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WATER GREMLIN PUBLIC HEALTH ASSESSMENT: PUBLIC COMMENT DRAFT levels.of lead present on the company's property, and the lack of access and rnovernent off=site that could.result in exposures, this. limited soil contamination from Water Gremlin does not represent a health risk to the comrnunity. C. Sub -Slab Soil Vapor —Water Gremlin Facility What is Vapor Intrusion? Volatile organic compounds are chemicals that easily evaporate into air. When chemicals evaporate from polluted soil :and from groundwater; they rise toward the ground surface. If these vapors -come into contact with a building, they may enter through cracks in the foundation,.around.pipes, or through a sump or drain system, and contaminate indoor air. This :process —when pollution moves from air spaces in soil to indoor air —is called vapor intrusion. If chernicaIs are present near .buildings, Vapor intrusion is investigated by collecting sub -slab samples by drilling small holes. through the foundation to sample soil va.por from Beneath the `build ing.: Intrusion Screening Values MDH and MPCA develop Intrusion Screening Values (ISVs), which are compared to indoor air or sub -slab soil vapor concentrations to help -determine when.actions may be needed to protect health. The ISVs represent an amount of a chemical measured in.micrograms per cubic meter, or µg/m3 that is safe.for people to breathe, A 33X ISV value Is an amount.of a chemical beneath a building that is not expected to result in indoor air amounts that exceed the ISV for that chemicaL.These values. are. designed to be protective for sensitive people, including children, pregnant women, and people. who already have health issues. There are two sets of ISVs—Residential and CommerciaVIndustrial—based largely on the amount of time people may spend at home (up to:24 hours a day, seven days:a week) or in the workplace (up to IQ hours per day, five days per week). Table.8 below provides the current:ISVs and 33X ISVs for TCE and trans-1,2-dichloroethylene: (t-DCE). Table 8: Intrusian Screening Values for TCE and t-DCE *ISVs for t-DCE.are based on the 2620. M D H Risk Assessm6nt.Advice. Vapor intrusion investigation and mitigation apt the Water Gremlin facility In June 2019, TCE was found in sub -slab soil vapor samples collected from beneath.Water Grem Iin's facility above 33X Industrial ISVs (up to 120,000 µg/m3) in 20 of 25 samples collected (Wenck, 2019). t- DCE was also found in soil vapor beneath:the building in every sample, with -many samples having very high concentrations up to 530,000 µg/m3:.High t-D.CE soil vapor concen.trations.beneath the. building (many located beneath the coating rooms).led to IVIPCA ordering. Water Gremlin to suspend operation of the. coating lines on August 22,2019. 29