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Groundwater Monitoring and Sampling 1 The relative elevation of the tops of the wellheads for wells MW-1, MW-2 and MW-3 were surveyed on January 5, 1996, and resurveyed for accuracy on January 25, 1996 On January 8, 1996, the depths to water in the wells were measured to evaluate the direction and magnitude of ' the groundwater gradient beneath the site On January 8, 1996, the new wells were developed using pumping and surge techniques until the produced water was relatively free of sediment At ' least ten well volumes (casing and sandpack) were purged from each well prior to collecting groundwater samples Temperature, pH, water elevation, and electric conductivity were 1 monitored and allowed to stabilize Groundwater samples were collected using disposable bailers, ' one dedicated to each well Groundwater samples collected from all monitoring wells were submitted using chain-of-custody record to Argon Mobile Labs for analysts of TPHg and BTEX using EPA methods 8015 (modified) and 8020, respectively, for TPHmo using EPA method 1 8015, and for total lead Purged water was stored on-site in 55-gallon drums approved for r� hazardous liquid storage pending laboratory analyses 1 Analytical results for groundwater samples are contained in Table 2 Groundwater monitoring ' data are contained in Table 3 Copies of monitoring data sheets are contained in Appendix 111, and copies of chain-of-custody records and laboratory results are contained in Appendix IV � 1 RESULTS OF INVESTIGATION 1 Site Geology ' Site bonng logs and sediments encountered during drilling suggest that the site is generally underlain by two lithologic units The upper unit, located from depths between 3 and ' approximately 14 feet bgs, is sandy silty clay The bottom unit, located from depths of 10 feet bgs to the bottom of the borings, is silty clay Soil above the shallow sandy silty clay layer is W W5113TSA dm 4 SMTN 1