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

ASPECT CONSULTING 52 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025 whether there is contaminated soil that requires excavation and off-Site disposal prior to the City’s filling and abandonment of the swale. In one test pit, the excavator bucket broke an 8-inch-diameter concrete pipe at approximately 3 feet below ground surface. The pipe, which ran from east to west, appeared to contain a small amount of water. This broken pipe was decommissioned using procedures described in the Work Plan for Second Interim Action (Aspect, 2019b). The sampling results documented concentrations of selected metals (Arsenic, copper, nickel, and zinc) in soil exceeding preliminary cleanup levels (PCLs) applied in this RI/FS. However, there were no exceedances of MTCA industrial PCLs based on human direct contact at any location in the swale. Concentrations of TPH and PAHs in the samples were below respective PCLs. Following discussion with Ecology, the City agreed with Ecology to take the following remedial actions—documented in a Cleanup Action Plan (CAP) Memorandum (Floyd|Snider, 2021)—to ensure that the conditions at the Utility Property are protective of human health and the environment and will be included in the K-C Upland Area CAP as the only remedial requirements applicable to the Utility Property. The CAP Memorandum for the City Utility Property is included as Appendix D. The City grubbed the swale area to remove vegetation and then backfilled it with the uncontaminated sand. A temporary earthen berm was then constructed along the southern property boundary to separate drainage on the Utility Property from the Port’s property to the south. The entire Utility Property, including the swale, will eventually be paved except for areas of landscaping or open space and the stormwater and combined sewer treatment and storage structures. Any areas that are not contained under paving must have data showing that surface materials (within the top 3 feet) meet MTCA Method A industrial cleanup standards. The City will apply an Environmental Covenant on the Utility Property requiring its use remain industrial and requiring maintenance of pavement and clean surface materials in landscaped areas (Floyd|Snider, 2021; Appendix D). In 2024, the City is undertaking demolition of selected existing waste treatment infrastructure, including the above-grade portions of the effluent pump station building, the gravity thickener buildings, metal-frame storage building, process mechanical infrastructure, chemical storage tanks, above-grade conveyance pipes, and other interior fixtures throughout the facility. The project includes pre-demolition abatement of regulated building materials identified in the City’s regulated building materials assessment for the facility. Subgrade pipelines and tanks to be retained will be video- inspected and cleaned to remove residual process materials or scale, with chemical testing and proper disposition of materials removed. Likewise, soils requiring excavation to accomplish demolition or utility replacement will be chemically tested and disposed of properly. The parking lot on the northeast side of the parcel will remain largely unchanged. Areas disturbed by demolition will be repaved following construction to