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Water Authority staff inspect leak in Pipeline 4

Pipeline 4 Repairs Underway in North San Diego County

A recently discovered leak in a section of a pipeline in North County will be repaired in coming months while Pipeline 4 returns to service.

Crews have installed bulkheads in the pipeline to isolate a portion of Pipeline 4 for repairs. This will allow the pipeline to continue treated water deliveries throughout the county in a modified fashion starting the week of Sept. 16 and restores full service to retail water agencies. With the leaky section isolated, crews will make necessary repairs.

Four Water Authority member agencies – Fallbrook PUD, Rainbow MWD, Valley Center MWD, and Vallecitos Water District – have taken steps to manage water supplies while the pipeline was shut down to install the bulkheads.

Carbon fiber section will protect pipe

In August, Water Authority crews detected a leak in the 90-inch diameter Pipeline 4, one of five major pipelines the agency operates. The leaky section is near Camino Del Rey in Bonsall, in an area with no adjacent homes or business.

To find the cause of the leak, the Water Authority dewatered the pipe starting Sept. 9. Preliminary results of the investigation are that a weld seam, connecting a steel pipe section to a pre-stressed concrete cylinder pipe, separated in an area of very high water pressure.

The Water Authority is preparing to install a carbon fiber liner to give the pipeline several more years of service while a longer-term solution is developed and deployed.

After repairs are completed, a second 10-day shutdown of Pipeline 4 will be needed to remove the bulkheads and return the pipeline to full, normal operations.

Proactive approach keeps pipelines healthy

As part of its proactive approach to asset management, the Water Authority continually assesses and rehabilitates pipelines serving the San Diego region. The agency operates 310 miles of large-diameter pipelines, along with 1,600 aqueduct-related structures, and approximately 100 metering/flow-control facilities.

Approximately 82 miles of the pipelines are pre-stressed concrete cylinder pipes. These types of pipes were installed between the early 1960s and late 1980s, and have experienced premature failures and shown areas of degradation.

By relining the pipes or conducting timely repairs with the latest technology, the Water Authority has avoided major pipeline failures for more than decade.

 

Pipeline relining is an efficient technique that extends the lifespan of pipes while minimizing costs and impacts to nearby communities. Photo: Water Authority

Innovative Pipeline 5 Relining Completed

San Diego County Water Authority crews completed relining a segment of Pipeline 5 in Fallbrook and San Marcos in late July, reaching a milestone in a strategic, multi-decade pipeline relining program. The 2.3-mile segment of Pipeline 5 was relined with new steel liners that are planned to last for more than 75 years.

The proactive pipeline relining program is a crucial part of asset management efforts that improve the reliability of San Diego County’s water supplies.

30-year pipeline relining program

Since the relining program began in 1991, nearly 47 miles of pre-stressed concrete cylinder pipe have been rehabilitated. This constitutes more than half of the total PCCP in the Water Authority system. The remaining 35 miles are expected to be rehabilitated by 2027.

The Pipeline 5 project was conducted in eight segments to minimize impacts to the nearby communities of Fallbrook and San Marcos.

Proactive measures to protect infrastructure

Pipeline relining is an efficient technique used on long stretches of pipelines. It involves inserting new steel liners into the existing pipes. The new liners can extend the lifespan of the pipe by several decades.

“Relining our existing pipes is quicker and more cost-effective than excavating, removing and replacing an entire pipeline,” said Gary Olvera, senior construction manager at the Water Authority. “In partnership with our member agencies, the Water Authority has developed an efficient and proactive plan to ensure continued water supply reliability for the entire region.”

New steel liners can extend the lifespan of a pipe by several decades. Photo: Water Authority

New steel liners can extend the lifespan of a pipe by several decades. Photo: Water Authority

Innovative technique to minimize impacts

To access Pipeline 5, crews excavated dirt to create eight 25-foot by 60-foot access portals spaced roughly 525 to 2,500 feet apart. During construction, crews eliminated two of the originally planned portals, helping save more than $217,000. Most of the work was then performed underground, inside the pipe.

Once the new liner was installed, the joints were welded together. Then, each new steel liner was coated with a cement mortar lining. Finally, the portals were backfilled, the pipeline was disinfected, and the pipe was put back into service.

A welder works inside the pipe to connect the new joints. Photo: Water Authority

A welder works inside the pipe to connect the new joints. Photo: Water Authority

Maintaining regional water supply reliability

Large-diameter pipelines operated by the Water Authority and its 24 member agencies extend approximately 310 miles to convey water throughout San Diego County.

Approximately 82 miles of the pipelines are pre-stressed concrete cylinder pipes. These types of pipes were installed between the early 1960s and late 1980s and some are nearing the end of their service life.

By relining the pipes ahead of time or conducting timely repairs with the latest technology, the Water Authority and its member agencies avoid pipeline failures and improve the reliability of future water supplies.