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Second Quarter 2005 Groundwater Monitormg Report <br /> Cohn Property,3755 Munford Avenue,Stockton,California <br /> Page 4 <br /> CONCLUSIONS <br /> Laboratory analytical results indicate the site has been impacted by petroleum hydrocarbons <br /> Concentrations of TPHg and BTEX are elevated in groundwater monitoring wells MW-1 through <br /> MW-4, MW-6 through MW-8 and the onsite domestic well TBA was the only oxygenate <br /> detected onsite, all other oxygenates sampled were below laboratory detection limits The <br /> equipment blank sampled contained concentrations of benzene, possibly due to laboratory or <br /> sampling error <br /> Groundwater elevations increased an average of 1 94 feet this quarter compared with the <br /> previous sampling event conducted by ATC <br /> RECOMMENDATIONS <br /> Apex recommends continued quarterly groundwater monitoring The next sampling event will <br /> occur in September 2005 <br /> ADDITIONAL ACTIVITIES PERFORMED AT SITE <br /> • Apex is currently preparing a workplan proposing the installation of an ozone air sparge system <br /> and updated site conceptual model The soil vapor extraction system installation is nearly <br /> complete, and will be operational in mid August 2005 <br /> ATTACHMENTS <br /> Figure 1 Site Vicinity Map <br /> Figure 2 Site Plan Map - <br /> Figure 3 Groundwater Contour Map June 30, 2005 <br /> Figure 4 TPHg in Groundwater Isoconcentration Map June 30, 2005 <br /> Figure 5 Benzene an Groundwater Isoconcentrataon Map June 30, 2005 <br /> Table 1 Well Construction Details <br /> Table 2 Groundwater Elevation Data <br /> Table 3 Groundwater Analytical Data <br /> Table 4 Historical Groundwater Elevation Data <br /> Table 5 Historical Groundwater Analytical Data <br /> Appendix A Apex Standard Operating Procedures <br /> Appendix B Field Data Sheets <br /> Appendix C Laboratory Analytical Report and Chain-of-Custody Form <br /> • <br />