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QUARTERLY GROUNDWATER MONITORING REPORT <br /> 1309 Ease Yosemite Avenue M",,, Celiforras <br /> ' GROUNDWATER MONITORING <br /> 41 Groundwater <br /> ' Aegis personnel collected measurements of the depths to groundwater in wells <br /> MW-113, MW-2, MW-3, MW-4, and MW-5 Over the past 6 months, since <br /> ' August 30, 1991, groundwater levels have risen in all wells (Figure 3) an average of <br /> approximately 1 66 feet (Table 1) On the basis of the January 17, 1992, <br /> measurements, groundwater is estimated to flow to the northwest (Figure 4) at an <br /> ' average gradient of approximately 0 0016 ft/ft For August 30, 1991, the flow <br /> direction was estimated to be to the west-northwest <br /> ' Previous groundwater levels are summarized in Table 1 All groundwater elevation <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 <br /> 1 procedures (SOP) included as Appendix A Figure 4 and Figure 5 are potentiometric <br /> surface maps of the shallow water-bearing zone on October 21, 1991, and <br /> January 17, 1992, respectively <br /> 4 2 Water Sarrigling and Analysis <br /> On October 21 , 1991, and January 17, 1992, Aegis personnel collected groundwater <br /> samples from the five groundwater monitoring wells at the project site The samples <br /> were collected according to the Aegis SOP in Appendix A, and delivered under <br /> ' chain-of-custody to NET Pacific, Inc , of Santa Rosa, California, a state-certified <br /> laboratory, for chemical analyses <br /> ' The samples were analyzed for concentrations of- <br /> • total petroleum hydrocarbons (TPH), as gasoline, by EPA Method 5030, <br /> ' and, <br /> ' • benzene, toluene, ethylbenzene, and total xylenes by EPA Method 8020 <br /> Groundwater analytical results obtained to date, including data reported by previous <br /> ' consultants, are summarized in Table 2 Concentrations of TPH, as gasoline, and <br /> benzene reported for samples collected on October 21, 1991 , and January 17, 1992, <br /> are also shown on Figure 6 and Figure 7 respectively Copies of the laboratory <br /> ' analytical reports and chain-of-custody forms are included in Appendix B <br /> ' 90-ODBG RPT 2 <br />