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Off-Site VEC and De Minimis Environmental Conditions

At a recent industry summit, I participated in a panel discussion on Vapor Encroachment Conditions.  We were given case studies where a Phase 1 Environmental Site Assessment had been completed and the consultant had classified a condition as a Vapor Encroachment Condition.  The panelists were asked to opine on whether or not these conditions were Recognized Environmental Conditions (RECs).  For a run down of the two Phase 1 ESA case studies, click here

In the discussion, the panelists generally agreed on the importance of considering the target property and the off-site concern as a specific location in space and not a “star” on the map.   We also agreed that the client risk tolerance was an important consideration.  


Recognized Environmental Condition?


I raised a technical issue that related specifically to the definition of a recognized environmental condition and the de minimis exclusion.   For a vapor encroachment condition to be considered a REC it must not fall within the definition of a de minimis condition:   if the VEC is neither a health concern nor a regulatory concern, then it is easily defined as de minimis.  


De Minimis/Human Health Conern:

“…conditions that generally do not present a threat to human health…”

If a vapor encroachment condition represents a threat to human health either for the current use or for a planned use of the property, then the environmental professional should classify the VEC as a recognized environmental condition.  

De Minimis/Regulatory Enforcement:

“…would not be the subject of an enforcement action if brought to the attention of appropriate governmental agencies.”


This was the most interesting part of the panel discussion as ASTM is a little vague.   I interpret this section to mean “would the owner of the target property be subject to a regulatory enforcement action”; as opposed to “would the owner of the off-site property be subject to enforcement action.”    This is a huge distinction, as the target property owner is very rarely subject to enforcement action for an off-site release.  

Someone in the room debated this subject with me.   My argument back was that you do not consider the countless LUST, CERCLIS, and NPL sites in the surrounding areas to all be RECs, right?   Why not?  These sites are all subject to regulatory enforcement action.   We don’t consider every nearby release site a REC simply because the owner of the off-site property is subject to a regulatory enforcement action (without other reason to believe that the off-site release has impacted the subject property or presents a human health risk to the subject property occupants).

In the end, I think that ASTM E1527’s definition of a recognized environmental condition could be clarified on this point.

Is a VEC a REC?

If more than 99% of VECs do not meet the regulatory enforcement portion of the de minimis standard, then the much larger concern for a VEC to be a REC is whether it represents a human health concern.    

There were clients at the conference that expressed greater sensitivity on this issue.   To address these needs, the Phase 1 ESA consultants should fully discuss the vapor encroachment condition and if it does not meet the definition of REC, still include the discussion as an environmental issue (or some classification of elevated risk that is less than a REC).  

In conclusion, the focus of the off-site vapor migration investigations should be on vapor intrusion conditions (vapor potentially inside a building, not just at the property line) and the corresponding threat to human health.