Desalination removes salts from the ocean or brackish water to produce fresh water through distillation or filtration. The Bay Area’s five largest water agencies — the Contra Costa Water District, the East Bay Municipal Utility District, the San Francisco Public Utilities Commission, the Santa Clara Valley Water District and Zone 7 Water Agency — are jointly exploring a regional desalination project that would provide an additional water source, diversify the area’s water supply, and foster long-term regional sustainability. The Bay Area Regional Desalination project could consist of one or more desalination facilities, with an estimated total capacity range of 10 to 50 million gallons per day.
Project Goals and Benefits
- Provide a reliable water supply source available during contract delivery reductions, extended droughts, and emergencies such as earthquakes or levee failures.
- Allow other major facilities such as treatment plants, water pipelines, and pump stations, to be removed from service for maintenance or repairs.
- Minimize the potential for adverse environmental impacts.
- Leverage existing and contiguous infrastructure to meet demands and minimize costs.
What’s Been Done to Date
In May 2003, the partner agencies initiated a pre-feasibility study to identify fatal environmental or technical flaws for a regional facility to serve the original partner agencies. The study concluded there are at least three locations in the Bay Area where a regional desalination facility could be located. The agencies then conducted a feasibility study to refine the institutional, technical, environmental and scientific merits of a regional facility. Public presentations and informational materials were provided in Fall 2006 to inform the public on what had been conducted and the next steps.
Following the Feasibility Analysis, the State Department of Water Resources awarded the agencies a $1 million grant to fund a small-scale pilot project. Contra Costa County was selected as the best location for a pilot desalination plant, and a pilot plant operated at the Contra Costa Water District's Mallard Slough Pump Station from October 2008 to April 2009. The pilot desalination plant tested pretreatment options, membrane performance, and approaches for brine disposal. The Pilot Plant Testing at Mallard Slough Engineering Report was finalized in June 2010, and concluded that desalination is technically feasible at the Mallard Slough Pump Station location.
Zone 7 Water Agency joined the Bay Area Regional Desalination Project partner agencies in June of 20l0, at the beginning of an Institutional Feasibility Analysis to evaluate feasible desalination scenarios.
Current Status
At the conclusion of the Institutional Feasibility Analysis the partners jointly developed a project description including the proposed location and capacity. The Project under consideration would use water from the Delta withdrawn at CCWD's Mallard Slough Pump Station, located in eastern Contra Costa County to produce 20 mgd desalinated water for delivery to the Parties. Water produced by the Project could be blended with supplies from CCWD, EBMUD (Mokelumne Aqueduct), or both. Other Parties would receive Project water through transfers or wheeling. The water from the Project could be fully treated (two-pass Reverse Osmosis (RO)) or require further treatment (one-pass RO) depending on delivery point into either the CCWD or EBMUD system. The proposed project would operate continuously in all year-types, with the possibility of storing water (including by exchange or transfer) in CCWD's Los Vaqueros Reservoir when demand from the Parties is less than plant capacity. Storage in Los Vaqueros Reservoir could provide flexibility to optimize the Project yield. The intake of the desalination plant would rely on a combination of new or modified water rights (i.e., water rights from CCWD and/or other nearby municipalities), based on availability. One of the options for disposal of the desalination plant brine include blending with discharges from wastewater treatment plants located in the vicinity of the desalination plant, including the Central Contra Costa Sanitary District and the Delta Diablo Sanitation District. Power to the desalination plant could be provided by Pacific Gas and Electric, the current power supplier at Mallard Slough Pump Station or nearby power plants; the Parties are continuing to investigate alternative renewable energy applications for the Project.
In October 2011 the partners executed a Memorandum of Agreement to conduct a Site-Specific Analysis to further evaluate the project under consideration. Along with a dedicated outreach effort, studies being conducted as part of the Site-Specific Analysis include a Hydraulic Analysis, Delta Modeling, Fisheries Modeling, Storage Optimization, and Greenhouse Gas Reduction Analysis. Public meetings describing the Site-Specific Analysis are expected in Spring 2012, with a presentation of results in Spring 2013.
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