In a busy day for vapor intrusion, last week the U. S. Environmental Protection Agency made several announcements about vapor intrusion.
First, it announced it had submitted a draft rule to the White House OMB seeking to add vapor intrusion to the pathways evaluated under the Hazard Ranking Scoring (HRS) System for National Priority List (NPL) Superfund sites. Additionally, EPA published two new sets of technical guidance on assessing vapor intrusion. One guidance document has been prepared for assessing vapor intrusion from leaking petroleum underground storage tank sites, and the other guidance document is aimed at assessing vapor intrusion for sites with non-petroleum contamination.
Draft Rule on Assessing Vapor Intrusion as Part of Site Hazard Ranking
With respect to EPA’s draft rule adding assessment of vapor intrusion to the Hazard Ranking Scoring process, this is the Agency’s second effort at adding the vapor intrusion pathway to the other types of pathways which are already considered in evaluating and then listing a site on the National Priorities List. The same version of the rule was previously submitted to, but then withdrawn from, OMB consideration.
EPA believes now that it is necessary to evaluate vapor intrusion in scoring of sites for the NPL in order to ensure that health risks associated with vapor intrusion are addressed and cleaned up as part of Superfund remediations. Opponents to the process, however, believe that adding assessment of the vapor intrusion pathway to the NPL HRS scoring system will lead to more sites being listed on the NPL, despite the belief that EPA’s Superfund program is already taxed. If the draft rule receives OMB approval, the rule will be published as a Notice of Proposed Rulemaking in the Fall of 2015.
New Vapor Intrusion Guidance
With respect to new vapor intrusion guidance, EPA published guidance both on performing vapor intrusion assessments where the source is petroleum vapor from leaking underground storage tanks (“Technical Guide for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites,” EPA 510-R-15-001, June, 2015) (hereinafter “PVI Guidance”) and for vapor intrusion risks associated with all other types of sites and non-petroleum chemicals (“OSWER Technical Guidance for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air,” OSWER Publication 9200.2-154, June, 2015) (hereinafter “OSWER VI Guidance”).
According to EPA, the existing 2002 (“OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils,” EPA530-D-02-004) guidance on vapor intrusion assessment is replaced by the two new PVI, and OSWER VI Guidance documents. In promoting the two new sets of guidance, EPA indicates that the mitigation measures advocated in the new guidance are “more cost-effective” than mitigation measures considered in the previous draft guidance, and EPA is also advising its new approach to testing for vapor intrusion is more “flexible,” including sampling indoor air or sampling the external sub-slab area.
While comprehensive, and containing certain “user-friendly” features, the new draft guidance for vapor intrusion is not without controversy. EPA has acknowledged that its 2002 draft guidance indicated that OSHA, and not EPA, would take the lead in looking at occupational exposure to vapor intrusion. In the new guidance, EPA seems to back off its previous acquiescence to OSHA’s primary jurisdiction where there is occupational exposure, and merely mentions that there are Memoranda of Understanding (MOUs) between OSHA and EPA dated November 23, 1990, and February 1991, which govern the Agencies’ relative responsibilities (but of course those MOUs pre-date vapor intrusion as a current focus of concern). Tellingly, in Section 7.4.3 of the OSWER VI Guidance, EPA specifically states its reasons for its recommendation that EPA standards, as opposed to OSHA PELs or TLVs, should be used for evaluating VI human health risks for workers in non-residential buildings. EPA bases its conclusions on what it characterizes as OSHA’s own recognition that its PELs are “outdated and inadequate for ensuring protection of worker health.”
LUST PVI GUIDANCE
The LUST PVI Guidance is less substantial, both in terms of technical information and volume, than the OSWER VI Guidance, and is on its face aimed at EPA regulatory personnel investigating and assessing petroleum vapor intrusion (PVI). Nevertheless, the guidance indicates it is intended for all “UST regulators and practitioners.” The PVI Guidance looks at petroleum hydrocarbons (PHCs) in diesel, gasoline, and jet fuel related volatile organic chemicals (VOCs) such as BTEX, methane generated from anaerobic biodegradertory of petroleum products, and is focused on providing screening criteria based on the distance between PVI sources and potential receptors.
It is interesting to note the PVI Guidance states it is applicable to “…new and existing releases of PHCs and non-PHC fuel additives from leaking USTs and to previously closed sites where the implementing agency has reason to suspect that there may be a potential for PVI.” [Emphasis added]. Despite that statement, the PVI Guidance does acknowledge that it “…does not impose legally binding requirements on implementing agencies or the regulated community”; and, thus, the guidance should not be read as triggering a need for VI assessments at closed LUST sites.
Other features of the PVI Guidance are two “user-friendly” features: a Table, and separate Flowchart, each summarizing EPA’s recommended actions for addressing PVI at LUST sites, and an entire section discussing computer modeling of PVI.
OSWER VI GUIDANCE
Of the two VI policies published June 11, the OSWER document on non-petroleum VI is the more robust of the documents published, with 245 pages of technical guidance. One of the stated purposes of the OSWER Guidance is to “…promote national consistency in assessing the vapor intrusion pathway …” while providing a“…flexible screening based approach to assessment…”. As with the PVI Guidance, the OSWER VI Guidance is ostensibly aimed at any CERCLA , RCRA or Brownfield sites being evaluated by EPA, or for authorized state RCRA corrective action programs or state-led CERCLA sites, however, it is expected that particularly in states with fledgling VI policies, the OSWER Guidance will become the standard for VI assessments and mitigating measures.
Features of the OSWER VI Guidance include a comprehensive guide to preliminary and detailed VI sampling and assessment technologies in myriad settings (VI in inclusion zones, settings with multiple buildings evaluating concurrent indoor and ambient air sources, etc.). The guidance also discusses strategies for risk assessment under numerous exposure scenarios. Finally, there is a lot of attention focused on mitigation systems in buildings, and subsurface remediation.