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3.0 PHYSICAL SETTING The site is located in Township 3 North, Range 6 East, Section 4, of the United States Geological Survey (USGS) 7.5-Minute Series, Lodi North, California Quadrangle Topographic map, 1967 (photorevised 1980). According to the map,the elevation of the Site is approximately 37 feet above mean sea level. The Site is located approximately one-quarter mile south of West Turner Road on an unnamed access road and is adjacent to and west of the South Main Canal. No on-site surface water bodies were illustrated on the topographic map, and no surface water bodies were observed on the Site at the time of the ATC site visit. A "Radio Tower" building is depicted on the topographic map. A copy of the topographic map is included in Figure 1. The Site is located in the Sacramento Valley, a long valley filled with Cretaceous, Tertiary, and Quaternary marine and continental sediments. The Site is situated on the flood plain of the 4" Mokelumne River. Sediments mapped in the region of the Site are Quaternary alluvial deposits of the Modesto Formation(Jennings, 1977). L.. The Soil Survey of San Joaquin County, by the United States Soil Conservation Service, 1992, classifies the soil underlying the Site as the Tokay fine sandy loam with 0 to 2 percent slopes. According to the Soil Survey, this soil is made up of very deep, well-drained loam, on low fan LW terraces. It formed from alluvium derived from granitic rock sources. Soils consist of sandy and fine sandy loam from surface to at least 60 inches below ground surface (bgs). Permeability is moderately rapid and available water capacity is high. Runoff is slow and the hazard of erosion is slight. The depth to groundwater at the Site has been mapped at a depth of about 40 feet below ground surface based on the Lines of Equal Depth of Water Wells, Fall, 1992 Map by the San Joaquin County Flood Control and Water Conservation District. Based on the groundwater elevation L contours, groundwater regionally flows in a northwesterly direction. Surface topography in the site vicinity slopes very gently to the west-southwest. Actual local groundwater flow directions can be • influenced by other factors such as the presence of underground structures, variations in subsoil conditions, and potential man-made influences (i.e., production wells), none of which were considered for this assessment. Four quarters of groundwater monitoring on the site by ATC found that groundwater generally flowed to the southwest. L. 4.0 NO FURTHER ACTION CRITERIA ti.. The Regional Board issued a document entitled "Recommendations For Preliminary Investigation And Evaluation Of Underground Tarek Site, No Further Action Request," dated March 1, 1994 (Draft Revision October 1996). A copy of this document is presented in Appendix A. It describes �- the criteria by which the Regional Board addresses requests for no fiu'ther action on LUST sites. Based on the history of the AT&T site, ATC believes that it falls under the category of"criteria for Iow risk ground water designation" sites. The four criteria for closure of low risk sites are listed below, with comments addressing each concern: ATC Associates Inc. 3 Project No.53.75126.6001