Comprehensive Transportation Plan - March 2019

When crossing streams, the bridge needs to be aligned to cross perpendicular to and at the narrowest section of the stream channel to minimize impacts. The bridge span and height of the bridge cords will be controlled by the floodway and impacts to the base flood elevation of streams. The bridge length must be designed to provide the endbent 10 to 20-feet offset from the top of bank. Scour documentation will be required to justify the endbent locations. Elevations need to be, at a minimum, high enough to pass the 25-year storm and receive necessary FEMA approvals. When feasible, the 100-year storm event elevations must also be accommodated. A 15-foot approach slab with flared safety rail must be on both sides of the bridge. All abutment and foundation design must be completed and sealed by a professional structural engineer. All pedestrian bridges will require local building, storm water, land disturbance, and floodplain development permits as well as FEMA approval. Figure F-14 shows bridge widths and clearances.

Figure F-14. Bridge Widths and Clearances

Retaining Walls Retaining walls need be designed in accordance with NCDOT retaining wall standards. Engineering judgement needs to be used when determining the site-specific wall type but options include mechanically stabilized earth (MSE) walls, concrete block walls, and soldier pile walls. See NCDOT wall type details in Figure F-15 and Figure F-16. The full size NCDOT Standard Drawing plan sheets can be found on the Connect NCDOT website. Where appropriate, an anti-graffiti application needs be applied to retaining walls. Safety rails are required when a wall greater than 30 inches in height is proposed. Upon approval by the Town, the safety fence maybe eliminated if the edge of path is offset greater than 5 feet or the existing condition above the wall does not warrant the safety rail.

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