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Portion of San Marcos pipeline will be relined to carry desal water

SAN MARCOS — In order to withstand the pressures that a particular stretch of pipeline in San Marcos will undergo once desalinated water begins to flow through it, the pipe will first have to be relined with steel. 

That is according to Bill Rose, director of engineering for SDCWA (San Diego County Water Authority). On Tuesday, Rose provided the City Council with an update on the pipeline project that will connect the city to the as yet built Carlsbad Desalination Plant.

Though bids to find a contractor for the pipeline project will go out next week, the awarding of the project is expected by the Nov. 21 water Board meeting.

The relining project has an estimated start date of the first of the year, Rose said.

Once started, construction is slated to be finished by May 2015, according to Rose.

The relining process will be done to what SDCWA refers to as “Pipeline 3.”

The pipeline was constructed in the late-1950s, Rose said. It has carried water from north to south throughout its entire service life. But once the project is finished, the desalinated water will flow north to the Twin Oaks Valley Water Treatment Plant.

“The reason that we are relining the pipeline is it wasn’t designed for the kind of pressures that it’s going to see as a result of pumping the desalinated water all the way up to the Twin Oaks Water Treatment Plant,” Rose said.

The SDCWA has alerted businesses and residents to the upcoming work on Pawnee Street to Rancho Santa Fe Road and including the San Marcos Village and El Dorado Park.

There will be six locations in the city where the SDCWA will be accessing the pipeline in order to reline the pipe, which, Rose said, will improve its structural capabilities.

Rose said the relining was “far less intrusive and less expensive than actually fully replacing this pipeline.”

The desalination plant will be connected to an aqueduct in San Marcos by a 10-mile long pipeline, which has already started to be laid.

“For San Marcos, the Vallecitos Water District will be taking a direct connection off of the desalinated water,” Rose said. That water, he added, will be serving most of the downtown corridor area.

In 1991 the county was almost entirely dependent on receiving water from the Metropolitan Water District of Southern California, and now, according to Rose, the water supply has been diversified significantly and will continue to do so through the year 2020.

By the year 2020, the county expects to be receiving 7 percent of their water supply from the desalination plant.