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„ r .1 visual observations regarding turbidity were recorded. A minimum of three well casing volumes was purged from each well prior to sampling. The wells were allowed to recover and samples were collected from each well using dedicated disposable bailers. Groundwater well purge and sample logs are contained in Attachment 1. The groundwater samples collected from each well were submitted to State-certified Argon Laboratories, Inc. (Environmental Laboratory Accreditation Program Certificate No. 2359) for chemical analyses of TPHg by EPA Method 801513; benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA Method 8021B; and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA), tertiary amyl ether (TAME), di-isopropyl ether (DIPS), 1,2-dichloroethane (1,2-DCA), and ethyl dibromide (EDB) by EPA Method 826013. Groundwater Flow Direction DTW was measured in MW1 through MW10, VW1, VW2, and CW on December 6, 2004. Water levels ranged from 25.96 to 30.29 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 0.34 feet since September 2004. The water level data were used to develop a groundwater elevation contour map (Figure 3). Shallow groundwater beneath the site flowed toward the northeast. The average hydraulic gradient on December 6, 2004, was calculated to be approximately 0.012 ft/ft or approximately 63 ft/mile. A summary of groundwater monitoring data is presented in Table 1. Groundwater Analytical Results TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits in groundwater samples collected from MW1, MW6, MW7, VWI, and VW2. The groundwater samples collected from MW2, MW4, MWS, MW6, MW7, MW9, MW10, and CW contained low concentrations of MTBE ranging from 0.9 micrograms per liter(ug/1) to 6.6 ug/l. None of the groundwater samples collected contained detectable concentrations of ETBE, TBA, TAME, DIPS, 1, 2-DCA, or EDB. The samples collected from MW3, and MW8 contained no detectable concentrations of any of the analytes of interest. A summary of analytical results is presented in Table 2. Groundwater laboratory data sheets and chain- of-custody documentation are contained in Attachment 2. REMEDIATION SYSTEM Remediation System Background The installation and startup of the remediation system at the site is detailed in ATC's Remediation Systema Installation Report for the Farmer Property, 610 North Hunter Street, Stockton, California, dated April 8,2003. Figure 4 shows the layout of the remediation system equipment compound, associated piping, and remediation well net work at the site. Table 3 provides the well completion detail. A more detailed description of each of the system components follows. s:lenviro162596Iquartlyl4gr-2004.doc 3