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3-0 INVESTIGATIVE RESULTS <br /> 3.1 Groundwater Monitoring_Results <br /> The shallowest groundwater in this portion of the city of Lodi is reported to occur under unconfined <br /> conditions(Environmental Forensic Investigations, 2002) On April 7, 2004 the highest point measured <br /> from the monitoring wells was 7 50 feet (msl)and occurred in monitoring well PT-MW-4 The lowest <br /> elevation of the groundwater surface measured from the monitoring wells was 6 76 feet (msl)and occurred <br /> in monitoring well PT-MW-6 A summary hydrograph for monitoring well PT-MW-1 is presented as <br /> Figure 5 <br /> The average depth to groundwater surface m the sic monitoring wells was approximately 46 feet below <br /> ground surface(bgs) The groundwater surface has risen about 0 4 foot since the last monitoring event <br /> (November, 2003) <br />' Electrical conductivity concentrations in the monitoring well water samples were determined to range from <br /> 125 to 255 pmhos/cm This low-conductivity value is typical of reported electrical conductivity values of <br /> local groundwaters found near the Mokelumne River(Figure 2) Concentrations of electrical conductivity <br /> in waters from the Mokelumne River are reported to range from 200 to 350 gmhos/cm because the relative <br /> short distance from watershed source in the Sierra Nevada and Quaternary alluvial terrain the waters <br /> traverse(Page, 1986) <br /> Temperature and pH concentrations in the monitoring well waters is typical of I'groundwater encountered <br /> in the Lodi area(Environmental Forensics Inc, 2002) <br /> 3.2 Groundwater Analytical Results <br /> Groundwater analytical results indicate maximum concentrations of petroleum hydrocarbons and related <br /> gasoline fuel constituents present in the monitoring wells for this quarter monitoring event are as follow <br /> I Constituent Concentration Well <br /> benzene 230 gg/L PT-MW-1 <br /> toluene 580 jig/L. PT-MW-1 <br /> ethylbenzene 550 gg/L PT-MW i <br /> xylene 2100 gg/L PT-MW-1 <br /> TPH Gasoline 13,000 gg/L PT-MW-1 <br /> MTBE 3 3 µg/L PT-MW-3 <br /> M ND <br /> ET ND <br /> TBA 6 3 µIL PT-MW-1 <br /> DLPE ND <br /> TAME ND <br /> 1,2-DCA 12 µg/L PT-MW-3 <br /> 1,2-EDB 5 7 µg/L PT-MW-3 <br /> • <br /> M—\DTnvuonnimmiTamwTexaw\Repoms 033104QMRwN 4 <br />