PFAS Program Logo

Drinking Water Resources

Public Water System PFAS Information and Resources


In April 2019, the State Water Board issued specific orders to airports, landfills and adjacent water systems, identified as potential PFAS source locations. Data from more than 600 water system sites adjacent to nearly 250 airports with fire training areas and municipal solid waste landfills within California have been received by the State Water Board in response to these specific orders.  The assessment of this data obtained by these actions is a prolonged undertaking and additional analysis will be conducted in the coming years.  Selection of the location of public water supply (PWS) wells sampled was based on the following criteria:

  • Within 2 miles of a commercial airport* and/or within 1 mile of a municipal solid waste landfill that received Investigative Orders on March 20, 2019
  • Resampling of PWS wells sampled during the 2013-2015 US EPA’s Third Unregulated Contaminant Monitoring Rule (UCMR 3)
  • Within 1 mile of UCMR 3 sampled PWS wells that had detections of PFOA and PFOS

*Certified by Federal Aviation Administration per Title 14 Code of Federal Regulations Part 139

The Division of Drinking Water required the Public Water Systems to sample the PWS wells quarterly for four consecutive quarters.

In August 2020, the Division of Drinking Water issued a General Order to expand the PFAS testing of Public Water Systems based on the 2019 PFAS sampling results.

Public Water Supply Well Results

The State Water Board is providing charts of the 2019/2020 results on this webpage. The 2019/2020 and future public water system results are found on the PFAS GeoTracker Mapping Tool.

The 2019/2020 dataset of PFAS results for the PWS wells sampled during the 1st, 2nd, 3rd, and 4th Quarter is available for download in this file: (pfas_monitoring_Q1Q2Q3Q4)

In this dataset and on the following charts, if a water system sampled a well more than once in a quarter, the concentration equals to the average concentration for that analyte. Additionally, PFOA or PFOS concentrations reported at less than the reporting limit are shown as zero.

Charts for 2019/2020 Data

Charts #1 and #2

Charts number one: This chart shows the frequency of detections for PFOA. The increment along the X-axis equal to the NL for PFOA (5.1 ppt).
Charts number two: This chart shows the frequency of detections for PFOS. The increment along the X-axis equal to the NL for PFOS (6.5 ppt).

 - A series of two charts are shown. Each chart shows the frequency of detections for PFOA and PFOS, respectively for all results less than 70 ppt for PFOA or PFOS. The first column along the X-axis is equal to the NL for PFOA (5.1 ppt) or PFOS (6.5 ppt). Each column within each concentration range represents a quarter of data.

Charts #3 and #4

Chart number three: This chart shows the frequency of detections for PFOA chemicals analyzed.
Chart number four: This chart shows the frequency of detections for PFAS chemicals analyzed.

 - A series of two charts are shown. Each chart shows the frequency of detections for PFOA and PFOS, respectively for all results for PFOA or PFOS. Each column within each concentration range represents a quarter of data.

Chart #5 – Detections by All PFAS Chemicals

Chart number five: This chart displays the frequency of detections versus each of the PFAS chemicals analyzed.

 - This chart displays the frequency of detections versus each of the PFAS chemicals analyzed. Each column within each concentration range represents a quarter of data.

Chart #6 – Detections by All PFAS Chemical Classes

Chart number six: This chart displays the frequency of detections versus PFAS class.

 - This chart displays the frequency of detections versus PFAS class. The PFAS classes used are:

  • Cl-PFESAs = 11Cl-PF3OUdS, 9Cl-PF3ONS

Perfluoroalkyl acids (PFAAs) include PFCAs and PFSAs. Each column within each chemical class represents a quarter of data.

  Subscribe to our Email Lists

To receive email notices about upcoming information, please go to our Subscription page and signup to our email lists.

For Drinking Water regulations and other drinking water-related information,
(Click on the “Drinking Water” section)
For PFAS events or announcements,
(Click on the “Water Quality” section)
  • 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).

  Additional information about PFOA and PFOS can be found at can be found at the DDW PFOA and PFOS 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

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, and nearly 250 locations such as airports with fire training and response areas, and municipal solid waste landfills are being reported to the State Water Boards and will continue to be collected until into early 2020. More water system data will be requested in the area of other types of sources in 2019, including industrial sites. The assessment of this data will be used to determine data information gaps. Additional and more assessment will be required in the coming years.

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 PFOA/PFOS webpage.

Subscribe to our Per- and Polyfluoroalkyl Substances (PFAS) email list to receive notifications and the latest updates. After subscribing, you will need to check your email host for a confirmation email to complete the subscription.

Email Address: (required)
Your Full Name: (required)
(e.g. John Smith)

  Subscribe to our other email lists. See the "Water Qualitysection.

Questions? Comments?