the will have a uniform side length of
8', and will provide 309 square feet of covered, shaded rest area beyond the 8' wide boardwalk that
crosses through the landing, with only 182 square feet of coVered landing being located within the
impervious area setback zone. The octagonal landing is proposed to be covered, using cedar
shingles, in the interest or providing a safe and shaded rest location alang the Cross Gity Trail. The
shaded a�ea will provide a safe area for pedest�ians and cyclists to rest without impeding traffic on
the walkway leading to and from the Cross City Trail. The cedar shingle covering will not concentrate
stormwater and will allow rainfall to sheet f(ow off the roof and onto the elevated boardwalk or the
sandy uplands adjacent to the AIWW in the project area.
The proposed elevated boardwalk will continue towards and across the MHW line from the octagonal
landing, crossing over a coastal marsh (wetland W1) and continuing beneath the existing structure of
the Heide Trask Drawbridge approach span between the second and third support bents. The
boardwalk will be elevated sufficiently such that the bottom of the decking material will be a minimum
of 3' above the substrate supporting the coastal wetland. Due to spacing requirements in the vicinity
of the existing NCDOT bridge span supports, the elevated boardwalk will utilize micropifes for support
instead of timber pilings.
The boardwalk will continue to the southwest beneath the Heide Trask approach span, crossing
aboVe another coastal wetland (wetland W2). The boardwalk will again be elevated Sufficiently thaf
the bottom of the decking material will remain a minimum of 3' above the substrate supporting the
coastal wetland. On the south side of the bridge, the proposed walkway will turn and slope upwards,
continuing landwa�d from MHV1! out of the 30' impervious area setback zone. Once beyond the 30'
setback, the walkway will transition back to an 8' wide paved asphalt path, continuing up to US 74/76
and Airlie Road.
The project will be construcfed entirely within existing NCDOT right-of-way, so calculating imperviaus
area resulting from the proposed projecf is a unique challenge, however, by applying a 20' width
along the proposed centerline of the walkway (the typical width of a multiuse path easement}, the
total impervious surface a�ea resulting from the proposed project is 27.9%. Overall, only a minor
amount of impervious surface will be constructed by the proposed project, primarily resulting from the
asphalt spurs that tie in to existing sidewalk paths. The project will be subject to the requirements of
the North Carolina State Stormwater Permitting Program.
It is anticipated that this project will proceed with authorization from the US A�rny Corps of Engineers
(USACE) General Permit No. 197800056 allowing maintenance, repair, construction, or installation of
piers, docks, and boathouses. The corresponding NCDWR Water Quality Certification No. 3883 wi[I
also be required for the proposed project.
Overall, the proposed project seeks to improve pedestrian safety and public utilization of this
historically disturbed area adjacent to the AIWW and US 74176: The proposed boardwalk width of 8'
is necessary for safe public use, and is the minimum width that allows two-way traffic along the
multiuse path. Due to careful alignment selection, only minimal impacts will result to the two coastal
wetlands and jurisdictional waters of the US within the project area, solely as a result of the
placement of support pilings.
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