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Report on Additional Site Assessment 7 <br /> 7-Eleven Inc.,Store#19976, 1399 N. Main St.,Manteca, California March 5,2001 <br /> All purge water generated during the monitoring and sampling event was stored in a Department of <br /> Transportation (DOT)-approved 55-gallon drum pending characterization and proper disposal. Waste <br /> documentation will be forwarded if requested. <br /> 4.0 RESULTS <br /> 4.1 Geology and Hydrogeology <br /> The site is located in the middle of the northern San Joaquin Valley. Shallow stratigraphic units in the <br /> vicinity of Manteca are mapped as Quaternary dune sand overlying the Quaternary Modesto.Formation <br /> which consists dominantly of arkosic alluvium (California Division of Mines and Geology, 1991, Geologic <br /> Map of the San Francisco-San Jose Quadrangle, 1:250,00). <br /> Subsurface soils consist of sand and silty sand to approximately 10 feet below grade, underlain by clayey <br /> silt and silt to approximately 25 feet below grade, and fine-to coarse-grained sand, clayey silt and clayey <br /> silty sand to the total depth of investigation. Recent boring logs are included in Appendix A; historical <br /> data are included in the previous reports. <br /> During recent drilling, groundwater was first encountered at 16- 18 feet below grade (equilibrating at <br /> near 18 feet below grade). Groundwater flow in the shallow and deeper parts of the water bearing zone <br /> as mapped from data collected on October 12, 2000,is to the northwest(Figures 3 and 3A). <br /> Sensitive receptor survey results were reported to the SJCPHS in April 1999. Land use in the immediate <br /> site vicinity is generally light commercial. State Department of Water Resources data indicated twelve <br /> water supply wells within 2,000 feet of the subject site, five of which are within 1,000 feet of the site. <br /> According to a telephone conversation between the City of Manteca Engineering Division and IT <br /> Corporation personnel, there are no municipal water supply wells within 1 mile of the site. The nearest <br /> municipal supply well is located at the corner of Northgate Drive and Hoyt Lane, approximately 1.25 <br /> miles west(crossgradient) of the site. <br /> r , <br /> 19976ASA . <br />�F <br />