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CWA approves MOU with Camp Pendleton for desal plant

The San Diego County Water Authority (CWA) board voted to approve a Memorandum of Understanding (MOU) with Marine Corps Base Camp Pendleton for the performance of planning activities for the proposed Camp Pendleton Seawater Desalination project.

The MOU approved by the CWA board April 22 covers non-Federal use of real property, non-interference with base activities, coastal development and other state permits, indemnification, designated representatives, natural and cultural resources, designated activities, data acquisition, off-shore investigations and water sampling, on-shore investigations and surveys, power service, public outreach, environmental review, general coordination and miscellaneous provisions.

It also includes a process for CWA employees and contractors to access the base. The study does not guarantee that the desalination plant will actually be built.

In May 2009, a feasibility study report was provided to the CWA’s Water Planning Committee which indicated that a seawater desalination plant on Camp Pendleton would be feasible in the absence of any unexpected environmental or other legal obstacles.

In addition to the environmental and permitting issues, prerequisites include an agreement with the United States Marine Corps to locate the facility and conveyance pipelines on Camp Pendleton, defining roles and responsibilities for the various parties, and amending the CWA’s capital improvement program to add the desalination plant.

The seawater desalination plant would provide desalinated water to the San Diego County Water Authority, Camp Pendleton, and possibly the Municipal Water District of Orange County. It would produce between 50 and 150 million gallons per day (mgd) of desalinated water.

In November 2005 the County Water Authority, in conjunction with the Municipal Water District of Orange County, approved a consultant contract with RBF Consulting to conduct a detailed feasibility study for a potential seawater desalination plant on Camp Pendleton. The study included detailed feasibility evaluations of conveyance, intake, and discharge facilities as well as environmental and permitting requirements, cost estimates, and project implementation issues.

At one time the project was proposed to be located near the San Onofre Nuclear Generating Station, allowing for the use of the ocean intake and discharge tunnels for the abandoned Unit 1 power plant.

After the feasibility study was initiated, Southern California Edison expressed concern that the presence and operation of a desalinated facility could complicate the operation of the nuclear power plant and hinder future regulatory compliance. The proposed location was moved to the southwest corner of Camp Pendleton adjacent to the Santa Margarita River.

A total of eight potential locations were evaluated, and two sites were considered viable for a facility producing between 50 and 150 mgd.

The CWA’s Urban Water Management Plan calls for 89,600 acre feet of desalinated water by 2030. A capacity of 50 mgd equates to 56,000 acre feet while 150 mgd would translate to 168,000 acre feet. The buried infrastructure would be built to accommodate the 150 mgd ultimate capacity while the initial development would likely build a plant to handle 50 to 100 mgd with subsequent modular 50 mgd expansions.

In addition to increasing the reliability and quality of water on the base, including the creation of the possibility of blending desalinated water with Camp Pendleton’s well water, the new ocean outfall which would serve the desalination plant could also provide a wastewater disposal option for Camp Pendleton.

The plant’s energy requirements, estimated at 40 megawatts for 50 mgd and 100-110 megawatts for 150 mgd, may lead to the building of an energy cogeneration plant which could also be used to provide emergency power to the base.

Cogeneration through natural gas turbine generators would require approximately five acres for that supplemental facility, and the use of some solar, wind or wave-generated hydroelectric energy could also contribute to the plant’s power needs while helping meet greenhouse gas offset requirements.

The capital expenses for a 50 mgd plant, including the conveyance infrastructure designed for the eventual 150 mgd production, are estimated to be between $1.2 billion and $1.3 billion while the capital costs for a 100 mgd plant are estimated at $1.7 billion to $1.9 billion. The facility cost breaks down to 57 percent for treatment facilities, 28 percent for conveyance, and 15 percent for intake and discharge facilities. The annual operation and maintenance costs are estimated at $42-50 million for 50 mgd and $79-96 million for 100 mgd.

CWA staff expects to discuss potential financial support from the Municipal Water District of Orange County this month, and it is possible that the Department of Defense may fund part of the expense.

The Camp Pendleton desalination plant is not expected to go into service until 2018. The CWA’s 2020 supply portfolio without the desalination project includes receiving 12 percent of its water from the Metropolitan Water District of Southern California’s Colorado River Aqueduct allocation and 17 percent of its supply from MWD’s State Water Project allocation.

The 2020 supply portfolio with a 100 mgd Camp Pendleton desalination project increases desalination from 10 percent to 19 percent of the CWA’s supply while reducing Colorado River Aqueduct imports to 8 percent and the State Water Project take to 12 percent.

The offshore outfall, which would be constructed with both seabed pipelines and outfall tunnel sections, would include a diffuser system to achieve salinity dilution requirements. In addition to the possibility of use by Camp Pendleton for wastewater effluent from the South Region Tertiary Treatment Plant, the outfall could also be used for the Santa Margarita River Conjunctive Use Project being developed by Camp Pendleton and the Fallbrook Public Utility District.

The technical studies are expected to take place from mid-2010 to late 2011, and the study and project cost data will be incorporated into the 2012 update of the CWA’s Regional Water Facilities Master Plan which will evaluate the Camp Pendleton project along with other supply alternatives. The environmental documentation process is expected to begin around mid-2010 and take approximately two years.

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