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I v 0 A S S O C I A T E S I N C wells MW1 through MW5 The samples were collected after purging a minimum of three well volumes and stabilization of electric conductivity, pH, and temperature Field purge logs are 1 presented in Appendix B Subsequent to purging, groundwater was sampled and transferred to appropriate sample containers, using clean, disposable bailers with bottom emptying devices to reduce volatilization In addition, a groundwater sample was collected from the irrigation well (IWSW) located southwest of the site near the Ripon Elementary School on April 12, 2002 and a groundwater sample was collected from the irrigation well (IWNW) located northwest of the site near the Ripon High School on May 30, 2002 Thesam roundwater les collected from each well were submitted to State -certified Argon g P Laboratories, Inc for chemical analysis of TPHg and TPHd utilizing EPA method 8015 modified and BTEX utilizing EPA method 8020 22 Hydrogeology 2.2.1 Fourth Quarter 2001 Event Water level measurements were collected from wells MW1 through MW5 on October 10, 2001 Water levels ranged from 24 02 to 24 91 feet below the tops of the well casing elevations The water level data were used to develop the groundwater elevation contour map (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southwest The average hydraulic gradient on October 10, 2001 was calculated to be 0 0006 ft/ft or approximately 3 ft/mile A summary of groundwater monitoring data is presented in Table 3 t2.2.2 Second Quarter 2002 Event Water level measurements were collected from wells MW1 through MW5 on April 12, 2002 Water levels ranged from 22 73 to 23 64 feet below the tops of the well casing elevations The water level data were used to develop the groundwater elevation contour map (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southwest The average hydraulic gradient on October 10, 2001 was calculated to be 0 0005 ft/ft or approximately 2 ft/mile A summary of groundwater ' monitoring data is presented in Table 3 2.3 Analytical Results 2.3.1 Fourth Quarter 2001 Event ' The groundwater samples collected from wells MW1, MW3, MW4, and MW5 contained no detectable concentrations of TPHg, TPHd, BTEX, MTBE, ETBE, DIPE, TAME, or TBA The groundwater sample collected from well MW2 contained no detectable concentrations of TPHd, benzene, toluene, ethylbenzene, MTBE, ETBE, DIPE, TAME, or TBA The groundwater w 1130991reportslclosure doc 2