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Ms. Carol Oz <br /> August 12, 1999 Project 791700 <br /> Page 8 <br /> from the northern and western ends of the UST excavation (SW-N and SW-W) contained <br /> TPHG at concentrations of 364 and 1,840 mg/kg, respectively. Benzene was detected in <br /> one soil sample in the northeastern corner of the UST excavation at a concentration of <br /> 0.19 mg/kg (T-3-N). Benzene was also detected in sidewall sample SW-N at a <br /> concentration of 0.545 mg/kg. All other UST excavation samples did not contain benzene <br /> at concentrations exceeding method reporting limits. MTBE (by USEPA method 8260) <br /> was detected in all six of the UST excavation samples. In addition, all four of the sidewall <br /> samples contained concentrations of MTBE above method reporting limits. UST <br /> excavation samples contained concentrations of MTBE ranging from 9.2 to 272 mg/kg. <br /> The northwestern corner sample (T-1-N) contained the highest MTBE concentration. <br /> Sidewall samples contained concentrations of MTBE ranging from 0.221 to 23.8 mg/kg. <br /> Sidewall soil sample taken from the northern wall of the UST excavation (SW-N) <br /> contained the highest concentration of MTBE. <br /> Piping and dispenser samples generally contained low non-detectable concentrations of <br /> toluene and total xylenes. With the exception of sample P-6, TPHG and benzene were not <br /> detected. MTBE concentrations ranged from 0.114 to 33.2 mg/kg. <br /> Limited overexcavation was conducted in two localized areas beneath pipingtrenches and <br /> dispensers due to strong petroleum hydrocarbon odors and high PID readings. Soil <br /> samples taken from the overexcavated locations were taken at 7 feet bgs. Soil samples <br /> collected in the vicinity of the former dispenser islands (D-7/8) and the product delivery <br /> piping(PL-6) contained detected TPHG concentrations of 1.2 to 7,040 mg/kg. <br /> Soil and fill material removed from the UST complex and piping trenches SP-1 were <br /> characterized and removed from the site by Dillard Trucking, Inc. for disposal at BFI <br /> Landfill, Vasco Road, Livermore, California. Excavation backfilling activities were <br /> completed on July 19, 1999 , and the former UST complex, dispenser areas, and product <br /> delivery piping areas were resurfaced. <br /> Additional site assessment activities are proposed, including three CPT borings to be <br /> conducted along the eastern boundary of the site. The CPT borings and sampling are <br /> scheduled to be conducted on August 23 and 24, 1999. <br /> CP\E:\ARCO\2186\REPORTS\2186P105.DOC-95 Isg:l mm <br /> YC�tt2CtCQC <br />