Pipeline 6 consultant contract approved

The San Diego County Water Authority approved a consultant contract with Rick Engineering Company for aerial surveying and mapping services for the Pipeline 6 project.

The CWA board action July 26 authorized the contract for up to $100,020. The contract covers only the 11.7-mile segment of CWA responsibility and not the portion to be constructed by the Metropolitan Water District of Southern California (MWD). The information will be used in future planning studies to determine the feasibility of alternative alignments, facility locations, preliminary design details, environmental impacts, and other implementation issues.

Pipeline 6 is expected to carry between 470 and 630 cubic feet per second (cfs) of water and would connect Lake Skinner with the CWA’s Twin Oaks Diversion Structure. The 470-630 cfs rate equates to 300 to 400 million gallons per day (mgd), and the 400 mgd figure would increase the CWA’s imported water capacity by 45 percent.

Pipeline 6 is expected to be an untreated water pipeline, which would allow the conversion of one of the existing untreated water pipelines into a treated water pipeline. That would increase treated water capacity from approximately 600 cfs to approximately 900 cfs while increasing untreated water capacity from less than 800 cfs to about 1,000 cfs.

The north reach of the project, which has already been completed, serves Temecula and covers the first seven miles between Lake Skinner and Anza Road at DePortola Road in Temecula. The southern portion which will serve San Diego County is not currently needed, so financial priorities have been placed elsewhere although right-of-way acquisition has begun to allow needed easements to be obtained at a lower cost. Other work on the future pipeline is also in progress.

A worst-case scenario incorporates a nine-year timeframe for the south reach. Pipeline 6 is not expected to be needed until 2018, although if the CWA can implement a seawater desalination program Pipeline 6 can be delayed until 2023.

The total length of Pipeline 6 is approximately 31 miles. The construction plans envision mostly open trench construction, primarily within existing or planned streets, for the first 12 1/2 miles from Lake Skinner including the already-completed north reach. The next portion of the pipeline would be installed in a tunnel approximately 6 1/2 miles long. The MWD responsibility area currently terminates near the south tunnel portal just north of the San Luis Rey River, and the CWA will construct the remaining 11.7 miles from that point to the Twin Oaks Diversion Structure.

Pipeline 6 was first studied in 1987 as part of a general review of MWD’s distribution system. When the MWD board of directors certified an environmental impact report in 1993, the pipeline was identified as being nine to ten feet in diameter. Part of the easement in that EIR is on a property which has since been purchased by the Pechanga Indian Reservation, and MWD is looking at an eastern bypass around that property which would connect to the EIR-cited alignment south of the border between Riverside and San Diego Counties. That option could move the north tunnel portal to south of the county line.

MWD is in the process of conducting additional geotechnical and hydrological studies for the tunnel area. Those investigations are expected to be complete in 2008.

The aerial surveying and mapping contract with Rick Engineering will include orthophotos, topographic information, and planimetric features. In addition to identifying potential environmental impacts, the mapping information will help perform hydraulic analysis and develop hydraulic profiles.

The CWA issued a request for proposals to solicit surveying and mapping services for the Pipeline 6 project in May. Seven firms responded by the June deadline, and three were interviewed. A selection panel cited Rick Engineering’s past experience, comprehensive understanding of project needs, and a scope of services providing greater coverage and flexibility as key factors in selecting Rick Engineering for the contract.

The surveying and mapping are expected to be complete in November, and in December the CWA will begin a feasibility and alignment study, to be completed in June 2009. The nine-year timeframe includes that study.