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2.0 SITE CHARACTERISTICS <br />2.1 General <br />The Arcady Oil Company disposal site is located on the outskirts of <br />Holt, California in the County of San Joaquin. The site is approximately <br />11 acres in area; the distribution of fuel is suspected to be within a 5 <br />acre area in the northern sector of the site. Drawing 1 shows the location <br />of the site relative to Whiskey and Trapper Sloughs. <br />Since the early 1960's the land has been used as a landfill for <br />drilling muds. The site was opened in 1960 and closed in May, 1984. As <br />part of closure and post closure requirements, Arcady Oil Company <br />implemented a program of waste characterization and hydrogeological <br />investigation. Twelve monitoring wells were installed around the perimeter <br />and downgradient of the site (see Drawing 2). In August 1985 one set of <br />soil and groundwater samples were collected and analyzed for priority <br />pollutant metals and volatile halocarbons by Arcady Oil Company and the <br />results were submitted to RWQCB. Chromium, lead, and barium were detected <br />in the soils at all locations sampled. The drinking water standard for <br />lead was exceeded in water samples taken from two wells. Volatile <br />halogenated organics were not detected. <br />2.2 Geologic Considerations <br />The Sacramento-San Joaquin Delta is part of the Central Valley <br />geomorphic province. The basin is filled with sedimentary deposits. <br />Nonmarine late Tertiary and Quaternary sedimentary deposits in the area <br />range in thickness up to 3000 feet. The rise in the ocean level occurring <br />after the glaciation at the end of the Holocene period (about 10,000 years <br />before the present) caused a more rapid rate of sedimentation leading to <br />development of layers of unconsolidated sand, silty sands, silts and clays <br />2-1 I",