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Paq• 2 <br /> GEOLOGICAL AND HYDROGEOLOGICAL OVERVIEW <br /> According to information contained within the September, <br /> 1991 WaterWork assessment , the Reeve' s site is located on <br /> level terrain underlain by flood plain deposits of <br /> Pleistocene and Holocene age that are composed of sediments <br /> similar to , and probably conformable on, underlying <br /> deposits of alluvium and Tulare formation. The flood plain <br /> deposits are light to dark-brown and grey clay, silty sand, <br /> and organic materials with locally high concentrations of <br /> salt and alkali . Stream channel deposits of sand and <br /> gravel are also included. <br /> Groundwater within the shallow water bearing zone occurs <br /> less than ten feet below grade at the site as well as over <br /> most of the Tracy area General groundwater gradient is to <br /> the north. The flood plain deposits of the shallow water <br /> bearing zone have well developed soil profiles and, <br /> consequently, exhibit poor permeability. The base of the <br /> shallow zone is poorly defined and probably is from five to <br /> twenty feet below ground surface <br /> • QUARTERLY COMPLIANCE MONITORING_ OF _THE .OW-SITE WELLS <br /> Sampling of the three on-site, 4-inch inside-diameter <br /> groundwater monitoring wells (MW-1 , MW-2 , and MW-3) was <br /> performed on March 31 , 1995 with the approval of Mr . <br /> Michael Infurna of San Joaquin County Department of Public <br /> Health Services , Environmental Health Division (PHS/EHD) . <br /> Depth to water and total depth of each of the wells were <br /> measured using an electric tape and the volume of water <br /> within each well casing was computed. Each well was then <br /> purged using a BK Hand Pump until the groundwater was free <br /> of significant sand, silt , and/or other grit , and <br /> temperature , pH, and electrical conductivity readings <br /> stabilized In this case, over three well volumes of water <br /> were removed from -each well . Measurements acquired <br /> attendant to sampling appear on the well monitoring forms <br /> enclosed in Appendix A. <br /> Subsequent to the purging of each well , a groundwater <br /> sample was collected from the BK Pump discharge line (a <br /> clean polyethylene tube) . Each sample was introduced into <br /> one-liter amber glass sample bottles and Volatile Organic <br /> Analysis (VOA) vials Each sample container was promptly <br /> • fitted with a teflon-lined screw cap , labeled, placed on <br /> ice, and transported under chain of custody to Priority <br /> Environmental Labs of Milpitas Analyses of samples <br />