20E021 - Advantages and Limitations to Vapor Intrusion Modeling for Risk-Based Decision Making
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Background/Objectives: Analytical and numerical models have been used to evaluate key fate and transport phenomena that influence the vapour intrusion (VI) pathway.

Additionally, models are frequently used to quantify VI risks and develop corrective action goals. The utility of modeling for risk-based decision making has been questioned due to uncertainties associated with the accuracy of the model results. Models often fail to provide useful information when the conceptual framework for the model is inconsistent with site conditions (e.g., ignoring the effect of natural vadose-zone biodegradation on chemical fate) or model input parameters are not representative of site conditions. However, when appropriately applied, model can provide a useful line of evidence for VI assessments. This presentation will provide examples to illustrate how models can be effectively used in VI assessments while acknowledging their limitations.

Approach/Activities: The first step in using a model for a VI assessment is to identify an suitable model that will capture the key characteristics of the site. Various models are available to evaluate the VI pathway, and it is important to understand their limitations when selecting the methodology to be used for a specific application. The next step is to determine technically defensible model input parameters based on site conditions that account for the variabilities and uncertainties of the various factors that influence VI. Understanding the sensitivities of each input parameter on model outcomes is a critical factor in the data evaluation process. Lastly, the uncertainties of the model output must be considered in the interpretation of the results for risk-based decision making.

Results/Lessons: Learned VI model results can provide an effective additional line of evidence for evaluating the VI pathway at contaminated sites. However, it is important to understand the limitations of the models and confirm that appropriate input parameters based on site conditions are used. Also, the uncertainties of the model results should be recognized in the application of the modeling.

Publication Summary

  • Geosyntec Authors: Robert Ettinger
  • All Authors: Robert Ettinger
  • Title: EcoForum 2020 eConference
  • Event or Publication: Event
  • Practice Areas: Vapor Intrusion Assessment and Remediation
  • Citation: Geosyntec will deliver five presentations and one keynote at EcoForum 2020 eConference on September 14-18, 2020.
  • Date: September 14-18, 2020
  • Location: eConference
  • Publication Type: Platform Presentation