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detected However, PHC concentrations in the follow up samples collected approximately 5 feet below the initial samples, were significantly attenuated relative to the initial concentrations in the initial samples No EDB was detected in any of the samples Lead was detected at 6 to 12 4 milligrams per kilogram (mg/kg) in the initial samples from the north ends of both tanks, but was not detected in the follow up samples at 16 feet bsg ' On August 7, 1998 soil borings B3-1, B3-2 and B3-3 were installed and soil samples were collected at 5-foot intervals beginning at 10 5 feet up to 40 5 feet bsg No PHCs were detected in the ' uppermost soil samples collected from 10 to 11 feet bsg, or in the two lowermost samples collected at 35 and 40 feet bsg, in any of the three borings PHCs in soils were first detected at 16 feet bsg in boring B3-2, and at 20 feet bsg in B3-1 and B3-3 The highest levels of PHCs in soils were ' detected in the sample collected from 15 5 to 16 0 feet bsg in boring B3-2 This sample contained 2,100 mg/kg TPHg and 8 4 mg/kg benzene ' Uppermost groundwater samples were collected at 12 and 13 feet bsg in borings B3-3 and B3-2, respectively The sample from B3-2 contained trace amounts of PHCs (0 00042 benzene mg/1), 1 while no PHCs were detected in the sample from B3-3 Groundwater sampled from boring B3-1 at 22 feet bsg, within the zone of strong petroleum odor, contained the highest concentrations of PHCs in groundwater samples, with 1,600 mg/l TPHg The depth-discrete water sample collected from ' 31 to 35 feet bsg in boring B3-2 contained 2 7 mg/l TPHg and 0 06 mg/l benzene, indicating that dissolved phase PHCs are present in the coarser grained sediments below the zone of PHC- impacted soils From May 18, 1999 through June 2, 1999, three groundwater monitoring wells were installed within a few feet of corresponding previous soil borings All wells were drilled with 8-inch hollow- stem auger to depths of 36 to 40 feet to allow installation of 35 feet of well casing Wells are constructed of about 10 feet of blank, 2-inch diameter, schedule 40 PVC casing above 25 feet of 2- inch diameter, 0 02-inch factory-slotted PVC screen Waterproof traffic-rated vaults were installed ' several inches above ground and the surface was finished with concrete graded away from the vaults to reduce surface infiltration The elevation of the three monitoring wells was then surveyed by a CA Registered Civil Engineer 1n addition, each of the wells were developed between May 21, ' 1999 and June 7, 1999 by a combination of bailing, surging, and pumping until all appreciable fines were removed from the well casing GROUNDWATER MONITORING ACTIVITIES Monitoring Well Sounding On May 16, 2002, WGR Southwest, Inc 's (WGR's) John Terayskis and Port of Stockton's Mike Luksic and Brian Kelley sounded and sampled the Port's former UST Site No 3 monitoring wells MW3-1 through MW3-3 Prior to sample collection, each well was gauged, visually check for free product using a disposable bailer, and then purged of a minimum of three well-volumes of water using a vacuum truck and ' dedicated stingers Parameters were checked twice prior to sampling Well gauging data, 11 th qtr ust sA6 d.c 4