Agenda - 04-01-2008-3a - Laserfiche WebLink

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2 3. Conduct an environmental assessment process required for projects that may impact species identified on the National Endangered Species list, including a field meeting with qualified ecologists to ensure demolition, construction and final design of the bridge will have no negative impacts on the high level of aquatic species habitat, water quality, and other natural heritage features of the New Hope Creek area. Bridge Design Revised: The County has previously forwarded to NCDOT a letter outlining the concerns raised by the NHCCAC. In response, the NCDOT has revised the design to remove interior bents and associated 55-foot rip-rap causeway in the .streambed. The existing structure has two bents (one of either side) at the stream edge. Bents for the new structure will be outside the water channel on the dry bank area, which eliminates the need for rock causeway. The concrete piers of the existing bridge will remain because removing those would cause disturbance of the streambed. Orange County's Transportation Advisory Committee member has also brought these concerns to the attention of the NCDOT Division 7 Board of Transportation member at a meeting to discuss the Transportation Improvement Program. The following address the three requests stated in the resolution: 1. NCDOT Structure Design has considered a bridge that would allow for an under bridge pedestrian trail. Such structure would require a bridge span in excess of 200-feet and would add another span, doubling the cost of the project and extending completion of the project two-three years because of additional studies needed for design and right-of-way requirements. (The 2005 estimate for the bridge replacement was $737,000.) The New Hope Corridor Open Space Master Plan, adopted in April 1991, calls for a wildlife corridor, but does not propose a pedestrian trail along this part of the creek. The Master Recreation and Parks Work Group recommendations, adopted by the BOCC in April 2000, calls for rural trails links fora "North Chapel Hill/Rural Buffer corridor linking Booker Creek Greenway, Northern Community Park, Duke Forest, New Hope Creek (including TLC lands and Duke Forest) back to the New Hope Creek Corridor and the Durham County line." NCDOT intends to replace the bridge with a 28-foot wide structure that includes two 10-foot lanes with 4-foot offsets and bicycle safe rails, maintaining the low chord (approximately the same roadway grade as the existing structure). The existing bridge is lower than the 100- yearflood elevation. The Orange County Floodplain Administrator approved a "No Rise/No Impact "certification for the bridge because the design called for the deck to be slightly below the 100-year flood, but allowed more flood water to pass underneath. than does the existing bridge due to the new design's increased transverse open area under the bridge. There is no evidence that the existing structure causes floodwater to backup upstream, so the proposed new structure should not cause floodwater to backup for the above stated reason. To raise the bridge, the superstructure must clear the 25-year (design year) and 100-year (base flood) water surface elevations, and have much deeper foundations, more land clearance and disturbance.