Project–At–A–Glance

WSIP Region
Bay Division

Location
Multiple Locations

Current Status
Planning

Project Cost
$2M

An alternatives analysis and a partial condition assessment of the Bay Division Pipelines (BDPLs) were performed as part of the BDPL Reliability Upgrade - Pipeline Project (CUW-36802). The study raised concerns for the two pipeline reaches of BDPL No. 4 that are constructed of Prestressed Concerete Cylinder Pipe (PCCP), which is typically used in large diameter applications.  PCCP has a history of sudden failures, and the SFPUC has experienced two major failures prior to 2003.  The original condition assessment, which included a desktop study and limited field investigations, identified potential for both seismic risks (associated with the gasketed joints) and questionable life expectancy (due to concerns for corrosion of the pre-stressed wires). 
 
Description
This project, which is substantially completed, conducted a detailed condition assessment of the two reaches of pipeline.  The first reach of concern (Reach 1) is 8.6 miles long and 96 inches in diameter. The second reach of concern (Reach 4) is 8.0 miles long and 84 inches in diameter.  The condition assessment included an electromagnetic survey, seismic risk analysis, corrosion survey, visual inspection, and field investigations. 

The assessment identified six reaches of pipe that are potentially distressed and considered high-risk for failure.  During initial investigations, the condition of one distressed pipe segment (Pipe 1558) was determined visually to be particularly deteriorated, and immediate emergency repair was recommended.  The project funded emergency repair, using post-tension exterior tendon repair, for this segment.  For the other five potentially distressed pipe segments that were identified using electromagnetic survey, recommendations were made for excavation to confirm pipe condition in these areas, and repair if needed.  Additional work on the condition assessment and corrosion survey may identify further pipe reaches of concern.  Any additional required repairs would be scheduled based on urgency and funded through the Water Enterprise’s Repair and Replacement (R&R) Program.

Note: Schedule and cost information shown may vary from the 2007 Approved WSIP Schedule and Budget. The information shown reflects the current forecast information published in the latest WSIP Quarterly Report.