Sniffing Out Vapor Intrusion

Transcription

1 Portfolio Media. Inc. 860 Broadway, 6th Floor New York, NY Phone: Fax: Sniffing Out Vapor Intrusion Robert Howard Latham & Watkins LLP John Everett Latham & Watkins LLP Law360, New York (February 09, 2012, 12:56 PM ET) -- In October 2011, the California Department of Toxic Substances Control (DTSC) issued final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, intended for use by, among others, regulators, responsible parties, developers, community groups and consultants.[1] The final guidance recommends a step-wise approach for evaluating the vapor intrusion exposure pathway at sites where volatile chemicals are present in the subsurface. Importantly, the final guidance adds several recommendations to the DTSC s 2005 interim final guidance potentially increasing the time and cost associated with development of contaminated sites. In this article, we present a brief primer on vapor intrusion, describe the DTSC s multiphase approach for evaluating and mitigating vapor intrusion, and detail the key steps recommended in the final guidance. A Brief Primer on Vapor Intrusion Vapor intrusion is, simply put, the migration of subsurface chemicals into overlying structures. As the United States Environmental Protection Agency (EPA) explains, volatile chemicals, i.e., those having a tendency to disperse as fumes or vapor, in contaminated soils or groundwater may emit vapors that migrate through the soil into indoor air spaces.[2] Vapors may move through permeable construction materials or seep through cracks in building foundations; once in overlying structures, such chemicals may be inhaled by humans. Thus, vapor intrusion simply describes another pathway by which humans may be exposed to chemicals present in soil or groundwater.

2 Compared to other exposure pathways, the vapor intrusion pathway is quite complex. Atmospheric conditions such as wind, air pressure and precipitation change rapidly and significantly impact chemical concentrations in indoor air.[3] Moreover, most human-occupied structures have heating, ventilation and cooling (HVAC) systems, which also greatly affect chemical concentrations in indoor air. Were these variables not enough, many chemicals of concern are also commonly present in indoor air as a result of sources unrelated to soil or groundwater contamination. For instance, many volatile organic compounds (VOCs) are present in common architectural coatings and cleaning, disinfecting and degreasing products. Accordingly, elevated concentrations of certain chemicals in indoor air may simply be the result of alternative emissions sources. Thus, understanding and evaluating the vapor intrusion pathway, which is relatively simple in theory, can prove quite difficult in practice. For this reason, thoughtful and well-organized guidance is critical for the regulated community. Yet, perhaps because of this complexity, regulators have been slow to finalize guidance: the DTSC s guidance had remained in interim form for roughly seven years, while the EPA is still finalizing guidance issued in draft form in Vapor Intrusion Regulation and the Morass of Vapor Intrusion Guidance Though vapor intrusion is technically an air quality issue, to date, federal and state agencies tasked with investigating and regulating hazardous waste sites have primarily regulated vapor intrusion. In California, the Legislature enacted Assembly Bill 422 in 2007, requiring that any assessment of health or ecological risk prepared pursuant to a response action or under the California Superfund Act include a reasonable maximum estimate of exposure to volatile chemicals that may enter indoor air.[4] In California and other jurisdictions, numerous guidance documents exist for vapor intrusion evaluations, creating a confusing array of recommendations that may, in some instances, be in conflict. The EPA issued its draft guidance in 2002 and has pledged to release a final, revised guidance document by fall 2012.[5] More than 30 states have also published specific vapor intrusion guidance documents or other guidance with substantial directions and recommendations for evaluating the vapor intrusion pathway.[6] In addition, the Interstate Technology & Regulatory Council (ITRC), a self-described state-led, national coalition of personnel from state and federal regulatory agencies, tribes and public and industry stakeholders, published A Practical Guideline for assessing the vapor intrusion pathway in 2007.[7] Finally, in 2008, the American Society for Testing and Materials International (ASTM) published what it hoped would be standardized guidance for the assessment of vapor intrusion in real estate transactions.[8] In California, with the release of the final guidance, the DTSC has helped clarify this morass. Absent

3 special circumstances, the DTSC s final guidance should be considered the most up-to-date, defensible approach to evaluating the vapor intrusion pathway in California.[9] DTSC s Multi-Phase Approach for the Evaluation and Mitigation of Vapor Intrusion As a threshold matter, the final guidance is not a regulation and does not impose any requirements or obligations on the regulated community, but provides a technical framework for evaluating vapor intrusion. [10] Nonetheless, because the final guidance will be used by the DTSC during the administrative process when considering the sufficiency of vapor intrusion evaluations, the regulated community would be well served to incorporate these recommendations into its planning. To be clear, the final guidance does not function alone or supersede all prior guidance; it is the centerpiece in a multiphase approach recommended by the DTSC for evaluating and mitigating vapor intrusion.[11] As further described herein, the DTSC has published or expects to publish separate advisory guidance for the following: active soil gas investigations, vapor intrusion mitigation, public participation coordination and the remediation of chlorinated VOCs in vadose zone soil. Further, the documents comprising the DTSC s multiphase vapor intrusion approach supplement more general, pre-existing guidance for assessing exposure pathways including the DTSC s Preliminary Endangerment Assessment Guidance Manual and EPA s Risk Assessment Guidance for Superfund.[12] Turning to the DTSC s multiphase approach, the Advisory for Active Soil Gas Investigations (2003 advisory) helps guide the initial site characterization phase in the DTSC s multiphase approach.[13] This document was derived from a joint effort between the DTSC and the California Regional Water Quality Control Board, Los Angeles Region, to ensure that consistent methodologies are applied during active soil gas investigations to produce high-quality data for regulatory decision-making. [14] The 2003 advisory is intended for use at sites potentially affected by VOCs, methane and hydrogen sulfide; it recommends methods for project management, as well as various sample collection and analytical methods.[15] A revised Advisory for Active Soil Gas Investigations was released in March 2010 for public comment, and the DTSC is currently finalizing that document.[16] If an initial site characterization reveals the presence of a volatile chemical that may pose a vapor intrusion risk, the final guidance outlines the second phase of the DTSC approach evaluating that vapor intrusion risk. If a vapor intrusion risk is present, then a response action is warranted. The DTSC recommends a dualpronged response action that includes: (1) active remediation of the vapor source, and (2) mitigation of indoor air exposure and long-term monitoring. Active remediation may be guided by the DTSC s Proven Technologies and Remedies Guidance, Remediation of Chlorinated Volatile Organic Compounds in Vadose Zone Soil (PTR guidance).[17] As its

4 name implies, this document applies only to sites where chlorinated VOCs are present in unsaturated soils above the water line. The PTR guidance is intended to expedite and encourage cleanup of such sites in a manner consistent with federal and state hazardous waste laws. With regard to mitigation, the DTSC released a final Vapor Intrusion Mitigation Advisory in October 2011.[18] This document is intended to guide the development and implementation of vapor intrusion mitigation systems, which function to mitigate the intrusion of chemicals until remediation at the source is complete. Finally, the DTSC s final guidance recommends expanded public participation throughout the vapor intrusion investigation, evaluation and response process. The DTSC s initial Vapor Intrusion Public Participation Advisory is pending and will supplement the existing Public Participation and Procedures Manual. DTSC s Final Guidance: Explaining the 11-Step Approach Underscoring the complexity of vapor intrusion problem solving, the DTSC recommends an 11-step approach to evaluate the vapor intrusion pathway: Step 1: Identifying Spills and Releases This initial step is common to all site investigations. In addition to standard procedures, the final guidance recommends that physical features relevant to the vapor intrusion pathway should be noted in characterization reports, including building foundation type/condition and features that may serve as vapor intrusion pathways, e.g., elevator shafts, floor drains, piping. Step 2: Site Characterization This step is also common to all site investigations. The final guidance recommends that multiple lines of evidence, i.e., data sources, be used to characterize the site and develop a conceptual site model. The DTSC lists more than a dozen lines of relevant evidence and notes that, while not every data source is needed, multiple lines of evidence yield a more comprehensive understanding of the site. Step 3: Evaluate Whether the Exposure Pathway is Complete Here, the DTSC recommends that the evaluating party examine two factors: (1) the volatility and toxicity of chemicals in the subsurface, and (2) whether existing or planned structures at the site are close enough to the subsurface chemicals to render vapor intrusion possible. The DTSC notes that buildings within 100 feet of sufficiently volatile and toxic subsurface contamination should be considered at risk for vapor intrusion; however, 100 feet of separation is not always sufficient to eliminate the vapor intrusion threat. Step 4: Evaluation of Acute Hazard in Existing Building When the vapor intrusion pathway appears to be complete and a site may pose a vapor intrusion threat,

5 an evaluating party should proceed to this step. Pursuant to this fourth step, buildings should be investigated to determine if certain indicators are present. Any one of the following indicators would trigger the need for indoor air sampling later under Step 9: odors; physiological effects in occupants, e.g., headaches, nausea, eye and respiratory sensitivity; wet basements and fire or explosive conditions. Of course, if fire, explosive or other emergency conditions are present, safety considerations dictate that emergency personnel should be contacted immediately. Step 5: If No Acute Hazards Exist, then the Evaluating Party Should Proceed to a Preliminary Screening Evaluation In this step, available subsurface data should be used to estimate vapor intrusion into overlying structures. The DTSC provides a table of attenuation factors[19] to be used for various building types in Table 2 of the final guidance. The DTSC recommends that all lines of evidence be used in conducting the preliminary screening evaluation. Step 6: Additional Site Characterization If Step 5 reveals a potentially significant human health risk, the evaluating party should perform an additional site characterization. The purpose of this step is to develop additional data and site-specific attenuation factors, versus the generally applicable attenuation factors used in Step 5. For sites with existing buildings, the evaluating party should sample the air under a raised foundation or, where a building is constructed upon a slab foundation, sub-slab air. The DTSC recommends notifying the public[20] prior to conducting such sampling. Step 7: Analyzing Data This step is closely related to Step 6 and simply describes the manner in which the data collected in Step 6 should be analyzed. The DTSC recommends the use of the California version of the EPA s Vapor Intrusion Model to calculate site-specific attenuation factors. Step 8: Building Survey and Work Plan Development Note that where no additional data is needed, such as when comprehensive sampling has been performed as part of Step 2, an evaluating party may skip Steps 6 and 7 and proceed to Step 8. In any event, Step 8 building survey and work plan development should only be completed when an evaluation reveals a potentially significant human health risk. In this step, the DTSC describes the tasks that should be completed prior to indoor air sampling. Among other things, these tasks include: 1. Visiting the site and inventorying/surveying the buildings that may be at risk recording the type of building, use, occupancy, foundation type and condition; 2. Developing a sampling methodology;

6 3. Describing procedures for data evaluation and interpretation; 4. Developing a contingency plan; 5. Notifying the public; and 6. Completing the DTSC s building screening and survey forms. Step 9: Indoor Air Sampling Here, the DTSC recommends a number of parameters and guidelines for indoor air sampling, ranging from the duration and number of samples to the protection of individual privacy rights. As with each step, an evaluating party should pay close attention to the DTSC s recommendations to ensure that sampling is done in a robust, defensible manner. Step 10: Evaluation of Indoor Air Sampling Results and Response Actions The DTSC provides guidelines for interpreting indoor air samples and responding to risks. Notably, the DTSC opines that it is not usually possible to conduct sufficient sampling for a rigorous statistical evaluation and recommends that risks should generally be estimated in a conservative fashion by using maximum concentrations. The DTSC recommends a number of factors for consideration in analyzing sampling results, such as whether the chemicals of concern are present in ambient air and/or as a result of alternative emissions sources. The DTSC recommends further action if quantitative risk results are above certain risk thresholds. Step 11: Mitigate Indoor Air Exposure, Monitoring and Implementation of Engineering Controls Finally, if the health risk evaluation reveals a significant hazard or risk, an evaluating party should perform the last step mitigate indoor air exposure, monitoring and implementation of engineering controls. While the Vapor Intrusion Mitigation Advisory contains much more comprehensive guidance for Step 11, the DTSC notes several common mitigation techniques and observes that, where removal or reduction of source contaminants may not be possible, engineering measures and institutional controls may be necessary to protect human health. Summary of Changes in the Final Guidance It is important to note that the final guidance contains several new provisions and/or recommendations. Most notably, the DTSC recommends the following in the final guidance: Incorporation of the multiple lines of evidence approach advocated in the ITRC s 2007 guidance. Thus, for instance, soil sampling alone might not be sufficient to assess the threat of vapor intrusion at a given site depending upon the conditions at the site, additional data points such soil vapor sampling and/or groundwater sampling should be considered. Installation of permanent soil gas monitoring wells in certain instances. Sampling performed exterior to a building s foundation should be performed closer to the contamination source, rather than nearer to the surface; the DTSC contends that soil vapor

7 concentrations under a building may be higher than at comparable depths exterior to the building s foundation. Changing the sub-slab attenuation factor for slab-foundation buildings from.01 to a more protective value of.05; using this input, mathematical modeling will result in estimates of VOCs in indoor air five times higher. Greater public notification and participation throughout the evaluation process, though these requirements are largely uncertain, pending publication of the DTSC s public participation guidance for vapor intrusion. Inclusion of all exposure pathways in a cumulative analysis of the health risks associated with vapor intrusion as part of Step 10. Adoption of the EPA s use of the 100-foot buffer zone as an indicator of whether additional screening should be performed, though, as noted, special circumstances may require further screening even when this buffer is in place. In addition to these and other changes, the final guidance includes recommendations on a host of new sampling techniques and procedures, pathway assessment procedures and analytical methods. Conclusion On the positive side for the regulated community, the DTSC s up-to-date final guidance substantially reduces the uncertainty posed by the morass of conflicting guidance documents. The DTSC considered these documents and revised its interim final guidance to generate, in the DTSC s view, technically defensible and consistent approaches for evaluating vapor intrusion. [21] Accordingly, the regulated community can follow the DTSC s final guidance as a road map to generate robust, defensible analyses. However, the final guidance is not without problems: it lengthens the vapor intrusion evaluation process materially and potentially adds additional sampling and analysis components, thereby increasing the time and costs associated with vapor intrusion evaluation. Moreover, it is unclear pending release of the DTSC s public participation guidance what the proper scope of public participation should be.[22] Whether or not increased certainty balances out the time and cost, the regulated community should be on alert to learn and, where prudent, implement the recommendations in the final guidance. --By Robert M. Howard and John W. Everett, Latham & Watkins LLP Robert Howard is a partner and John Everett is an associate in the environment, land and resources department of Latham & Watkins, based in the firm s San Diego office. The opinions expressed are those of the authors and do not necessarily reflect the views of the firm, its clients, or Portfolio Media, publisher of Law360. This article is for general information purposes and is not intended to be and should not be taken as legal advice. [1] California DTSC, Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (October 2011), available at (last visited Dec. 27, 2011). [2] EPA, Office of Solid Waste and Emergency Response, Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils, at 4, EPA530-D (hereinafter EPA Draft Guidance ) (2002), available at ) (last visited Dec. 27, 2011).

8 [3] See Wisconsin Dept. of Health and Family Services ( DHFS ), Guidance for Professionals, Chemical Vapor Intrusion and Residential Indoor Air, at 1 (hereinafter Wisconsin Guidance ) (2003), available at (last visited Dec. 27, 2011). [4] Cal. Health & Safety Code ; Cal. Water Code [5] EPA Draft Guidance. [6] See, e.g., Parsons, Final Vapor Intrusion/Indoor Air Guidance Survey, prepared for the Massachusetts Department of Environmental Protection (July 2010) (noting that, as of July 2010, more than 29 states had published such guidance). [7] Interstate Technology & Regulatory Council, Vapor Intrusion Pathway: A Practical Guideline (2007), available at (last visited Dec. 27, 2011). [8] American Society for Testing and Materials, E Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions (2008), available at (last visited Dec. 27, 2011). [9] Though DTSC notes that its Final Guidance and the EPA s draft guidance both describe technically feasible and consistent approaches for evaluating vapor intrusion, the regulated community should note that the EPA has come under fire for failing to revise the EPA Draft Guidance and that significant revisions can be expected. For instance, in a report released by the EPA Office of the Inspector General (OIG), the OIG concluded that the EPA Draft Guidance has limited purpose and scope, fails to account for evolving risk assessment science and contains dated toxicity values. The Office of Inspector General Report, Lack of Final Guidance on Vapor Intrusion Impedes Efforts to Address Indoor Air Risks, At a Glance (2009), available at (last visited Dec. 27, 2011). [10] See Final Guidance, at 1. [11] See DTSC s Flow Diagram of Key DTSC Documents, (last visited Dec. 27, 2011). [12] Final Guidance, at 2. [13] The 2003 Soil Advisory was jointly published by DTSC and the California Regional Water Quality Control Board, Los Angeles Region. Advisory Active Soil Gas Investigations (2003), available at: (last visited Dec. 27, 2011). [14] Id. [15] Id. [16] See DTSC s Flow Diagram of Key DTSC Documents. [17] California DTSC, Proven Technologies and Remedies Guidance Remediation of Chlorinated Volatile Organic Compounds in Vadose Zone Soil (2010), available at (last visited Dec. 27, 2011). [18] California DTSC, Vapor Intrusion Mitigation Advisory (October 2011), available at (last visited Dec. 27, 2011).

9 [19] An attenuation factor is a mathematical modeling input parameter that attempts to capture the percentage of a volatile chemical moving from a given location into indoor air. For instance, no attenuation (decrease) is presumed to occur between a building s crawlspace and the indoor air thus, the attenuation factor is 1.0. Using this and other inputs, model users can estimate the amount of volatile chemicals entering indoor air. See Final Guidance, at B-1 (Appendix B). [20] DTSC refers the user to its forthcoming public participation guidance for a determination of how to appropriately conduct public outreach, leaving some important questions unanswered. For instance, would the public include only occupants? Residents of neighboring residences? Users of neighboring non-residential structures? The broader community? In Step 8, which details preparations for indoor air sampling, DTSC suggests that public notification may be accomplished by notifying occupants of the affected structure. [21] Final Guidance, at 1. [22] Pending release of that document, the regulated community can look to the recommendations in DTSC s more general guidance. See California DTSC, Public Participation Manual (October 2001), available at PublicParticipationManual.pdf (last visited Dec. 27, 2011). All Content , Portfolio Media, Inc.