Atlantic RBCA Guidance for Vapour Intrusion Assessments


Atlantic RBCA Guidance for Vapour Intrusion Assessments
(December 2016)

Atlantic PIRI is currently revising the technical document entitled Atlantic RBCA Guidance for Vapour Intrusion Assessments (December 2016). The expected release of the revised technical document is in early 2019. As outlined below, there will be two important changes to the technical document.

Revision to Vapour Intrusion Screening Levels (VISLs)

In Appendix B, Table B1, Tier II Vapour Intrusion Screening Levels (VISLs), there will be a revision to the Residential/Agricultural Vapour Intrusion Screening Levels (VISLs) for Soil Vapour. Atlantic PIRI is retracting the current VISLs for Soil Vapour for Residential/Agricultural land use until the revised version of the Atlantic RBCA Guidance for Vapour Intrusion Assessments (December 2016) is released in early 2019.

Revision to Biodegradation Factor

Atlantic PIRI will also modify Appendix D of Atlantic RBCA Guidance for Vapour Intrusion Assessments (December 2016). Specifically, the proposed modification will incorporate a biodegradation factor of 10 into the calculation of the VISLs for Soil Vapour, Sub-slab Vapour, and Indoor Air.

The Canadian Council of the Ministers of the Environment (CCME) (2014) currently applies a bioattenuation factor to the Soil Vapour Quality Guidelines to account for the expected amount of degradation. In Tier I, CCME recommends a bioattenuation factor of 10, with additional consideration reserved for Tier II and Tier III. The inclusion of the bioattenuation factor into the calculation of the VISLs will reflect harmonization with the CCME as per the CCME Harmonization Agreements respecting environmental standards where each Atlantic Minister ensures an equivalent level of environmental protection with CCME standards.

How will these revisions affect site assessments?

Based on a preliminary review, the revisions will not result in more conservative VISLs. Atlantic PIRI does not anticipate any requirement for the re-evaluation of sites that have already been assessed using the VISLs in the current Table B1 in Appendix B.
For sites currently being evaluated using the Residential/Agricultural VISLs for Soil Vapour from Table B1 which have now been retracted, Atlantic PIRI recommends that the Site Professional conduct the assessment using the revised VISLs, scheduled for release in early 2019.
If you have questions about this Technical Advisory you may contact Atlantic PIRI or your provincial environmental regulator.

Atlantic RBCA Guidance for Vapour Intrusion Assessments

This document supercedes the User Guidance for Soil Vapour and Indoor Air Monitoring Assessments (Atlantic PIRI, 2006). Please refer to the Guidance for Vapour Intrusion Assessments Implementation Procedure (December 2016) for information on the implementation process for this new guidance.

As a result of feedback obtained through a public review, this guidance has been updated to remove all specific reference to chlorinated solvents. This is based on Health Canada’s recommendation that the most recent toxicity reference values published by the US EPA be used for the assessment of sites contaminated with perchloroethylene (PCE, also known as tetrachloroethylene) and trichloroethylene (TCE). Please refer to Implementation Procedure and Technical Bulletin #2 for PCE and TCE (December 2016) for further details.

Provincial regulatory staff may be contacted regarding any questions on this new guidance or the changes related to the chlorinated solvents toxicological information.