Lessons from the Failure of Two Reclaimed Water Lines in California

摘要

The Landfill Reclaimed Water Distribution System consists of two pump stations and two force mains. Pump Station No. 1 pumps into a 640 m (2100 ft) long 90 cm (36 in) diameter Force Main under a static head of 150 m (500 feet). Pump Station No. 2 pumps into a 1125 m (3700 ft) long 75 cm (30 in) diameter Force Main under a static head of 90 m (300 ft). Both pipes are Ductile Iron Pipes with TR Flex joints, wrapped in polyethylene sheets and were supplied by U.S. Pipe. The lines were tested under a static pressure of 2000 kPa (300 psi) after completion. Subsequently the pipelines were connected to the discharge headers and tested under a static pressure of 2000 kPa (300 psi), at which time significant movements were observed at the pump station piping at both Pump Station No. 1 and Pump Station No. 2. The authors were engaged by the Sanitation District to investigate movements observed on the pipe headers at both Pump Stations during the pressure tests. This investigation focused on the adequacy of the design of the entire system, and the installation procedures during construction of the project. The manufacturer's recommended installation procedures are also reviewed. This paper reports on the details of this investigation and how appropriate corrective actions were taken to stop further movements in the lines once the pipelines were put back into service.