Vapor intrusion occurs when off-gases from soil and groundwater contamination migrate into indoor air at occupied structures. Previously this hazard drew little attention, but in the last few years it has become a hot-button issue in the field of environmental due diligence and regulation compliance. REPSG’s due diligence group has evaluated the current ASTM Standard E 2600-08, “Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions,” and also the planned revisions to this standard which are due out in May 2009. These reviews are integral to keeping REPSG’s approach to Potential Vapor Intrusion (pVI) issues at remediation sites and in due diligence studies on course.
The United States Environmental Protection Agency’s (EPA’s) All Appropriate Inquiries (AAI) Rule (40 CFR Part 312) set the standard for conducting Phase I Environmental Site Assessments (ESAs) to meet the test of the so-called “innocent purchaser defense” under the federal Superfund (or CERCLA) program. The purpose of performing an ESA is to allow the user to assert liability protections under Superfund. The AAI regulation references ASTM E 1527-05 “Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessments (ESA) Process” (Phase I ESA), indicating that it may be used to comply with the requirements of AAI.
AAI and ASTM E 1527-05 establish a standard, minimum baseline that is considered reasonable to provide a user with information about the environmental quality of a property. The main difference between AAI and ASTM E 1527-05 is that the AAI regulations include only contaminants that are CERCLA hazardous substances included in the federal Superfund program. Petroleum compounds are explicitly excluded from consideration under AAI but the potential for liability in other federal and state petroleum contamination laws and regulations are considered in Phase I ESAs.
The ASTM vapor intrusion assessment standard, ASTM E 2600-08, was developed with the intention of creating a standard procedure to assess vapor intrusion as it relates to property transactions. Vapor intrusion as a potential recognized environmental condition (REC) is not new and is considered to be incorporated into indoor air quality as a ‘non-scope consideration,’ in the same way as asbestos-containing materials, lead-based paint, mold, etc.
UPCOMING REVISIONS TO ASTM E 2600-08
Potential revisions currently under consideration by the ASTM Vapor Intrusion Task Group include:
- Clarifying that the prescriptive part of the standard, Tiers 1 and 2, constitute VI screening which is only a part of the full VI assessment;
- Clarifying that a pVIC only identifies the potential for vapors to reach the sub-surface of the target property, and does not necessarily result in an indoor air quality problem;
- As a non-scope consideration under E 1527, a pVIC should not necessarily create a REC on the target property (it is a business risk);
- Reword what is required under Tier 1 and Tier 2 so that it is easier to understand;
- Eliminate the secondary area of concern (AOC) as it is unnecessary; and
- Include a flowchart of Tier 1 and Tier 2 screening.
A revised E 2600 is expected to be approved in the fall of 2009 and would be published by ASTM toward the end of the year.
Concerns about vapor intrusion from soil and/or groundwater contamination at a site are not new, although the issue is receiving more attention. REPSG has consistently emphasized a pragmatic, fact-based, cost-conscious approach to this issue. We generally recommend that the mitigation of potential vapor intrusion issues be designed into development or redevelopment plans. There are several techniques that can be employed including engineering and/or institutional controls, as well as constructing structures that are intrinsically safe (e.g., elevated structures with ventilation between occupied areas and the ground).
Mitigating vapor intrusion concerns can be accomplished at developed sites through the installation of ventilation systems and sub-slab depressurization systems, similar to those used for mitigating radon, as well as sealing cracks and openings in structures to eliminate vapor pathways. The selection of the most appropriate measure takes careful consideration of the nature of the contaminant, the soil types present, and many other factors. REPSG’s decades of experience in facilitating the redevelopment of industrial sites gives us a substantial advantage in dealing with this issue.
To date, one of the most effective engineering controls employed by REPSG to mitigate vapor intrusion concerns during redevelopment has been the utilization of intrinsically safe building design. For a recent major project in Wilmington, Delaware, REPSG utilized the combination of a soil gas vapor membrane and intrinsically safe building designs, which was successful in eliminating human exposure to contaminants, and allowed for the safe redevelopment of the site for residential use.