Saving Big Money and Prohibiting Interceptor Failure Through Rehabilitation by Using Centrifigally Cast Concrete Pipe, City of Westlake, Ohio

In 2007 the City of Westlake conducted a condition assessment for its sanitary interceptor, which was constructed in the 1960's. The interceptor (36”-60” diameter) has an average dry weather flow of 6 MGD and has a tributary area of 142 miles of sewer. This assessment was based on a neighboring community that had an interceptor failure, which flooded multiple basements. The City concluded that various areas in the interceptor had corrosion of the concrete pipe caused by hydrogen sulfide.The hydrogen sulfide corrosion was concentrated around trunk lines that discharged into the interceptor at drop manholes. These drops caused severe turbulence in the line, which released large amounts of hydrogen sulfide. At most locations the corrosion was only seen about 25' on each side of the manhole and the remainder of the pipe was in good condition. Due to budget constraints rehabilitation of the entire pipe from manhole to manhole was not an option. Cured In Place Pipe rehabilitation was reviewed first as a solution, however since the entire run was not being performed this option for this size was not available. The City then decided to perform the rehabilitation by using centrifugally cast concrete pipe (CCCP) with an antimicrobial agent.The CCCP coating was being applied on the surface of the prepared pipe by a spin caster at a thickness of a 1/2”. The pipe was prepared by removing all organic matter and corroded concrete to sound pipe, which at some locations was greater than 1“ in depth. The antimicrobial agent hinders thiobacillus bacteria growth on the surface of the pipe, which stops the process of hydrogen sulfide gas converting to sulfuric acid. The City was able to rehabilitate more linear feet for the money and have both a structural and protective coating installed for the areas of corrosion.