CWA approves Pipeline 3 non-destructive testing

Non-destructive testing will be performed on the segment of Pipeline 3 between the San Diego County Water Authority delivery point and the Twin Oaks Valley Treatment Plant.

A unanimous SDCWA board vote May 22 approved an amendment to the CWA’s professional services contract with Pure Technologies US, Inc., to provide non-destructive testing services and condition assessment of Pipeline 3. The amendment adds $1,077,000 to the amount of the contract, bringing the contract’s total value to $2,196,000.

The CWA’s Asset Management Program monitors CWA assets in order to maximize their life expectancy. The CWA’s pipeline system totals approximately 300 miles with welded steel pipe accounting for approximately 40 percent, prestressed concrete cylinder pipes and reinforced concrete pipes each representing approximately 28 percent of the system, and bar-wrapped pipe being used for approximately 4 percent.

The Asset Management Program includes the use of the latest technologies to address the condition of aging pipelines. In July 2013, the CWA authorized a $1,119,000 professional services contract with Pure Technologies to provide non-destructive testing services and condition assessment of Pipeline 4 from the Twin Oaks plant to Paint Mountain near the Olivenhain Reservoir. The work in which Pure Technologies used magnetic flux leakage technology was considered a pilot project.

Magnetic flux leakage uses magnets to generate a magnetic field in the steel wall of the pipeline. If the magnetic field pattern is uniform, the steel has no flaws. If the pattern is distorted, flaws exist in the steel. The distortion can be analyzed to determine the size and location of the steel corrosion and if repairs are needed.

“This tool is really useful,” said CWA operations and maintenance manager Nathan Faber.

The magnetic flux leakage testing for Pipeline 4 was completed in October 2013. The testing of approximately 1,500,000 square feet of pipeline found 1,107 corrosion locations, although most of those were smaller than the size of a quarter with wall loss averaging 29 percent and the total amount of corroded area totaling about five square feet. “The pipe is really in good shape, much better than we expected,” Faber said.

The data was then downloaded, and CWA staff can monitor specific segments for low pressure. “We’ll watch some areas,” Faber said.

The pilot project also allowed Pure Technologies to improve their data download process, increasing the likelihood that the Pipeline 3 work will be done on schedule. The Pipeline 4 condition assessment took 22 calendar days, one more than the 21 days which had been scheduled.

Pipeline 3 was built in 1959 and is a welded steel pipe which lacks a corrosion-inhibiting cathodic protection system. CWA staff visually inspected Pipeline 3 from the delivery point to the Twin Oaks plant in 2000.

The work is scheduled to be performed in October and November. Thirty-day notices will be provided to residents whose right-of-way will be impacted, and all work will be performed between 7 a.m. and 7 p.m. The inspection will coincide with the shutdown of Pipeline 3 which will be part of the re-lining project associated with the widening of State Route 76 which includes a bridge over the CWA’s Second Aqueduct.

“We’ll shut down Pipeline 3 but we’ll still have treated water, so it shouldn’t impact the member agencies,” Faber said.