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February <br /> Bridgestone/Firestone, Inc, 400 N. El Dorado, Stockton, California <br /> February 2, 1994 Site Assessment Report —RMI 207201 Page 3 of 12 <br /> Based on these laboratory findings, Ryan-Murphy returned to the site on September 10, <br /> 1991, and installed two soil borings adjacent to the north and south walls of the pit <br /> which formerly contained tanks 4 and 5 Laboratory analyses of the soil boring samples <br /> were primarily nondetect The low concentrations of gasoline and diesel observed were <br /> well below state action levels <br /> The results of the soil boring samples indicated that the volume of impacted soil was <br /> ' relatively small, therefore, overexcavation was performed on November 12, 1991, in an <br /> attempt to remove the impacted soil Overexcavation was limited due to structural <br /> restrictions and the property boundaries (the east wall was not overexcavated) <br /> ' Verification soil samples collected following the overexcavation contained petroleum <br /> hydrocarbon concentrations exceeding applicable California action levels <br /> ' Analytical results from the April 25, 1991, removal samples (east wall only), the <br /> September 10, 1991, drilling samples, and the November 12, 1991 , overexcavation <br /> samples are included in Appendix 8.7 <br /> 30 SUBSURFACE INVESTIGATION <br /> ' 3.1 Boring Location <br /> On October 13 and 14, 1993, Ryan-Murphy and its drilling contractor, Spectrum <br /> Exploration, Inc , of Stockton, California, installed five soil borings at various <br /> locations on the subject property (three were located outside the building and two <br /> ' were located inside) Due to the presence of contamination (based on field <br /> screening and observations) boring location SB-4 was selected in lieu of one of the <br /> original boring locations proposed in the work plan This modification was <br />' implemented to define the horizontal limits of contamination within the property <br /> boundaries, and to minimize collection of replicate data One soil boring (SB-3) was <br /> completed as a vapor extraction well, and one soil boring (SB-5) was completed <br /> as an observation well for potential use in a vapor extraction system Soil boring <br /> locations are illustrated on the Soil Boring Location Diagram in Appendix 8 3 <br />' Mr Knoll (SJCEHD) was at the site periodically during the drilling and sampling <br /> activities and was provided with PID readings and other field data <br /> 1 <br />' RYAN-MURPHY, INCORPORATED � <br /> Enwhnmental C°ndniciiion Minagement Lai Angelis <br />