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1 Hydro&eo Consultants ' 5.4 Groundwater Results ' The analytical results for the groundwater samples collected at two hours (13 30, 3116/02), six hours (17 30, 3/16/02), 12 hours (23 30, 3/16/02), 18 hours (5 30, 3/17/02), and 24 hours (11 15, 3/17/02) during the pumping test from MW-5 are summarized in ' Table 7 Laboratory reports and chain-of-custody documentation are included in Appendix B ' The sample results indicated that elevated levels of TPHg, BTEX, and MTBE were detected Concentration for TPHg ranged from 42 1 mg/L at the beginning of the test to ' 54 2 mg/L at the end of the test, with a general increasing trend throughout the test A similar increasing trend was observed for toluene (4 23 mg/L — 6 14 mg/L) Benzene on the other hand had a decreasing trend during the test with the highest concentrations ' being detected at the beginning of the test (3 12 mg/L) and the lowest concentration being detected at the end of the test(1 62 mg/L) Ethylbenze concentrations ranged from 1 99 mg/L at the beginning of the test to 2 23 mg/L at 12 hours Xylene concentrations were lowest at the beginning of the test (8 05 mg/L) and maximum concentrations were detected at 18 hours (12 4 mg/L) MTBE concentrations also indicated a slight decreasing trend during the test with maximum concentrations being detected in the first sample ' collected at 2 hours (2 0 mg/L) and the lowest concentration being detected at hour 24 (1 34 mg/L) 6.0 AQUIFER TEST CONCLUSIONS ' The differences between the aquifer properties calculated from the pumping well drawdown and recovery and the observation well drawdown results is most likely the result of the following conditions • The pumping well MW-5 is completed In mostly fine grained sediments with a higher permeability zone of sand to silty sand from 65 to 70 feet below grade, thus the ' delayed well response measured in the observation wells, followed by a recovery period, was most likely the result of this heterogeneity in sediments and resulting differences in yields from the various zones, including potential vertical movement of ' water • The observation wells are completed in different zones than the pumping well MW-5, ' some do not penetrate the sandy layer at 65-70 feet, and many of these wells only partially penetrate the aquifer Thus the data obtained from the observation wells is less reliable than the data obtained from the pump well • This conclusion is further supported by the non linear drawdown measured in each of the observation wells (Figures 7, 8, and 9) and by the non linear relationship of ' maximum drawdown observed with respect to distance away from the pumping well (Figure 10) 1 ' Thrifty Oil TQC 9171 Aquifer Test and RAP Rpt Page I I