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WATER GREMLIN PUBLIC HEALTH ASSESSMENT: PUBLIC CdMMgNT 611-APT On August23, 2019, 12-additional sub -slab samples were' collected beneath the Water Gremlin building in areas that were not pi evfously sampled to determine the. extent of the high vapor concentrations (Wenck, 2020). Only three-of�these additional sample locations had exceedances of. the Ind ustria.I..ISV for TCE (236 µg/m3 to 1,920 µg/m3) and one location had a vinyl chloride excee.dance at 22,10.0 p.g/m3. There were no exceeda aces for t-DCE or any other compounds in the August 2019.samples. Figure 8, shown below, is a map of the June and August2019-sub-slab soil vapor sampling results for TCE and t-DCE, This map also shows the exterior soil vapor results around the property discussed below in :section :D. Soil Vapor. Figure 8: TCE and t-DCE?n Sol/ Vapor Sampling Results To address the potential for vapor intrusion at the Water Gremlin facility, .a temporaryvapor mitigation system that include6 both a sub -slab depressurization system and a soil vapor extraction system was installed:and began operating by mid-September,(Wenck, 2020). The soil vapor extraction system was installed to remove deeper sources of volatile contamination beneath the building. The temporary systems:wera..replaced by a permanent system In -late. December'2020 (M. Ginsbach, MRCA - personal communication, March 4, 2021). Weekly sub -slab and indoor airsampiing began in January 2020 and continues to this day to help better understand the soil vapor contamination on the property. Sampling results have been somewhat variable over time, but generally indicate that the mitigation system.is. effective. 29