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<br /> June 30, 1992z���
<br /> Unocal Station No. 6981, Stockton, California
<br /> were detected in water samples from wells MW-1 through MW-5 after installation in
<br /> January 1990. Coliform bacteria were detected in samples from wells MW-2, MW-3, and
<br /> MW-5 Ground water has not been present in wells MW-1 through MW-5 since October
<br /> 1990 The direction of groundwater flow in February 1990 was towards the northeast with
<br /> a gradient of 0 005 to 0 0063
<br /> CURRENT WORK
<br /> oil Borings and Well Installation
<br /> A geologist from RESNA was at the site between March 2 through 5, 1992, to observe
<br /> Woodward Drilling of Rio Vista, California, drill five 8- and 10-inch-diameter soil bonngs
<br /> (B-6 through B-10) A RESNA geologist returned to the site on March 9 and 10, 1992, to
<br /> observe Western Strata Exploration of West Sacramento, California, drill three 10-inch-
<br /> diameter soil borings (B-11, B-12, and B-13) The boring locations are shown on Plate 2
<br /> Our field methods are summarized in an attachment to this report
<br /> Soil samples were collected during drilling at approximately 5-foot intervals, identified using
<br /> visual and manual methods, and classified according to the Unified Soil Classification
<br /> System (Plate 3) Descriptions of materials encountered are presented in the Logs of
<br /> Borings (Plates 4 through 21) The materials consisted predominately of silt, with some
<br /> layers of clay, silty sand, and silty gravel Ground water was encountered in borings B-8 and
<br /> B-10 at approximately 55 feet below surface grade and at approximately 61 feet below
<br /> surface grade in boring B-7
<br /> Boring B-9 was backfilled to ground surface with a neat cement slurry Ground-water
<br /> monitoring wells MW-6, MW-7, and MW-8 were constructed in borings B-7, B-8, and B-10,
<br /> respectively Vapor-extraction wells VW-1, VW-2, VW-3, and VW-4 were constructed in
<br /> borings B-6, B-11, B-12, and B-13, respectively Monitoring well and vapor-extraction well
<br /> construction is shown on the Logs of Borings
<br /> Cuttings generated during drilling were placed in covered metal bins, and left at the site
<br /> pending disposal. At Unocal's request, Dillard Trucking of Byron, California, disposed of
<br /> the cuttings at BFI Landfill in Livermore, California, and the Laidlaw facility in
<br /> Buttonwillow, California, copies of the manifests are attached
<br /> On March 24, 1992, Tom O Morrow, a state-licensed land surveyor, surveyed the locations
<br /> and elevations of monitoring wells MW-6, MW-7, MW-8, and the locations of vapor-
<br /> extraction wells VW-1, VW-2, VW-3, and VW-4
<br /> 0305psil
<br /> 38032-7 2
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