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1444 MARIPOSA ROAD <br /> WKA No 2938 05 <br /> August 26, 1999 <br /> Page 4 <br /> as gasoline (6,800 mg/kg),benzene(95 mg/kg), toluene (550 mg/kg), and total xylenes (670 <br /> mg/kg) Because further excavation would require sloping of the side walls, the decision was <br /> made to drill exploratory soil borings to further evaluate the vertical and lateral extent of <br /> hydrocarbon contamination <br /> March 1993 <br /> Four soil borings (B 1 through B4) were drilled between March 29-31, 1993 at the site Boring <br /> B 1 was constructed approximately five feet easterly of the excavation and extended to a depth of <br /> 86 5 feet Drilling was discontinued when ground water was encountered in the boring at a depth <br /> of approximately 85 feet The location of each soil boring is presented in Appendix B, exhibit 2 <br /> Geologic cross-sections of subsurface soil in the vicinity of the former UST excavation are <br /> included in Appendix B, exhibits 3 and 4 <br /> Soil borings B2 and B3 were drilled at approximate 30° angles from vertical beneath the location <br /> of former underground storage tanks to vertical depths of 71 and 81 feet below site grade The <br /> soils in these borings consisted primarily of silty clays and clayey silts, two thin sand layers were <br /> observed at depths of approximately 49 to 53 feet and 63 to 68 feet Boring B4 was constructed <br /> approximately ten feet westerly of the excavation to a depth of 49 5 feet A slight petroleum <br /> odor was noted in each of the four soil borings Analytical results of selected soil samples from <br /> the four soil borings revealed relatively low concentrations of petroleum constituents at a depth <br /> of 75 feet below surface grade A summary of analytical results of soil samples obtained from <br /> borings B l through B4 are included in Appendix A, exhibit 2 Copies of soil boring logs are <br /> included in Appendix C <br /> October 1993 <br /> Three soil borings (MW1, MW2 and MW3) were drilled with a truck-mounted Mobile B-61 drill <br /> rig equipped with 10-inch diameter hollow-stem augers Soil samples were collected from each <br /> boring at five-foot maximum intervals Selected samples were placed in an ice chest containing <br /> iWALLACE KUHL <br /> Recycled paper Er ASSOCIATES INC <br />