3815_PGSF WMVD Pkg 2_Vol 4-2_03.03.2026_BXWA_Certified

ASPECT CONSULTING PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 13 occurrences of gravel, concrete, brick, wood, and charcoal debris, and wood chips/sawdust. Figures 2-5 through 2-7 are east-west-trending geologic cross sections across the Upland Area; Figure 2-4 shows locations of the cross sections along with the Upland Area explorations used to prepare the cross sections. Explorations logs from the collective Upland Area explorations used in the RI are provided in Appendix B. Beneath the fill is native Snohomish River alluvium, the same material (interbedded sand and silt) that was hydraulically placed as dredge fill. Glacially overridden soils are present at depths ranging from about 30 to 60 feet beneath grade in the eastern portion, and sloping to depths ranging from 90 to 120 feet below grade beneath the western portion of the Upland Area (Shannon and Wilson, 2014). Within the west-center portion of the Upland Area, the historical Log Pond was filled between approximately 1979 and 1981 to create upland for storage of wood chips produced at Scott Paper’s Riverside facility in east Everett. The subsurface explorations drilled within the Log Pond footprint indicate its fill soil is siltier than the dredge fill soil present across most of the rest of the Upland Area. A former Scott Paper employee stated that he had witnessed construction/demolition debris (originating outside the mill property), debris from the mill, and barrels (drums) be placed within the eastern portion of the Log Pond during its filling. Based on investigations within the Log Pond, the silty fill soil contains demolition debris including concrete rubble, wood (including burnt), metal, and brick. However, the collective information collected (e.g., see Section 4.2.7), including a surface geophysical survey across the entire area, test trenching in one area, drilling of 13 shallow soil borings, 13 deep borings, 4 shallow monitoring wells, and 5 deep monitoring wells, and soil and groundwater sampling and analysis provides no evidence for buried containers of chemicals within the Log Pond fill soil. Beneath the Log Pond fill, which was observed to range in thickness from 29 to 46 feet, a sawdust layer, ranging in thickness from about 2 to 10 feet, was encountered overlying native soil, as discussed further in later sections of this report. Native soil in the Log Pond was observed at depths ranging from 29 to 52 feet bgs. 2.4.4.2 Groundwater Flow System A shallow unconfined (water table) water-bearing zone occurs within the fill, overlying the underlying siltier native tidal flat deposits. The water table within the fill is relatively shallow, generally ranging in depth from 1 to 4 feet below grade in the Upland Area’s eastern areas to 6 to 12 feet below grade in its western areas. Consequently, groundwater flows generally from east to west across the Upland Area, with discharge to the East Waterway; however, depending on the alignment of the shoreline, groundwater directions may flow locally toward the northwest or southwest. For example, in the south end of the Upland Area, groundwater locally flows to the southwest toward the off-loading dock slip. Because of its geometry extending inland, the slip is an area of converging groundwater flow and thus substantial groundwater discharges to it from both the Upland Area and the Port of Everett property on its south side. During calm (not windy) conditions at lower low tide, subtidal groundwater discharge has been observed as subtle ripples on the water surface along the south end of the slip.