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and temperature were measured in groundwater purged from the monitoring wells, and visual
<br /> observations regarding turbidity were recorded A minimum of three well casing volumes was purged
<br /> ' from each well prior to sampling The wells were allowed to recover and samples were collected from
<br /> each well using dedicated disposable bailers Groundwater well purge and sample logs are contained in
<br /> Attachment 1
<br /> The groundwater samples collected from each well were submitted to State-certified Argon Laboratories,
<br /> Inc (Environmental Laboratory Accreditation Program Certificate No 2359) for chemical analyses of
<br /> ' TPHg by EPA Method 80158, benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA Method 8021 B,
<br /> and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA),
<br /> tertiary amyl ether (TAME), di-isopropyl ether (DIPE), 1,2-dichloroethane (1,2-DCA), and ethyl
<br /> dibromide(EDB) by EPA Method 8260B
<br /> Groundwater Flow Direction
<br /> ' Water level measurements were collected from MW1 through MW10, VW1, VW2, and CW on
<br /> September 14, 2004 Water levels ranged from 25 44 to 30 04 feet below the tops of the well casing
<br /> elevations, representing an average decrease in the water table elevation of approximately 1 11 feet since
<br /> ' June 2004 The water level data were used to develop a groundwater elevation contour map (Figure 3)
<br /> Shallow groundwater beneath the site flowed toward the northeast The average hydraulic gradient on
<br /> September 14, 2004, was calculated to be approximately 0 013 ft/ft or approximately 69 ft/mile A
<br /> summary of groundwater monitoring data is presented in Table 1
<br /> Groundwater Analytical Results
<br /> ' TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits in
<br /> groundwater samples collected from MWI, MW6, MW7, VWI, and VW2 The groundwater samples
<br /> ' collected from MW2, MW4, MWS, MW6, MW7, MW9, MWIO, and CW contained low concentrations
<br /> of MTBE ranging from 0 8 micrograms per liter (ug/1) to 10 ug/I None of the groundwater samples
<br /> collected contained detectable concentrations of ETBE, TBA, TAME, DIPE, 1, 2-DCA, or EDB The
<br /> samples collected from MW3, and MW8 contained no detectable concentrations of any of the analytes of
<br /> interest
<br /> The groundwater samples collected in September 2004 from MW9 and MW 10 contained slightly higher
<br /> concentrations of MTBE than the samples collected from these wells in June 2004, but are below the
<br /> Maximum Contamination Limit (MCL) for groundwater and are within historical ranges A summary of
<br /> analytical results is presented in Table 2 Groundwater laboratory data sheets and chain-of-custody
<br />' documentation are contained in Attachment 2
<br /> REMEDIATION SYSTEM
<br /> Remediation System Background
<br />' The installation and startup of the remediation system at the site is detailed in ATC's Remediation
<br /> System Installation Report for the Farmer Property, 610 North Hunter Street, Stockton, California, dated
<br /> April 8, 2003 Figure 4 shows the layout of the remediation system equipment compound, associated piping,
<br /> s lenviro1625961quart1yOgr-2004 doc 3 ATC Associates Inc
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