Is a VEC always a REC? The question has come to me a number of times since the E 2600-10 vapor encroachment screening standard was published by ASTM last month. The answer emphatically is NO.

First of all, it should be clear that a REC determination can only be made as part of an E 1527 Phase I. The REC definition in E 1527 does include consideration of hazardous substances and petroleum products that may encroach upon a property irrespective of their form (solid, liquid or vapor). The E 2600-10 standard provides a methodology that the environmental professional can use to evaluate the potential for vapors to encroach upon a property (referred to as a vapor encroachment condition or a VEC).

Secondly, if a VEC does exist, the environmental professional conducting the Phase I will have to determine whether or not this VEC constitutes a REC. One way of deciding whether or not a VEC constitutes a REC is to recognize that RECs do not include de minimis conditions, defined in E 1527 as conditions that do not present material risk of harm to public health and the environment, and would not be subject to enforcement action by the regulatory agency. If a VEC meets any of these "de minimis" conditions, the VEC would not likely be viewed as a REC.

Let me use some examples to illustrate the point.

(1) A VEC may exist because of groundwater contamination on the target property or near it, but it may not be a REC (under the de minimis clause) because the depth to groundwater is very deep, i.e., greater than the critical distance (defined in E 2600-10).

(2) A VEC may exist because of groundwater contamination on the target property or near it, but a REC may not exist (under the de minimis condition clause) because the distance between the nearest edge of the contaminated plume and the nearest structure may be considerable, i.e., greater than the critical distance (defined in E 2600-10).

(3) A VEC may exist because of groundwater contamination on the target property or near it, but a REC may not exist (under the de minimis condition clause) because the concentration of the contaminant in the groundwater is below the risk screening level for that contaminant as specified in the state's vapor intrusion guidance policy.

(4) A VEC may exist because of groundwater contamination on the target property or near it, but a REC may not exist (under the de minimis condition clause) because the building has been designed to be intrinsically safe from chemical vapor intrusion, i.e., there is no direct pathway for migrating vapors to reach human receptors.

These examples can provide some insight into how the environmental professional conducting the Phase I might use the de minimis condition clause in the REC definition to help determine whether or not a VEC constitutes a REC.