Vapor intrusion and indoor air quality due diligence during property transactions

Vapor intrusion (i.e. the migration of volatile chemicals from contaminated soil and/or ground water through the subsurface into overlying building structures) as a contributing indoor air has become a growing concern for property owners and prospective purchasers in recent years as it can cause significant indoor air quality problems. This is largely due to the increased focus on this issue by many state and federal regulators. Liability concerns include regulators re-opening cases for contaminated sites that were once considered “closed;” the stigmatization and devaluation of a property; and health concerns for building occupants. Additionally, many lenders are now taking a closer look at the issue of vapor intrusion and developing policies and procedures for dealing with it.

Although guidelines have been established by the United States Environmental Protection Agency (EPA) and many state regulatory agencies, including New York, New Jersey and Pennsylvania, to address the assessment and mitigation of vapor intrusion, these guidelines do not necessarily provide an industry-wide standard for the assessment of vapor intrusion.

In an effort to address this issue, ASTM International (ASTM), the voluntary industry standards development organization, published a standard in March 2008: ASTM E 2600, “Standard Practice for the Assessment of Vapor Intrusion Into Structures on Property Involved in Real Estate Transactions.” According to ASTM, the vapor intrusion assessment standard (ASTM E 2600) may be used as a voluntary supplement (i.e. a non-scope issue similar to asbestos, lead-based paint, radon, etc.) to the ASTM Phase I assessment standard that has long been recognized as the industry standard for the pre-acquisition assessment of a property to determine any existing or potential environmental issues.

Specifically, the ASTM vapor intrusion standard provides a four tiered approach to address the issue of vapor intrusion. The four tiers are as follows:

• Tier 1 – Initial Screening (Database Review) - A review of records within certain search radii of the subject property, based on information collected during Phase I, to identify sites where the conditions are such that vapor intrusion may likely be an issue of concern in connection with the subject property. If vapor intrusion can not be eliminated as a concern through the Tier 1 screening process, the person relying on the study is directed to proceed to Tier 2 (refined screening), or directly to Tier 3 (assessment) or Tier 4 (mitigation).

• Tier 2 – Refined Screening (Review/Collection of Sample Data) - A review of existing data (i.e. soil, soil gas or ground water samples) obtained from regulatory files (i.e. for site identified within the search radii and/or subject property) or the collection of samples (i.e. soil, soil gas or groundwater samples) to determine if vapor intrusion is a concern for the subject property. If vapor intrusion can not be eliminated as a concern through the Tier 2 screening process, the user is directed to proceed to Tier 3 or directly to Tier 4.

• Tier 3 – Vapor Intrusion Assessment - The implementation of more comprehensive vapor investigation activities (i.e. soil gas, sub-slab, ground water, indoor air sampling) to determine if vapor intrusion is a concern for the subject property. If vapor intrusion can not be eliminated as a concern through this process, the user may conduct additional investigative activities, or proceed directly to Tier 4.

• Tier 4 – Vapor Intrusion Mitigation - Vapor intrusion mitigation options, such as intrinsically safe building design, vapor barriers and sub-slab depressurization systems are Tier 4.

The prospective purchaser should evaluate whether it makes more sense to by-pass the vapor intrusion screening and assessment tiers (Tier 1 through Tier 3) and proceed directly to installing a mitigation system, especially in the context of developing a vacant parcel or redevelopment of a parcel. Vapor intrusion mitigation systems, such as sub-slab depressurization systems, can be installed with new construction at a relatively low cost and possibly for less than the cost of a vapor intrusion assessment. Additionally, a sub-slab depressurization system can often be easily and inexpensively installed within an existing building. Alternatively, it may also make more sense to proceed directly to the sampling options offered in Tier 2 and Tier 3.

These options should be discussed with the purchaser’s consultant to determine whether or not to add a vapor intrusion assessment to the scope of a Phase I assessment. Also, the prospective purchaser should be aware that the standard provides minimal guidance beyond the initial screening tiers and generally refers to federal and state (if they exist) guidelines.

Therefore, a prospective purchaser should look to retain a consultant to conduct a Phase I assessment of a property that has a clear understanding of vapor investigation and mitigation techniques and practices so that the purchaser can make an informed decision regarding the level of risk associated with vapor intrusion issues at the subject property.

Mr. Bisbort is with EWMA’s Mid-Atlantic Regional Office in West Windsor, NJ. He specializes in environmental assessments and remediation.

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