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Ms Mary Meays Page 3 <br /> April 14, 1991 g <br /> ' The laboratory findings indicate a slight increase in the concentration of <br /> TPH as gasoline and related petroleum compounds at MW-5 However, <br /> TPH as gasoline concentrations are below those encountered during the <br /> Second Quarter 1991 monitoring These trends suggest that gasoline <br /> continues to seep from contaminated soils into the groundwater in that <br /> area The gasoline and petroleum compounds have not migrated to the <br /> ' other wells, however <br /> Wells MW-1, MW-2, and MW-3 showed no detectable quantities of gasoline <br /> and petroleum compounds The absence of gasoline and related <br /> ' compounds in these wells is consistent with the results from previous <br /> quarterly investigations <br /> ' MW-4 also had no detectable quantities of gasoline and petroleum <br /> compounds MW-4 has shown a continued decrease in gasoline and BTEX <br /> compounds throughout the monitoring program, the absence of these <br /> ' compounds in this investigation appears to mark the culmination of this <br /> trend defined during previous quarterly monitoring activities The highest <br /> concentration of gasoline observed in MW-4 was only 2 1 mg/l during the <br /> second quarter of 1991 Thus, it is probable that MW-4 was situated on the <br /> margin of the area affected by gasoline from the UST <br /> The presence of EDB was not detected in any of the wells, nor has it been <br /> detected in previous quarters <br />' Analytical problems at the laboratory required that additional ground water <br /> samples be obtained on April S, 1992 for organic lead analysis The results <br /> indicate that no organic lead was detected These results for organic lead <br /> are consistent with those of previous quarters <br /> No total lead was detected in the samples which were analyzed The <br /> laboratory utilized EPA Method 6010 and reported a detection limit of 0 1 <br /> mg/L This method and detection limit are different from those utilized in <br /> previous quarterly ground water monitoring activities (EPA Method 7421 <br /> and a detection limit of 0 003 mg/L) All steps will be taken in future <br /> ground water monitoring activities to ensure that laboratory procedures <br /> and detection limits are identical to those of the previous quarters <br /> Additionally, ERM-West will utilize the services of Sequoia Analytical, the <br />' original laboratory on thus project <br /> 1 <br />