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Regional Groundwater Storage & Recovery

Project Information
April 2015
Winter 2021
Cost $114 Million
Project Phase
  • Phase I Construction Completion Summer 2019
  • Phase II Construction Completion Winter 2021
Additional Information

The information shown reflects the current forecast information published in the latest WSIP Quarterly Report.

Project Materials

Fact Sheet
Draft EIR Volume 1
Draft EIR Volume 2
Hydrogeologic conditions in the Westside Basin - 2005
Project Terms & Definitions
Usefull Links to Learn More About Groundwater

Need more information? Contact:

Elizabeth Cox


Project Update
The Regional Groundwater Storage & Recovery (RGSR) project includes the construction of up to 16 new recovery and test wells and facilities consisting of chemical treatment equipment, tanks, pumping systems, and associated pipelines. As of Fall 2020, the project is over 76% complete with twelve of the thirteen Phase 1 wells constructed and undergoing testing, and construction of the final Phase 1 well station underway.

The test wells for two Phase 2 well stations have been completed and a sixteenth well site has been selected. We anticipate completion in 2021. For regular construction updates, please visit our Peninsula Blog.

GSR Project Update

Groundwater Map
This project includes the installation of up to 16 new recovery well facilities in northern San Mateo County.


How the Project Will Work?
The concept of groundwater storage and recovery, also known as “conjunctive water management”, consists of storing water in wet years and recovering that water for use during dry years. As part of the RGSR project, surface water will be used instead of groundwater in wet years, allowing the groundwater to recharge through rainfall and decreased pumping. This will create a savings account of up to 20 billion gallons of groundwater that will be stored in the aquifer. 

In dry years, when less surface water is available, the saved water will be pumped from the new groundwater well recovery facilities at a rate of up to 7.2 million gallons per day. To put this into context, that amount of water could serve up to 24,000 homes. The RGSR project is designed to help diversify our water supply for drought protection and will ensure we are even more resilient during and after an earthquake or other emergency. The water quality from this stored supply will meet the California Department of Public Health requirements for drinking water supplies.

Wet Year
In wet years, municipal pumping is decreased and groundwater
fills the available aquifer storage space.
Dry Year
In dry years, groundwater is pumped from storage – the
“water savings account”.


A Regional Approach to Drought Protection

California Water Service Company, City of Daly City, City of
San Bruno and SFPUC celebrate signing of operating agreement.

A landmark agreement between the SFPUC and three San Mateo County organizations was finalized and signed in December 2014 to ensure long-term management and sustainability of the South Westside Groundwater Basin. The partnership with SFPUC, City of Daly City, City of San Bruno and California Water Service Company allows these agencies to operate the basin sustainably and provide us with a new 20-billion-gallon regional dry year groundwater supply. These San Mateo County agencies provide drinking water from two sources, local groundwater from the South Westside Groundwater Basin and surface water supplies from the SFPUC.

Groundwater Storage Around the Bay
In the Bay Area alone, similar conjunctive water management programs are being implemented by the Santa Clara Valley Water District (serving Campbell, Cupertino, Gilroy, Los Altos Hills, Milpitas, Monte Sereno, Morgan Hill, Mt. View, Palo Alto, San Jose, Santa Clara, Saratoga and Sunnyvale, and the towns of Los Altos and Los Gatos), the Alameda County Water District (serving Fremont, Newark, and Union City) and the Zone 7 Water Services Agency (serving Livermore, Pleasanton and Dublin). These programs have been operating successfully for decades.

Last updated: 11/20/2020 2:07:20 PM