2008 CPEO Brownfields List Archive

From: Lenny Siegel <lennysiegel@gmail.com>
Date: Wed, 28 May 2008 15:06:43 -0700 (PDT)
Reply: cpeo-brownfields
Subject: [CPEO-BIF] Review of ASTM's Vapor Intrusion Standard Practice
I have just reviewed ASTM 2600-08, "Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions." This document, published by ASTM (formerly known as the American Society for Testing and Materials) in March, is a significant step in the right direction. It provides purchasers of property and their environmental professionals with a systematic outline for evaluating and responding to the potential for the vertical migration of volatile contaminants from the soil and groundwater.

Most practical experience with vapor intrusion comes from sites with existing structures, and rightfully so. It made sense to address first those locations where people were already being exposed to toxic contaminants in their indoor air. However, most of the guidance documents and technical literature remained silent on what to do where construction is planned. The ASTM Standard Practice fills that gap.

It is a tiered, or sequential approach. The first tier, designed to accompany a Phase 1 Environmental Site Assessment, is a non-invasive screening to determine whether there is a potential for vapor intrusion at the target property. Tier 2 "applies semi-site specific numeric screening criteria to existing or newly collected soil, soil gas and/or groundwater testing results to assess whether or not a [potential Vapor Intrusion Condition] still exists. The Third Tier is a full-blown vapor intrusion assessment, which may include interior and/or exterior vapor sampling. Tier 4, which is implemented if actual or potential vapor intrusion is found, consists of mitigation - that is, institutional controls, engineering controls (including possibly source cleanup as well as vapor barriers and venting), or intrinsically safe building design.

As I read it, the ASTM Standard Practice is more of a guidebook than a guidance. That is, the environmental professional is asked to find and follow applicable legal guidance. Thus, the document serves only as an outline for the vapor intrusion assessment and response process. It doesn't tell the professional or his/her client where to avoid building, or where to install mitigation.

Even as a permissive - that is, not determinative - document, the ASTM Practice suffers from a serious flaw. For structures requiring mitigation, it fails to emphasize, or even specify, long-term management responsibilities. It simply suggests: "Operations and Maintenance - Proper operation and maintenance shall be performed as deemed appropriate and necessary by the user and qualified professional, based on information obtained during the [Vapor Intrusion Assessment], to verify that any mitigation system(s) implemented to address a [Vapor Intrusion Condition] (in the case of necessary mitigation) or a [potential Vapor Intrusion Condition] (in the case of pre-emptive mitigation) are operating properly to protect against a [Vapor Intrusion Condition]."

I am all too familiar with structures, including schools and homes, where incorporation of vapor mitigation into design is assumed, without sufficient proof, to provide long-term protection. Such mitigation works well - as long as it works. But someone needs to take responsibility for ensuring that passive mitigation systems remain intact, that active mitigation systems are operating properly, and that the indoor air remains safe to breathe.

As I said earlier, ASTM's Vapor Intrusion Standard Practice is a step forward. However, it suffers from a process that did not include input from representatives of the impacted public. It doesn't do enough to provide enduring protection to the occupants of buildings constructed with the help of investigations described by the Standard Practice.

Lenny Siegel


Lenny Siegel
Executive Director, Center for Public Environmental Oversight
a project of the Pacific Studies Center
278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918

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