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et ti <br /> J <br /> Q_""Grow d"Aw Morftwhi p Report <br /> 14900 West Frorrtage Road Manteca Csllfomla <br /> underground fuel storage tanks Delta installed four more monitoring wells, MW-5 through <br /> MW-8, in November and December 1989 Aegis began a program of monthly monitoring <br /> and quarterly sampling of the wells in January 1991. In November 1991, Aegis <br /> supervised drilling and completion of groundwater monitoring well MW-9 (Figure 2) The <br /> previous consultants' groundwater data, along with Aegis' data, are included in Table 1. <br /> GROUNDWATER MONITORING <br /> On January 21, 1993, Aegis personnel collected measurements of depths to groundwater <br /> in wells MW-1 through MW-9. Since October 1992, groundwater levels fell in wells MW-1, <br /> MW-4, MW-6, MW-7, and MW-9 (Figure 3) an average of approximately 0 078-feet, <br /> ranging from 0 01 to 0.14-feet (Table 1). Groundwater levels rose in wells MW-2, MW-3, <br /> MW-5, and MW-8 an average of approximately 0 21-feet, ranging from 0 06 to 0.32 feet <br /> Figure 4 is a potentiometnc surface map of the shallow water-bearing zone on January <br /> 21, 1993 On the basis of the January 21, 1993, measurements, groundwater flow <br /> direction is estimated to be generally to the southeast, at a gradient of approximately <br /> 0.0037 ft/ft <br /> Groundwater measurements are summarized in Table 1 All groundwater elevation <br /> measurements were made according to the Aegis standard operating procedures (SOP) <br /> . included in Attachment 1. <br /> WATER SAMPLING AND ANALYSIS <br /> On January 21, 1993, Aegis personnel collected groundwater samples from wells MW-1 <br /> through MW-9. The samples were collected according to the Aegis SOP included in <br /> Attachment 1, and submitted under chain-of-custody to NET Pacific, Inc , of Santa Rosa, <br /> California, a state-certified analytical laboratory The samples were analyzed for <br /> concentrations of: <br /> • totalEPA Methods etroleum hydrocarbons (TPH), as gasoline, by GC-FID/EPA I <br /> 5030/8015; and, <br /> • benzene, toluene, ethylbenzene, and total xylenes by EPA Method 8020 <br /> The analytical results are summarized in Table 2 The laboratory analytical reports and <br /> chain-of-custody form are included in Attachment 2. Figure 5 is a distribution map of <br /> TPH, as gasoline, and benzene in groundwater based on the data summarized in Table 2 <br /> 90-097F-QMR -2- <br />