San Diego planning large-diameter water pipeline

Contractors are designing a large-diameter transmission pipeline in the San Diego area to withstand extremely high working pressures.

March 21, 2001—As part of a phased plan to increase water supply to San Diego County, contractors are designing a large-diameter transmission pipeline to withstand extremely high working pressures was only one of many challenges successfully met by Black & Veatch in its work on the 9.7 mile, 108 inch diameter Rancho Pe�asquitos Pipeline for the San Diego (CA) County Water Authority. The project won awards of excellence in 2000 from San Diego chapters of the American Public Works Association and the American Society of Civil Engineers.

Part of a phased plan to increase the amount of water coming into arid and growing San Diego County, the $58 million pipeline can deliver up to 400 million gal/day (mgd) of untreated water to storage and treatment facilities.

To accommodate current, future, and emergency operations, the pipeline was designed to operate under three flow conditions: gravity, pressurized, and reverse. In pressurized mode, the pipeline has the potential for future hydroelectric power generation.

The steel pipe is 1-5/16 inches thick to handle working pressures exceeding 450 pounds/sq in. in some sections. Some of the three different types of joint designs took as long as 30 to 50 hours each to weld securely.

The project was further complicated by mountainous terrain, the need to blast and tunnel in urban and rural communities, and the fragile ecosystem of the Los Pe�asquitos Canyon Reserve, under which the pipeline passed. The project is a success on all counts.

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