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Agency (EPA) Method 8260, polycyclic aromatic hydrocarbons (PAHs) by EPA Method 8270D/SIM and metals including arsenic, chromium, and lead (total and dissolved) by EPA Method 200.8. 3. Data Evaluation and Reporting: Evaluated groundwater chemical analytical results relative to MTCA cleanup levels and Ecology-published natural background concentrations and prepared this report summarizing the results. 3.0 SITE BACKGROUND AND REGULATORY STATUS The City completed a Remedial Investigation (RI) of the Site in 2018 (GeoEngineers 2018a). The findings of the RI indicated that the Site met the eligibility criteria to use one of Ecology's model remedies for cleanup: Model Remedy 3 per "Model Remedies for Sites with Petroleum Contaminated Soils" (Ecology 2017).The Site "Cleanup Action Plan" (CAP)(GeoEngineers 2018b)was submitted to Ecology in late 2018; the CAP described the proposed cleanup action consistent with Model Remedy 3 for petroleum- contaminated soil,specifically, remedial excavation to the greatest degree practicable and implementation of an environmental covenant if needed as part of the cleanup action.Subsequent to submittal of the CAP, GeoEngineers completed a focused data gaps investigation at the Site to resolve data gaps identified in the CAP or in Ecology correspondence to the City. The data gaps investigation findings were submitted to Ecology in 2019 (GeoEngineers 2019). A MTCA soil cleanup was completed at the Site by the City in November and December 2019(GeoEngineers 2020). Cleanup actions included excavation and off-site disposal of soil containing carcinogenic PAHs (cPAHs) at concentrations greater than the MTCA Method A cleanup level, and the removal of one on-site sump containing residual sludge and debris which was characterized and disposed off-site. Approximately 3,043 tons of contaminated soil were removed from three remedial excavation areas (refer to the MTCA Cleanup Report Figures 3 through 6)for off-site disposal. The MTCA Cleanup Report for the Site was submitted to Ecology in 2020; the cleanup report included the proposed groundwater compliance monitoring plan for the Site (GeoEngineers 2020). The proposed plan included the installation of two new groundwater monitoring wells (MW-5 and MW-6) and groundwater compliance monitoring on a quarterly basis for a minimum of four consecutive quarters. Ecology opinions concurringwith the cleanup action and the proposed groundwater compliance monitoring plan are provided in Appendix A. The two new monitoring wells were installed in July 2020. Post-cleanup quarterly groundwater compliance monitoring was initiated in July 2020 and completed in July 2021 after five consecutive groundwater monitoring events.The fifth groundwater monitoring event(July 2021)was completed because diesel-and lube-oil range petroleum hydrocarbons had been detected at concentrations exceeding the MTCA Method A cleanup level in the groundwater sample from monitoring well MW-3 during the first quarterly groundwater monitoring event in July 2020.While this detection in MW-3 groundwater was considered anomalous based on previous sampling results, an additional monitoring event was performed to document four quarters of compliance groundwater data at the Site. The City requests a NFA determination for the Site on the basis of the opinions issued by Ecology for the soil cleanup described above,and the results of the post-cleanup groundwater monitoring presented in this report. GEOENGINEER� January24,2022 Page2 File No.0661-108-03