Insights Gained from October 2006 Failure of the Homestake Pipeline

On October 31, 2006, the Homestake Pipeline experienced a catastrophic failure. This 66-inch (1680 millimeter) diameter, 46-mile (74-kilometer) long, prestressed concrete (non-cylinder) pipeline (PCP) traverses Colorado's mountains and provides roughly 60 percent of the raw water for the Cities of Aurora and Colorado Springs. The Homestake Water Project, operator of the pipeline, had completed the first year of inspection in a multi-year condition assessment program and this inspection had stopped approximately 1 mile short of the future failure site. The failure occurred on the PCP at the transition point between steel and PCP pipe. The nature and apparent cause of the failure provide insight to potential vulnerabilities at similar transition points on the Homestake Pipeline and the importance of circumferential cracking in non-cylinder pipelines. The potential for failures at joint end-areas, which are "blind spots" for electromagnetic inspection, suggest caution be used when drawing conclusions from such inspections. The failure cause and the subsequent repair modified the planning for the subsequent years of condition assessment and resulted in a revised repair spool configuration and repair procedure.