On an average day, the City of San Francisco – its residents, businesses, and visitors – consumes about 60 million gallons of water. This water is supplied solely by the Hetch Hetchy Regional Water System. Developing local groundwater can help diversify our supply portfolio and ensure we have a local source for water should a drought, earthquake or other disaster interrupt our Hetch Hetchy supply.
How it Works
In April, 2017, the San Francisco Public Utilities Commission (SFPUC) began pumping groundwater from the Westside Groundwater Basin aquifer that extends to approximately 400 feet below the surface in San Francisco. The groundwater will be treated and blended with our regional drinking water supplies before it is delivered to our customers. Over the next few years we will continue adding groundwater in order to reach our goal of blending 4 million gallons a day (mgd) of treated groundwater with our regional water supplies by 2021.
Once the project is completed, the SFPUC will have 6 groundwater wells pumping up to 4mgd of groundwater from the Westside Groundwater Basin in San Francisco. The groundwater is treated with chlorine and then delivered to the Sunset and Sutro Reservoirs. The blended water will be served to more than half of the SFPUC's customers in the City. San Francisco’s drinking water supplies are tested daily with a network of instrumentation throughout our regional water system as well as through manual sampling.
A Reliable, Local Source of Water
On an average day the City of San Francisco – including our residents, businesses and visitors – will continue to rely primarily on the Hetch Hetchy Regional Water System, a system that combines the resources of the Hetch Hetchy Reservoir with 5 reservoirs in the Bay Area, for 60 million gallons of drinking water. On average, about 85% of our water is supplied by Hetch Hetchy and our local reservoirs provide the remaining 15%. Adding groundwater to our regional water supplies makes San Francisco’s water supply more reliable, particularly in the event of droughts and emergencies.
More than Just a Well!
The West Sunset Well Facility’s design includes features that will allow it to serve as an emergency drinking water supply. It can be connected to a generator for backup power, provide on-site disinfection, and be connected to a dedicated hydrant for filling water tanker trucks.
Water Quality: Our Highest Commitment
A Vital Project with Multiple Benefits
For the past decade, the SFPUC has collected water quality and quantity data from the Westside Basin aquifer. With our extensive testing and data collection we know that after groundwater to our regional water supplies, we will continue to provide our customers with high-quality drinking water that meets or exceeds all regulatory safety and quality standards set by the California State Water Resources Control Board, Division of Drinking Water, and the U.S. Environmental Protection Agency.
The San Francisco Groundwater Supply Project is an important component of the Water System Improvement Program
and provides both local and regional benefits.
- Local: Our environment and our city face many unknowns in the future from possible drought, earthquake and climate change. A local water source will give us more control over the use and operation of our water supplies.
- Sustainable: Groundwater is a renewable water source that is replenished through natural processes.
- Reliable: This project diversifies the city’s water supply portfolio, which will reduce our dependence on a single source, thus making us less vulnerable to disrupted services.
- Responsible: This project will coordinate closely with the SFPUC’s Westside Basin Groundwater Monitoring Program, a robust monitoring network, to make sure that we operate in a responsible and sustainable manner so that this groundwater basin will be available for generations to come.