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Conclusions and Recommendations <br /> Five borings were advanced in and around existing wells MW-3 and MW-9 The soil and <br /> sample data show that low levels of degraded TPHG occurred in capillary fringe soil <br /> samples Only one intermediate depth soil sample revealed one very low occurrence of <br /> Xylene observed at PB-14 at 22 feet Deeper underlying confining strata soil samples at <br /> PB-12 and PB-13 at 26 feet showed that contaminants were not detected Groundwater <br /> samples showed variable concentrations of TPHG and BTEX with the highest <br /> concentrations at PB-11 and 13 MTBE and oxygenates were not detected in any soil or <br /> zn <br /> groundwater sample <br /> Discussions with PHS EHD of the historic assessment data and the boring data presented <br /> in this report have resulted in modifying the workplan approach to ascertain whether <br /> additional sources of contaminants are present Wlule the data do not indicate another <br /> contaminant source near MW-9, the data do suggest that residual contarrunants may exist m <br /> the former tank pit area <br /> Wright recommends the following additional work tasks <br /> ® Conduct a surface geophysical survey with ground penetration radar to search for <br /> anomalous indications of possible contaminant sources If any are identified, then a <br /> subsurface search would be performed at the indicated area <br /> ® Perform utility location with the City of Tracy and Westside irrigation line owner to <br /> locate lines so that borings can be advanced to collect more lateral and vertical <br /> assessment data near MW-9 <br /> Inspect the welding building for indications of potential contaminant sources (such as <br /> oil/water separators and sand traps) <br /> o Advance exploratory borings through the former tank pit and east and south of MW-9 <br /> for additional vertical and lateral subsurface assessment in those areas <br /> Pending approval of the recommended work tasks by PHS EHD, the work will proceed <br /> The results of this work will be used to select appropriate cleanup approaches as needed for <br /> groundwater plume reduction Quarterly monitoring is scheduled to continue for the site <br /> Page 5 <br />