WA State Dept of Ecology 9/18/2023

Joel Haack January 6, 2023 Page 15 feet bgs. Groundwater depths in resource protection wells located 1,500 feet northwest and approximately 80 feet downhill of the Site average at approximately 6.5 feet bgs. Anticipated depth to groundwater at the Site is greater than 50 feet bgs. Water Supply: Drinking water is supplied to the Property by water mains operated by the City of Everett. Water for the City is sourced from the Spada reservoir, located approximately 25 miles east of the Site. The Site is located approximately 2.2 miles southeast of the nearest 10- year wellhead protection zone for a water supply well. Release and Extent of Contamination: Site conditions prior to remedial actions: Subsurface investigations at the LMGC Site were described in the Remedial Investigation, Everett Smelter Site, Everett, Washington, dated September 1995 (1995 RI). A total of 412 soil characterization samples were collected from 103 discrete locations at depths ranging from 0 to 2 feet bgs. Sample results indicated that concentrations of arsenic and lead were greatest on the east side of the Site, closest to the location of the former smelter (Figure 2). Soil samples collected in the vicinity of the Property contained arsenic above the Method A cleanup level (Figure 2). Due to the lack of shallow groundwater in borings and anticipated regional groundwater depth (greater than 50 feet bgs), soil leaching to groundwater pathway is not considered complete at this Site.Therefore, groundwater was not investigated. According to reports described in the 2022 CAR, fill soils were stored on the Property during retention pond construction to the south (Lake 5, Figure 2). Following a removal of a portion of the stockpiled fill material from the Property, samples were collected from shallow soil around the area of the stockpile. One soil sample, reportedly collected from the north side of the stockpile contained arsenic above the Method A cleanup level. A sampling report was not generated for this work; the precise location of this sample is unknown. A targeted subsurface investigation of the Property was conducted in 2019 to assess shallow soils on the north side of the Property. Four test pits were advanced to a maximum of 7 feet bgs in the northern portion of the Property (Lot 5 and Lot 6) to assess the concentrations of lead and arsenic in native soils (TP-1 to TP-4; Figure 4). Lead and arsenic were not detected above the Method A cleanup level at any sample. Based on recommendations in Ecology's 2020 Opinion, an expanded subsurface sampling plan was implemented at the Property.