Vapor Encroachment Screening

On June 14, 2010, ASTM published E2600-10, Standard Guide for Vapor Encroachment Screening on Property Involved in Real Estate Transactions. Vapor Intrusion is identified as a Recognized Environmental Condition (REC) in the ASTM E1527-13 Phase I Environmental Site Assessment Standard. If a Phase I Environmental Site Assessment does not consider vapor encroachment, it doesn’t comply with ASTM 1527-13. The Vapor Encroachment Screen is intended to identify the potential for vapors from hazardous substances and petroleum releases to reach structures located on the subject site. ASTM defines the term “Vapor Encroachment Condition” – presence or likely presence of “chemical of concern” vapors in the subsurface of the Target Property caused by the release of vapors from contaminated soil or groundwater or both either on or near the Target Property as identified by the Tier 1or Tier 2 procedures, {ASTM E2600-10}.

Preemptive Vapor Mitigation (PVM)

A method for eliminating a vapor encroachment condition as a recognized environmental condition. It is usually more cost effective to preemptively mitigate vapors, rather than perform extensive testing and re-testing, especially when known vapor sources have been identified on, or in close proximity to the target property. This is especially true for new construction where designing the mitigation system into construction is extremely cost effective.

ASTM E1527-13 Rationale for Including Vapor Encroachment Evaluation

The purpose of a Phase I Environmental Site Assessment (ASTM E1527-13) is to identify Recognized Environmental Conditions (RECs) for a property. A REC is defined as “…the presence or likely presence of any hazardous substances or petroleum products on a property under conditions that indicate an existing release, a past release, or a material threat of release into structures on the property or into the ground…”. ASTM does not differentiate between a “release” being solids, liquids, or vapors, only that the release be hazardous substances or petroleum products. Therefore, potential vapors encroaching on a target property need to be evaluated as potential RECs under ASTM E1527-13. It is universally accepted that migration of contaminated groundwater from a contaminated site to a target site is a REC, where as migrating vapors would also follow the same rationale.

Vapor Encroachment Screening

Tier 1 – Vapor Encroachment Screen is an investigation of all known or suspected contaminated properties within a given radius. The radius varies based on the “Chemical of Concern” at the contaminated site due to chemicals having different migration properties. Vapor Encroachment Screen distances can be up to 1/10 of a mile for petroleum contamination and up to 1/3 of a mile for other volatile compounds. The screening allows for the distances to be reduced for cross gradient and down gradient contaminated sites.

Tier 2 – If the Tier 1 assessment indicates a Vapor Encroachment Condition cannot be ruled out, the User can proceed to a Tier 2 Vapor Encroachment Screen. A Tier 2 investigation involves a more detailed analysis of available information as it relates to data already collected for the release. This may be groundwater monitoring data from a nearby site obtained through the State Environmental Department. If detailed information does not exist, the Tier 2 Vapor Encroachment Screening may include collection of invasive data such as groundwater and/or soil gas monitoring.

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