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

ASPECT CONSULTING 24 FINAL PROJECT NO. AS190583A-08  MAY 21, 2025 3.1.3 Removal and Investigation of Five USTs (1989-1990) Five USTs at the mill property were permanently decommissioned by removal in November and December 1989 (Landau, 1991). The USTs below are depicted on Figure 2-2. The capacity and contents of the USTs reportedly included the following:  One 250-gallon unleaded-gasoline UST (Tank No. 68);  One 1,000-gallon diesel-fuel UST (Tank No. 70); and  Three 12,000-gallon Bunker C fuel-oil USTs (Tanks No. 71, 72, and 73). As part of the UST decommissioning activities, soil and groundwater samples were collected and submitted for laboratory analysis. The laboratory analytical results indicated that releases of petroleum hydrocarbons had occurred at each of the UST locations. Based on the data, contaminated soil was excavated from each UST pit location. Following removal of the five USTs, Landau conducted a subsurface investigation in November and December 1990 to further assess soil and groundwater quality in the vicinity of the USTs. The investigation consisted of advancing seven soil borings, three around UST No. 68 and four around UST No. 70; collecting soil samples for laboratory analysis; completing the seven borings as groundwater monitoring wells; and conducting a groundwater sampling event. During the 1990 investigation, petroleum-related compounds were detected in soil and/or groundwater in these areas, as summarized in the Phase 2 ESA (Aspect, 2013a). During the Phase 2 ESA, residual petroleum contamination was identified in the UST 70 and USTs 71/72/73 areas, but not in the UST 68 area. In 2013–2014, K-C’s IA accomplished removal of contaminated material from the UST 70 and USTs 71/72/73 areas, as described in Section 3.4. 3.1.4 Investigation in Vicinity of Old Paint Shop (1994) In June 1994, a strong solvent odor and a thin floating layer of a viscous, brown-black substance were observed within a localized length of utility trench excavated proximate to the Central Maintenance Shop (also known as the salvage warehouse). The location is reportedly near a historical paint shop that operated until the early 1970s. This area is identified as HREC 5 in the Phase 1 ESA (AECOM, 2011). A grab sample of water within the trench was collected for chemical analysis of gasoline-, diesel-, and oil-range TPH, volatile organic compounds (VOCs), and polychlorinated biphenyls (PCBs). One VOC, p-isopropyltoluene (i.e., 4-isopropyltoluene or p-cymene), was detected in the water sample at a concentration of 11,000 micrograms per liter (µg/L), along with 380 µg/L gasoline-range TPH. Landau interpreted the p-isopropyltoluene to be a component of turpentine solvent used in the historical paint shop (Landau, 1994b). There are no marine- based or vapor intrusion (VI)-based groundwater screening levels for 4-isopropyltoluene. However, isopropylbenzene (cumene) has been used a surrogate compound for p-isopropyltoluene, based on similar chemical structure, in regulatory programs outside Washington State (Fehling et al, 2011). Subsequently, Landau conducted an investigation in August 1994 to assess soil and groundwater quality in the vicinity of the solvent occurrence. The subsurface investigation consisted of advancing seven soil borings and collecting soil samples and reconnaissance