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Soil and Groundwater Investigation Re ort ARCO Facility No 6100 Tracy, California Page 4 at approximately 106 5 feet Vapor extraction wells in the vicinity of the boring were again inspected for the presence of water, and again only VW-20 contained water (approximately 1 foot) Soil samples were collected from approximately 26, 50, 71, and 100 feet bgs and at approximately 10-foot intervals from 100 to 200 feet bgs Soils were classified on-site using the Unified Soil Classification System (USCS) Boring logs detailing soil stratigraphy are presented in Appendix A Soil descriptions on the boring logs between discreet sampling depths were derived from soil cuttings recovered as the soil was discharged from the borehole A soil sample from each interval was placed and sealed in a plastic bag to allow the accumulation of volatile organic carbon (VOC) vapors within the airspace in the bags A portable photoionization detector (PID) was used to measure VOC concentrations from each sample in parts per million by volume (ppmv) PID results are shown on the boring log in Appendix A PID results were also used to assist in determining which soil samples should be submitted for chemical analysis A total of twelve soil samples, including the waste composite sample collected from the • drill cuttings were submitted Sequoia Analytical Inc (Sequoia), a California state certified analytical laboratory, for chemical analysis Soil samples were preserved for chemical analysis by sealing the tubes with Teflon TM tape and plastic caps, and stored in a cooler with ice In addition, Delta submitted two samples from the boring (152 and 202 feet bgs) to Sierra Testing Laboratories, Inc of El Dorado Hills, California for permeability testing Soil removed from the borehole during drilling was placed in a soil bin and stored onsite Upon receipt of the laboratory results, Dillard Environmental, Inc will transport the waste soil to a licensed waste disposal facility Installation of Groundwater Monitorin2 Well Delta directed the installation of monitoring well MW-1 on August 29, 2000 The well was constructed using four-inch diameter, Schedule 40 PVC Neat cement was used to backfill the boring from 128 to 200 feet bgs on August 28, 2000 The cement cured for approximately 14 hours and provided a stable surface to construct the well Sand (#60) was used to backfill the boring from 128 to 120 5 feet bgs Bentonite was placed from 118 5 to 120 5 feet bgs as a bottom seal for the well A filter pack of#3 sand was placed in the annular space around the well from 92 to 118 5 feet bgs The well was screened from approximately 10 feet above and 10 feet below first encountered groundwater (95 to 115 feet bgs) at the time of installation Bentonite was placed from 89 to 92 feet bgs to • provide a sanitary seal for the well Neat cement was used to backfill the annular space around the well from the top of the sanitary seal to surface grade Approximately 80