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New ASTM Standard Aids Assessment of Vapor Intrusion Risks

10.01.2008

By Larry Kane, Attorney, Bingham Greenebaum Doll LLP

Over the last few years the Indiana Department of Environmental Management (“IDEM”) and U.S. EPA have given increased attention to the risks posed by potential exposure to volatile organic compounds (“VOC”) through migration of contaminants from subsurface soils or groundwater into residences and commercial and industrial buildings. This potential exposure pathway is commonly referred to as “vapor intrusion.” Vapor intrusion is a potential concern for residences or buildings located near soil or groundwater contaminated with VOC, such as chlorinated compounds used for dry cleaning or as industrial solvents, or petroleum.

In 2006 the IDEM released a draft pilot program guidance for assessing vapor intrusion risks. The IDEM’s guidance provides a sequential method to determine if a complete exposure pathway is present from the contamination source (soil or groundwater) through soil gas to a potential receptor in a home or building. If contamination is found to be present above screening levels within a specified distance from a building, the guidance recommends collection of sub-slab vapor or soil gas samples. If contaminants in soil gas samples exceed screening levels or soil or groundwater samples exceed screening levels by a certain amount, then indoor air sampling is required. Indoor air sampling is complicated by the presence of VOC from many common household products and other sources unrelated to soil or groundwater contamination as well as by changes in atmospheric conditions and other factors. Other states have taken differing approaches. The U.S. EPA has published a draft guidance at 67 Federal Register 71,169 (November 29, 2002).

As regulatory programs have developed screening and assessment procedures for vapor intrusion, businesses, lenders, consultants and others have become more aware of the potential risks and costs associated with vapor intrusion. Because of the increased awareness of potential vapor intrusion risks, there has been a growing interest in evaluating such risks in real estate transactions. Because assessment of indoor air quality is outside the scope of a Phase I environmental site assessments (“ESA”) conducted pursuant to ASTM E1527-05, ASTM International has developed a new, voluntary standard for evaluating vapor intrusion risks at property involved in a real estate transaction with respect to chemical compounds that may migrate into existing or planned buildings from contaminated soil or groundwater at the subject property or in close proximity to the property.

The new ASTM E2600-08 standard is entitled “Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions.” The standard establishes a tiered approach for prospective purchasers, lenders, investors and other users to conduct a preliminary screen to identify properties with a low risk of vapor intrusion followed by a more rigorous evaluation where the user desires more information where a higher risk of vapor intrusion may be present. While the standard describes the procedures for a more rigorous evaluation and mitigation approaches, the ASTM standard is geared toward quickly identifying properties that do not present a high risk of vapor intrusion.

The standard is designed to be used as a supplemental scope of work to a Phase I ESA conducted pursuant to ASTM E1527. The first screening level uses information collected during an E1527 Phase I ESA. If potential vapor intrusion conditions are identified during the initial screening, the standard provides for additional screenings which progressively increase the use of site-specific data. The ASTM E2600-08 can be obtained here.

When using the standard, the user should keep in mind that the screening process can be conservative, resulting in a presumption that a potential vapor intrusion condition exists without any supporting data. This may result in either the termination of a transaction or undertaking more expensive and intrusive testing to rebut the initial screening result. If vapor intrusion conditions are suspected, the IDEM’s guidance should be reviewed and a qualified environmental professional consulted. Additionally, users should be aware that a vapor intrusion assessment does not constitute “all appropriate inquiry” under CERCLA.

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