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By Joe Naiman
Village News Correspondent 

CWA approves completion notices, final change order for Moosa Canyon pipeline repair

 

Last updated 12/6/2019 at 2:30am



The completion of the emergency repair to the San Diego County Water Authority’s Pipeline 4 in Moosa Canyon led the SDCWA board to approve notices of completion which will release funds to the contractors, and the CWA board also ratified the final change order for the repair work.

The Nov. 21 CWA board action accepts the emergency repair work by J.F. Shea Construction Inc. and the carbon fiber repair work by Fibrwrap Construction Services Inc. as complete while also ratifying a $200,000 change order in the emergency contract with J.F. Shea.

“We successfully completed the emergency repair and we returned to normal operations of Pipeline 4, Nov. 10,” CWA engineering manager Neena Kuzmich 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 distributes treated water to member agency turnouts. Pipeline 3 is a steel pipe 72 inches in diameter, Pipeline 4 is a pre-stressed concrete cylinder pipe 90 inches in diameter and Pipeline 5 is a PCCP 96 inches in diameter. The pipelines are 40 feet apart from each other at their centers, which translates to 32 to 33 feet apart from each other at their perimeters.

CWA staff observed water discharging from the side slope of Moosa Creek, Aug. 2. When the water was sampled it was identified as treated water, which ruled out groundwater and narrowed the source to Pipeline 4 or the Rainbow Municipal Water District pipeline. The CWA and Rainbow developed a plan to conduct additional investigations to determine which pipeline was the source of the leak, and Aug. 6 CWA and Rainbow staff determined that the leak was from Pipeline 4. CWA acting general manager Sandra Kerl declared an emergency the following day. The emergency declaration, which exempted the CWA from the normal contract procurement process and from California Environmental Quality Act review, required ratification by the CWA board at the next board meeting, and that occurred on a unanimous vote Aug. 22.

Although the emergency declaration allowed the CWA to move forward without the environmental review process, the CWA coordinated with the environmental agencies. The operating pressure within Pipeline 4 at Moosa Canyon exceeds 300 pounds per square inch and a catastrophic failure could create considerable environmental damage as well as damage to Pipelines 3 and 5 and to a Rainbow pipeline in the area.

Kerl worked with two contractors who had previously provided work on the Second Aqueduct. J.F. Shea was authorized Sept. 5, to proceed on the installation and removal of two internal steel bulkheads and the temporary aqueduct pressure relief system near the Red Mountain Reservoir to provide pressure relief upon resumption of water deliveries.

Pipeline 4 was shut down Sept. 9 for the installation of the bulkheads to isolate the pipeline, which allowed for inspection to determine the specific repairs. The bulkheads were installed Sept. 10-11, and the pipeline was returned to service Sept. 18 although a second shutdown was necessary to remove the bulkheads.

Sedimentation from Moosa Creek was discovered Sept. 11 flowing into the pipe. The pipeline inspection also allowed for the determination of the repair method. Relining an internal section with carbon fiber composite is less invasive than pipeline excavation and replacement, which also would require more time and have more of an environmental impact.

CWA staff provided Fibrwrap with a notice of award Sept. 13. A unanimous CWA board vote Sept. 26 ratified a $950,000 contract with J.F. Shea for the repair of Pipeline 4 and a contract for $871,342 with Fibrwrap for the carbon fiber relining of Pipeline 4. The action also authorized the continuation of the emergency declaration.

The installation of the temporary aqueduct pressure relief system was completed Sept. 30. The initial Fibrwrap design was based on a preliminary review of the pipeline failure, but CWA staff conducted a forensic analysis which was completed Oct. 2.

The forensic analysis identified that higher thrust forces needed to be addressed, and the decision was made to add carbon fiber layers. The work involved 13 layers of fiber which total approximately half an inch thick, and the scope of work also installed anchor rings with epoxy coating at both ends to prevent water from settling behind the carbon fiber layers.

Fibrwrap began pipe preparation Oct. 3, and the carbon fiber design was finalized Oct. 10. The installation of the carbon fiber material began Oct. 10 and was completed Oct. 21. An Oct. 24 CWA board vote ratified a change order in the CWA’s contract with Fibrwrap which increased the contract by $140,409 for a total contract amount of $1,011,751 while also amending the scope of work to increase the number of carbon fiber layers.

Fibrwrap completed the carbon fiber composite relining repair Oct. 25. Pipeline 4 was shut down Nov. 4 to remove the bulkheads and disconnect the temporary aqueduct pressure relief system.

“We had about a mile of Pipeline 4 out of service,” Kuzmich said.

The final design of the pressure relief system included additional high-density polyethylene pipe, fittings and thrust restraint.

“The change order was related to additional work that was required for the temporary pressure relief system,” Kuzmich said.

The change order increased the final contract with J.F. Shea to $1,150,000.

During the construction the CWA retained 5% of the contract amounts with J.F. Shea and Fibrwrap. The CWA board acceptance of the project completion allows those funds to be released after a 60-day period following the recording of the notice of completion and the receipt of a signed conditional waiver and release of liens and claims from the contractors. J.F. Shea and Fibrwrap also provided faithful performance bonds; the J.F. Shea bond will remain for the two-year post-construction warranty period while the Fibrwrap bond will be effective for a five-year post-construction warranty period.

The design life expectancy of the carbon fiber lining is approximately 10 years.

“This is a temporary fix,” Kuzmich said. “The Water Authority will be performing a study on the conditions of the three pipelines in the area and then will be developing a long-term fix.”

Pipeline 3 and Pipeline 5 are also vulnerable to such leaks, so the long-term solution will also include protection for those pipelines. Kuzmich expects the comprehensive study to be complete during 2020, and the results of that study will determine the action to be brought to the CWA board.

 

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