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15 May 2019 <br />AGE Project No. 14-3002 <br />Page 2 of 17 <br />A geophysical survey was performed at the site by Ground Penetrating Radar System, <br />LLC. (GPRS) using Electromagnetic Induction (EMI). The EMI survey was performed to <br />locate subsurface anomalies and buried waste by detecting changes or differences in the <br />electrical conductivity of subsurface materials. The survey area was approximately <br />6.5 acres and included most of the site. The survey did not include the area of the former <br />power plant due to interference that would have been detected from the former <br />aboveground and underground structures in this area. <br /> <br />The EMI survey did not detect or identify any significant changes in electrical conductivity <br />in the subsurface of the site. A few isolated areas of minor conductivity changes were <br />identified, but most were associated with surface structures (reinforced concrete pad and <br />concrete monuments). However, the limited areas identified by the EMI survey were <br />investigated further during field activities. The GPRS Subsurface EMI Investigation <br />Report is included in Appendix C. <br /> <br /> <br />3.0. SOIL PROBE BORINGS <br /> <br />A total of forty-three (43) soil probe borings (B1 through B43) were advanced at the site <br />between 11 and 15 March 2019 to locate and identify buried waste and to investigate if <br />historical use of the property has adversely affected the subsurface of the site. <br /> <br />Initially, twenty-four (24) soil borings were proposed to locate and identify buried waste <br />and investigate the site. Following the EMI survey, ten (10) additional borings were added <br />to the scope of work for a total of thirty-four (34) borings. During the investigation, several <br />borings proposed in the central-western portion of the site were removed based on the <br />findings from borings to the south and east of this area. CVRWQCB staff approved the <br />removal of several borings in this area. However, once waste was encountered, several <br />additional borings were advanced to identify the limits of the waste. Five (5) additional <br />borings were advanced along the eastern property boundary and seven (7) additional <br />borings were advanced in the former power plant area to define the limits of the waste <br />cells encountered in these locations. <br /> <br />Borings B1 through B43 were advanced to total depths ranging between 5 feet and <br />20 feet below surface grade (bsg). The following is a summary of boring depths and <br />locations: <br /> <br />• B1 through B10 and B13 through B17 were advanced to 15 feet bsg in the southern <br />half of the site and along the eastern property boundary to locate buried waste and <br />collect samples for site assessment. <br />• B11 and B12 were advanced to 10 feet bsg in the stormwater retention basin to <br />locate buried waste and collect samples for site assessment (the basin is <br />approximately 4-5 feet deeper than the surrounding area).