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• 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 /> RECENT ENVIRONMENTAL COMPLIANCE ACTIVITIES <br />. In accordance with recommendations made in its September , <br /> 1991 report , WaterWork installed three , 4-inch diameter <br /> groundwater monitoring wells (designated MW-1 , MW-2 , and <br /> MW-3 ) and a series of soil borings at the locations shown <br /> on Figure 2 The monitoring wells have been developed and <br /> sampled most recently by EPM Technologies , Inc . on <br /> August 16-18 , 1993 EPM has also prepared and submitted a <br /> workplan for further characterization of the extent of soil <br /> and shallow groundwater contamination to PHS/EHD Copies <br /> of this workplan have been submitted to the City of Tracy <br /> and the Central Valley Regional Water Quality Control Board <br /> (RWQCB) <br /> WELL SAMPLING METHODOLOGY USED BY EPM <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 August 16 and August 18 , 1993 with the <br /> approval of Mr Michael Infurna of San Joaquin County <br /> Public Health Services , Environmental Health Division <br /> ( PHS/EHD) <br /> Depth to water and total well depth in each of the wells <br /> were measured using an electric tape and the volume of <br /> water within each well casing was computed Each well was <br /> then purged using a clean, disposable , polyethylene bailer <br /> or a submersible three-stage electric pump until the <br /> Page 2 <br />