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Section 3 <br /> 1Phase II Site Investigation Program <br /> 1 <br /> 3.1 Technical Approach <br /> 1 <br /> Based on the results of the preliminary site assessment, Tetra Tech conducted a Phase II site <br />' investigation around the UST The primary purpose of this site assessment was to collect <br /> samples around the UST to evaluate the extent of identified petroleum hydrocarbons <br />' Tetra Tech initially submitted a technical work plan, dated September 9, 1994, outlining a <br /> 1 proposed soil boring program around former Tank #2 Based on a regulatory review letter <br /> dated January 17, 1995, investigation was required only at Tank #3 An amended workplan <br /> was prepared and submitted on January 9, 1995 <br /> 1 <br /> The amended workplan outlined an investigation that included soil borings along the tank piping <br /> NField inspection of the piping (as inspected through access manholes) revealed that the piping <br /> was encased in secondary concrete containment with no obvious structural defects Following <br />' inspection, SJCPHS official Steve Sasson waived the requirement to investigate the soil along the <br /> pipeline <br />' Formal regulatory approval was issued by SJCPHS on January 30, 1995 to proceed with the <br /> proposed scope of work Drilling permits were also filed with SJCPHS prior to field <br />' activities Copies of all regulatory correspondence and permits are presented in Appendix B <br /> 3.2 Boring Locations <br />' The investigation consisted of drilling eight soil borings at the location of the UST All <br /> borings were placed around the UST to delineate the lateral extent of petroleum-contaminated <br /> soil Borings were drilled to depths ranging from 15 to 25 feet bgs All boring locations are <br />' presented in Figure 4 <br /> 1 <br /> TETRA TECH Stockton Developmental Center,Phase n Site Investigation Report Page 7 <br />