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January 3, 2025 <br />HWA Project No. 2021-159-21 <br />Geotechnical Engineering Report 6 HWA GEOSCIENCES INC. <br />Port Gardner Storage Facility <br />samples. Soil samples were collected at depths ranging from 7.5 to 17.5 feet, based on the <br />observed groundwater interface or (if present) field indications of contamination. All sampling <br />equipment was decontaminated prior to use with detergent solution, potable water, and distilled <br />water. <br />HWA returned to the site on October 30, 2023, and collected groundwater samples from each <br />monitoring well. Low-flow groundwater sampling methods were used to collect the samples, <br />utilizing a peristaltic pump at rates not exceeding 0.3 L/min, while monitoring a suite of water <br />chemistry parameters including dissolved oxygen, pH, temperature, and others. Once water <br />chemistry parameters had stabilized, (indicating that it was representative of formation water), <br />laboratory-supplied sample containers were filled following standard groundwater sampling <br />procedures. <br />All 2023 soil and groundwater samples were submitted to OnSite Environmental for chemical <br />laboratory analysis. One soil sample from each boring and both groundwater samples were <br />analyzed by the following methods: <br />• TPH-gasoline by NWTPH-Gx <br />• TPH-diesel and -oil by NWTPH-Dx <br />• Volatile Organic Compounds (VOCs) by EPA Method 8260D <br />• RCRA 8 Metals (Ag, As, Ba, Cd, Cr, Hg, Pb & Se) by EPA Methods 6010D/7471B (soil) <br />• Dissolved RCRA 8 Metals by EPA 200.8/7470A (water) <br />• Semi-Volatile Organic Compounds (SVOCs) with low level cPAHs by EPA Methods <br />8270E/SIM <br />• Polychlorinated biphenyl (PCBs) by EPA Method 8082A <br />Results of the 2022 and 2023 environmental testing are included in Table C-1 (soil) and Table C- <br />2 (groundwater), discussed in Section 3.5 below, and the laboratory reports are presented in <br />Appendix C. <br />2.5 PREVIOUS EXPLORATIONS BY OTHERS <br />Available information from previous geotechnical explorations performed at the site was <br />reviewed and utilized in this study. The previous explorations at the plant site include the <br />following: