Drinking Water Resources

Senate Bill (SB) 170 (Stats. 2021, SEC. 89) amended item 3940-106-0001 of Section 2.00 of the Budget Act of 2021) to appropriate $30 million from the General Fund to the State Water Resources Control Board (State Water Board) to address Per-and Polyfluoroalkyl Substances (PFAS). A budget addendum includes another $50 million allocated for fiscal year (FY) 2022/23 and $20 million for FY 2023/24. This funding is available for technical and financial assistance to drinking water systems to address PFAS in their water drinking water supply.

  More information is available on the Division of Financial Assistance Emerging Contaminants (EC) and Per- and Polyfluoroalkyl Substances (PFAS) Funding webpage.

Project Background and Sampling Progress

As authorized by California Assembly Bill 178 (passed in 2022), the State Water Board is performing a free water testing program for about 3,600 drinking water wells in disadvantaged communities. This testing is being completed at no cost to public water systems. This project started in 2024 and will continue through 2026.

What the Project Tests For

The project is checking for 25 different PFAS chemicals using EPA Method 533. Four of the 25 chemicals have notifications levels issued by the Division of Drinking Water. These chemicals may pose health risks if levels are too high. The four PFAS chemicals with notification levels are:

• PFOA – Notification Level: 5.1 parts per trillion (ppt)
• PFOS – Notification Level: 6.5 ppt
• PFHxS – Notification Level: 3.0 ppt
• PFBS – Notification Level: 500 ppt

A Notification Level (NL) is a nonregulatory, health-based advisory level established for contaminants in drinking water for which Maximum Contaminant Levels have not been established. NLs represent the concentration level of a contaminant in drinking water that does not pose a significant health risk but warrants notification.

Interactive Visualization Tool

You can use an interactive tool to see the current status of the testing project. Here's how it works:

Left Side: Map of Wells

Light blue dots = wells that haven’t been sampled yet
Dark blue dots = wells that have already been sampled
Hover over a dot to see details, like:

• Water System Name
• PWSID and PS Code (well ID numbers)
• Highest measured levels for each of the four PFAS

Right Side: Sampling Progress Chart

A bar graph shows how many wells have been sampled each month since April 2024.
The x-axis shows months, and the bars show the number of wells sampled.
At the bottom of each bar: total number of wells sampled so far.
At the top of each bar: a line graph showing the percentage of the project that’s complete.
Hovering over a bar shows:

• Year and month of collection
• Number of wells sampled for the first time that month
• Total number of wells sampled so far

How to Use the Tool

• Click on a dot (well) or bar (month) to filter the data in both parts of the tool.
• Use the lasso tool to select a group of wells on the map and see when they were sampled.
• Click "Sampled" in the legend to view only the wells that have already been tested.
• Click one or more bars in the graph to highlight the wells sampled during those months on the map.

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• In May 2016, the United States Environmental Protection Agency (US EPA) issued a lifetime health advisory for PFOS and PFOA for drinking water, advising municipalities that they should notify their customers of the presence of levels over 70 parts per trillion (ppt) in community water supplies. US EPA recommended that customer notifications include information on the increased risk to health, especially for susceptible populations.
• In July 2018, DDW established an interim notification level of 14 ppt for PFOA and 13 ppt for PFOS and a single response level of 70 ppt for the combined concentrations of PFOA and PFOS.
• In August 2019, DDW revised the notification levels to 6.5 ppt for PFOS and 5.1 ppt for PFOA. The single health advisory level (for the combined values of PFOS and PFOA) remained at 70 ppt.
• On February 6, 2020, DDW issued updated drinking water response levels of 10 ppt for PFOA and 40 ppt for PFOS based on a running four-quarter average.
• On March 5, 2021, DDW issued a drinking water notification level and response level of 0.5 parts per billion (ppb) and 5 ppb, respectively for perfluorobutane sulfonic acid (PFBS).
• On October 31, 2022, DDW issued a drinking water notification level and response level of 3 parts per trillion (ppt) and 20 ppt, respectively for perfluorohexane sulfonic acid (PFHxS).
• On June 27, 2025, the Division of Drinking Water initiated the process of revising notification and/or response levels for perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexane sulfonic acid (PFHxS) and establishing a notification level and response level for perfluorohexanoic acid (PFHxA).

  Additional information about PFOA and PFOS can be found at can be found at the Division of Drinking Water: PFAS Webpage.

  Find the name of a PWS provider nearest you or for a particular location - map your location or enter an address.

  Find contact information for a PWS provider on the DDW’s Drinking Water Watch website - enter the ‘Water System Name’.

  A map with your local DDW district engineer contact information.

  Announcements and background on the issuance of PFAS NLs and other Drinking Water NLs.

Priority Basin Project

In cooperation with the U.S Geological Survey (USGS), the GAMA Priority Basin Project provides a comprehensive statewide assessment of groundwater quality to help identify and understand the quality of our groundwater resource. The project began sampling public water system wells to assess the deeper groundwater resource typically used for public supply in 2002 (Public Supply Assessment) and shifted to phase two in 2013 by sampling domestic and small system wells to assess the more shallow groundwater resource used for domestic and small system supplies (Shallow Aquifer Assessment). Since 2002, the USGS has performed baseline and trend assessments for each study unit and has sampled over 3,000 wells to characterize the quality of the complete aquifer resource used for all drinking water supplies. The Shallow Aquifer Assessment is currently sampling its 11th study unit.

The GAMA Priority Basin Project began the analysis of PFAS compounds in the summer of 2019 by adding twenty-eight PFAS compounds (which include carboxylates, sulfonates, precursors, and next generation-polyfluoroether “replacement” compounds) to the regular sampling schedule. This means wells sampled for both the Shallow Aquifer Assessment study units in progress and the trends component wells (sampling occurs at 20 percent of previously sampled wells, every five years in both the Public Supply and Shallow Aquifer Assessments) will undergo this PFAS schedule. Data from these assessments are released quarterly and available for query/download from the GAMA Groundwater Information System (GAMA GIS).

On May 25, 2021, Fact Sheet 2021-3028: Sampling for Per- and Polyfluoroalkyl Substances (PFAS) by the Groundwater Ambient Monitoring and Assessment Priority Basin Project was published by the U.S. Geological Survey. This fact sheet describes the GAMA-PBP plans for sampling public-supply and domestic wells across California for PFAS and presents preliminary results for data collected in 2019–20.

If you have any questions about the GAMA Program PFAS sampling, please contact Dori Bellan at Dorian.Bellan@waterboards.ca.gov.

From 2013 to 2015, the US EPA, under the Unregulated Contaminant Monitoring Rule (UCMR 3), required all large water systems (i.e., water systems serving over 10,000 people) nationwide to collect and analyze more than 12,000 drinking water samples for PFOS and PFOA. In addition, some water systems serving less than 10,000 people reported approximately 400 drinking water results for PFOS and PFOA. This occurrence data identified 36 sources with PFOS detections and 32 sources with PFOA detections. A summary of the findings for California is available at on the EPA's website: Occurrence Data for the Unregulated Contaminant Monitoring Rule.

In March 2019, the Division of Drinking Water issued Health and Safety Code 116400 Orders to 600 water system sites. Nearly 250 locations in the vicinity of airports with fire training and response areas, and municipal solid waste landfills are being reported to the State Water Boards for four consecutive quarters.

In August 2020, the Division of Drinking Water issued General Order DW 2020-0003-DDW pursuant to Section 116378 of the California Health and Safety Code for the testing of PFAS. The Order requires sampling to start on or before December 31, 2020, and samples tested by an analytical laboratory accredited by the California Environmental Laboratory Accreditation Program (ELAP) using EPA Method 537.1. Orders were sent to 224 public water systems with 887 wells to expand on the detected results from the testing of PFAS in 2019-2020.

In February 2021, the Division of Drinking Water issued General Order DW-2021-0001-DDW pursuant to Section 116378 of the California Health and Safety Code for the testing of PFAS. The Order requires sampling to start on or before June 30, 2021, and samples tested by an analytical laboratory accredited by the California ELAP using EPA Method 537.1. Orders were sent to 150 public water systems with 356 wells to test for PFAS on-base and in the vicinity of Department of Defense sites.

Some analytical methods using liquid chromatography-mass spectrometry-electrospray ionization methods (LC/MS/ESI) can achieve reporting limits for PFOA and PFOS at the nanogram per liter (ng/L) level. For the UCMR 3 monitoring program, LC/MS/MS-EPA Method 537 (rev 1.1) was required with minimum reporting limits of 20 ng/L and 40 ng/L for PFOA and PFOS, respectively. In November 2018, revised US EPA Method 537.1 was published that can detect PFOA, PFOS, and 16 other per-and polyfluorinated alkyl substances. Compliance with the recently changed NLs to 5.1 ng/L (PFOA) and 6.5 ng/L (PFOS) will require reporting limits lower than what can be achieved with US EPA Method 537. US EPA Method 537.1 is reported to be able to achieve lowest concentration minimum reporting levels (LCMRL) of 0.82 ng/L (PFOA) and 2.7 ng/L (PFOS). An LCMRL is defined as the lowest true concentration for which the future recovery is predicted to fall, with 99% confidence, between 50 and 150% recovery of the matrix spike (US EPA, Method 537.1, 2018).

Further information regarding PFAS in drinking water may be found at the Division of Drinking Water: PFAS Webpage.

• General Orders Requiring Monitoring for PFAS in Drinking Water Sources

• Draft Proposed PHGS for PFOA and PFOS
• Drinking Water District Offices Map
• Example PFOA/PFOS Notification Letter: (PDF)
• PFAS Water Systems Orders - April 30, 2019
• Drinking Water Sample Collection for PER and POLYFLUORINATED ALKYL SUBSTANCES (PFAS) Sampling Guidance REVISED November 2022
• General Order Requiring Monitoring for PFAS in Drinking Water Sources