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3.0 FIELD ACTIVITIES <br /> 3.7.3.1 Sidewall Sample Results <br /> The sidewall sample results are summarized below and presented in Table 3: <br /> • BTEX was non-detect in all 16 of the final sidewall verification samples. <br /> • TPH-g was non-detect in 14 of the final 16 sidewall samples. Detected concentrations of <br /> TPH-g were 49 mg/kg(in sample number 13, 20-44W-67N-5.OSW),located at 5 feet bgs <br /> along the western boundary of the excavation,and 47 mg/kg (sample number 11,20- <br /> 44W-56.5N-5.OSW) at 5 feet bgs. <br /> • TPH-d was non-detect in 5 of the final 16 sidewall samples.The highest detected <br /> concentration of TPH-d was 3,100 mg/kg(detected in sample number 13,20-44W-67N- <br /> 5.OSW),located at 5 feet bgs along the western boundary of the excavation. <br /> • TPH-mo was non-detect in 6 of the final 16 sidewall samples. The highest detected <br /> concentration of TPH-mo was 160 mg/kg(detected in sample number 32,20-42W-108N- <br /> 5.OSW),located at 5 feet bgs along the western boundary of the excavation. <br /> The highest concentrations of TPH in verification samples were along the western boundary <br /> of the station, adjacent to the location of the former contactor towers and fluids production <br /> tank. Active utilities and existing site features limited access and constrained expansion of <br /> the excavation (Figure 3). <br /> 3.7.3.2 Bottom Sample Results <br /> The final bottom verification sample results are summarized below and presented in <br /> Table 3: <br /> • BTEX was non-detect in all 17 final bottom samples collected. <br /> • TPH-g was non-detect in 15 of the final 17 bottom samples. The highest detected <br /> concentration of TPH-g was 7.8 mg/kg(detected in sample number 16,20-25W-26N- <br /> 13.513),located at 13.5 feet bgs near the southern half of the excavation). <br /> • TPH-d was non-detect in 3 of the 17 final bottom samples.The highest detected <br /> concentration of TPH-d was 170 mg/kg(detected in sample number 17,20-22W-46N- <br /> 12.513),located in the middle of the excavation at 12.5 feet bgs. <br /> • TPH-mo was non-detect in 12 of the 17 final bottom samples. The highest detected <br /> concentration of TPH-mo was 35 mg/kg(detected in sample number 40,20-42W-112N- <br /> B-7.0) located in the northwest corner of the excavation. <br /> Deeper excavation in the area of bottom wall samples 16,17,and 40 was constrained by <br /> limitations of standard excavation equipment. Only sample 17(TPH-d at 170 mg/kg) was <br /> slightly above the TPH-d goal of 100 ppm. The average concentration of the three bottom <br /> samples was below the TPH removal goals. <br /> APPL Laboratories,Inc. conducted an internal review of the laboratory data and quality <br /> assurance/quality control protocols and procedures and concluded that the data collected <br /> from the site were of acceptable quality.A few surrogate recoveries were reported above the <br /> upper control limits,but these recoveries occurred infrequently across the analytical data <br /> set.All other surrogate recoveries were found to be within prescribed lab requirements and <br /> analytical holding times were met for all tests performed. <br /> SFO\(THORNTON COMPLETION REPORT_6.21-05.DOC) 3-6 <br />