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Hazen & Sawyer receives design contract for Moosa Canyon pipeline replacement

The San Diego County Water Authority approved a design contract with Hazen & Sawyer for the Moosa Canyon Pipeline Replacement project.

A unanimous SDCWA board vote Thursday, April 25, approved a $5,644,936 contract with Hazen & Sawyer, which is headquartered in New York but has a regional headquarters in Los Angeles and offices in Irvine and San Diego, to provide the design and engineering support services for the replacement of the CWA pipelines in Moosa Canyon. The contract scope of work will include subsurface investigation and engineering support during construction as well as preliminary and final design.

The CWA’s Second Aqueduct crosses Moosa Canyon near Interstate 15 and Camino Del Rey in Bonsall. The 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 August 2019, CWA staff observed water discharging from the side slope of Moosa Creek. 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 November 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 January 2020, 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. In November 2020, a CWA contract was awarded to CDM Smith, which is headquartered in Boston and has an office in Carlsbad, for a comprehensive planning study on Pipelines 3, 4 and 5 in the Moosa Creek area to identify needed long-term improvements which would extend the pipelines' service life for at least 75 years.

The planning study included 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 included recommending a preferred alternative which will address the vulnerabilities and extend the pipelines’ service life.

The study was completed in July 2022. The recommendation was to replace the high-risk portions of the Second Aqueduct pipelines in Moosa Canyon utilizing a tunneling methodology. Approximately 450 feet of each pipeline, or 1,350 feet total, which are susceptible to streambed erosion and seismic hazards will be replaced.

The California Government Code requires professional services agreements to be awarded based on demonstrated competence and the professional qualifications necessary for the satisfactory performance of the services required rather on the lowest price. CWA staff advertised a request for proposals to provide design and engineering support services Oct. 23, and four firms submitted proposals by the Dec. 11 deadline.

A selection panel reviewed the proposals and interviewed representatives of the four companies Jan. 11. The panel considered understanding of the scope of work, technical and specialized qualifications, past performance on similar projects and the ability to meet the project schedule. Hazen & Sawyer was recommended as the most qualified firm based on the company’s thorough understanding of the work including project site and operational challenges as well as extensive tunnel design experience. CWA staff negotiated the $5,644,936 contract amount with Hazen & Sawyer.

The Moosa Canyon Pipeline Replacement project is expected to be advertised for construction in winter 2027, and the construction is expected to be completed during summer 2030.

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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