The San Diego County Water Authority’s Board of Directors today approved a milestone project in the agency’s Pipeline Relining Program, authorizing the contract to rehabilitate more than four miles of large-diameter pipeline between Lake Murray and Sweetwater Reservoir.
The $28.6 million project is part of the Water Authority’s multi-decade program to rehabilitate prestressed concrete cylinder pipeline (PCCP) within the Water Authority’s conveyance system with steel liners to extend their service life and ensure continued system reliability. When completed, the Water Authority will have rehabilitated approximately 45 miles of PCCP and passed the halfway point toward achieving the program’s overall goal of relining all 82 miles of this type of pipeline in the Water Authority’s system.
“Pipeline relining is an important and often overlooked program that’s extending the life and reliability of the system we depend on every day to deliver water to our taps when we need it,” said Mark Muir, chair of the Water Authority Board. “Our innovative approach to relining also keeps costs down and reduces local impacts from construction.”
Instead of excavating the entire length of pipeline to install the steel liners, the Water Authority excavates the pipeline only at selected access points called portals. Crews then use special machines to move 40-foot sections of steel liner underground to where they are needed. This rehabilitation method is 40-60 percent less costly than traditional excavation, and results in far fewer surface impacts to adjacent communities.
Pipeline relining is one facet of the Water Authority’s overall Asset Management Program. The Asset Management Program also helps assess the health of the Water Authority’s conveyance system, which includes PCCP and other pipeline types, through technologies such as Remote Field Eddy Current, Acoustic Fiber Optic real-time monitoring, Magnetic Flux Leakage, and – most recently – Remote Field Technology. The assessments help the agency avoid pipeline failures by identifying potential risks in the system 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 pipeline system, which overall includes 310 miles of pipeline that ranges in diameter from 20 inches to 9 feet – large enough to drive a car through.
Pipeline condition assessment will continue during the Lake Murray to Sweetwater Reservoir Pipeline Relining Project, as crews will take advantage of the isolated sections of pipeline to assess the condition of the very first relining projects completed in the 1980s. These assessments will be done using Remote Field Technology.
The relining project will reinforce nearly 23,000 linear feet (4.3 miles) of the Water Authority’s Pipeline 3, including sections of 66-inch and 69-inch diameter prestressed concrete cylinder pipe. Crews will conduct most of the work underground inside the pipe, and will access the pipe through 17 portals. Much of the construction work will be located within public street rights-of-way in the City of La Mesa, underneath Baltimore Drive (south of the Laport Street-El Paso Street intersection), Nebo Drive (to University Avenue), and Spring Street. Work will extend to some unincorporated areas south of the city. Some portals within the unincorporated portion of the alignment will be located outside of roadways in undeveloped areas.
The project will not require closing these streets, but may reduce usable lanes in construction areas. The Water Authority is also coordinating with local water agencies, including the City of San Diego, Helix Water District and the Sweetwater Authority, to ensure construction activities do not interrupt water service to customers. For additional project details, including portal maps and information about construction impacts to roadways, go to www.sdcwa.org/lake-murray-sweetwater-reservoir-pipeline-3-relining-project.
Pre-stressed concrete cylinder pipes were commonly installed between the early 1960s and the late 1980s, servicing many large diameter water distribution systems throughout the world. 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, it has not been as reliable as predicted, and the Water Authority proactively began relining its sections of pre-stressed concrete cylinder pipe to reinforce them and extend their service life.
The project contactor, L.H. Woods & Sons Inc., is expected to begin the project in September and complete it in summer 2018.
For more information about the Water Authority’s Pipeline Relining Program, go to www.sdcwa.org/pipeline-relining. To learn more about how the Asset Management Program helps the Water Authority prioritize re-lining and other rehabilitation projects, go to www.sdcwa.org/asset-management.