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Final Remediation Plan Page 6 Ranch Market 23569 South Santa Fe Road Riverbank CA February 28 2001 S • On January 3, 2001, SECOR conducted the 151 Quarter monitoring and sampling event using the 10 groundwater monitoring wells and three domestic wells Details related to the distribution of gasoline adsorbed to soil and dissolved in groundwater at the Site are discussed in later sections of this report 2.6 Lithology Based on the description of the soil samples collected from the soil borings, the lithology at the Site consists mainly of sands and silts The lithology generally coarsens downward from sandy silt towards the groundwater surface to silty sand and sand found at depth Figures 4, 5, and 6 show the layout of the two geologic cross-sections through the Site, geologic cross- section A to A', and geologic cross-section B to B', respectively No obvious low permeability, confining Iayer of clay or silty clay was observed in the continuous core samples collected from the soil borings SB-1 or SB-2 Boring logs of the all soil borings drilled at the Site are included in Appendix A 2.7 Hydrogeologic Setting 2.7.1 Groundwater Gradient and Flow Direction Since December 1998, the depth to water in the Site well MW-1 has varied from 25 87 to 27 99 feet bgs (Table 3) The groundwater flows toward the South with a gradient of approximately 0 003 feet per foot (Figure 7) 2.7.2 Sensitive Receptor Survey SECOR performed a field survey and a Department of Water Resources (DWR) records search to identify industrial, municipal, or domestic wells within a 2000-foot radius of the Site Due to the presence of the Stanisluas River south of the site, and the fact that no wells were observed during the field search South of the river in Riverbank, California, the DWR well search was limited to north of the Stanislaus River, in San Joaquin County Well logs were not found at the DWR for the wells on the properties adjacent to the Ranch Market (wells DW-1 through DW-4, Figure 2) or the wells observed at distances greater than 1,700 feet North of Ranch Market (Figure 8) Only three wells were identified during the records review within the 2,000-foot search radius The wells identified are all South and down gradient from Ranch Market one at Jacob Meyers Park, approximately 700 feet away, one West of the Park, approximately 1,000 feet from the Site, and one to the East of the Park and East of Santa Fe Road, approximately 1,500 feet from the Site Table 4 presents a summary of the wells located during the DWR records review and field search A field check to identify sensitive receptors within a 2000-foot radius of the Site was conducted on August 11, 2000 A search was conducted for bodies of water that provide ecological habitat, schools and residential areas, and industrial, municipal, or domestic wells Sensitive receptors identified during the field search include the following • The Stanislaus River located approximately 1,200 feet to the South of the Site File FRP-report doe SECOR International incorporated