The Water Authority’s multi-decade effort to proactively protect the region’s water infrastructure took another big step forward in September, with the start of construction to reline more than four miles of large-diameter pipeline between Lake Murray and Sweetwater Reservoir.
The $28.6 million project, expected to conclude in summer 2018, is part of the Water Authority’s program to rehabilitate prestressed concrete cylinder pipeline with steel liners to extend its service life and ensure continued system reliability. When the project is completed, the Water Authority will have relined approximately 45 miles of prestressed concrete cylinder pipeline and passed the halfway point of relining all 82 miles of this type of pipeline in its system.
The Lake Murray to Sweetwater relining project will reinforce nearly 23,000 linear feet of the Water Authority’s Pipeline 3, including sections of 66-inch and 69-inch diameter prestressed concrete cylinder pipe. Project contactor L.H. Woods & Sons, Inc. will work mostly inside the pipe.
Much of the construction is in public street rights-of-way in La Mesa, specifically on Baltimore Drive, Nebo Drive and Spring Street. The project will not require closing streets, but will temporarily reduce lanes. Click here for project details, including portal maps and traffic alterations.
Construction also extends to unincorporated areas south of the city, and some portals there will be outside of roadways. Where portals are near homes, sound walls will be erected to minimize construction noise.
The Water Authority is coordinating with local water agencies – including the City of San Diego, Helix Water District, Otay Water District and the Sweetwater Authority – to ensure the upgrades do not interrupt water service.
Prestressed concrete cylinder pipes were commonly installed between the early 1960s and the late 1980s as part of large-diameter water distribution systems worldwide. This technology, which uses a combination of concrete and steel, initially appeared to have unparalleled inner pipe strength and be highly resistant to corrosion. However, prestressed concrete cylinder pipe has not been as reliable as predicted, and the Water Authority proactively began relining sections of it to extend its service life.
Instead of removing and replacing these pipelines in their entirety, the Water Authority uses an innovative approach and excavates pipelines at access points called portals. Crews use specialized machines to insert 40-foot sections of steel liner and place them inside existing pipelines. This technique is 40 to 60 percent less costly than traditional excavation, and it results in fewer community impacts.
Pipeline relining is one facet of the Water Authority’s Asset Management Program, which assesses the health of the agency’s conveyance system using technologies such as Remote Field Eddy Current, Acoustic Fiber Optic real-time monitoring, Magnetic Flux Leakage, and Remote Field Technology.
Proactive assessments help the Water Authority avoid pipeline failures by identifying potential risks before they cause problems. To date, the Asset Management Program has saved water ratepayers more than $200 million by prioritizing repairs, avoiding unnecessary work and maximizing the service life of the region’s large-diameter water conveyance system, which includes 310 miles of pipeline ranging in diameter from 20 inches to 9 feet.