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rn Mr Kyle Christie April 14, 1995 Page 2 The groundwater extraction system (GWES) at this site consists of one groundwater extraction well (well R) and a separator tank Groundwater is discharged directly to the City of Stockton sanitary sewer under a wastewater discharge permit The GWES is sampled on a monthly basis to ensure compliance with discharge requirements A soil vapor extraction/air sparge system (SVE/AS system) has been installed at the site and operation will begin in the first quarter of 1995 The SVE/AS system incorporates all of the soil vapor extraction, air sparge, and dual completion wells on the site In addition, well E-6 is connected to the system for use as a soil vapor extraction well. The SVE/AS system is operated under an Authority to Construct permit issued by the San Joaquin Valley Unified Air Pollution Control District Data generated during previous investigations indicated that hydrocarbon affected soil and groundwater has been defined at this site to the northwest, northeast, east and southeast. Hydrocarbons identified in the groundwater on the north side of the site may be co-mingled with hydrocarbon affected groundwater from the Chevron facility located across Benjamin Holt Drive to the north The County is requiring off-site investigation to the south of southwest of the site Geology and Hydrogeology The site is located in the Northwestern portion of the City of Stockton. The site is underlain by alluvial sediments of the Riverbank Formation which is a floodplain deposit of clay interbedded with discontinuous sand lenses. The topography is generally flat. The groundwater in this area occurs at depths of 10 to 18 feet below ground surface (bgs). Most drinking water wells in the area draw water from the more continuous interbedded sands and clays of the Laguna Formation at depths of greater than 150 feet. During drilling,soil samples were collected for lithologic identification and possible laboratory analysis. The lithology was recorded on borehole logs. A copy of the borehole logs is included with this report as Appendix E. The lithology encountered during the installation of wells MW-3 through MW-5 is consistent with soil encountered during previous investigations (interbedded clay, silt and sand). Figure 3 presents the surface representation of geologic cross sections A-A' (Figure 4) and B-B' (Figure 5). Summary of Work BC personnel supervised the installation of three off-site groundwater monitoring wells (MW-3 through MW-5) The well tnstallatton was conducted on December 21 and 22, 1994 Turner Explorations of Rancho Cordova, California, performed the drilling Well installation was conducted m accordance with BC's December 6, 1994 work plan. The wells were developed and sampled on January 5, 1995 The wells were surveyed for elevation and horizontal location by Psomas and Associates of Sacramento on February 24, 1995 The well • Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 1952\REPORTS\WELLNSTL.RPr