Clamping Down on PFAS: MassDEP Finalizes Waste Site Cleanup Standards and Proposes Drinking Water Standards
MassDEP’s march forward on regulating per- and polyfluoroalkyl substances (PFAS) continued in December with release of final revisions to the Massachusetts Contingency Plan (MCP) waste site cleanup regulations (310 CMR 40.0000) and draft revisions to the Drinking Water Regulations (310 CMR 22.00). (We provided background on PFAS and discussed previous steps in these efforts in our June 2018 and April 2019 newsletters.)
MassDEP finalized a waste site cleanup “GW-1” standard (for groundwater within drinking water source areas) of 20 parts per trillion (ppt) for the sum of six specific PFAS compounds. The six compounds, which are similar to each other in chemical composition, behavior in the environment, and toxicity, are:
Perfluorooctanoic acid (PFOA)
Perfluorooctanesulfonic acid (PFOS)
Perfluorohexanesulfonic acid (PFHxS)
Perfluorononanoic acid (PFNA)
Perfluoroheptanoic acid (PFHpA)
Perfluorodecanoic acid (PFDA)
The 20 ppt standard, first proposed in draft MCP regulatory revisions in April 2019, is lower than the 70 ppt guideline that DEP initially issued in June 2018 for five of these six compounds. MassDEP’s December 2019 technical support document explains that, after that guideline was issued, the federal Agency for Toxic Substances and Disease Registry and various states released toxicological evaluations for PFAS identifying toxicity thresholds lower than the value derived by USEPA, which DEP had relied on for its June 2018 guidance. After reviewing this new information, DEP’s Office of Research and Standards determined that addition of the sixth compound and lowering of the toxicity value were warranted by the available data. In a commentary issued with the final MCP regulations, DEP states that the 20 ppt value was criticized as too low by some commenters and too high by others; after evaluating all of the comments, DEP concluded that the proposed 20 ppt value was appropriate.
MassDEP is now proposing to adopt the 20 ppt total limit for these six PFAS compounds also as a Maximum Contaminant Level for public drinking water systems. Implementation under the proposed rule will be staggered by population served and type of system. Public water systems serving more than 50,000 consumers will be required to start monitoring for these PFAS compounds by April 1, 2020; systems serving from 10,000-50,000 consumers must start by October 1, 2020; and smaller systems must start by October 1, 2021. Transient non-community systems (such as recreational areas and campgrounds) must analyze one sample for PFAS and provide the results to MassDEP by September 30, 2022. The proposed regulations require certain remedial steps to be taken if PFAS are detected.
Given the extensive evaluation associated with issuance of the 20 ppt standard in the MCP regulatory revisions, it appears unlikely that MassDEP will modify this value in the drinking water regulations. However, DEP is seeking comments on other aspects of the regulations, including the staggered start timing, the monitoring scheme, consumer notices, compliance calculations, and other issues. Public hearings will take place from January 23-31, 2020, and written comments are due by February 28, 2020.