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to a state certified laboratory and analyzed for volatile organic hydrocarbons by EPA method 8020, <br /> total petroleum hydrocarbons (TPH) by EPA method 8015 modified, and MTBE by EPA method <br /> 8260 <br /> A summary of historic analytical sampling results are provided in Table 1, and copies of the <br /> analytical laboratory reports for this reporting period are contained in Appendix A <br /> Highest dissolved TPH,benzene,and MTBE concentrations recorded during the 2nd quarter of 1998 <br /> were 54,000 micrograms per liter (ug/L), 13,000 ug/L, and 2300 ug/L, respectively The highest <br /> dissdlved TPH, benzene, and MTBE concentration recorded during the 3rd quarter were 28,000 <br /> ug/L,4,500 ug/L, and 2,100 ug/L, respectively All highest dissolved concentrations were obtained <br /> from monitoring well MW-11 All other wells exhibited either very low concentrations or non- <br /> detect for these constituents TPH, Benzene, and MTBE distributions in groundwater during this <br /> reporting period are presented in Figures 2, 6,3, 7, 4 and 8 <br /> Since third quarter 1997, Thrifty has sampled for the requested Oxygenates Di-isopropyl Ether, <br /> Ethanol, Ethyl-tert Butyl Ethyl,Methanol, Tert-Amyl Methyl Ether, Tert-Butanol, and Methyl tert- <br /> Butyl Ether by method 8260 Analytical results are included in Appendix A <br /> Summary and Recommendations <br /> On May 27, and August 26, 1998, quarterly groundwater monitoring was performed in all existing <br /> monitoring wells at Thrifty Oil Co #172 Free-hydrocarbon was not detected in any of the <br /> monitoring wells, but up to 13,000 ug/L dissolved benzene, and 2,300 ug/L MTBE were detected <br /> in monitoring well MW-11 <br /> On September 12, 1997 Thrifty submitted a Corrective Action Plan (CAP) to the San Joaquin <br /> County Environmental Health Division (SJCEHD) <br /> An addendum to the CAP was submitted to the SJCEHD on June 11, 1998 A meeting between <br /> Thrifty Oil Co and the SJCEHD is scheduIed for on November 19, 1998 in Stockton, Ca, in order <br /> to review the CAP and discuss remedial alternatives for this site <br /> All interpretations expressed in this report are based upon review of data collected by EMC Should <br /> you have any questions or require additional information, please contact either of the undersigned <br /> at(562) 921-3581 <br /> Written By Reviewed By <br /> on Fri.A�Inclisen Bryan Van Wagner, RG, CH <br /> Environmental Geologist Hydrogeologist <br /> cc File <br />