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

ASPECT CONSULTING PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 51 plug upland pipes from the former mill that were open to the East Waterway and thus represented potential conduits for groundwater discharge to the Waterway. In addition, the 2019 IA Work Plan included a plan for monitoring groundwater pH throughout the removal of CM on the Site (discussed in Section 4.5), and potential implementation of contingency action(s) to neutralize groundwater pH if the removal action creates an increase in groundwater pH that poses a risk to the adjacent East Waterway. The second IA employed the same general procedures for excavation dewatering and soil removal/handling as the first IA and achieved permanent removal of an additional 17,610 tons of contaminated material from the Upland Area. In addition, approximately 2.28 million gallons of contaminated groundwater were removed from the collective excavation areas for treatment and discharge to the POTW via sanitary sewer, in accordance with a City DA. Finally, 18 inactive shoreline pipes were either removed, plugged, or capped at the shoreline and at a distance approximately 75 feet inland (if present) to prevent discharge to the East Waterway. In addition, in September 2019, the City decommissioned their CSO pipe (via filling accessible portions [i.e., manholes] with a low density flowable concrete mix) that traversed the Upland Area and discharged via outfall PS04 beneath K-C’s pier in the southwest portion of the Site; the City completed the process by placing a plug in the end of the pipe under the pier in March 2021. All excavations produced during the IA were backfilled with uncontaminated sand backfill and compacted. The second IA procedures and data are detailed in the Report for Second Interim Action (Aspect, 2021), which is included in Appendix A. The second IA did not conflict with or eliminate reasonable alternatives for the Upland Area final cleanup action in accordance with WAC 173-340-430(3)(b). All data representing in-place soil (i.e., representing current conditions) generated during the second IA are incorporated into this RI/FS. 4.4 City of Everett Investigation and Cleanup of Drainage Swale on their Property (2019-2021) In July 2019, City purchased from K-C the approximately 10 acres containing the former mill wastewater treatment plant portion at the north end of the Upland Area which corresponds to RI Unit E discussed in Section 6 of this RI/FS. The City purchased the property (termed “Utility Property”) to repurpose the wastewater treatment plant facility (WWTP) for operation by the City’s Public Works Department as an element of the City’s combined sewer overflow (CSO) control program. The existing WWTP will be integrated into the City’s wastewater system by converting the existing infrastructure into a combined sewage storage facility and constructing new sewers to convey wastewater to and from the facility. The new facility, named the Port Gardner Storage Facility (PGSF), will be used to temporarily store combined sewer flows until the collection system has the available capacity to convey flows to the Everett Water Pollution Control Facility. The PGSF is scheduled to be put into active service by December 31, 2027. In October 2019, Floyd|Snider, under contract to the City, conducted soil sampling in four test pits excavated to depths up to 6 feet within the shallow drainage swale located along the southern boundary of the Utility Property. The goal of the sampling was to inform