The Most Recent Vapour Intrusion Guidance for Ontario

On September 26, 2013, the Ontario Ministry of the Environment (MOE) published a “Draft Technical Guidance: Soil Vapour Intrusion Assessment” (

This new document (which replaces the November 2010 document), is still labeled as “Draft.”  However, it should be carefully considered, especially if you have potential vapour intrusion (VI) issues.  Also, unlike the 2010 version, the 2013 guidance document has a publication number (8477) and does not have the disclaimer “Do Not Cite or Distribute.”  Does this suggest that this guidance document will also be accompanied by more “regulatory enforcement teeth”?  If you have a potential VI issue that may be affected by this new guidance document, you may want to consult with your legal counsel.

When comparing the 2013 guidance to the 2010 version, the following differences are noted:

  • Chapter 7 (Methods for Discerning Contributions of Background from Indoor Sources) was removed.  This chapter may have been removed to avoid suggesting any specific method.
  • Changes to the “Recommended Health-Based Indoor Air Target Levels for Selected VOCs” in Appendix IV (Note: This was incorrectly listed in the Table of Contents as Appendix VI)

1. Higher Criteria values for Petroleum Hydrocarbons (PHC) F1 and F2.
2. New Criteria for cis-1,2 trichloroethylene (1,2-DCE) and trans-1,2-DCE – previously there were no criteria listed in Appendix IV.
3. New Criteria for PHC-F2 Aromatic (>C12-C16) and Aliphatic (>C12-C16) – previously there were no criteria listed in Appendix IV.

We often refer to VI as a potential Pandora’s Box when not approached with the proper scientific and strategic rigor for good reason; don’t undertake any VI assessment without a well-reasoned plan.  If you have questions about VI and what it could mean to your site assessment and remediation efforts, contact Dr. Khaled Chekiri ( or Andrew Tymec ( at 519-979-7300.


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