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

ASPECT CONSULTING PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 55 Site (Landau, 2021c) and for the K-C Upland Area (Landau, 2021d). Both plans were prepared by the Port to guide intrusive activities during the Norton Terminal MIE project and were adopted by the City for their CSI Project. Each trench section was shored using slide rails and steel sheets and left open while crews completed installation of each pipe section; final excavation depths ranged between approximately 10 and 18 ft below existing grade. All material excavated from the ExxonMobil/ADC Site was exported for landfill disposal (Landau, 2022b). Material excavated from the K-C Upland Area was field-screened and segregated into four categories: soil suitable for reuse, potentially contaminated soil, geotechnically unsuitable soil that did not have field-screening indications of contamination, and concrete and treated wood debris (Landau, 2022b). Materials deemed unsuitable for reuse were stockpiled, chemically tested for waste profiling, and properly disposed of offsite. As documented in the CSO Construction Report (Landau, 2022b), quantities of materials excavated and disposed offsite included:  7,962 tons of potentially contaminated soil from the combined Exxon/Mobil Site and K-C Upland Area were thermally treated and landfilled at the Cadman Delta Remediation Facility in Everett, Washington.  11,254 tons of soil from the Upland Area deemed to be geotechnically unsuitable and not potentially contaminated was disposed of at the OMA Construction Mountain Loop Mine located in Maple Valley, Washington.  125 tons of treated wood from the Upland Area was disposed at the Columbia Ridge Subtitle D landfill in Arlington, Oregon. Concrete rubble excavated from the trench was recycled at a permitted recycling facility. The excavated soil reused as backfill material is now located under the low-permeability cap installed during the Port’s third IA. During trenching and pipe installation, approximately 11,884,200 gallons of groundwater were pumped from the shored trench areas, treated to remove settleable solids in weir tanks, and then discharged to the City’s sanitary sewer system under a Discharge Authorization. No additional treatment or removal of NAPL or other contaminants was necessary to meet City discharge criteria before being discharged to the sanitary sewer. Nine pipes encountered during trenching were cut, water in them was pumped out, treated, and discharged to sewer, and both open ends of the pipe were grouted. Prior to placement in the trench, the imported aggregate backfill was chemically tested to document compliance with PCLs (Landau, 2022b). 4.8 Third Interim Action (2021-2023) In May 2021, Ecology, the Port, and K-C executed a second amendment to the Agreed Order to allow for the performance of a third IA, to be completed concurrently with the MIE project. The third IA was led by the Port and performed in conjunction with initial site development to put the Site back into productive use to support the Port’s marine terminal activities. The third IA was performed in accordance with the Interim Action