IEA_AARST_Radon_Reporter_JUNE_2024

14 | June 2024 VAPOR INTRUSION Wisconsin’s Vapor Intrusion Partnerships, Public Outreach And Passive Sampling By Jennifer Borski, Department of Natural Resources, Vapor Intrusion Team Leader In response to the growing concerns associated with chemical vapor intrusion, the Wisconsin Department of Natural Resources (DNR) introduced a comprehensive statewide effort that includes partnerships with other agencies, public outreach and training, targeted state-funded investigation and mitigation at priority sites and the use of alternate sampling technology. The DNR’s efforts have resulted in greater awareness of the health risks associated with vapor intrusion and investigation and mitigation of vapor intrusion risks at sites throughout Wisconsin. The DNR oversees responsible parties who conduct investigations and clean up environmental contamination in Wisconsin. Investigations typically include an evaluation of soil, groundwater and soil gas samples to determine the severity of the plume and how far the contamination has spread. As part of the investigation, the environmental consultant evaluates the potential for vapors to off-gas from the contamination and result in accumulation in indoor air. When the air people breathe in nearby buildings is affected by the contaminant or “plume,” it is expected that a mitigation system be installed to protect human health. However, there are several sites where the responsible parties are unknown or unable/unwilling to proceed with the required work. For example, progress in investigating the contamination has stalled or the contaminated property has been abandoned by the original causer. Because vapor intrusion from some contaminants can present acute (short- term) human health risks, the DNR selected three environmental consulting firms through a competitive procurement process to perform state-funded work at vapor intrusion sites throughout the state where investigations have stalled. Although certified mitigators are not currently required for vapor intrusion mitigation in Wisconsin, two of the contractors selected for this effort are certified by the National Radon Proficiency Program (NRPP) and experienced with vapor intrusion mitigation. The DNR developed a method, coined the Vapor Intrusion Risk Evaluation and Response (VIPER) Program, to assess risks and prioritize stalled sites with the potential for vapor intrusion. Considerations include: • The concentrations of the chlorinated solvents, tetrachloroethene (PCE) and trichloroethene (TCE), in soil, groundwater and soil gas. • Vapor impacts to sanitary sewers. • The number of buildings at risk for vapor intrusion. • Surrounding land use. • The population within 100, 300 and 500 feet of the source of contamination. • The Center for Disease Control & Prevention (CDC) ‘s Social Vulnerability Index (SVI) rating for the location. The sites selected for evaluation in 2023 and 2024 included six dry cleaners, a formalwear facility with suspected dry cleaning and three industrial operations that historically utilized TCE. The scope of work for each location includes collecting vapor samples in sanitary sewers, within rights-of-way and beneath and within residences. When investigating vapor intrusion at residential properties, vapor investigations include the sampling of sub-slab vapor, indoor air on each level (e.g., basement, crawl space, first floor and second floor) and outdoor air. If a sump is present, sump water and the headspace from the temporarily sealed sump will be sampled as well. Traditional vapor investigations use evacuated canisters over a 24-hour period to collect discrete (grab) samples from exterior soil gas, sanitary sewers, sub-slab vapor and indoor air. The DNR has transitioned to using passive samplers over a one-to-two-week sampling duration for vapor intrusion investigations and is encouraging the use of passive samplers for vapor investigations in Wisconsin.