Rescinding Portions of the 2013 Vapor Intrusion (VI) Guidance Document

Michigan Department of Environment, Great Lakes, and Energy sent this bulletin at 06/20/2017 03:48 PM EDT

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The Department of Environmental Quality (DEQ) developed the 2013 Guidance Document for the Vapor Intrusion Pathway (2013 DEQ VI Guidance) to provide information to DEQ staff and their contractors conducting investigations and remedial or corrective actions at sites with potential VI issues.  The document is available as a technical reference to assist any party conducting activities to address volatilization to indoor air.

The DEQ has the following modifications to the 2013 DEQ VI Guidance: 

1. Rescission of Screening Values:  The DEQ rescinds Appendix D of the 2013 DEQ VI Guidance.  The vapor intrusion screening values provided in Appendix D.1 (i.e., Residential Vapor Intrusion Screening Values) and in Appendix D.2 (i.e., Nonresidential Vapor Intrusion Screening Values) of the 2013 DEQ VI Guidance no longer reflect the DEQ’s determination of values that represent the best available information regarding the toxicity and volatilization to indoor air exposure risks posed by the hazardous substances as required by Section 20120b of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended.  Because Appendix D has been rescinded, the values in Appendix D may no longer be utilized to conduct a site-specific evaluation of the volatilization to indoor air pathway (VIAP).

Site-Specific Evaluation:  Conditions that must exist in order for the generic criteria to apply are found in the Part 201 Administrative Rules for the generic Groundwater Volatilization to Indoor Air Inhalation Criteria (GVIIC) and the Soil Volatilization to Indoor Air Inhalation Criteria (SVIIC) [R 299.14(2) and R 299.24(2)].  If those conditions are not met and therefore the generic criteria do not apply, a site-specific evaluation of the inhalation risks must be conducted.  Details regarding these conditions are contained in Appendix C of the 2013 DEQ VI Guidance Document - Checklist for Determining if Generic Volatilization to Indoor Air Inhalation Criteria Apply.  These rules also contain a provision that allows the use of representative soil gas concentrations to demonstrate compliance with criteria for the VIAP [R 299.14(5) and R 299.24(5)].  This evaluation relies upon satisfying site-specific soil gas criteria. 

Request for Site Specific Criteria:  As noted above, when the generic criteria do not apply or when a person choses to rely upon representative soil gas concentrations to evaluate the VIAP, a person must conduct a site-specific evaluation.  The DEQ will assist with the development of site-specific criteria that may be used for the site-specific evaluation.  Please contact the appropriate DEQ Remediation and Redevelopment Division District Office for guidance on how to request assistance.  Alternatively, a person may generate site-specific criteria and submit the necessary information to the DEQ for review and approval. 

2. Rescission of Alternate Approach Considering Biodegradation:  The DEQ also rescinds Appendix B.3 of the 2013 DEQ VI Guidance – Alternate Approach for Investigating Vapors for Petroleum Hydrocarbons Considering Biodegradation.  In place of this document, the DEQ views the ITRC Technical and Regulatory Guidance Web-Based Document, Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation, and Management (PVI-1, 2014) as suitable for a petroleum vapor intrusion assessment pursuant to the relevant statutory provisions.

If you have questions please call the DEQ District Office where your site is located.