EA performed comprehensive vapor intrusion studies and developed vapor intrusion conceptual site models at eight Air National Guard installations nationwide. Studies ranged in size from single building evaluations to 11 concurrent evaluations of individual buildings at an installation. EA utilized historical site soil and groundwater investigation data to optimize sampling programs and establish data management procedures for the collection of >2,000 groundwater, sub-slab, indoor, and ambient air/vapor samples and radon sample at buildings on-base. We installed >340 sub-slab soil gas points to complete sub-slab soil gas assessment beneath buildings and foundations, and performed leak-check tracer gas testing at sub-slab points to ensure quality data. We utilized radon sampling to evaluate the background source potential and estimate building-specific attenuation rates as well as Hazardous Air Pollutants Onsite (HAPSITE) meters to track, identify, and sample indoor air sources of volatile organic compounds currently being stored or used in occupational settings. EA is conducting a multiple-lines-of-evidence evaluation to determine completeness/incompleteness of vapor intrusion pathways; lines-of-evidence include sub-slab soil gas and indoor air, background
outdoor air, real-time indoor air screening and analysis (HAPSITE), differential pressure monitoring, radon sampling, contaminant of concern ratio assessment, and groundwater spatial data. We are modeling volatile organic compound and radon data to estimate building attenuation rates and comparability/applicability of calculated rates and performed a baseline risk assessment using EPA Risk-Based Screening Levels for indoor air. Recommendations were provided based on analytical results to assist an informed risk-management decision regarding future management of the vapor intrusion pathway.
