In December 2012 we reported on some of the challenges created by the vapor intrusion pathway under the Act 2 brownfields program in Vapor Intrusion and Act 2 – Imperfect Together. This is an update.
On January 29, 2013, the Department convened a meeting of the vapor intrusion subcommittee of the Cleanup Standards Scientific Advisory Board at the Rachel Carson Building in Harrisburg. We reviewed and discussed a proposal from the Department for how vapor intrusion could be managed under a Statewide Health Standard (“SHS”) clean-up and possible paths forward to update the existing guidance. The meeting included worthwhile discussion on number of aspects of this difficult subject.
If nothing else, our discussions brought into sharp focus the biggest challenges the CSSAB and Department face in revising the vapor intrusion guidance:
- Soil gas samples. Given growing concern about the reliability of soil gas samples taken from outside the footprint of an existing building (see recent NJ 2013 VI Technical Guidance treatment of this issue, Section 3.3.2, Alternative Soil Gas Sampling), whether near-building and “exterior” soil vapor sampling can and should play a role in evaluation of the vapor intrusion pathway.
- Future development. Especially in light of the concern noted above about the reliability of exterior soil gas sampling, how to establish a SHS mechanism for vapor intrusion analysis for sites (and parts of sites) that do not yet contain buildings to prevent vapor intrusion analysis for future development from undermining the certainty of an Act 2 release of liability.
- Screening values for indoor air, ground water, soil gas, sub-slab soil gas and/or soil.
- On what basis to establish appropriate screening values for groundwater and subslab soil gas that are protective but not overly conservative? Is Johnson-Ettinger still the appropriate model to use?
- How to make screening values established from modeling more relevant and useful for a wider range of sites where, e.g., soil types or depths to contaminant may differ from the model’s assumptions.
- How to mitigate effects on existing releases of liability when revised screening values are established that likely will differ by orders of magnitude from the values in the 2004 guidance.
- Whether meaningful screening values can be established for soil sample results, or whether any amount of volatiles in soil samples could justify further steps to evaluate the vapor pathway even in the SHS context.
- Whether to use the existing DEP toxicity values or the IRIS values set by the United States Environmental Protection Agency in calculating screening values.
- Timing. The Department is anxious to move forward with guidance for SHS clean-ups. There was considerable sentiment within the subcommittee that the current 2004 guidance, in particular the screening values in that guidance, needed to be updated as soon as reasonably possible. However, one consideration is that USEPA has not issued a revision of its 2002 vapor intrusion guidance (initially targeted for November of 2012) and some interested parties, including our office, have submitted formal requests urging that USEPA issue its fundamentally rewritten guidance as a draft for public comment before issuance of a final document.
The Department and the subcommittee will be working through each of the these issues as we move toward revised guidance in the coming year. The full CSSAB meetings for 2013 are set at the moment for April 11, 2013 and October 23, 2013.