The San Diego County Water Authority is rehabilitating one of its main water lines in the San Carlos neighborhood of San Diego as part of a multi-decade program to extend the lifespan of 82 miles of aging pipes across the region.
The $21.2 million project – known as the Mission Trails to Lake Murray Pipeline Relining Project – will lengthen the service life of the 6-foot diameter pipe under Jackson Drive by at least 75 years. Relining is 40 to 60 percent cheaper than replacing pipe, and it is less disruptive to the environment and surrounding communities.
Mission Trails to Lake Murray Pipeline Relining Project
Note: Worksite photos are available upon request.
Construction crews started working in Mission Trails Regional Park and near Lake Murray in August. They are relining about 3.5 miles of pipe with steel liners that are up to a half-inch thick. Work will not affect water service to homes and businesses. The Water Authority has coordinated with San Diego city officials to guide traffic through the construction corridor without closing streets. Work will be done by summer 2013.
“This project is an important part of our commitment to ensuring the regional water supply system will continue to deliver water safely and reliably,” said Brent Fountain, construction manager for the Water Authority. “We’ve literally been planning for years to meet this goal with as little impact on the community as possible.”
Inserting the liner is a technically challenging exercise. Crews have dug three large holes – called portals – in Jackson Drive to access the buried pipe. Then, they cut apart the pipe and remove approximately 40 feet of it so the liner can be inserted. A specially designed motorized cart guides the collapsed liner into place, sometimes hundreds of feet from the portal. After the liners are positioned and expanded, they are welded together and the steel is lined with mortar.
Concrete pipe under Jackson Drive was installed in the 1970s as part of the Water Authority’s Second Aqueduct. That segment of pipe serves as a main supply line for the city of San Diego and other Water Authority member agencies in the southern half of the county.
The Water Authority’s Pipeline Relining Program is designed to replace sections of Pre-Stressed Concrete Cylinder Pipe (PCCP) installed from the early 1960s to the 1980s. Made from steel and concrete reinforced with steel wiring, PCCP was widely considered state-of-the-art technology at the time. However, water users have found the pipe to be less reliable than initially thought, prompting the Water Authority to reinforce the pipes and minimize the chances for pipe failures that are far more costly to repair than doing planned upgrades.
Through the relining program, work has been scheduled based on condition of the pipes and other factors. To date, the Water Authority has relined approximately 30 miles of PCCP.