Desalination removes salts from the ocean or brackish water to produce fresh drinking water through filtration or distillation.br>
The Bay Area’s five largest water agencies — the Contra Costa Water District (CCWD), the East Bay Municipal Utility District (EBMUD), the San Francisco Public Utilities Commission (SFPUC), the Santa Clara Valley Water District (SCVWD) and Zone 7 Water Agency (Zone 7) — 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. Although the agencies’ collective demands from the project have varied between 50 million gallons per day (mgd) and 120 mgd at various times since the concept was first put forward for study in 2002, the agencies have always remain committed to leveraging the regional aspect of the project to maximizing efficiency and minimizing the environmental footprint. Based on the projected collective demand of approximately 50 mgd from the project, ongoing studies assume a project size of 10-20 mgd to serve the agencies’ needs. Because not all agencies have demands at the same times and by optimizing storage availability, a 20 mgd facility would suffice to serve approximately 80% of the total demand from this project for the agencies.
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.
At the conclusion of the Institutional Feasibility Analysis, the agencies determined that the Oceanside site in San Francisco and the Near Bay Bridge site in Oakland were not feasible for further consideration. The agencies also reviewed other sites in the vicinity and determined that the Mallard Slough pump station continued to afford the agencies the most flexibility (it has connection points to both CCWD and EBMUD) and would require the least construction of new infrastructure (which would present both environmental effects and higher costs). The agencies also revised their demands based on more current projections following the economic downturn, resulting in the collective project demand being reduced to approximately 50 mgd.
Based on this institutional analysis, the agencies determined that they needed to investigate some key questions that are site-specific:
- Can EBMUD move sufficient water through its system to meet the demands of Zone 7, SFPUC and SCVWD in all years?
- How would a regional project affect the water quality in the vicinity of Mallard Slough and the nearby outfalls?
- What effect would water quality changes have on fish habitat?
- What would be the regional project’s contribution to climate change? How, and to what extent, can the greenhouse gas effects be reduced or eliminated?
- To what extent can storage be used to optimize the capacity of a regional facility?
These questions were the basis for the site-specific studies that were completed by the agencies in 2014. The results of the studies provided the following answers:
- Hydraulic modeling completed by EBMUD verified that up to 20 mgd could be wheeled to the Hayward Intertie at least 90% of the year, and 10 mgd to Zone 7 through a proposed new intertie over 95% of the year (assuming 2040 system demands and planned improvements).
- Operations of a 20 mgd plant at Mallard Slough would not have a significant impact on water quality or beneficial uses in the area under existing or forecast conditions (<0.25% EC).
- Sensitive fish species are present in the vicinity of the treatment plant in February – May, and mitigation for any potential impacts would be incorporated into the project design.
- Energy use and associated greenhouse gas emissions is less than other desalination projects because of a) existing facilities and b) brackish source water. It would be even lower except that pumping and treatment for delivery routes adds energy consumption.
- The option to store water in Los Vaqueros could help meet over 80% of agencies’ collective drought needs (based on hydrologic history).
Information on the site-specific analysis is shared through our website as well as through various public presentations made throughout our service areas. Check the “What’s New” section of our homepage to see what opportunities may be coming up for future participation. You may also contact us at our Contact Page for more information, or for help finding what you are looking for on our website.
With the site-specific studies completed, the agencies have determined the Bay Area Regional Desalination Project is technically feasible. The next step is to revisit the role of the project within the context of each agency’s changing water supply and demand picture through 2030. While the agencies continue to evaluate the need and benefits of the project individually, collectively, the agencies are embarking on a study to look more broadly at all the available opportunities to optimize the sharing of water resources across the region. In this context, the agencies will consider the use of existing supplies as well as new supply through desalination. By taking a more holistic and regional approach to water supply planning, the agencies hope to make the best use of scarce resources to serve the future needs of the Bay Area.
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