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S E C ® R ARCO 595 May 5, 2004 Page 3 In addition to dispersing survey forms, SECOR conducted a physical search of the area During the site visit, a domestic well (well 7/DW-2) was Identified on the northern portion of the Auto Factory property, and a well (well 8/DW-3) was found in a fenced compound west of the Auto Factory r property Conversations with a Denny Boy Restaurant employee revealed that the well on the Auto Factory property (well 7/DW-2) served both the Auto Factory and the Denny Boy Restaurant Well 8/DW-3 was located in an unmarked fenced compound Details of Its well construction are known, however, the well is most likely an irrigation well As indicated in SJCEHD letter dated October 26, 4 2000, no public water is distributed along the Highway 99 East Frontage Road (SECOR's Site Assessment Report, dated December 11, 2001) Remedial Action Summary Approximately 189 tons of soil generated during the removal of the underground facilities and the trenching for new piping were disposed of at BFI Landfill in Livermore, California in 1999 t In March 2002, four 1,000-pound granular activated carbon (GAC) vessels were installed near the wellhead of DW-1 to treat the groundwater supply to the nearby Welnerschnitzel business A groundwater extraction (GWE) system was activated on April 8, 2002 Extracted groundwater from DW-1 is routed through two cartridge filters, two GAC vessels plumbed in series, and a particulate filter The treated groundwater is routed to the Wemerschnitzel main water supply line at a maximum capacity of 30 gallons per minute (gpm) The GWE system is checked on a weekly basis, and water samples are collected monthly at the influent, midpoint, and effluent sampling ports within the GWE system As of February 2004, approximately 489,513 gallons of water have been treated Groundwater treatment system performance data is included as Table 6 r GEOLOGIC AND HYDROGEOLOGIC SETTINGS Site Geology and Hydrogeology Geologic cross-sections for the site are presented In Figures 3 and 4 and depict the following conditions r • Interbedded layers of sand/silt mixtures and clay/silt mixtures encountered from ground surface to approximately 103 feet bgs h • Interbedded layers range in thickness from approximately 3 to 40 feet • During initial well installation at the site in 2000, first groundwater was generally encountered at approximately 58 feet bgs The groundwater elevations have declined over the last two years an depth to groundwater at the site Is currently 66 to 68 feet bgs ' s • The groundwater aquifer beneath the site appears to be an unconfined aquifer Depth to groundwater measurements are included in Tables 3 and historical gradient table is included as Table 5 HYDROCARBON DISTRIBUTION Hydrocarbons in the Unsaturated Zone Concentrations of TPHg, benzene, and MtBE in soil are illustrated on Figures 3 and 4 Maximum }r't� • adsorbed concentrations are located in the vicinity of the pump Islands and product line The e� maximum adsorbed concentrations were detected beneath the dispensers at approximately 3 to 5 a _1 \ARCO\05951Reports\Site Conceptual Model doc r