CWA approves contracts for assessments of pipelines

The San Diego County Water Authority approved three professional services contracts to conduct condition assessments of pipelines in the northern part of the SDCWA’s First Aqueduct.

The Sept. 27 CWA board vote authorized contracts of $2,242,000 to Pipeline Inspection and Condition Analysis Corporation, $1,001,000 to Pure Technologies U.S. Inc. and $480,000 to Diakont Advanced Technologies Inc. The contract with Diakont is for a four-year period while the other two contracts are for four-year periods with an option to renew for two additional years.

The First Aqueduct pipelines are the oldest in the CWA’s system. Pipeline 1 was constructed in 1947, and Pipeline 2 was constructed in 1952. Both are primarily reinforced concrete pipes, while 2.75 miles of welded steel pipe are utilized in high-pressure siphons. The reinforced concrete pipes have an embedded steel cylinder in areas with enough pressure to warrant those, and in low-pressure areas the embedded steel cylinder is not used.

The northern section of the First Aqueduct runs from the delivery point, where the CWA takes water from the Metropolitan Water District of Southern California six miles south of the San Diego County line, to Hubbard Hill in Escondido while the southern section conveys water from Hubbard Hill to the San Vicente Reservoir in Lakeside. The northern section includes the Lilac, Red Mountain and Oat Hills tunnels.

A condition assessment of the First Aqueduct requires not only the appropriate technology but also a system shutdown to isolate the pipelines for a long enough period of time. Although no condition assessment has previously been performed, technological developments along with reduced water demands now allow for such an inspection. In February, the CWA issued a request for proposals for condition assessment services. Five firms responded by the April 12 deadline, and after proposal evaluations and interviews three firms were selected for negotiations.

The use of multiple firms not only allows for concurrent assessments but also allows contractors to be selected for specific technologies to be used in the condition assessment. Acoustic leak detection is an in-service detection of joint leaks, which is a known problem with aging reinforced concrete pipe. Robotically mounted laser profilometry is the comprehensive high-resolution mapping of internally corroded welded steel pipe. Robotically mounted electromagnetic acoustic transfer provides localized wall thickness determination on internally corroded welded steel pipe. Remote field technology provides comprehensive wall thickness determination on reinforced concrete pipe. Near-field electromagnetics provides comprehensive reinforcing bar assessment for non-cylinder reinforced concrete pipe.

CWA staff will request contracts for the 34-mile southern section in the future. The condition assessment of the entire aqueduct is expected to be a nine-year process.