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The Impacts of New Environmental Protection Agency (EPA) Vapor Intrusion Guidance
Monday, May 6, 2013

EPA recently issued two draft guidance documents on vapor intrusion and will accept comments on them through May 24, 2013. If finalized in current form, these guidance documents would formalize and enhance EPA’s existing practice of prioritizing vapor intrusion as a central issue in environmental remediation and could result in increases in the expense and effort required from responsible parties to achieve compliance for cleanup of contaminated sites conducted under federal authorities such as CERCLA or RCRA. They could also be highly influential in clean-ups overseen by state regulators.

Lastly, while intended for use in the regulatory context, recommendations in these guidance documents may be used to establish a standard of care in litigation involving vapor intrusion (e.g., RCRA citizen suits or common law toxic tort litigation).

Vapor intrusion is the migration of hazardous vapor from contaminated soil or groundwater into an overlying building.  It is considered potentially harmful to human health, creates risks in real estate transactions and financing due to potentially diminished property values and environmental liability, increases exposure in toxic tort litigation, and, in the federal regulatory context, is considered a pathway of possible exposure that must be evaluated as part of the evaluation and selection of a site remediation plan.

The first of these two guidance documents was prepared by EPA’s Office of Solid Waste and Emergency Response (OSWER) and is a comprehensive set of technical and policy recommendations regarding indoor air contamination arising from subsurface-source vapor intrusion attributable to all classes of volatile, or vapor-forming, chemicals (VI Guidance).[1]  The VI Guidance modifies and expands draft guidance on vapor intrusion issued by the agency in 2002 (2002 Draft VI Guidance), which provided general direction for evaluating the potential for vapor intrusion pathways at cleanup sites but omitted any measures for delineation and mitigation of potential risks.[2]  In a 2009 report, EPA’s Office of the Inspector General (OIG) recommended that EPA update the 2002 Draft VI Guidance to reflect the numerous technical and policy advancements made since that time in both the public and private sectors. 

The second guidance document was prepared by EPA’s Office of Underground Storage Tanks (OUST) and is focused on investigations and assessments at petroleum contaminated sites where vapor intrusion by petroleum hydrocarbons may occur (Petroleum VI Guidance).[3]

VI Guidance

The VI Guidance presents a step-by-step vapor intrusion assessment plan, beginning with gathering and evaluating data for an initial conceptual site model, through collecting and evaluating additional data from various sources, and culminating in a risk assessment.  According to EPA, the VI Guidance addresses the recommendations made in the OIG’s 2009 report and takes into consideration more recent guidance developed by states and other technical working groups.  Some of the elements in this document may well trigger an increase in expense in addressing VI risks and lengthen the site evaluation process.

  • Superfund Five-Year Reviews: At Superfund sites that require five-year reviews,[4] EPA will gather data on vapor intrusion pathways and assess the sufficiency of the selected remedy for follow up in the five-year review report.  Therefore, according to the VI Guidance and related Directive 9200.2-84,[5] the five-year review process could result in the re-opening of established Superfund remedies to address vapor intrusion, “even if vapor intrusion was not addressed as part of the original remedial action.[6]
  • Preemptive Mitigation/Early Action: EPA recommends consideration of engineered methods to reduce vapor in buildings (e.g., by installing a radon-type detection system or vapor barriers), even in the absence of all pertinent lines of evidence necessary to characterize the vapor intrusion pathway.  Any such measure would be an early effort to cut off exposure before completing investigations, but would not address the subsurface vapor source.  The agency’s rationale is that installation of engineered exposure controls in buildings is typically more cost-effective and less disruptive than conventional vapor intrusion investigations and subsurface characterization.  Once preemptive mitigation measures are installed, however, that may conclude only an initial step rather than complete remediation.  In the context of brownfields programs, treating preemptive mitigation now as only an interim solution may affect long term redevelopment plans.
  • Aggregate Noncancer Health Risk: Even when the exposure level for each contaminant at a site is below screening levels and it is assumed that each “acts independently (i.e., there are no synergistic or antagonistic toxicity interactions among the chemicals)”, the VI Guidance nevertheless proposes that a risk manager aggregate the individual noncancer health risks associated with each contaminant exposure to determine whether a response is warranted.  The aggregated risk is reflected in a “noncancer hazard quotient” that would ultimately drive the response.  This approach could be overly precautionary if the aggregated sum overstates the actual risks presented by the individual constituents.  Furthermore, the VI Guidance recommends use of multiple lines of evidence in calculating and evaluating these risks, a process that may prolong response decisions and negatively affect situations where quick resolution of VI issues is paramount (e.g., brownfield redevelopment projects).  On the other hand, evaluation of multiple lines of evidence may be more advantageous to the extent it provides for a more informed view of likely risk.
  • Background Levels: Time-integrated sampling of volatile chemicals (as opposed to short-duration, or “grab” sampling) at multiple locations in and around a site is, in EPA’s view, necessary to distinguish among potential sources of these chemicals (i.e., ambient sources, indoor sources, or vapor intrusion).  In the past, generic values of historic background concentrations have been used to characterize ambient or indoor source concentrations.  However, EPA now recommends against the use of these generic values, even those from peer-reviewed sources, and instead asserts that only site-specific data (e.g., sub-slab, indoor air, and ambient air sampling data) should be used.  This recommendation will likely lead to improved accuracy and better understanding of site conditions, while at the same time increasing the time and cost related to characterization efforts.

Petroleum VI Guidance

The 2009 OIG report expressed concern that EPA’s 2002 Draft VI Guidance did not address petroleum vapor intrusion at UST sites.  The proposed Petroleum VI Guidance seeks to address that concern for UST sites and RCRA-driven activities undertaken by private UST owners and operators.  In addition to the traditional chemicals found in petroleum products (such as benzene), the Petroleum VI Guidance would require consideration of vapor risks associated with gasoline additives (such as MTBE) and chemicals that develop from biodegradation of petroleum in soil and groundwater (such as methane).

As proposed, at least two parts of the Petroleum VI Guidance may, in comparison with past experience, result in increased response costs and delays for responsible parties.[7]  First, the Petroleum VI Guidance rejects the notion that a single sampling event is a sufficient basis to conclude that further vapor intrusion investigation is unnecessary because “periodic monitoring and sampling over more than one annual cycle is generally needed” to address fluctuations in groundwater levels and contaminant plumes over time.  Second, the Petroleum VI Guidance includes a number of recommendations that suggest EPA seeks to reduce reliance on models.  Specifically, when modeling requires the use of literature values due to the unavailability of site-specific data, EPA “recommends that an uncertainty analysis be conducted to provide error bounds on predictions of the computer model,” and that the results of any modeling exercise be verified with field data. 

Considerations for Both Guidance Documents

In conclusion, both of these proposed guidance documents signal an increased focus on vapor intrusion within EPA.  As they are amended and finalized, there is a limited opportunity to comment on them to try to encourage a final guidance that is workable and effective for remediation of sites with vapor intrusion issues.  There may be ways to improve the guidance by clarifying where there is site-specific flexibility and where the guidance is overly prescriptive.

Notably, these guidance documents may help define the standard of care in the context of RCRA citizen suits or common law toxic tort litigation.  Clarifying key assumptions in the guidance may buffer some of that impact.

Even though these guidance documents are in draft form and will likely be subject to considerable comment, EPA regions and states can be expected to consult and employ them during what may be a long interval before they are finalized.  To the extent EPA or a state regulatory agency does so and an affected party disagrees with aspects of the guidance at issue, parties should be aware that the draft guidances are non-binding on their face.  The documents state that they do “not impose any requirements or obligations on the [EPA], the states, or the regulated community.”  Accordingly, parties should be free to suggest alternative, technically sound approaches to regulators.  Moreover, because these documents are solely drafts and have not been tested by external expertise that will be provided in public comment, reliance on them in their current state is arguably premature.

Given the potential long term impact on cleanup requirements, interested parties should evaluate the guidance and strongly consider submitting comments to EPA by May 24, 2013.  In light of the complex technical issues involved, interested parties may also wish to request that EPA extend the comment period.

[1] EPA OSWER, “Final Guidance for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Sources to Indoor Air” (Apr. 11, 2013)

[2] EPA OSWER, “Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils” (Nov. 29, 2002).  This draft document was never finalized.

[3] EPA OUST, “Guidance for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites” (Apr. 9, 2013).

[4] Section 121 of CERCLA (42 U.S.C. § 9621) requires that remedial actions that result in any hazardous substances, pollutants, or contaminants remaining at the site be re-evaluated every five years to ensure that the remedy is and will continue to be protective of human health and the environment.

[5] “Assessing Protectiveness at Sites for Vapor Intrusion: Supplement to the ‘Comprehensive Five-Year Review Guidance’” (Nov. 14, 2012).

[6] In a related context, EPA officials have already acknowledged that later discovery of vapor intrusion at Superfund sites may trigger parties to litigate over whether site remedies provided for in consent decrees should be revisited under the reopener provisions in those decrees.  SeeInsideEPA, “EPA Official Says Vapor Intrusion May Drive Suits To Reopen Cleanup Pacts” (May 3, 2013), available at http://insideepa.com/201305032433234/EPA-Daily-News/Daily-News/epa-official-says-vapor-intrusion-may-drive-suits-to-reopen-cleanup-pacts/menu-id-95.html?s=mu. 

[7] These issues may also be relevant in scenarios involving vapor intrusion from sources other than those covered by the Petroleum VI Guidance.  However, because these points were emphasized in that guidance document, we highlight them here.

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