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

ASPECT CONSULTING 70 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025 the collective data provided on Tables 6-7 and 6-8 for soil and groundwater, respectively. The sub-slab and indoor air data (all constituents) for the warehouse (in Unit A) are presented by themselves (Tables 6-15a through 6-15d). In addition to presenting them in unit-specific data tables, the data from the shoreline monitoring wells, intertidal porewater/seep samples, and the surface water samples are presented by themselves (Table 6-22) for presentation of shoreline water quality (Section 6.5.7). For each constituent, the tables provide the medium-specific PCLs, and concentrations exceeding respective PCLs are highlighted. Table 6-6 provides explanatory notes and defines the abbreviations used in Tables 6-7 through 6-22. As described in Section 5.3.2, the soil PCLs based on groundwater protection are different for unsaturated soil versus saturated soil (see Tables 5-3 and 5-4). Each soil sample in the data set has been designated as either unsaturated or saturated soil based on a conservatively high water-table condition measured in May 2014. The soil data tables referenced in this section present the designation for each soil sample as saturated or unsaturated soil, and the exceedance designations in the data tables account for that difference. The soil data tables present each soil sample’s depth interval below the future grade that is currently provided for in design specifications for the third IA (refer to Section 4.7). A vast majority of the soil samples were collected when the CM was in place, and the boring logs in Appendix B, and prior documents for the Site, include sample depths relative to the grade existing at the time they were collected, which are different than presented in this report. Accordingly, the soil data tables in this document also include the elevation24 for each soil sample interval to provide an absolute reference. In accordance with MTCA, the PCLs for cPAHs and dioxins/furans are based on the total toxic equivalent quotient/concentration (TEQ) of the most carcinogenic compound in those constituent groups, as follows:  Total cPAHs (TEQ) is the toxic equivalent concentration of benzo(a)pyrene calculated in accordance with MTCA (WAC 173-340-708[8][e]) to evaluate the human health toxicity of cPAH mixtures. Nondetected values are included in the summation at one- half the laboratory’s analytical reporting limit.  Total 2,3,7,8-TCDD (TEQ) is the toxic equivalent concentration of 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) calculated in accordance with MTCA (WAC 173-340-708[8][d]) to evaluate the human health toxicity of dioxin/furan mixtures. Nondetected values are included in the summation at one-half the reporting limit. In addition, the total toxic mobility equivalent concentration (TMEQ) for total cPAHs was calculated to evaluate the potential for cPAH mixtures in soil to impact groundwater through the leaching pathway. The total cPAH (TMEQ) was calculated in accordance with the procedures outlined in Ecology’s Implementation Memorandum #10 (Ecology, 2015c). The total cPAH (TMEQ) is compared to soil PCLs for the protection of groundwater (Section 5.3.2.2) while the total cPAH (TEQ) is compared to soil PCLs for 24 Elevations relative the NAVD88 vertical datum.