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

ASPECT CONSULTING 54 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025 Monitoring of groundwater pH throughout the CM removal project was conducted as a component of the second Interim Action to assess whether the action created an increase in groundwater pH that posed a risk of migration to the East Waterway. The pH monitoring was conducted in general accordance with the pH monitoring plan included as Appendix E to the Work Plan for Second Interim Action (Aspect, 2019b). Monitoring of 35 wells positioned downgradient of the active CM excavation work over more than 4 months of CM removal documented no pH increase attributable to the CM removal action. The collective pH monitoring data demonstrate that removing the more than 250,000 tons of CM from the Site did not create migration of high-pH groundwater toward the East Waterway. The pH monitoring is detailed in Appendix F to the Report for Second Interim Action (Aspect, 2021). 4.6 MIE Geotechnical Explorations (2020-2022) Between September 2020 and August 2022, Landau Associates completed three separate phases of geotechnical investigation of the Upland Area on behalf of the Port to support the MIE project. The work included advancement of 10 soil borings (MIE-SB-1 through MIE-SB-10) to 30 feet bgs, 3 soil borings (B-1-2022 through B-3-2022) to 80 feet bgs and excavation of 12 exploratory test pits to evaluate groundwater pH (TP-1 through TP-8) or to evaluate subsurface conditions to inform structural design (TP-1-2022, TP-2-2022, TP-2R-2022, and TP-3-2022). During advancement of the borings, soil was field screened and select soil samples were collected for chemical analysis. The results of this work are summarized in the July 15, 2021, memorandum regarding Maritime Industrial Expansion Project Geotechnical Borings (Landau, 2021a) and the January 3, 2023, memorandum regarding K-C Warehouse Seismic Assessment (Landau, 2023). The sample locations are identified on Figure 2-4. Field screening did not indicate potential contamination at any soil from the MIE- series borings (Landau, 2021a). Odors, elevated PID measurements, or sheen were noted in borings B-2-2022 and B-3-2022 (Landau, 2023). Soil samples collected from the borings were screened against the IACLs established for the K-C Second IA. Most of the analytical data from the soil samples were either nondetect or detected at concentrations below the IACLs, with a few minor exceedances noted for TPH, cPAHs, and metals (Landau, 2021a and 2023). Investigation-derived waste from the exploration programs was profiled and properly disposed of. 4.7 Combined Sewer Main Improvements (2022) Between March and June 2022, the City constructed their Combined Sewer Main Improvements (CSI Project) that involved excavating an approximately 3,300-foot-long deep utility trench aligned south to north through the middle of the Upland Area, from the Federal Avenue right-of-way (within the ExxonMobil/ADC cleanup site) south of the Upland Area to the City’s Utility Property on the north end of the Upland Area (alignment shown on Figure 2-4). Intrusive activity in both the ExxonMobil/ADC and K-C Sites were conducted in accordance with the Soil and Groundwater Management Plans for the ExxonMobil/ADC