Vapor Mitigation

The migration of chemical vapors from subsurface contamination into buildings has become an increasingly urgent topic for many Texas property owners. Vapor Intrusion (VI) is defined as the movement of volatile chemical vapors from contaminated soil or groundwater into nearby buildings.  VI sometimes gets confused with Vapor Encroachment, which is the presence or likely presence of volatile chemical vapors in the vadose zone on a property.  For instance, a vacant property could have vapor encroachment arising from a contaminant plume migrating from another property, but not vapor intrusion (due to the lack of a building).  Recent emphasis by the lending industry and by TCEQ coupled with a general awareness of VI is mostly responsible for the urgency.

The TCEQ in several recent vapor encroachment cases has required responsible parties to conduct VI assessments. Unfortunately, there are no specific TCEQ rules or guidance regarding VI assessments, however, ASTM E2600-15[i] provides a very good summation of the various methods available to the Environmental Professional.  Some of the acceptable methods used are:

Groundwater Sampling and Use of a Site-Specific Model

  • Soil Gas Sampling and Use of a Site-Specific Model
  • Subslab Soil Gas Sampling and Use of a Site-Specific Model
  • Indoor Air Sampling