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

ASPECT CONSULTING PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 111 limits for cPAHs at shoreline wells at LP-MW-02 and MW-06 were elevated during initial sampling events, but subsequent sampling events had reporting limits below the PCL. The deep sawdust layer contains TPH-D+O, PAHs, and PCBs at concentrations exceeding the soil PCLs. However, groundwater samples collected from deep wells screened across the sawdust layer do not contain TPH-D+O or PAHs exceeding the groundwater PCLs, indicating that these contaminants are not leaching from the organic-rich sawdust at levels that result in exceedances of the PCLs. PCB congeners were detected above the groundwater PCL in four Log Pond Area wells, including both shallow and deep wells, but are not present in shoreline wells above the PCL. The highest concentrations of NH3 in Upland Area groundwater were detected at inland well LP-MW-01 within the Log Pond Area, which was a large storage area for wood chips for decades during mill operations; this well also had the highest groundwater pH measured on Site37. Subsurface wood waste also exists in the Log Pond fill from past filling activities. Considerably lower-level NH3 exceedances were detected at the Log Pond shoreline wells LP-MW-02 and MW-06, but they are still three times the PCL based on surface water exposure. Within the intertidal zone adjacent to Unit C, NH3 and H2S were each detected at concentrations exceeding PCLs in one of two porewater samples. No NH3 or H2S exceedances were detected in samples of East Waterway surface water collected along the toe of the Log Pond Area’s rip rap slope, demonstrating the rapid attenuation of these compounds within oxygenated water. The existing analytical data for soil and groundwater within the Log Pond Area of Unit C provide sufficient information for the development and evaluation of cleanup action alternatives in accordance with MTCA. 6.5.5 Unit D The explorations and IA areas within Unit D, including IA compliance soil sample locations, are depicted on Figure 6-D1. For current conditions following the IA, the constituents detected in one or more samples of Unit D media at concentrations exceeding their respective PCLs are as follows:  TPH-D+O in soil  Total cPAHs (TEQ) in soil and groundwater  Total xylenes in soil  Arsenic, copper, mercury, and nickel in soil and groundwater  Lead and zinc in soil  Dissolved sulfide in groundwater and intertidal porewater/seeps 37 NH3 concentrations correlate directly with pH (refer to Appendix H).