Failures of Prestressed Concrete Cylinder Pipe (PCCP) throughout North American municipal water transmission systems since the 1970's has led to the development of a myriad of rehabilitation technologies. Besides removing and replacing full sections of distressed pipe with new pipe, the most widely used method of rehabilitation of PCCP is the structurally independent, Type IV relining of the host pipe with steel cylinders. Referred to as Steel Cylinder Relining or Sliplining, both of these semi-trenchless technologies allow a fully structural renewal of long lengths of PCCP in an economical and expeditious manner. The differences between Relining and Sliplining are discussed from the standpoint of manufacture, flow capacities, design, planning, installation and corrosion protection. The paper also provides a description and comparison of other rehab technologies.

Fast set, high solids polyurethane has been used as a coating for the interior and exterior of steel water transmission pipelines since the late 1980s, but it wasn't until 1999 that the American Water Works Association (AWWA) approved Standard C222 for polyurethane coating of steel pipe and fittings. Over the course of the following decade, the coating system gained wide acceptance for water transmission pipelines among many major water utilities. In 1997, Denver Water installed 8,090 lineal feet of 108-inch diameter steel water pipe with an interior coating of 20 mil thick polyurethane. As this was the utility's first use of polyurethane, Denver Water has undertaken testing of the pipe polyurethane lining during scheduled shut downs of the pipeline in 1999, 2002, 2006, 2009 and 2011. This paper presents what Denver Water learned from its field inspection and testing program of this early-generation polyurethane lining system. Physical and visual testing has thus far yielded favorable results, proving the integrity of the polyurethane lining after fourteen years of service.

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