Contact: Mark
Phone: (518)391-2359
email: MarkS@AlpineEnv.com

Vapor Encroachment

On June 14, 2010, ASTM published E2600-10, Standard Guide for Vapor Encroachment Screening on Property Involved in Real Estate Transactions. Vapor encroachment screening is now a required part of an ASTM 1527-05 Phase I, and by reference, the Environmental Protection Agency's "All Appropriate Inquiries (AAI)" rule. In short, if a Phase I Environmental Site Assessment does not include a vapor encroachment evaluation, it does not comply with ASTM 1527-05 or EPA AAI.

The Vapor Encroachment Screen is not intended to assess Vapor Intrusion into structures on the Target Property; rather, it is intended to identify the potential for vapors from hazardous substances and petroleum releases to reach the target property. 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)

An emerging method for eliminating a vapor encroachment condition as a recognized environmental condition is Preemptive Vapor Mitigation. It is often 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.  The cost for Preemptive Vapor Mitigation in existing construction is often in the $1.00 to $2.00 per square foot range, and rarely exceeds $2.50 per square foot in large buildings (> 20,000 sq ft). Preemptive vapor mitigation in existing large commercial buildings generally ranges between $1.50 and $3.00 per square foot.  In contrast, spray on vapor barriers commonly exceed $5.00 per square foot.

Vapor Mitigation Electrical usage in new construction vapor mitigation system is commonly 0.2 kW-Hrs/sq. ft. per year. At the U.S. average electrical rate of $0.0862 per kW-Hr, a 20,000 square foot new construction building costs $345 or 1.7 cents per square foot, per year in electricity.

ASTM E1527-05 Rationale for Including Vapor Encroachment Evaluation

The purpose of a Phase I Environmental Site Assessment (ASTM E1527-05) 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 E1527-05.   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.

Tier 1 Vapor Encroachment Screen

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 Vapor Encroachment Screen

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.