Objective:
This project is designed to demonstrate the applicability of lower-cost alternatives for sampling and analysis of volatile organic compounds (VOC) in indoor air and soil gas during investigation of subsurface vapor intrusion to indoor air. Chlorinated solvents are among the most common compounds of concern in soil and groundwater at Department of Defense (DoD) sites, and these compounds can pose an unacceptable human health risk via vapor intrusion even at very low concentrations. Laboratory analysis of indoor air, outdoor air, or soil gas samples by Environmental Protection Agency (EPA) Method TO-15 is currently the most common method used for vapor intrusion assessments, which typically cost $250 to $400 per sample, depending on the reporting limit required. Passive diffusive sampling and analysis can be 30 to 50% less expensive. Several quantitative diffusive gas sampling techniques are currently available; however, a comparative study is needed to identify whether and under which conditions the passive samplers provide good quality data before they will be accepted by most regulatory agencies. Technology Description: Four distinct types of passive diffusive samplers will be tested against two active gas sampling methods under controlled laboratory conditions and under field conditions at a DoD site to be selected during the conduct of the work. Each of the passive diffusive samplers contains an adsorbent media that traps VOCs over time during exposure of the sampler to indoor air or soil gas. They each have different materials of construction and geometries that make them sufficiently different to justify comparative testing. Each method has been developed to a certain degree for indoor air quality monitoring. None were specifically designed for soil gas monitoring, although the benefit of having data from both soil gas and indoor air is very attractive for vapor intrusion assessments, so the proposed research is designed to test their applicability to soil gas as well. Target concentrations for vapor intrusion assessments are lower than many other indoor air quality monitoring target levels (e.g., occupational monitoring) so the capability of the passive samplers will also require assessment at low concentrations. Expected Benefits: The passive samplers have at least four significant benefits: 1) they are much less expensive than Summa canisters; 2) they can be used consistently by different operators with minimal training; 3) they can be deployed over relatively long periods of time, which would provide a long-term average concentration more suitable for assessing risks over long exposure periods and minimize temporal variability inherent in shorter term samples; and 4) they are significantly smaller and less obtrusive than Summa canisters, and therefore less disruptive to occupants of buildings being monitored. This project is specifically designed to provide sufficient comparative testing data under both controlled laboratory conditions and under real-world field conditions to provide regulatory agencies the solid scientific basis they need to accept passive samplers as a tool for vapor intrusion assessment. (Anticipated Project Completion - 2011) Principal Investigator: Mr. Todd McAlary Geosyntec Consultants, Inc. 130 Reseach Lane, Suite 2 Guelph, ON N1G 5G3 Telephone: (519) 822-2230 Ext. 239 E-mail: tmcalary@geosyntec.com DoD Liaison: Dr. Sam Brock HQ AFCEE/TDN 3300 Sidney Brooks, Building 532 Brooks City-Base, TX 78235 Telephone: (210) 536-3253 Fax: (210) 536-5989 E-mail: Samuel.Brock@brooks.af.mil
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