A new MassDEP Technical Support Document confirms that the agency has screened almost 1,000 closed TCE sites and anticipates that about 200 sites require follow up due to the potential for human health impacts due to vapor intrusion into the air of overlying buildings. The document, entitled MassDEP Bureau of Waste Site Cleanup’s Plan for Evaluating Potential Imminent Hazards from Trichloroethylene (TCE) Vapor Intrusion at Closed Sites, confirms the ongoing efforts first reported in the last edition of this newsletter. While MassDEP is prioritizing these sites and then contacting the landowners, MassDEP encourages potentially responsible parties to review site information to determine if action is warranted.

In addition, MassDEP is continuing to work on revising its Vapor Intrusion Guidance based on public comments received in February 2015, and expects to issue a revised draft for public review this Summer.

Emerging Contaminants

MassDEP has identified the ten chemicals or groups of chemicals as “priority emerging contaminants” during its most recent Waste Site Cleanup Advisory Committee meeting in May:

  • perchlorate;
  • 1,4 dioxane;
  • tetrachloroethylene (PCE);
  • trichloroethylene (TCE);
  • royal (or research) demolition explosive (RDX);
  • tungsten;
  • cyanotoxins;
  • nanoparticles;
  • polybrominated diphenyl ethers (PBDEs); and
  • personal pharmaceutical and care products (PPCP)

Emerging contaminants are given special consideration either because they are newly identified in the environment and therefore the fate, transport, and risks associated with the pollutant are not well understood, or because the scientific understanding of the pollutant has changed and therefore what is required to achieve cleanup may also change, affecting decisions at new sites as well as reopening cleaned up sites. C. Mark Smith, Director, Office of Research and Standards for MassDEP, also stated perfluorinated chemicals (PFCs), chlorate, and non-aroclor polychlorinated biphenyls (PCBs) may be added to this list.

MassDEP also indicated many of these chemicals were tested for in large public water supply systems as part of the third round of testing under the federal Unregulated Contaminant Rule, including PFOA (perfluorooctanoic acid), PFOS (perfluorooctane sulfonate), chlorate; and 1,4 dioxane, and that some of these contaminants have been identified in public water systems. For example, PFOA and PFOS were identified in the public water system in Hyannis, MA, and Smith explained that MassDEP worked with the village to develop treatment techniques to lower the levels of PFOA and PFOS to below the EPA drinking water health advisory level, which was recently revised to 70 ppt. The source of the PFOA and PFOS to the Hyannis water supply is not known, but MassDEP is working to identify the source or sources and require remediation of the contamination under the state cleanup law.

Urban Fill

In 2014, MassDEP modified the approach to urban fill sites through regulatory amendments that allow “downtown brown” sites to be closed without remediation or a deed restriction if certain criteria are met. The regulations raised questions as to how environmental remediation consultants would determine which sites qualify for these new provisions, as well as how the new rules would be implemented. Nearly two years later, MassDEP is issuing its first public review draft and is accepting comments on the proposed guidance until June 30, 2016.

The amended regulations expand the concept of “background” to include contaminated soils when the contamination is “attributable to Historic Fill.” Historic Fill has a complex definition in the regulation but can be understood to be contaminated soil placed on a site prior to 1983 that contains relatively low levels of metals, hydrocarbons, and/or PAHs due to pervasive use and release of such materials at the time. Contamination that is identified as Historic Fill does not need to be addressed in a risk characterization and does not require remediation – because it is background. However, because “Historic Fill” may in fact pose some risk, ongoing requirements apply, which can be described in the closure report or in a deed restriction.

The key question not answered by the regulations is how does someone show a particular site contains Historic Fill? This is especially important in Massachusetts because environmental remediation consultants known as licensed site professionals (LSPs) make this decision subject to audit by MassDEP. The proposed draft guidance helps answer this question.

The draft guidance indicates that LSPs should use a “well-developed Conceptual Site Model” and “multiple lines of evidence” in drawing a conclusion that contaminated soil is Historic Fill. The multiple lines of evidence include site history to confirm there is no on-site source and that the fill was put in place prior to 1983, and a subsurface investigation to characterize and delineate the fill. Additional evaluations to identify ash may be appropriate. While de minimis levels of contamination are consistent with Historic Fill, elevated levels may suggest an on-site source. As such, as a general matter, the higher the concentration of the contaminant, the more robust the evidence to demonstrate that the fill is Historic Fill.