Development of More Cost-Effective Methods for Long-Term Monitoring of Soil Vapor Intrusion to Indoor Air Using Quantitative Passive Diffusive-Adsorptive Sampling Techniques

ER-200830

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.

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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.

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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 - 2012)

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Interim Results

As of July 2010, laboratory experiments under controlled conditions are approximately 70% complete.  Familiarity testing (to show that the conditions of concentration, temperature and humidity are stable and controllable), ANOVA testing (to measure intrinsic variability in ostensibly identical experiments), and inter-laboratory testing (to measure variability between analytical laboratories) have been performed.  Fractional factorial testing (a series of experiments systematically varying the five conditions of concentration, face velocity, exposure time, temperature and humidity in the test chambers to assess their influence on sampler performance), is currently underway and 8 of 18 tests have been completed.  High concentration laboratory testing (experiments where the concentrations are in the range of interest for soil vapor instead of indoor or outdoor air and the face velocity is very low) is forthcoming.  The first field event is being conducted in mid-July and is focused on soil gas sampling, since none of the passive samplers were specifically designed nor have been extensively tested for this application. Interim results are planned to be presented at the ESTCP/SERDP specialty meeting on vapor intrusion in Salt Lake City on August 16 and 17, 2010.

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Points of Contact

Principal Investigator

Mr. Todd McAlary

Geosyntec Consultants, Inc.

Phone: 519-822-2230 x239

Fax: 519-822-3151

Program Manager

Environmental Restoration

SERDP and ESTCP

Document Types

  • Fact Sheet - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
  • Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
  • Guidance - Instructional information on technical topics such as protocols and user’s guides.
  • Workshop Report - Summary of workshop discussion and findings.
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