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Q, <br /> aLswtmr Grier WanCarkm Report <br /> 5391 F Street,Banta.California <br /> GROUNDWATER MONITORING <br /> Groundwater <br /> On July 22, 1991,Aegis personnel collected measurements of the depth to groundwater <br /> in wells MW-1 through MW-6. Over the past 3 months, since July 22, 1991, groundwater <br /> levels have fallen in all wells (Table 1, Figure 4) an average of approximately 0.07-feet. <br /> Based on depth-to-groundwater measurements, the groundwater flow direction is <br /> estimated to be to the east (Figure 3) at an average gradient of approximately 0.002 ft/ft. <br /> Figure 3 is a potentiometric surface map of the shallow water-bearing zone. <br /> Previous groundwater levels are summarized in Table 1. All depth-to-groundwater <br /> measurements were made from the referenced wellhead elevations, measured to the <br /> nearest 0.01 foot, and conducted according to the Aegis standard operating procedures <br /> (SOP) included in Attachment 1. Wellhead elevations, surveyed by previous consultants <br /> or their agents, are referenced to mean sea level. <br /> Water Sampling and Analysis <br /> On July 22, 1991, Aegis personnel collected groundwater samples from monitoring wells <br /> MW-1 through MW-6. The samples were collected according to the Aegis SOP included <br /> in Attachment 1, and delivered under chain-of-custody to Coast-to-Coast Analytical <br /> Services of San Luis Obispo, California, a state-certified analytical laboratory. The <br /> samples were analyzed for concentrations of: a)total purgeable petroleum hydrocarbons <br /> (TPH), as gasoline, diesel#2,jet fuel, kerosene,Stoddard solvent, and mineral spirits, by <br /> F CAL DHS (TPH Draft) Method; and b) benzene, toluene, ethylbenzene, total xylenes <br /> } (BTBX), 1,2-dichloroethane (EDC), and ethylene dibromide (EDB), by EPA Method <br /> i 8240/8260 (GC/MS). The analytical results_ are summarized in Table.2. Analysis for <br /> diesel was initiated for all the wells with samples collected on February 1, 1991. <br /> Subsequent analysis for diesel, in May 1991, only included samples from MW-1, MW-3, <br /> and MW-6. Analysis of samples collected on July.22; 1991, included testing all wells for <br /> diesel. The analysis indicated concentrations of diesel in samples from MW-1, MW-2, <br /> MW-3, MW-4, and MW-6. The analytical reports and chain-of-custody form are included <br /> in Attachment 2. A summary of the analytical results is presented in Table 2. Figure 6 <br /> is a distribution map of concentrations of benzene and TPH, as gasoline, in groundwater. <br /> '2" <br /> 90-099B.FPT - - - - <br />