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CWA approves shutdown schedule for Pipeline 5 work at Moosa Creek

In 2019, the San Diego County Water Authority repaired a leak to a pipeline in Moosa Canyon. That repair was followed by an assessment of the other two SDCWA pipelines in the area, and one of those was found to be at risk so the CWA will be making repairs to that pipeline.

A CWA board vote, Feb. 27, authorized CWA general manager Sandra Kerl to take the necessary contracting and other actions for the repairs on Pipeline 5 in Moosa Creek. The current schedule includes shutdowns March 30 through April 5 for the installation of isolation bulkheads and May 18 to May 24 for the removal of the bulkheads as well as carbon fiber lining work expected April 6 through May 15.

May 24 is the Sunday of Memorial Day weekend, and the actual shutdown schedule will likely be revised as the repair work progresses.

“Our pipes are very big, and if they don’t work well it’s a very big event," Kerl said.

The CWA’s Second Aqueduct includes Pipelines 3, 4 and 5. Pipelines 3 and 5 provide untreated supply to CWA member agencies while Pipeline 4 conveys treated water to member agency turnouts. Pipeline 3 is a steel pipe 72 inches in diameter and was built in 1958. Pipeline 4 is a pre-stressed concrete cylinder pipe 90 inches in diameter which was built in 1970. Pipeline 5 is a PCCP 96 inches in diameter, built in 1982. The pipelines are 40 feet apart from each other at their centers, which equates to 32 to 33 feet apart from each other at their perimeters.

In August 2019 CWA staff observed water discharging from the side slope of Moosa Creek, and four days later a leak in Pipeline 4 was identified as the cause. The CWA contracted for repair work, which included a shutdown to remove isolation bulkheads was completed Nov. 10.

Additional carbon fiber layers addressed higher thrust forces, and since the design life expectancy of the carbon fiber lining is approximately 10 years, the CWA opted to study all three pipelines along the Second Aqueduct to develop a long-term fix. The comprehensive study is expected to be complete during 2021, and the results of that study will determine the action which will be brought before the CWA board.

“Moosa Creek continues to have erosion,” Martin Coghill, CWA operations and maintenance manager, said.

“This location has become a real challenge,” Marty Miller, CWA Engineering and Operations Committee chair, who is on the board of the Vista Irrigation District and is the VID representative to the CWA board, said.

The Pipeline 4 leak led CWA staff to conduct an inspection of Pipeline 3 and Pipeline 5 in late January, when both of those pipelines could be drained for access during a planned maintenance-related shutdown. Pipeline 3 was found to be in good condition with no signs of distress.

“We do actually have an issue with Pipeline 5,” Coghill said. “It’s beginning to yield.”

The operating pressure within Pipeline 5 at Moosa Canyon exceeds 400 pounds per square inch, so a catastrophic failure could create considerable environmental damage as well as damage to Pipelines 3 and 4 and to a Rainbow Municipal Water District pipeline in the area.

“It would be pretty catastrophic if it went,” Rainbow general manager Tom Kennedy, who is Rainbow’s representative on the CWA board.

The immediate action taken was the mitigation of risk through limited flow changes. The proactive repair authorized Feb. 27 will be followed by a canyon wide analysis to determine a long-term solution.

“We’ve learned some things we need to be looking at in the assessment of our pipelines,” Kerl said.

“I think that it was a really great catch for staff to be doing the inspection,” Lois Fong-Sakai said, who is one of the City of San Diego representatives on the CWA board.

The authorization of Kerl to issue contracts allows those contracts to be issued before the March 26 board meeting. The CWA expects to issue contracts for carbon fiber design, carbon fiber installation, bulkhead installation and removal and acoustic fiber optic cable removal and reinstallation.

The preliminary cost estimate for the four contracts combined is $1,910,000 not including CWA staff time expenses. The contracts will be issued through a competitive acquisition waiver process rather than through the normal competitive procurement process.

“It’s critically important, and I look forward to working with staff,” Kennedy said.

“This has been very challenging for all of the member agencies,” Kerl said. “The member agencies have been working with us.”

Joe Naiman can be reached by email at [email protected].

Author Bio

Joe Naiman, Writer

Joe Naiman has been writing for the Village News since 2001

 

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