Workshop 5, Why You Should Monitor Indoor Radon, Differential Temperature, and Pressure During Chlorinated Vapor Intrusion Assessments
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While chlorinated vapor intrusion (CVI) is a complex and challenging-to-assess phenomenon largely due the apparently endless number of hard-to-identify, measure, and predict factors influencing the resulting variable indoor air concentrations; the in-depth study of a few readily-measurable/available Indicators and Tracers (I&T) has shown some impressive correlations with indoor CVOC concentrations due to CVI in the buildings studied to-date.

Documentation of I&T measurements can significantly increase the quantitative confidence in the probability of measuring the exposure levels of most concern (e.g., RME or 95UCL) to that well above the random probability of typical individual sample efforts (~5%). Foremost among the I&T metrics is radon (Rn) which is a wide-spread naturally-occurring tracer of soil gas intrusion, mixing and retention in indoor air. The evidence and conceptual understanding indicates that the indoor concentration of Rn incorporates the effects of indicators such as temperature (a potential CVI driver), as well as pressure changes (including barometric, wind speed, and building operations) and integrates their effects across both space and time. More specifically indoor Rn levels integrates their actual effects on soil gas intrusion and indoor air concentrations, in the specific building and under the conditions being investigated. While outdoor temperatures and pressures are readily available from nearby weather station records, the changes in indoor levels of radon, temperature and pressure can be measured "continuously" with relatively inexpensive meters. This workshop will review new evidence for I&T that have shown correlations with indoor CVOC concentrations in data-rich studies of many buildings (including those with complex preferential pathways) and report the evidence from new building types and climate zones. Presentations will include the results of a study of the "antecedent" I&T-levels leading up to indoor CVOC concentrations above the 95th percentile for these buildings, as well as an introduction to technology for automated I&T "triggered-sampling" methods and discussions on selecting I&T "trigger-rules" for automated sampling. The workshop will also present and discuss I&T "Fact Sheets" to assist regulators (& other stakeholders) collecting and/or reviewing I&T evidence supporting CVI Investigations. Additionally, there will be a report on the use of I&T to address spatial variability (i.e., to prioritize among buildings over the source area). Finally, the workshop will hold a panel/open discussion further exploring the conclusions of our previous workshop, with the question: Does the I&T evidence we have now support a general recommendation to: "Document the indoor radon, differential temperature and pressure levels at least at the time of CVOC sampling, and surrounding baseline periods for comparison, to allow and improve future understanding and interpretations of the buildings" intrusion levels at the time of CVOC sampling?"

Publication Summary

  • Geosyntec Authors: Chase Holton
  • All Authors: Chase Holton
  • Title: The Association for Environmental Health and Sciences (AEHS) Foundations' 30th Annual International Conference on Soil, Water, Energy, and Air
  • Event or Publication: Event
  • Practice Areas: Vapor Intrusion Assessment and Remediation
  • Citation: Geosyntec practitioners will present at the Association for Environmental Health and Sciences (AEHS) Foundations' 30th Annual International Conference on Soil, Water, Energy, and Air on March 16-19, 2020. The conference will be held at the DoubleTree Mission Valley in San Diego, California.
  • Date: March 16-19, 2020
  • Location: San Diego, California
  • Publication Type: Course Instruction