PFAS Information

Due to their long-term and widespread use and persistence in the environment, most people in the United States have been exposed to PFAS. There is growing evidence that long-term exposure above specific levels to certain PFAS can lead to cancer and adverse health effects to fetuses during pregnancy or breastfed infants, the liver, immune system, and thyroid.

People are exposed to PFAS by working in occupations such as chemical manufacturing and processing and firefighting, eating food contaminated from cookware, packaging or containing PFAS due to bioaccumulation (e.g., fish, meat, eggs, and leafy vegetables), drinking water contaminated by PFAS, and using, touching or breathing products treated with PFAS (e.g., carpets, upholstery, cosmetics, and clothing). PFAS have also been found in soil, household dust, and numerous other recurring routes of exposure as well.  

Federal Environmental Protection Agency (EPA) Efforts

In 2024, the U.S. EPA issued national Maximum Contaminant Limits (MCL) for six PFAS chemicals. Public water systems were required to complete initial monitoring for PFAS by 2027. Beginning in 2029, public water systems where PFAS has been detected in drinking water above one or more of these MCLs are required to take action to reduce levels of PFAS and provide notification to the public.

Federal Regulatory Enforceable Levels for PFAS in Drinking Water Sources (nanogram per liter or parts per trillion [ppt])

State of California Division of Drinking Water (DDW) Efforts

The State of California also has adopted advisory levels for four PFAS chemicals – a notification level as well as a response level. Notification level represents the concentration level of a contaminant in drinking water that warrants notification. Response level represents the concentration level of a contaminant in drinking water at which water systems should take additional actions such as taking a water source out of service or providing treatment.

Other state-level actions have been taken on PFAS. For example, California has banned the use of PFAS in food packaging and infant and children’s products.

State Regulatory Advisory Levels for PFAS in Drinking Water Sources (nanogram per liter or parts per trillion [ppt])

The federal MCLs and California advisory levels are set at parts per trillion (PPT) ranging from 3 to 5,000, depending on the specific PFAS chemical. Sometimes this measurement of concentration is also expressed as nanograms per liter. For reference, one part per trillion is equivalent to one drop of water in 20 Olympic-sized swimming pools.

According to national water management experts, the most significant action needed to eliminate the presence of PFAS in the environment, animals, and humans is to remove these chemicals from the stream of commerce. Some manufacturers and consumer products companies have begun phasing out the use of PFAS and developing alternatives. DSRSD is actively advocating for the removal of PFAS from industrial and consumer products at the state and federal level.

PFAS has been detected in municipal drinking water wells in the Tri-Valley. Zone 7 Water Agency, the Tri-Valley’s water supply wholesaler, has mapped a known area of PFAS (referred to as the “footprint”) in the main groundwater basin where some drinking water wells are located. It’s important to note that the majority of drinking water in the Tri-Valley is imported surface water from major California rivers and the Delta.

More information about the presence of PFAS is available in DSRSD’s Water Quality Report: https://www.dsrsd.com/water-quality-report

Ongoing monitoring is being conducted to further understand the presence and movement of PFAS in the groundwater basin, as well as sources that may be contributing PFAS to groundwater. Where PFAS has been detected over the state’s notification level, notifications have been made to the public.

Zone 7 Water Agency - – which supplies drinking water to DSRSD – continues to operate its water supply systems to ensure the water supply from PFAS-affected groundwater wells remains below the response levels.  In 2023, Zone 7opened a new Ion Exchange PFAS Removal Treatment at their Stoneridge well location and is in the process of planning, designing, and building another PFAS treatment facility that is projected to be in operation in Spring 2025. These facilities effectively treat water from impacted wells to below any response level for PFAS.  Zone 7 has proactively removed drinking water wells from service where PFAS has been detected at the state’s response level, and PFAS treatment has not yet been installed.

Wastewater treatment facilities are not “producers” or users of PFAS and do not utilize PFAS chemicals. Rather, they are “receivers” of PFAS because they receive wastewater from residential and commercial sources containing PFAS.

Traditional wastewater treatment operations do not eliminate PFAS. Monitoring at DSRSD’s wastewater treatment plant has detected PFAS in incoming water (influent), outgoing water (effluent), and solids that are separated from water during treatment (biosolids).

A study was conducted to determine if the PFAS detected at the wastewater treatment site were migrating off-site or contributing to the PFAS footprint in the main groundwater basin in the Tri-Valley. Operations that were evaluated were lagoon operations - where biosolids are initially deposited for decomposition - and the underground injection of these decomposed solids for long-term disposal. Treated wastewater effluent was not evaluated, since it is piped directly to San Francisco Bay.

The study concluded that the wastewater treatment site is not contributing in any significant way to downstream surface water or downgradient groundwater PFAS concentrations. The study also found minimal, if any, potential for future impacts to municipal water sources in the Livermore Valley Groundwater Basin. The occurrence of PFAS detected in monitoring wells at the site is contained to a very small and shallow area and almost exclusively in a low-permeability clay layer that exists between the surface and the underlying upper aquifer (referred to as Aquiclude). This clay layer is approximately 40-50 feet thick beneath the lagoons and disposal site and acts as a natural barrier to restrict vertical and horizontal migration of constituents of concern, including PFAS, to off-site locations. This clay layer is up to 70 feet thick beyond the site boundaries. The estimated travel times for constituents of concern in shallow groundwater at the disposal site to the nearest surface water or aquifer locations down-gradient of the site are multiple decades or even centuries long.

The study also looked at whether recycled water used to water landscapes could be contributing to PFAS in the groundwater basin. The study concluded that there is only minor overlap between areas irrigated with recycled water and the detected PFAS footprint that has been mapped in the Main Basin, which indicates a lack of any contribution of PFAS from recycled water.