Free California water report: PFAS & lead levels for every water system, worst-affected cities, and EPA violations. Check your ZIP.
California's water system is the most engineered and contested in the nation. The state's roughly 39 million residents depend on an interconnected web of sources: the State Water Project (pumping Sacramento-San Joaquin Delta water south), the Central Valley Project (federal), the Colorado River via the Metropolitan Water District, local surface reservoirs, groundwater basins, desalination plants, and an expanding network of recycled water facilities. The sheer scale of this system – spanning 800 miles from north to south – means that water quality varies dramatically by region, by source, and by season.
The State Water Resources Control Board (SWRCB) and nine Regional Water Quality Control Boards oversee drinking water for approximately 7,400 public water systems. California's Central Valley, the most productive agricultural region in the country, faces groundwater contamination from nitrates, pesticides, and naturally occurring arsenic. Coastal cities deal with saltwater intrusion and industrial legacy contamination. Desert communities in the Inland Empire depend on groundwater that has been compromised by military and industrial PFAS.
Drought has been a recurring force multiplier. During dry years, reduced surface flows concentrate contaminants, and utilities increase groundwater pumping – sometimes from basins with known contamination. According to SWRCB data, more than 300 California water systems have been out of compliance with one or more drinking water standards at some point in the past five years.
California has the most documented PFAS contamination of any state, driven by a combination of military installations, aerospace manufacturing, semiconductor fabrication, and firefighting foam use at airports and industrial facilities. The EPA's UCMR5 monitoring has confirmed what state testing had already begun to reveal: PFAS is present across large swaths of the state's water supply.
California's response has been the most aggressive in the nation. The SWRCB established notification levels of 5.1 ppt for PFOA and 6.5 ppt for PFOS, and response levels of 10 ppt and 40 ppt respectively – all stricter than the 2024 federal MCLs. The state is also developing MCLs for additional PFAS compounds beyond PFOA and PFOS, putting California ahead of federal regulators on breadth of coverage.
Groundwater contamination is particularly concerning in the San Fernando Valley (Los Angeles), the Inland Empire (San Bernardino and Riverside counties), Orange County, and the Sacramento area. These regions combine military base proximity, aerospace industry history, and heavy groundwater dependence. According to the SWRCB's PFAS investigation data, over 200 public water supply sources in California have detected PFAS above notification levels.
California has more military installations with confirmed PFAS contamination than any other state. The scope is staggering:
Marine Corps Base Camp Pendleton in San Diego County has confirmed PFAS in groundwater from AFFF use across the base. Contamination has been detected in monitoring wells and nearby waterways.
Edwards Air Force Base in Kern County, where decades of flight testing included extensive AFFF use, has documented PFAS in groundwater beneath and around the base.
Marine Corps Air Station Miramar in San Diego has confirmed PFAS contamination linked to firefighting foam. The base sits above groundwater that connects to the San Diego region's supply network.
Travis Air Force Base in Solano County has acknowledged PFAS contamination in surrounding groundwater, affecting communities in the Fairfield and Vacaville area.
Vandenberg Space Force Base on the Central Coast, Naval Base Ventura County (Point Mugu and Port Hueneme), Naval Air Weapons Station China Lake, and Beale Air Force Base have all been identified by the Department of Defense for PFAS investigation or confirmed contamination.
In the Inland Empire, the former Norton Air Force Base and March Air Reserve Base have left PFAS plumes in groundwater that local utilities must now manage. The Department of Defense has identified California as having the highest concentration of PFAS-affected installations in its nationwide assessment. See our military bases page for the complete list and current status of each site.
California's regulatory framework for PFAS is the most advanced in the country. The SWRCB has established notification levels, response levels, and is developing enforceable MCLs that will cover a broader range of PFAS compounds than the federal rule. Utilities that detect PFAS above notification levels must inform the SWRCB and their customers. Utilities that exceed response levels must take the source out of service or install treatment.
The state has also funded PFAS investigations through its PFAS Investigation Order, which required airports, refineries, and other potential sources to test for PFAS in groundwater and report results. This proactive approach has generated a PFAS dataset far larger than what UCMR5 alone would provide.
Under SWRCB's drinking water program, all public water systems in California must report PFAS monitoring results. The state has also allocated funding to assist small and disadvantaged water systems with PFAS treatment infrastructure, recognizing that many of the hardest-hit communities are in lower-income areas that cannot afford treatment upgrades on their own.
California's size means regulatory capacity varies. Large urban utilities have the resources to test, treat, and report. Small systems serving farmworker communities in the Central Valley may lack the technical and financial capacity to address PFAS even when it is detected.
For background on PFAS science and health effects, see our PFAS guide.
California's water quality varies more within the state than between California and most other states. A resident in San Francisco drinking Hetch Hetchy reservoir water faces a fundamentally different profile than a resident of Riverside on contaminated groundwater.
1. Check your ZIP code at the homepage to see PFAS and other monitoring data specific to your water system. We compile UCMR5, SWRCB, and utility data in one place. 2. If you are in a high-PFAS area – West San Fernando Valley, parts of the Inland Empire, Orange County near former bases, Sacramento suburbs – a reverse osmosis filter is the most effective household solution. Our water filter guide details which systems are certified for PFAS removal. 3. In the Central Valley, nitrates and arsenic may be equal or greater concerns than PFAS. Our guide covers filtration for these contaminants as well. 4. Request a detailed water report for your address to see historical trends and how your system compares to state thresholds.
California has more PFAS data than any other state – and more contamination to track. Check your specific location to see what the data shows for your water system.