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r Clayton ,N1RONWNTm CO,NSLfLTANT5 Quaternary (recent) San Joaquin Formation alluvium according to the California Department of Conservation, Division of Mines and Geology. According to the USGS Manteca, California, 7-1/2 minute topographic quadrangle map, the elevation of the site is approximately 3 feet above mean sea level. The regional topographic slope trends to the northwe terly parallel with the San Joaquin River. Regional surface drainage would tend to follow the slope. Based on California Division of Oil and Gas maps, the site is not located within an oil or gas field. Based on information from the Water District, the depth to groundwater under the subject site is approximately 30 to 35 feet and g oundwater flow direction is northwesterly. However, the site is over an area that is actively pumped for irrigation water and the groundwater flow direction may vary. No known faults transect the site. In addition, the area is not located within a fault- rupture hazard zone as defined by the 1972, State of California Alquist-Priolo Special Studies Zones Act. However, the site is surrounded by fault zones and could be subject to ground motion during earthquakes associated with these faults. According to the City of Manteca, records indicate that this site is not located within a 100- or 500-year flood zone and is, therefore, not in an area that has a potential for flooding. 4.1 FIELD RESULTS The soil encountered was a fine- to medium-g ed sand from the surface to a depth of approximately 8 feet below grade. At this de th, clayey silt was encountered which continued to the maximum depth of the tree boreholes. Groundwater was not encountered at the maximum depth of 10 feet be ow grade. The PHYremeasured 0 to 1.8 parts per million (ppm) on the soil samples collected from the boreholes (Appendix Q. The low-level readings on the PID are likely interference associated with the high moisture c ntent in the samples, not with YOC vapors. During the drilling and sampling, Clayt n did not detect any fuel-like or chemical-like odors or staining. 4.2 LABORATORY RESULTS The laboratory reported no detection of gasoline benzene, toluene, ethylbenzene, and xylenes (BTEX), or organic Iead in any of the soil samples, at the laboratory detection limits specified in the laboratory reports (Appendix D). A summary of laboratory results are included in Table 1 (Appendix A). 4 4014.00.REP CO FIDENTIAL AND PRIVILEGED