City officials in Norwich, Connecticut, discovered an unusual problem involving 2,695 ft of 14-in. force main pipe in September 2019. The gritty materials, pumped on a regular basis, had worn away the bottom of the 45-year-old cast iron pipe. Over time, the pipe walls were breached by the materials, allowing an inflow of heavy amounts of ground water when the system was not pressurized, affecting its overall capacity. Given the location of the pipe along a steep rocky embankment on one side and its proximity to active railroad tracks on the other, it would have been a costly dig and replacement. To add to the challenges of the situation, the deteriorated pipe lay buried just a few hun- dred feet from the Thames River. The City of Norwich contracted Michels Corp. to address the situation without the need for surface disruptions. Once under contract, Water Lining Program Manager Mark Lucas worked with the experts at Premier Pipe, Interplastic Corp. and North American Composites to engineer a 9-mm, two glass-layer designed liner that would be installed to repair the worn pipe. This liner produced a flex modulus of more than 1 million psi, allowing for a thinner CIPP composite to gain maximum flow through the force main. Norwich Public Utilities (NPU) designed and installed five access pits and removed the air relief valves prior to the crew arrival. They also installed the relief bypass system which stretched the entire project length to 2,700 ft. The 12-in. HDPE SDR17 bypass system had to be partially buried to allow for crew and railroad access to the entire site. NPU provided railroad flaggers and their crews also manned and maintained the bypass system throughout the duration of the project. Funding for the program was supported fully by NPU.
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