Vapour Intrusion: A Significant Regulatory Driver in Ontario?

With July 1st on the horizon, you may be thinking about getting together with friends and family for a picnic and celebration of Canada Day.  But July 1, 2011, also holds significance for businesses affected by the changes to Ontario Regulation (O.Reg.) 153/04, O.Reg. 511/09, as amended, which becomes effective on this date. 

The specific concern for many in the regulated community is how the new standards will impact site assessments and when the Ministry of the Environment (MOE) will publish technical guidance for soil Vapour Intrusion (VI) assessment.  The O.Reg. 511/09 regulatory standards for soil and groundwater are based on, among other pathways, soil to indoor air and groundwater to indoor air pathways.  It should be noted that 30 out of the 98 (non-metal) standards for chemicals reported in Table 2 (standards for soil residential land use, potable water scenario) are based on soil to indoor air calculations.  It would seem based on this information that VI to indoor air is important to the MOE.  This focus on VI is why the regulated community is anxious to see guidance from the MOE.   

It is important to note that the calculations conducted by the MOE to derive the published soil standards assumed generic (often conservative) site conditions.  Consequently, soil at a given site may have chemical concentrations exceeding soil standards, but this may not automatically translate into exceeding indoor air concentration limits.  The MOE will likely allow the use of site specific conditions to calculate site specific screening levels that still ensure that indoor air concentrations are within acceptable criteria.  Because of the prescriptive nature of the O.Reg 511/09 Amendments, the MOE will likely be as prescriptive in the upcoming technical guidance relating to VI assessment.

As new information becomes available, we will provide updates. For a more detailed discussion on VI sampling methodologies, see our article in Environmental Science and Engineering or click here

We hope you take time to enjoy your Canada Day holiday, and if you have any questions about environmental site assessments, remediation, permitting, or specific questions about VI, please feel free to contact our office at 519-979-7300.


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