Key Points to Know About PFAS in Soil
Efforts to address per-and polyfluoroalkyl substances (PFAS) in drinking water began in the early 2000s – prompting action and federal mandates that resulted in enforceable federal drinking water standards. In April 2024, the U.S. Environmental Protection Agency (EPA) established drinking water Maximum Contaminant Levels (MCLs) for Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonic acid (PFOS), Perfluorononanoic acid (PFNA), Perfluorohexanesulfonic acid (PFHxS), and HFPO-DA (GenX Chemicals).
While efforts to address PFAS in drinking water gained mainstream attention and resulted in new regulations, little has been done to address PFAS in soil, which is the primary source of these “forever chemicals” that leach into groundwater and contaminate our drinking water.
With few federal guidelines and only a limited number of states that provide guidance and standards that address PFAS in soil, it is important to have some context surrounding this complex issue and the latest regulatory information as it becomes available. Even though PFAS pollutants are excluded from most environmental policies, PFAS in soil are increasingly becoming a liability that sometimes involves insurance for such industries as manufacturing, chemical production, waste management, and real estate development.
This article discusses screening guidance values and cleanup standards that are protective of groundwater, variations in state and federal levels, as well as what levels of PFOS and PFOA in soil most likely will impact groundwater above the federal drinking water MCLs. Although not binding limits, guidance levels can serve as the basis for regulatory action and are a useful tool for due diligence and risk assessment, while cleanup standards usually require investigation and corrective action once concentrations exceed the soil standard protective of groundwater.
Here are three key points, along with insight and analysis based on the most regulated PFAS compounds, which are PFOA and PFOS. Data is provided by the Interstate Technology and Regulatory Council (ITRC), as well as correspondence and discussion with each of the regulatory agencies that have established either PFOA and PFOS guidance levels or cleanup standards for soil protective of groundwater.
- EPA has no enforceable PFAS soil standards requiring action
EPA provides guidance for only primary regional screening levels (RSLs) used for human health site risk assessments. Currently, PFAS-related soil standards and guidance values are left up to each individual state, resulting in a wide range of variability across the country. Twenty-three states have established PFAS soil standards or guidance values, with only 12 of those states providing standards or guidance values protective of groundwater. Five of the twelve states: Maine, New Jersey, New York, Hawaii, and Washington, as well as EPA, have updated their PFAS soil protective groundwater values over the past two years.
It should also be noted that many states’ soil protection of groundwater values is now based on outdated information or the state’s groundwater standards or guidance values and not the more stringent federal EPA drinking water MCL. Notably, New Jersey, Alaska, Massachusetts, Pennsylvania, Connecticut, and Texas are the only states that have soil standards protective of groundwater while Florida, Hawaii, Maine, Nebraska, New York, and Washington, have established guidance values. The remaining 38 states do not have standards or guidance values protective of groundwater for PFOS or PFOA.
- There are Two Main Reasons for the Lack of PFAS Soil Standards
Soil is contaminated with PFAS from a variety of sources – some of which include manufacturing, fire training, and landfilling activities, to name a few. These activities often impact groundwater and surface water used for drinking purposes. Once in the soil above the water table, these pollutants function as a continuing source of contamination by leaching PFAS into the groundwater because of precipitation infiltration through soil and fluctuating groundwater levels.
Most of the regulatory attention is focused on removing PFAS from our drinking water rather than developing and enforcing soil regulations that require action to address the source of PFAS contamination. So why is this? Two potential explanations:
- State agencies lack the environmental specialty and regulatory framework to develop and enforce PFAS soil regulations protective of groundwater and surface water.
- PFAS in soil not protective of groundwater often expand across large areas compared to other contaminants such as petroleum and chlorinated constituents, which are typically contained in soil to a smaller location. This is because PFAS lack degradation properties and are easily transported by wind and surface water over large areas, not to mention it only takes low levels in soil to contaminate groundwater above the drinking water standard as compared to petroleum and the other contaminants. This is coupled with the lack of effective remedial technologies to achieve low PFAS values protective of groundwater and return the groundwater to its original state.
- It’s Easy for PFAS in Soil to Contaminate Groundwater
Another question often raised is how much PFAS in soil does it take to impact groundwater above the drinking water standard? PFOA and PFOS for all 12 states and EPA soil values protective of groundwater are shown in Table 1. Of note, EPA has established the lowest levels for PFOA and PFOS guidance values protective of groundwater when compared to those established by states. Two states, Maine and Texas, have higher than expected values protective of groundwater. In Maine, the PFOA guidance value protective of groundwater is 17 parts per billion (ppb), while in Texas the PFOS value is 50 ppb. Both values are considered higher than expected to protect groundwater to achieve the federal drinking water MCL.
Table 1
PFOS & PFOA Soil Standards/Guidance
*Calculated value based on PFAS soil concentration and SPLP laboratory result.
Some states such as New York and New Jersey allow for the development of site-specific PFAS soil values protective of groundwater[1]. A soil test is often used to simulate the conditions where rainwater passes through the soil column and leaches into groundwater carrying soluble materials. This procedure is called the Synthetic Precipitation Leaching Procedure (SPLP). It is a method used by many regulatory agencies to assess the potential for site specific soil to leach contaminants such as PFAS and metals into groundwater and surface waters.
For example, the New York State Department of Environmental Conservation (NYSDEC) recommends if PFOA or PFOS are detected in soil at or above 1 ppb, the soil should be tested by SPLP and the leachate analyzed for PFOA and PFOS. If the SPLP results exceed the state and federal MCL, then the source of backfill should be rejected due to the concern that the backfill could function as a source of PFOA or PFOS and potentially contaminate groundwater above the NYSDEC drinking water MCL. It has been First Environment’s experience – when testing soil for PFAS where PFOS or PFOA exceed 1 ppb one to three feet above the water table – that when this same soil is analyzed using SPLP, the leaching results for PFOS and PFOA typically exceed the state and federal drinking water MCL.
In New York, PFAS soil and water guidance values and drinking water MCL standards only pertain to PFOA and PFOS. The NYSDEC Soil Cleanup Objective (SCO) Guidance values protective of groundwater for PFOA is 0.8 ppb and PFOS is 1.0 ppb. Site-specific remedial objectives for protection of groundwater can also be presented for evaluation to NYSDEC as well as the Connecticut Department of Environmental & Energy Department (CTDEEP). Development of site-specific remedial objectives for protection of groundwater require analysis of additional soil parameters relating to leachability. These additional analyses can include soil pH and cation exchange capacity and/or use of SPLP, although the NYSDEC and CTDEEP have not provided a clear procedure or soil calculation as New Jersey has to determine the site-specific remedial objective for PFOA and PFOS protective of groundwater.
Takeaways
- Of the 12 states with PFAS soil guidance values or standards that are protective of groundwater, New Jersey, Alaska, Texas, Connecticut and Massachusetts are the only ones identified that have cleanup standards while the remaining eight states have guidance values that do not have binding limits. However, they can serve as the basis for regulatory action and for due diligence and risk assessment.
- Through numerous PFAS investigations, First Environment has determined that PFOA and PFOS soil concentrations above 1 ppb within a few feet of the groundwater table will, more likely than not, contaminate groundwater or surface water exceeding the 4 parts per trillion (ppt) federal drinking water MCL. This indicates the soil will not be protective of groundwater.
- Based on a review of state standards and guidance values, there is significant variability in PFOA and PFOS soil thresholds established to protect groundwater. Some states have set limits exceeding 1 ppb, particularly those in the double-digit range, which are unlikely to be protective of groundwater. This conclusion is supported by our testing experience, as well as guidance from the EPA and states that have established protective groundwater values below 1 ppb.
[1] New Jersey sets site-specific values for migration to groundwater on a case- by case- basis using the Synthetic Precipitation Leaching Procedure (SPLP) as described in N.J.A.C 7:26D. Default values are not set because of the variability in partitioning coefficients and complexity of PFAS-soil interactions. The New Jersey Department of Environmental Protection (NJDEP) PFAS SPLP Calculator is used to calculate soil migration to groundwater (MGWc) criteria for PFAS. The MGWc is then used to determine the soil remediation standards for PFAS (SRS-MGW)
