The "most polluted urban stream in North Carolina" had been a distinction carried by Rocky Branch since 1978. In the late 1980s, the North Carolina Department of Environmental and Natural Resources stepped in with a water-quality management plan to change this title, and a Con/Span bridge became an essential part of it.
Renovating the stream quickly turned into a multifaceted restoration project. Over time, eroded stream banks along Rocky Branch had led to collapsed culverts and storm-water pipes. Replacement of these deficient pipes and culverts was key in reducing the pressure on stream banks during storm events and reducing stream bank erosion. In addition to the large-scale restoration plan was a vision to connect the Raleigh Greenway system with the multi-use path on the North Carolina State University's campus.
Contech Bridge Solutions provided a Con/Span structure that met both of these application needs. The precast concrete roadway crossing addressed environmental concerns and could be constructed with minimal traffic disruption.
"The bottomless arch culvert allowed us to provide a 48-ft span under Pullen Road that accommodates both the stream and greenway path within a restricted time period during the summer break for the university," said Sea Grant Water Quality Specialist Barbara Doll. Doll pointed out that summer break was the only possible time period to close Pullen Road, a highly trafficked route during the school season, and rework the stream crossing. "We could not have completed the work during this short time period using any other option and still achieve the same goals."
The new Con/Span overpass will increase the creek's floodplain capacity, thus improving stream stability. It also allows pedestrians to pass safely beneath Pullen Road, a main campus access route. The improved roadway will now provide a connection to Pullen Park and the city's greenway system, expanding the network of public green space.
The construction process included clearing 6 acres of land, restoring 1,580 linear ft of stream and constructing 2,000 linear ft of greenway. The completed 48-ft span Con/Span structure rests on pedestal walls and deep foundations.
"It's exciting to see the Rocky Branch recovery process beginning to take place," said Doll. "It may take some time to get back its full aesthetic value, but there will be no more banks falling in, no more sediment being carried away."
Rocky Branch has become the starting point for inland stream restoration, a critical part of improving coastal water quality. The stream flows more than a mile through North Carolina State University, and it was important to minimize campus disruption while maximizing the funding resources contributing to the $4 million restoration project. The high-profile plan received its funding from the state department of transportation, a Clean Water Management Trust Fund grant, a grant from the Environmental Protection Agency, North Carolina State University and the Federal Emergency Management Agency for damage relief after Hurricane Fran struck the area.
"NCSU was looking for a classic style of bridge and one that was easily constructed or installed when we set about doing the road design for our Centennial Campus," said Steve Bostian, project manager for North Carolina State University. "We have been very pleased with the Con/Span arch culvert and how it blends in with the overall campus architecture and environment."
The Rocky Branch stream is expected to be a national model forurban stream revitalization.