The Town of Chapel Hill is a beautiful community and is the home of The University of North Carolina. The town is especially sensitive to the impact of construction on the environment. Elliott Road has a traffic count of over 7,000 vehicles per day and is the home to many businesses that would be affected by any type of road closure. Also, because the flow of water through the failing culvert pipes is from Booker Creek, which is prone to flooding and has historically caused major damage when it does so. Consultants were hired to study the Booker Creek Watershed, hoping to improve the quality of water and reduce flooding. The consultants recommended several ways to implement flood control improvements, and improving culverts is on the list. Consequently rehabilitating the existing structure to handle the load bearing requirements of Elliott Road, while providing maximum hydraulic capacity was extremely important.
Hydrostructures, of Pittsboro, North Carolina was contacted in the fall of 2013, because they had participated in stormwater evaluation for the town. Hydrostructures is a civil engineering firm, which provides inspection, evaluation, mapping, and design of wastewater, stormwater and water collection, conveyance, and distribution infrastructure. They were chosen to determine the best solution to repair the failing culverts. “We began by making a matrix with ten different options, and then narrowed those down to three or four,” says Tom Stevens, the design engineer with Hydrostructures. “ We considered a variety of round pipe options as well as cured in place liners, spray on liners, structural aluminum liner plate and spiral wound-coil liners”. There were 10 selected criteria on which the alternatives were evaluated from most to least important, relative to each other: Flow Capacity, Design Life, Increased Structural Integrity, Adaptability, Total Cost, Environmental Impact, Community/Traffic Disruption, Permitting Difficulty, and Contractor availability. Ultimately Precision Pipe and Products’ InfraSteel arched smooth wall steel liner was determined to be the best product for the job.
Precision Pipe and Products first inspected the failing structure in the January of 2014 because Dave Easter with Hydrostructures was familiar with Precision Pipe and Products’ InfraSteel culvert rehabilitation system, and thought that InfraSteel’s Smooth Wall Carbon Steel liner might just be the solution to the problem. InfraSteel matches the radii of the existing structure and Hydrostructures’ report noted it “is conducive to providing large cross-sectional area for flow capacity at low creek flow depth” and “its smooth surface/ low manning’s “n” also increases flow capacity”. InfraSteel has unmatched structural integrity because of the inherent strength of steel, and it was noted in the report to have “impressive material testing data”. Hydrostructures determined that InfraSteel met both their structural and hydraulic requirements, and could also be extended to provide for future expansion of Elliott Road.