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Ms Mary Meays Page 4 July 14, 1991 iEDB was not detected in any of the wells, nor had it been detected in previous quarters No organic lead was detected in any of the groundwater samples that were analyzed These results for organic lead are consistent with those of previous quarters Total lead was detected in the samples that were analyzed, but at levels below its Maximum Contaminant Level (MCL) in drinking water The data were obtained from unfiltered and HNO3-preserved groundwater samples that had resided at the laboratory for 15 days before extraction and analysis It is highly probable that the results reflect lead from dissolved sediment in the unfiltered sample Subsequent monitoring activities will be conducted on filtered water samples to minimize the effect of any dissolved sediment Former Tgnk Eii1p, #2 At Former Tank Site #2, groundwater level contours (Figure 2) indicate a groundwater gradient that is oriented towards the south-southeast This pattern differs slightly from that which was observed during the First Quarter 1992 monitoring activities During 1991 monitoring activities, groundwater flow directions were oriented in directions ranging between southwest and southeast The variability in flow direction is probably due to the influence of tide-induced water level changes in the adjacent Stockton deep water channel Tidal data for the Stockton area is provided in Table 4 The groundwater level at MW-2A was 0 12 feet lower than was previously measured In contrast, groundwater levels in the surrounding wells were between 0 89 and 186 feet higher than previously measured This contrast provides further evidence that the groundwater in MW-2A is perched The laboratory data (Table 3) indicate that MW-1A continues to have the highest measured concentrations of TPH-G and related petroleum compounds The concentration of TPH-G increased from the previous measurements Furthermore, benzene and xylenes concentrations increased, while toluene and ethylbenzenes concentrations decreased from the previous analysis The fact that MW-1A has the highest observed concentrations at Tank Site #2 may be attributed to the possibility that tidal fluctuations have spread these constituents from the UST northward However, no groundwater elevation data have been obtained to show a northern groundwater gradient at any time Further monitoring may provide more information about the gasoline and related petroleum constituents at MW-1A TPH-D measured in groundwater at MW-1A was similar to that which was previously observed in this well