Alternative Water Supplies

Los Vaqueros Reservoir Expansion

Located in northeastern Contra Costa County, Los Vaqueros Reservoir is owned and operated by Contra Costa Water District (CCWD). CCWD, the SFPUC, and other Bay Area Water agencies formed a Joint Powers Authority in 2021 to evaluate a potential expansion to the existing reservoir to increase water storage and supply reliability and benefit the south of-Delta ecosystem and fisheries. For more information about this project, visit the Contra Costa Water District's Los Vaqueros Reservoir Expansion Project website.

Los Vaqueros Expansion Water Conveyance Alternatives

While evaluating the Los Vaqueros Expansion Project, the SFPUC began to explore the potential transport, transfer, or exchange of water from Los Vaqueros to our Regional Water System. The SFPUC continues to assess possible conveyance pathways between the Regional Water System and partner agencies to expand the SFPUC’s access to water transfer markets.

Several alternatives under consideration involve use of the South Bay Aqueduct, including delivery to San Antonio Reservoir and exchanges with regional partners. Potential partners include the South Bay Aqueduct Contractors (ACWD, Zone 7 Water Agency, and Valley Water), particularly any agency identified as a feasible transfer partner. Of the current options, only delivery to San Antonio Reservoir would involve direct transfer of South Bay Aqueduct water into the SFPUC’s Regional Water System. All conveyance options currently under consideration depend upon reliable delivery through the South Bay Aqueduct, a State Water Project facility owned and operated by the California Department of Water Resources. 

In addition to these conveyance options, other alternatives may be viable, such as construction of a new intertie with the East Bay Municipal Utility District (EBMUD).

Calaveras Reservoir Expansion

Calaveras Reservoir, located in Alameda and Santa Clara counties, currently stores water from the local Alameda Creek Watershed. This project evaluates the possibility of making the reservoir larger to also store water from our Regional Water System. No expansion of water rights from the local watershed is anticipated. An expanded reservoir could hold an additional 94 billion gallons of water storage, up from the current 31 billion gallons.

The proposed project would include raising the New Calaveras Dam, increasing the capacity of the outlet structures and the spillway, and the addition of any transmission and pumping facilities needed to bring regional water system water to Calaveras Reservoir. Constraints including water availability and transmission to the reservoir will need to be evaluated.

Daly City Recycled Water Expansion

We are evaluating providing recycled water to irrigate 13 cemeteries and a few smaller irrigation customers in Daly City instead of groundwater from the South Westside Basin groundwater aquifer. By irrigating with recycled water, we save the groundwater for drinking. The recycled water would come from Daly City’s Wastewater Plant, which could produce up to 3 million gallons of water per day of recycled water during the irrigation season.

We are working closely with Daly City, and the irrigation customers located within California Water Service Company’s (Cal Water) service area. Cal Water has taken a direct role in the development of the project with us.

Additional information can be found in the following reports:

• Combined Results of the Recycled Water Treatment and Delivery System Expansion Feasibility Studies (Carollo, 2009)
• Final Initial Study/Mitigated Negative Declaration (IS/MND) (SMB Environmental, 2017)
• Preliminary Design Report and 30% Drawings (Volume 1, Volume 2, Volume 3) (Carollo, 2017)
• Feasible Alternatives Evaluation (Carollo, 2022)

Satellite Recycled Water

For over five years, new development projects in San Francisco that are larger than 250,000 square feet have been required to install and operate on-site non-potable water systems to treat and reuse available water from sinks and drains, rainwater, and foundation drainage to flush urinals and irrigate plants.

Some new large-scale construction projects have dual plumbing for the use of recycled water onsite but currently do not have a source for recycled water to flush toilets and urinals. The Satellite Recycled Water Project would provide a treated recycled water supply to these dual plumbed buildings. This project would include a small centralized tertiary treatment facility, storage tank, and transmission lines that would be located nearest to a majority of the end uses.

This project would provide an appropriate water supply source for non-potable irrigation, as well as commercial and industrial uses not addressed by the Non-Potable Ordinance (NPO).

Bay Area Regional Reliability SWAP

Eight of the Bay Area’s largest water utilities formed a partnership in 2016 to explore opportunities to transfer and exchange water between water utilities to meet water supply demands, particularly during droughts and emergencies. The intent is to leverage existing infrastructure and connections that already exist between the partnering agencies.

Called the Bay Area Regional Reliability (BARR) Partnership, the group includes the following member agencies: 1) Alameda County Water District (ACWD), 2) Bay Area Water Supply & Conservation Agency (BAWSCA), 3) Contra Costa Water District (CCWD), 4) East Bay Municipal Utility District (EBMUD), 5) Marin Municipal Water District (MMWD), 6) the San Francisco Public Utilities Commission (SFPUC), 7) Valley Water (formerly Santa Clara Valley Water District and 8) Zone 7 Water Agency.

Currently, the BARR Partnership is planning to test water transfer scenarios through a Shared Water Access Program (SWAP) so that future transfers can be implemented more readily in times of drought or emergency.

Potable Offset Potential

We launched a study to assess additional programs and/or policies that we could possibly implement in San Francisco to offset drinking water demands from new developments in San Francisco. This extensive study evaluated case studies from around the world. At this time, none of the case studies explored would work for San Francisco's context. Either because existing programs are already as successful as the case study, or would not be applicable in San Francisco. However, the SFPUC continues to explore new ways to conserve and reuse water, recover resources, and diversify the City's water supply.

Bay Area Brackish Water Desalination

Together with several fellow Bay Area water agencies, we are investigating the possibility of treating brackish water (water with more salinity than freshwater but less than sea water) from Contra Costa Water District’s existing Mallard Slough intake in Contra Costa County. This project would rely on available capacity in an extensive network of existing pipelines and facilities that already connect the agencies. It would also require the construction of new facilities and upgrades to existing infrastructure to accomplish.

This project is a partnership between: Contra Costa Water District (CCWD), SFPUC, Valley Water, and Zone 7 Water Agency. East Bay Municipal Utility District (EBMUD) and the Alameda County Water District (ACWD) may also participate.

The project could provide 10 to 20 million gallons of water of a new drinking water supply to all of these water agencies. The SFPUC would not directly receive desalinated water but would take delivery of water through a series of transfers and exchanges.

ACWD -USD Purified Water Partnership

We are working with our partners at Alameda County Water District (ACWD) and Union Sanitary District (USD) to determine the feasibility of transmitting enhanced recycled water from USD’s wastewater facility to Quarry Lakes to recharge the Niles Cone Groundwater Basin for uses in ACWD’s service area. The water added to ACWD’s groundwater aquifer would be offset by less water taken from the SFPUC’s regional water system. 

Enhanced recycled water is highly-treated wastewater that undergoes multiple treatment processes to exceed drinking water quality standards.

While the potential volume of supply will be determined through a feasibility evaluation, prior studies indicate the potential for at least 4 million gallons of water per day of new supply.

Additional water supply could also be directly transmitted to the SFPUC through a new intertie between ACWD and SFPUC. A range of scenarios considering treatment capacity, distribution potential and feasibility are being considered through an evaluation between the three partner agencies.

More information is available in the Woodard & Curran Purified Water Feasibility Study, published in August 2023.

PureWater Peninsula

We are studying the feasibility and impacts of transporting highly-treated wastewater from Silicon Valley Clean Water and/or the City of San Mateo into our Crystal Springs Reservoir in San Mateo County. This enhanced recycled water (highly-treated recycled water that exceeds drinking water quality standards) would blend with water in Crystal Springs Reservoir before being treated at the nearby Harry Tracy Water Treatment Plant for transmission to customers. We could provide 6 to 12 million gallons of water per day from this project.

We are working closely with the wastewater agencies, Cal Water, Redwood City and BAWSCA on this project. We are in the process of conducting analyses on the feasibility and constructability of this option.

Further information is available in the following reports:

• Phase 1 Initial Study (Kennedy Jenks, 2017)
• Phase 2 Concept Study (Kennedy Jenks, 2019)
• Phase 3 Title XVI Feasibility Study (Kennedy Jenks, 2022)
• Basis of Design Report (Kennedy Jenks, 2024)

South Bay Purified Water

We are collaborating with the cities of San Jose and Santa Clara to study a joint purified water project. A feasibility study was completed in 2023 to evaluate an initial concept where a facility would produce 6.5 million gallons per day in wet and normal years to serve San Jose and Santa Clara, and ramp up to 10 million gallons per day in dry years to serve additional dry-year supply to the Regional Water System. More information can be found in the South Bay Purified Water Project Feasibility Study published in July 2023.

PureWaterSF Exploration

In 2018 – 2019 we piloted a project in our own headquarters to collect, treat, and serve purified water. We are looking into possibly expanding this idea on a larger level to collect wastewater from one of our wastewater treatment plants and treat it with a multi-stage, multi-barrier advanced treatment process that meets drinking water standards. The treated water would then be blended at one or more of San Francisco's drinking water reservoirs. This treatment and distribution process is referred to as treated water augmentation, and State regulations are still under development (anticipated by 2023).

We completed a feasibility study to explore the size and scope of purified water opportunities, and to develop a plan for next steps. 

SF Purified Water Opportunities Study May 2022

Groundwater Banking

A groundwater bank works much like a regular bank where you store money when it is available, and then withdraw it when you need it. In this case, we would look for opportunities in the San Joaquin River Basin to use surface water from our system in wet years to bank in the groundwater aquifer and in the dry years the groundwater would be used to free up additional Tuolumne River water for use. A feasibility study of this option is included in the proposed Tuolumne River Voluntary Agreement. 

Dry Year Transfers

In dry years when water is scarce, we could purchase additional water from another agency with water to spare in order to meet customer demand. In theory the SFPUC has been considering dry year water transfers since 2008, but without success to date. This requires a willing buyer and a willing seller and a connection between the two systems in order to make the transfer. We have pursued drought year transfers with the Modesto Irrigation District and the Oakdale Irrigation District in the past. We will continue to pursue potential transfer options on the Tuolumne River and throughout the San Joaquin Valley.

Inter-Basin Collaborations

Called inter-Basin Collaborations, this is a partnership among several agencies in a river basin that can take advantage of the annual hydrology of each river system to mutual benefit. For example, one river system in the basin may spill more excess water in wet years than another river system and the excess water could be used to meet either fishery requirements or other needs to allow the other river system to retain water in storage. Then the stored water could be used in dry years to provide the water to meet obligations in both river systems. Inter-Basin collaborations could also take the form of groundwater banking or water transfers.

There are a number of potential collaborations among and between the San Joaquin tributaries that could develop additional water supplies, some of which could be utilized to enhance fishery flows. There are also potential collaborative non flow measures (i.e. improved and augmented hatchery activities on the Merced River) that could benefit all of the tributaries.

A feasibility study of this option is included in the proposed Tuolumne River Voluntary Agreement. Any collaboration would need to protect the interests of all participants.

Alternative Water Supply Planning Reports

• 2023-2024 Alternative Water Supply Annual Progress Report
• June_2023_AlternativeWaterSupplyQuarterlyReport
• March_2023_AlternativeWaterSupplyQuarterlyReport
• December_2022_AlternativeWaterSupplyQuarterly Report
• September 2022_Alternative Water Supply Quarterly Report
• June 2022_Alternative Water Supply Quarterly Report
• March 2022_Alternative Water Supply Quarterly Report
• December 2021 Alternative Water Supply Quarterly Report
• September 2021 Alternative Water Supply Quarterly Report
• June 2021 Alternative Water Supply Quarterly Report
• March 2021 Alternative Water Supply Quarterly Report
• December 2020 Alternative Water Supply Quarterly Report
• August 2020 Alternative Water Supply Quarterly Report
• June 2020 Alternative Water Supply Quarterly Report