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CDM Smith given planning study contract for Moosa Canyon pipeline

The San Diego County Water Authority awarded CDM Smith the planning study contract for the repair or replacement of the SDCWA pipelines in Moosa Canyon.

The CWA's Nov. 19 board vote authorized a $600,000 contract with CDM Smith for the engineering services. The planning study is expected to take approximately ten months to complete.

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 untreated 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 Aug. 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 in Nov. 2019. Additional carbon fiber layers addressed higher thrust forces until a longer-term fix could be identified and implemented.

The Pipeline 4 leak also 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, but Pipeline 5 was found to have signs of distress in the same area of the Pipeline 4 failure and a follow-up engineering analysis indicated that Pipeline 5 was overstressed and at risk for failure. Contracts for repairs to Pipeline 5 were issued and the work was completed in May 2020.

The carbon fiber lining is considered to be a temporary repair which will last for approximately ten years. The comprehensive study on Pipelines 3, 4, and 5 in the Moosa Creek area will identify needed long-term improvements which would extend the pipelines' service life for at least 75 years.

The planning study will include gathering and reviewing data, performing engineering studies and analyses, and identifying and evaluating alternatives to rehabilitate or replace the three pipelines within the study area. The scope of work also includes recommending a preferred alternative which will address the vulnerabilities and extend the pipelines' service life.

CWA staff prepared a request for proposals and advertised the professional services contract for bid on Aug. 20. A non-mandatory meeting for potential bidders was held Aug. 28, and representatives from 19 firms attended. Five companies submitted proposals by the Sept. 30 deadline.

A panel of CWA staff interviewed representatives from all five teams to assess understanding of the scope of work, technical and specialized qualifications, familiarity with similar projects, and past performance including the company's ability to meet schedules and control costs. CDM Smith, which is headquartered in Boston and has an office in Carlsbad, was deemed to be the most qualified company.

Author Bio

Joe Naiman, Writer

Joe Naiman has been writing for the Village News since 2001


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