AWWA ACE63097

Prestressed Concrete Cylinder Pipe (PCCP) water mains are designed to withstand cyclic high pressure surges; however, repeated spikes over a period of time can cause catastrophic failure of the pipeline as the integrity of the pipe is gradually degraded. This was the case for a surface water refill line in the City of Houston's water system. On June 8, 2004, the 42-inch prestressed concrete cylinder pipe supplying potable surface water to one of the City's Water Pump Stations failed and flooded several residential properties. After failure of the water line, the City enlisted two area consulting firms to further investigate the cause of the failure, review operational procedures, and simulate in a computer model the conditions that led to the failure. In a proactive step, the City of Houston also called for the consultants to assess the potential for damage to the refill lines servicing two other water pump stations with similar operational procedures, and recommend preventative measures against future water refill line failures. Combining efforts, the consulting team utilized two transient analysis software packages to develop representative models of the three water systems. The comparative transient analyses performed on the failed system confirmed the peak pressures that occurred at the failure site and the procedural changes required to mitigate possible failures in the future. Includes 3 references, table, figures.