Professional Judgment in VEC-REC Determinations

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Professional Judgment in VEC-REC Determinations (9 Comments)
Monday, December 20, 2010 9:59 AM

Entry by abuonicore

As an instructor for the ASTM E 2600-10 VEC training course, I noticed some confusion over where professional judgment is applied. Should professional judgment be applied when conducting a Tier 1 screen in E 2600-10 so that there are the least number of properties contributing to a vapor encroachment condition and requiring further investigation? Or should professional judgment not be applied in E 2600-10 when deciding whether or not a contaminated property is creating a VEC, but rather be applied in the E 1527-05 Phase I when determining whether this VEC is a REC? My response is that professional judgment can be applied in either place. For example, assume the soil between the target property and a chlorinated solvent-contaminated property located 90 feet down-gradient from a target property is a relatively impermeable silty clay. Under the E 2600-10 Tier 1 screen, this contaminated property would represent a condition that could cause a VEC since the contaminated property is within 100 feet of the target property, and vapors, according to the critical distance definition in E 2600-10, could potentially reach the target property assuming the path of least resistance is in that direction. One approach is to identify the contaminated property in the example as creating a VEC under E 2600-10 since it is within 100 feet of the target property and then, when evaluating if this VEC is also creating a REC in the E 1527-05 Phase I, use the soil characteristics rationale to support your professional opinion that the VEC would not represent a REC. On the other hand, professional judgment can be applied just as well in the E 2600-10 Tier 1 screen to conclude that the down-gradient contaminated property in this example does not represent a VEC because of soil characteristics. In this latter case, the property then need not even be addressed as a potential REC in the Phase I.

The choice as to where professional judgment is better applied remains an open issue, or at least an issue to be dealt with on a case-by-case basis. With respect to my example, an advantage to applying it in the E 2600-10 Tier 1 screen is that it can eliminate a nearby contaminated property that potentially may create a VEC from any further consideration in the Phase I. An advantage to applying it in the Phase I (as part of the REC determination) is that it can simplify E 2600-10 Tier 1 screening.

It would be interesting to hear your rationales for where you would prefer to apply professional judgment with respect to VEC determination in Tier 1 screening under E 2600-10. Would your preference be to eliminate the contaminated property potentially creating a VEC in E 2600-10 Tier 1 screening, or would you prefer to keep it as a VEC and then use professional judgment to eliminate it from further consideration in the REC evaluation in E 1527-05?