This means the joint venture of Kiewit Infrastructure West and J.F. Shea can begin construction on the plant around the first of the year and set its sights on a 36-month completion date.

The six-acre project sits next to the Encina Power Station, on the ">Agua Hedionda Lagoon. Its water will come from the outflow of the power station, which uses seawater for cooling. This runoff will be transported to the desalinization plant via a 72-inch, 2,000-ft pipeline. 

Once in the 65,000-sq-ft desalinization plant, the water will be filtered and sent 10 miles through a 54-inch pipe, where it will connect with SDCWA aqueduct in the city of San Marcos.

MacLaggan says the biggest construction challenge will be working on a constrained site, so close to an operating power plant.

“We don’t have the luxury of a lot of open space to site this facility on the coast,” he says. “We are going to have to carefully time our interconnector to the power plant and San Diego aqueduct so we don’t interfere with their operations.”

By late 2015, the Carlsbad facility is scheduled to begin start-up testing. Commercial operations are expected early the following year. Poseidon’s plant will produce 48,000 to 56,000 acre-ft of desalinated seawater annually, roughly one-third of all water generated in San Diego County.

Two Water Authority member agencies, Vallecitos Water District and Carlsbad Municipal Water District, will purchase a combined total of 6,000 acre-ft of the desalinated water as their own local supply under separate agreements with the Water Authority.