Skip to main content

PFAS Maps Overview

The PFAS in Drinking Water Maps (PFAS Maps) are an interactive series of maps for exploring both the US EPA Unregulated Contaminant Monitoring Rule (UCMR) 3 (2013-2015) Data and the results of the California Water Boards' 2019-2020 PFAS Investigation.

The map series is divided into four sections and can be used to see:

  1. How many drinking water systems in California detected PFAS contaminants in the 2013-2015 and 2019-2020 sampling periods
  2. Which PFAS contaminants were detected in each water system in 2019-2020
  3. Potential sources and average concentrations of PFAS contaminants in 2019-2020
  4. The concentration of PFOA and PFOS found in each water system in 2019-2020, two contaminants that the California's Office of Health Hazard Exposure Assessment established notification levels for.

Interactive components in the map series include:

  • Moving back and forth between the two sampling periods (2013-2015 vs. 2019-2020) in maps found in #1 Water systems that detected PFAS in 2013-2015 and 2019-2020
  • Clicking on each water system or sources in maps #2-4 to yield popup windows with additional information (i.e. Public Water Service Identification, county name, population served, service connections, total number sampled, etc.)
  • For additional information on how to use the maps, please refer to the detailed instructions page.

Frequently Asked Questions:

Why are there more detections in 2019-2020?

The frequency of PFAS detections varies between the UCMR3 sampling (2013-2015) and the California Water Boards sampling (2019-2020) based on the detection limits and types of PFAS measured. For more information about sampling methods, please click here.

Are the sampled water systems in 2013-2015 in the same as those tested in 2019-2020?

The California Water Boards 2019-2020 PFAS Investigation retested some water systems sampled in 2013-2015, but the selection of systems for testing in 2019-2020 focused on water systems close to landfills and airports, which are possible sites of PFAS contamination. For this reason, there is not very much overlap between the systems tested in 2013-2015, and those tested in 2019-2020.

Why isn't there a boundary for some water system samples?

Some water system sample results displayed in maps #2-4 may exist outside of the water system service areas (boundaries) collected by Tracking California. These samples (displayed as dots on the map) identify individual sampling sites rather than a water system boundary, which contains multiple sampling sites. For more information on Tracking CA's water boundary tool, please click here.

Why did some systems test for PFAS so many times?

During Phase 1 of the California Waterboards sampling approach, impacted drinking water sources identified by the 2013-2015 Third Unregulated Contaminant Monitoring Rule monitoring efforts and adjacent small systems were required to be sampled. Throughout the sampling process, in instances where an initial sample was detected above the notification level or the sample came back positive, a system may have also been resampled. In instances where a positive result for a source was followed by a confirmation sample result less than the laboratory method-reporting limit, a second confirmation sample may have been taken. For more information on the sampling methodology, please click here.

If a system had PFAS during testing, does that mean the water still contains PFAS today?

Systems where PFAS was detected during sampling may not necessarily represent the levels that are in the water today. Many systems have begun taking action to treat or reduce PFAS in the water. Moreover, the process to test water from these systems is ongoing. To stay up to date on current and future PFAS detections in California, please visit the California Water Resources Boards PFAS geotracker.