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RPCEIVED <br /> ASSESSMENT REPORTNV1QNNiA . HEALTH <br /> Submarine PERMIT/SERVICES <br /> Harding Way <br /> Stockton, CA <br /> ' 1. 0 INTRODUCTION <br /> Geological Audit Services, Inc. (GeoAudit) has been retained by Ms. <br /> Deborah Reade, on behalf of the Campodonico and Tiscornia Trusts, <br /> to complete the assessment of hydrocarbon contamination at the site <br /> of a former Exxon gasoline station at the intersection of Harding <br /> ' Way and Madison Street in Stockton, California (Figure 1) . The <br /> assessment was performed in accordance with GeoAudit's "Proposal <br /> for Site Assessment" dated June 9 , 1993 and Interim Workplan dated <br /> June 25, 1993 and amended July 29, 1993 . San Joaquin County Public <br /> Health Services - Environmental Health Division (PHS/EHD) is the <br /> lead agency for enforcement of underground storage tanks laws at <br /> the referenced - site. This report contains the results of this <br /> ' assessment and the data obtained from quarterly groundwater <br /> monitoring. <br /> M2 .0 BACKGROUND <br /> ' 2. 1 Previous Investigations <br /> It is our understanding that investigation of soil and possible <br /> groundwater contamination has been ongoing at this site since 1990. <br /> ' Four groundwater monitoring wells and numerous borings have been <br /> drilled, and trenches or excavations have been dug in several parts <br /> of the site. Contaminated soil was encountered in several of the <br /> ' excavations and borings, and was removed from the excavations and <br /> stockpiled on site. No contamination was detected in soil samples <br /> from three of the four monitoring wells, or in the five sets of <br /> ' groundwater samples that have been collected. Based on these <br /> results, the previous consultant recommended that the site be <br /> closed without further assessment or remediation. <br /> However, PHS/EHD requested further assessment of soil contamination <br /> in the vicinity of monitoring well MW-4 on the northern portion of <br /> the property (Figure 2) . Low concentrations of xylene, <br /> ethylbenzene, and toluene had been detected in soil samples at <br /> depths of 21, 31, and 36 feet in that well. In addition, PHS/EHD <br /> requested that MW-3 be destroyed and replaced by a new well, due to <br /> a poor completion job that resulted in unreliable water level data <br /> ' and prevented collection of groundwater samples. The requested work <br /> was performed in August and September 1993 and is described in the <br /> following sections. <br /> ', 1 <br />