Overview of Major Changes in EPA Draft Guidance for Vapor Intrusion


Courtesy of Integrated Environmental Services, Inc.

The following provides a brief summary of the Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway From Groundwater and Soils (Subsurface Vapor Intrusion Guidance). November 2002, EPA530-F-02-052.

Major Points:

This draft guidance supersedes the draft RCRA EI Supplemental Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway (Dec. 2001). It does not supersede State guidance.

  • EPA stresses the following:
  • This is a guidance document, not a regulation
  • States are free to use and accept other technically sound approaches
  • This guidance does not impose any requirements or obligations on EPA, States, or the regulated community

This draft guidance is suggested for use at RCRA Corrective Action, CERCLA, and Brownsfields sites, but is not recommended for use at Subtitle 1 Underground Storage tank sites (these sites should continue to use risk based decision making approach as described in OSWER Directive 9610-17).

OSHA and EPA have agreed that OSHA generally will take the lead role in addressing occupational (workplace) exposures. Therefore, in general, EPA does not expect this guidance be used for settings that are primarily occupational (see footnote on page 3).

EPA recognizes the complicating factor in evaluating the potential chronic risk from vapor intrusion due to the potential presence of the same chemicals at or above background concentrations (from ambient (outdoor) air and emission sources in the building such as household solvents and cleaners) that may pose separately or in combination with vapor intrusion, a significant human health risk.

EPA recognizes that indoor air sampling results can be misleading because it is difficult and sometimes impossible to eliminate or account for contributions from background sources.

EPA suggests the use of this guidance at sites where contamination is located 100 feet or less in depth or is located in close proximity (100 feet laterally or vertically) to existing or planned buildings

EPA states in the context of the current guidance that “… we do not believe that confirmatory sampling will generally be necessary in that context”. EPA also states that “ … not recommending confirmatory sampling is appropriate because of the conservative nature of the assumptions made”. They are referring to the assumptions in the J&E model.)

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