Pipeline 5 at Moosa Creek shut down for repair work

The repair work for one of the San Diego County Water Authority pipelines in Moosa Canyon will be done this month, and two shutdowns of the SDCWA pipeline will sandwich the carbon fiber relining.

“We shut down Pipeline 5, and we are currently in the process of installing two internal steel bulkheads,” Neena Kuzmich, engineering manager with CWA, said. “We just started a shutdown Monday.”

That Monday was March 30.

“It’s a seven-day shutdown of Pipeline 5, and that’s to facilitate the carbon fiber repair,” Kuzmich said.

The CWA’s Second Aqueduct includes Pipelines 3, 4 and 5. Pipelines 3 and 5 distribute 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 and 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 including 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.

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.

Pipeline 5 was found to have signs of distress in the same area of the Pipeline 4 failure. A follow-up engineering analysis indicated that Pipeline 5 was overstressed and at risk for failure.

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.

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 authorization of Kerl to issue contracts allowed contracts to be issued before the March 26 board meeting.

The contracts were issued through a competitive acquisition waiver process rather than through the normal competitive procurement process. J.F. Shea Inc. was issued a contract for the Pipeline 5 bulkhead installation and removal March 17, and FibrWrap Construction Services Inc. was given the Pipeline 5 carbon repair contract during the final full week of March.

J.F. Shea was given the construction contract for the repair of Pipeline 4, and FibrWrap received the Pipeline 4 carbon fiber relining contract. These contracts were also issued through a competitive acquisition waiver. The March 26 CWA board meeting included a briefing on the progress of the Pipeline 5 repairs but no action items for the pipeline.

The installation of the isolation bulkheads will allow flow from the rest of the pipe, and the relining will follow the installation of the bulkheads.

“It’s a carbon fiber reinforced polymer,” Kuzmich said. “FibrWrap will take about three weeks to install the carbon fiber.”

A second shutdown will be required to remove the bulkheads.

“We’re anticipating the second shutdown to remove the bulkheads in early May,” Kuzmich said. “The carbon fiber requires about a week to cure in there before it can have water contact. The shutdown in May allows us to have that adequate cure time.”

Due to the coronavirus quarantine CWA administrative staff members have been working from their homes since March 18. The contractors will also utilize caution to minimize the chance of infections.

“They are following the proper protocol with the coronavirus,” Kuzmich said.

That includes handwashing stations, limiting the number of workers on-site along with separation between workers and ensuring that all of the workers are feeling physically healthy.

“The contractors are addressing it every morning,” Kuzmich said.

The repair will be followed by a canyon wide analysis to determine a long-term solution. The request for proposals for a permanent solution study is expected to be issued in early summer.

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