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an KLEINFELDER
<br /> 1 EXECUTIVE SUMMARY
<br /> This is a report of Kleinfelder's fourth quarter 2002 groundwater monitoring for the former Disco
<br /> Facility located at 110 Filbert Street in Stockton, California.
<br /> On December 6, 2002, twenty monitoring wells and three piezometers were sounded for depth to
<br /> groundwater. On December 9, 2002, six monitoring wells were sampled by Kleinfelder. The
<br /> monitoring wells sampled were MW-DIS-I Is, MW-DIS-11d, MW-DIS-12, MW-DIS-13, MW-
<br /> DIS-14s, and MW-DIS-14d. The monitoring wells were sampled in accordance with the
<br /> "Groundwater Monitoring Frequency Decision Tree"developed by CH2M Hill.
<br /> The depth to groundwater ranged from 44.51 feet below the top of the well casing (MW-DIS-
<br /> lls) to 53.60 feet below the top of the well casing (MW-DIS-12 and 14d). Groundwater
<br /> elevations for the monitoring wells ranged from—33.70 feet (MW-DIS-10) to —33.96 feet (MW-
<br /> DIS-9). Groundwater flow direction at the site is estimated to be towards the southeast at
<br /> approximately 0.0005 ft./ft.
<br /> The 6 groundwater samples were analyzed for the .following analysis: benzene, toluene,
<br /> ethylbenzene, xylene, Total Petroleum Hydrocarbon as gasoline (TPH-g), 1,2-Dichloroethane
<br /> (1,2-DCA), 1,2-Dibromoethane .(EDB), tert-Butyl Alcohol (TBA), and the oxygenates Di-
<br /> isopropyl Ether (DIPE), Ethyl t-Butyl Ether (ETBE), Methyl tert-Butyl Ether (MTBE); and tert-
<br /> Amyl Methyl Ether(TAME).
<br /> There were no detections of TPH-g, benzene, toluene, ethylbenzene, xylene, EDB, TBA, DIPE, .
<br /> ETBE, or TAME in the groundwater samples collected for laboratory analysis.
<br /> 1,2-DCA was detected in .three groundwater samples MW-11s, MW712, and MW-14s at
<br /> concentrations of 170 ug/l, 0.66 ug/l and 4.4 ug/l, respectively. The detected concentrations of
<br /> 1,2-DCA did not exceed the Primary Maximum Contaminant Level (PMCL) for 1,2-DCA of 5
<br /> ug/1 in two of the three samples.
<br /> The six groundwater samples were also analyzed for the oxygenates MTBE, DIPE, ETBE, and .
<br /> TAME. Only MTBE was detected in one groundwater sample (MW-DIS-14s) with a
<br /> concentration of 2.5 ug/l. This marks the third consecutive detection of MTBE in MW-DIS-14s.
<br /> As stated above, the oxygenates MTBE, DIPE, ETBE, or TAME were not detected in the
<br /> remaining five groundwater samples submitted for laboratory analysis. The PMCL for MTBE is
<br /> 13 ug/l and the Secondary Maximum Contaminant Level (SMCL) for MTBE is 5 ug/l. The
<br /> detected concentration of MTBE in MW-DIS-14s does not exceed the PMCL, but does exceed
<br /> the SMCL.for MTBE in water. PMCLs are derived from health based criteria, whereas SMCLs
<br /> are derived from human welfare considerations such as taste and odor.
<br /> 12280-MON/S`I'03R225 Page 1 of 12
<br /> 2003,Kleinfelder,Inc February 5,2003
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