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

ASPECT CONSULTING 38 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025  Investigated soil and groundwater quality at the Diesel AST Area just north of the northeast portion of the distribution warehouse; the area includes the AST (within secondary containment structure) and associated diesel pump station that began operation in the mid-1990s. The investigation identified oil-range TPH in surficial soil west of the Diesel AST, which did not appear to be related to it. The groundwater sample at that location had no exceedances. Detected concentrations of TPH in soil from borings next to the AST and diesel pump house were less than screening levels, while total cPAHs and naphthalene were greater than unrestricted screening levels in one or more soil samples. The groundwater sample from that location contained no exceedances for TPH or naphthalene, and a marginal exceedance for total cPAHs.  Investigated potential impacts to soil and groundwater associated with the Hydraulic Barker Building. The results identified concentrations of oil-range TPH and cPAHs in soil exceeding unrestricted soil screening levels. Soil concentrations of copper, mercury, and zinc also exceeded respective unrestricted soil screening levels based on groundwater protection, but detected groundwater concentrations were less than respective groundwater screening levels.  Conducted Upland Area-wide sampling and analysis of the fill soil at 15 accessible locations outside of distinct operational areas (“General Fill”). The results detected diesel- and oil-range TPH, cPAHs, lead, and/or dioxins/furans greater than the screening levels at one or more of 15 locations. Follow up assessment included the following:  Additional investigation was conducted to further delineate the petroleum exceedance detected in saturated soil at the GF-B-9 location. TPH exceedances were not detected in immediately downgradient groundwater, but the lateral extent of soil TPH exceedances was not defined. The distribution of PAHs in the 10- to 11-foot soil sample from GF9-MW-1 suggested a creosote-like source.  Additional investigation was conducted to further delineate the shallow soil lead concentration (659 mg/kg) exceeding the unrestricted screening level at the GF-B-11 location, which was recommended for IA removal.  Oil-range TPH detected in shallow soil at the GF-B-14 location was attributed to adjacent contamination from the Associated Oil Company ASTs area, and was recommended for removal as part of the IA for that area.  Evaluated groundwater quality in monitoring wells located on the upgradient (east) side of the Upland Area and along the shoreline downgradient (west) of it (most wells were sampled twice; some shoreline wells had one sample and some had three samples). It was noted that most wells were sampled only during the dry season between June and September 2012 (only six of the wells had both wet and dry season sampling). Metals (arsenic, copper, nickel, and/or zinc) and ammonia were the only constituents detected exceeding respective screening levels in groundwater collected from the 15 shoreline wells. Arsenic, copper, nickel, and ammonia exceedances were commonly detected in groundwater across the Upland Area, and may be influenced by geochemically reducing conditions in the organic-rich fill from which the uplands were created. However, the 2012 groundwater metals analyses did not include