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

ASPECT CONSULTING PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 39 reductive precipitation (EPA Method 1640) to minimize analytical interferences due to salinity. In accordance with the RI/FS Work Plan, that procedure was applied for the RI/FS analyses of brackish groundwater samples (discussed further in Section 6). The detected un-ionized ammonia groundwater concentrations in three of the 15 shoreline wells— REC1-MW-9, MW-06, and REC6-MW-6—exceeded the 0.035 µg/L screening level based on chronic exposure for aquatic organisms in surface water. Detected metals concentrations were less than screening levels in groundwater from the two upgradient wells. 3.3 Hazardous Waste Accumulation Unit Closure (2012) In association with mill demolition, Aspect oversaw and documented RCRA clean closure of the mill’s 90-day HWAU (“haz waste cage”), in accordance with the state Dangerous Waste Regulations (WAC 173-303-610) and Ecology implementation guidance for clean closure (Ecology, 2005). The structure was not a RCRA Treatment, Storage, and Disposal Facility, and was, therefore, exempt from requirements in WAC 173-303-610 (closure and postclosure) and 173-303-620 (financial assurances), except for WAC 173-303-610(2) and 173-303-610(5). The HWAU is located on the southeast corner of the former log pond and is shown on Figure 2-2 (co-located with item number 12 in the legend). Following the demolition contractor’s final removal of waste materials from the accumulation unit, but prior to its demolition, Aspect conducted a visual inspection of the unit to document cracks in the structure and observe for evidence of a release from it. Aspect also collected four fully penetrating core samples of the concrete floor slab for analysis of gasoline-, diesel-, and oil-range TPH, RCRA 8 metals, semivolatile organic compounds (SVOCs), VOCs, and PCBs. Detected concentrations in the concrete were less than Method A soil screening levels and Method B direct contact-based soil screening levels for unrestricted use (see Table 3-1 of the RCRA Closure Report discussed in the paragraph below); however, analytical reporting limits for cPAHs exceeded unrestricted cleanup levels for the concrete samples. The structure’s concrete demolition debris was disposed of at CEMEX’s landfill in Everett. Following removal of the structure, Aspect sampled soil within the footprint of the structure for analysis of gasoline-, diesel-, and oil-range TPH, RCRA 8 metals, SVOCs, VOCs, and PCBs. Soil concentrations were less than respective unrestricted soil screening levels. Following the mill closure, and demolition and soil testing of the accumulation unit, Aspect prepared a RCRA Closure Report for the mill (Aspect, 2013b). The RCRA Closure Report can be viewed on Ecology’s website using the weblink provide in Section 1. The Closure Report documents the waste management history of the mill, and describes the disposal of remaining chemical inventory during the mill closure/demolition, the inspection, analytical testing and proper disposition of the 90-day hazardous waste accumulation unit structure, and analytical testing of the underlying soil. Finally, the RCRA Closure Report summarizes Ecology’s November 2012 hazardous waste inspection conducted during the mill closure/demolition process, during which Ecology concluded that the waste management activities were being conducted in accordance with the requirements of Chapter 173-303 WAC (Ecology, 2012d).