Throughout the past decade, the risk of subterranean toxic vapors intruding into indoor environments has been getting closer examination from a concerned public as well as from scientists and the environmental regulatory universe.
The model below depicts intrusion of volatile organic compounds (VOCs). Common sources of such vapors are chlorinated solvents from dry cleaning operations, machine shops and industrial operations, and volatile petroleum products from underground storage tank systems. Some of these compounds are antagonistic to human health.
In 2011, the Department of Toxic Substances Control (DTSC) in the California EPA released its Final GUIDANCE FOR THE EVALUATION AND MITIGATION OF SUBSURFACE VAPOR INTRUSION TO INDOOR AIR (VAPOR INTRUSION GUIDANCE) document providing a step-wise approach to assessing the risk to inhabitants of buildings at sites where subsurface contaminants could potentially enter the indoor environment as vapors.
Get it at https://www.dtsc.ca.gov/AssessingRisk/upload/Final_VIG_Oct_2011.pdf
In addition, DTSC created the Vapor Intrusion Mitigation Advisory on mitigation and remediation of vapor intrusion.
Get it at http://www.dtsc.ca.gov/SiteCleanup/upload/VIMA_Final_Oct_20111.pdf
The Advisory provides a framework for adequate decision-making to
- determine whether mitigation is appropriate,
- establish the proper mitigation system to implement, and
- ensure that the implementation is sustainable for the duration of mitigation.