The Massachusetts Department of Environmental Protection (“MassDEP”) has finalized its enforceable Maximum Contaminant Level (“MCL”) drinking water standards for a group of six per- and polyfluoroalkyl substances (“PFAS”) after proposing similar regulatory provisions in December 2019. Under the new regulations, the MCL is set at 20 nanograms per liter (i.e., 20 parts per trillion) for the sum of the concentrations of these six distinct PFAS contaminants: perfluorooctane sulfonic acid (“PFOS”); perfluorooctanoic acid (“PFOA”); perfluorohexane sulfonic acid (“PFHxS”); perfluorononanoic acid (“PFNA”); perfluoroheptanoic acid (“PFHpA”); and perfluorodecanoic acid (“PFDA”). No later than December 31, 2023, and every three years thereafter, MassDEP will review the science and state of PFAS analytical/treatment methodologies to determine whether these drinking water standards should be amended.
In general, existing water systems that serve more than 50,000 individuals are required to begin initial monitoring on January 1, 2021; existing water systems that serve more than 10,000 but fewer than 50,000 individuals are required to begin initial monitoring on April 1, 2021; and existing water system that supply 10,000 or fewer individuals are required to begin their annual monitoring on October 1, 2021. The initial monitoring period requires that water samples be taken quarterly for one calendar year. Water systems that detect a concentration of the six PFAS substances greater than the MCL are required to report the detection to MassDEP within seven days and are also required to alert the public within 30 days.
For reference, other states have typically adopted MCLs for individual PFAS compounds, not one enforceable drinking water standard for a group of PFAS contaminants. Vermont has set drinking water standards, for example, at 20 parts per trillion for several individual PFAS compounds. Michigan has adopted an MCL for PFOA of 8 parts per trillion, but an MCL for PFHxS at 51 parts per trillion.