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WATER GREMLIN PUBLIC HEALTH ASSESSMENT: PUBLIC COMMENT DRAFT In July 2020 and March 2021, four sub -slab vapor sampies.were col.lected.beneath the Water .Grem iin South Campus building, as shown on the map above. Multiple VOCs Were detected in all four samples, but no results:were above Industrial 33X.ISVs. For more discussion of indoor air results and Water Gremlin worker exposure:from.vapor intrusion, see the section below titled Worker and Worker Family Exposures..— Indoor Air. D. Soil Vapor Because of the high concentrations of contaminants in sub -slab vapor beneath the Water Gremlin facility, additional soil vapor samples surrounding the facility were needed to. determine the extent of the vapor plume and ensure it was not migrating off -site. Four rounds of soil vapor sampling.covered both the MPCA-defined non -heating season (Sam pies collected. in August and October) and heating season (December and January.) (Wenck; 2020). In August.2019,15 soil vapor samples were collected on Water Gremlin property surrounding the facility to determine if vapor was traveling.off--site towards residential areas, Nine of the sampling locations did not detect TICE ort-DCE,.The other six samples had. levels well below the residential 33X ISVs (up to 11 µg/m3 for TCE and up to 12 µg/m3 fort=DCE) (Wenck, 2020)..These.low concentrations in soil vapor and the a.dditional.distance to the nearest homes indicate that people living in the. area. are hot. afFected by soil vapor from Water Gremlin. In october 2019, 8 additional soil vapor samples were. collected adjacent to the Water Gremlin building; mainly to. the east and South to complete sampling for soil vapor surrounding the building: Two sample l.ocatio.ns adjacent to the building's south side exceeded: a 33X ISV — one sample had TCE at 281 µg/m3; another had Vinyl chloride at 559 µg/m3 (Wenck, 2020}. In December 2019, a1123 soil vapor sample locations were resampled to collect data during the heating season per the MPGA's vapor intrusian:best management practices (Wenck, 2020)..t7DCE was. not detected in any of these samples. TCE was only detected in 3 samples, at.1.3, 1.5, and 455.}ig/m3. The 33X 15V exceedance.locations for TCE and.t-DCE for all of. the data are shown in Figure 8 above. Unexpectedly, the solvent tetrachIoroethylene, or PCE, was.detected 1n every sample and exceeded the Fes idential 33X ISV of 110 µg/m3 in 1.3 samples; up to.189 µg/m3. The PCE exceedances were theorized to be due to contamination in the sampling or lab equiprnent. Because. the December PCE. exceedances could.not be explained, 16 locations were resampled in. January 2020. There were no exceedances. of the 33X ISVs and. only five of the samples detected PCE, up to.H.7 µg/m3. Two other 33X ISV exceedances a.ccurred 1n December, one of naphthalene and one of ethyl b.enzene. Neither of these compounds were detected. in their January samples. The soil vapor data coIIected.surroundIng the Water Gremlin build1ng.demonstrates that the high concentrations of sub=soil vapor at Water Gremlin are not migrating off -site. Soil vapor contamination from Water Gremlin.does not cause a health risk in the community, E. Sediment Surface water bodies at the Water Gremlin property include.Lambert Creek; t h ree. sto rmwater retention ponds (east, west, and south), and wetlands. 5ediment8amOle results for lead taken from these features were compared to MPCA'sSedim.en.t Quality Targets (S.QTs). Level I SQTs are contaminant concentrations in ppin that. provide a high level of protection. for sediment -dwelling organisms. Level 1.1 a