Orange County Branch Newsletter

June 2014


Carlsbad Desalination Plant

by Brett Schickling, EIT

At the EWRI June lunch, Bob Yamada, Water Resources Manager at the San Diego County Water Authority (SDCWA), and Peter MacLaggan, Vice President at Poseidon Water, presented an overview of the Carlsbad Desalination Plant. The construction of the Carlsbad Desalination Plant, along with a 5-mile conveyance pipeline that is 56-inches in diameter, started construction last year and is currently approximately 50 percent complete. The plant is scheduled to begin delivering water to customers in San Diego County in late 2015.  The Carlsbad Desalination plant will be the largest desalination plant in the Western Hemisphere.

Last year, the SDCWA and Poseidon Water signed a 30-year purchase agreement that committed SDCWA to purchasing up to 56,000 acre-feet of year per year from the Carlsbad Desalination Plant. Under the agreement, Poseidon Water would own and operate the plant for up to 30 years, with a buyout option after 10 years. After 30 years, SDCWA has the option to purchase the plant for $1. SDCWA will operate and maintain the 5-miles of conveyance pipeline.  Additionally, as part of the ruling by the Coastal Commission, an 85-acre wetland restoration project will be undertaken by Poseidon to offset environmental impacts of the plant.

The capacity of the plant will account for 7% of SDCWA’s water supply, and will diversify the current water portfolio by increasing the percentage of local water supply distributed to customers in the area. Currently, SDCWA imports more than 75% of its water from the Colorado River and the Bay Delta. The project comes with a cost, however, as water rates are expected to increase just over $5 per typical household per month when the plant comes on line.

 The plant is designed to deliver 50 million gallons per day (MGD) through the 56-inch conveyance pipeline where it will connect with SDCWA’s Second Aqueduct. The water will then travel through a pipeline that will be converted from gravity flow to pressurized flow in order to reverse the flow direction, where it will be stored in a clearwell at the Twin Oaks Valley Water Treatment Plan in San Marcos. At the Twin Oaks plant the desalinated water will be blended with treated water and delivered to customers through existing infrastructure.