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Bridgestone/Firestone,Inc. 400 N. EI Dorado, Stockton, California February 2, 1994 Site Assessment Report— RMI 207201 Page 10 of 12 f Based on information gathered from the San Joaquin County, Flood Control and Water Conservation, Spring 1993, Groundwater Report, the depth to groundwater at the site is estimated at approximately 50- to 55-feet below the surface The Groundwater Report included two maps Lines of Equal Elevation of Water In Wells, and Lines of Equal Depth to Water in Wells, which were constructed from groundwater elevations collected from water wells in the spring of 1993 The 50- to 55-foot depth to groundwater is based on the equal depth and equal elevation Imes as plotted on each of the maps In addition, two F soil borings completed at the site in September 1991 were advanced to 41 5-feet below the surface Soil conditions at this depth were still dry 5.0 QUALITY ASSURANCE All activity undertaken by Ryan-Murphy at this site was performed according to quality assurance guidelines and standard operating procedures. Field screening, sampling, sample preservation, shipping, holding times, and analytical testing procedures and criteria were applied in accordance with EPA reference document SW-846 6 0 FINDINGS Groundwater was not encountered in any of the soil borings completed at the site to date (as deep as 41 5-feet below the surface) Based on the observed extent of vertical contamination (approximately 25-feet below the surface), the medium-dense slit below the contamination, the impermeable surfaces at the site which preclude surface water infiltration, and the established depth to groundwater, it is unlikely that groundwater would be impacted by a release at the site. Field observations and PID readings did not correlate with the analytical results from soil samples collected from three of the five soil borings The PID readings and physical observations gathered during the October 1993 field activity indicate that subsurface hydrocarbon vapors exist in the S13-1, SB-2, and SB-3 boring locations from approximately 13- to 25-feet below the surface Soil samples collected from SB-4 and SB-5 (east of the UST pit) showed no indication of contamination Based on the data collected to date, and a verbal request b Mr Knoll of the SJCEH q Y D, a Soil Remediation Plan will be prepared and submitted to the SJCEHD RYAN-MURPHY, INCORPORATM Dcnver w Envi vunental Construction Management Low Anger