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

ASPECT CONSULTING 42 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025 first interim action, its sampling and analysis was conducted in accordance with the Interim Action Plan (Aspect, 2012c). Analytical results of the CM showed concentrations of chemicals above MCTA cleanup levels including metals, PCBs, TPH, and cPAHs. Following complete removal of the CM in 2020, as required by Ecology, those sampling data are no longer representative of current Site conditions and are not further discussed in this RI/FS. In total, 390 soil samples, 208 groundwater samples, 14 air samples, 19 intertidal porewater/seep samples, six surface water samples, and two seawater reference samples were collected and analyzed during the RI data collection effort, in accordance with the RI/FS Work Plan and several subsequent addenda to that Work Plan described below. Additional field parameter measurements, without laboratory analysis, were also made at numerous groundwater locations in February, May, and August 2016, and March, July, and September 2017, and at several intertidal seep locations in August and October 2016. In addition, monitoring for pH in groundwater was conducted across the Site during complete removal of the CM in 2020. The full data set used in the RI/FS, incorporating data collected during the 2012 Phase 2 ESA, 2013 RCRA closure, both interim actions, CM removal, and the RI activities spanning several years, is described in Section 6.1. The samples of soil, groundwater, air, porewater/seeps, and surface water were submitted for chemical analyses using analytical methods specified in the Quality Assurance Project Plan (QAPP; part of the Appendix A to Aspect, 2013c) or subsequent Work Plan Addenda. Pyron Environmental (Pyron) or Laboratory Data Consultants, Inc. (LDC), under subcontract to Aspect, completed independent Level III data quality validation of the analytical data generated during most of the RI, RCRA closure, and both IAs following procedures specified in EPA Contract Laboratory Program (CLP) functional guidelines. Aspect conducted independent validation of analytical data collected during the IA groundwater monitoring and supplemental RI data collection, excluding PCB congener analyses which were validated by Pyron. Based on the validation, all analytical data were of acceptable quality for their intended purposes. The data qualifiers resulting from the validation are included in the data tables in this report and are included in the data uploaded to Ecology’s Environmental Information Management (EIM) database. The data validation reports for the RI data collection program are provided in Appendix C. Aspect maintains copies of the numerous raw laboratory reports, and they are available upon request. Site-wide groundwater level monitoring was conducted in each accessible monitoring well in the Upland Area on four occasions, using an electric well sounder graduated to 0.01 foot. Each of the four rounds was completed within an approximately 2-hour period (“snapshot”) during a middle tidal stage to avoid low and high tide conditions. The first Site-wide snapshot of water level measurements (71 wells) was conducted in November 2013. The second round (103 wells) was conducted in May 2014 and included the additional monitoring wells that had been installed that month for IA confirmational monitoring. The third round (102 wells) was conducted in February 2016, in conjunction with the IA confirmational groundwater monitoring event. The third round (68 wells) was