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KLEINFELDER Xylene concentrations in the source area wells and piezometers tested this quarter also showed increases (ranging from 83 ug/1 to 26,000 ug/1) over the previous quarterly results. The concentration of ethylbenzene in 4 of the 5 source area samples also increased this quarter (ranging from 27 ug/l to 4,500 ug/1). Only I source area piezometer showed an increase in the benzene concentration (NP1-70') whereas the remaining 4 samples from the source area showed decreases in the concentration of benzene. The toluene concentration in MW-2 increased this quarter while the other 4 source area samples decreased or remained unchanged compared to the previous sample date. 1,2-DCA concentrations increased in 2 of the 5 source area samples (MW-1 and NPI-70'), decreased in 2 samples and remained unchanged in I sample compared to the previous sample event in each well. EDB increased in only 1 sample (NPl-80'), decreased in 1 sample and remained the same in 3 samples. DOWNGRADIENT AREA The 7 downgradient well samples showed only a single increase of TPH-g (MW-I ls). There were no detected concentrations of any of the BTEX compounds in any of the downgradient wells this quarter. Additionally, there were no EDB concentrations detected at or above the laboratory reporting limit. TBA concentrations in each of the downgradient samples analyzed f decreased to non-detectable concentrations compared to the results from last quarter. The concentrations of 1,2-DCA detected in the downgradient wells increased in 2 of the 7 samples (MW-1ls and MW-14s), remained non-detect in 4 samples, and decreased in 1 sample (MW-15). Only the sample collected from MW-15 was analyzed for the fuel oxygenates MTBE, DIPS, ETBE, and TAME this quarter and showed non-detectable results. Though well below their pre-remediation concentrations, the 1,2-DCA increased in a total of four wells (MW-1, NP1-70, MW-11s, and MW-14s) and the EDB increased in NPI-80'. Based upon the depth of the monitoring wells, which range from 70 feet to 108 feet bgs, compared to the depths of the ozone and air sparging wells at 140 feet bgs, it appears that the sparging continues to lift deeper contamination into the screened zones of the monitoring wells during the treatment process. We anticipate that this lifting effect, and consequential resonation in concentrations, that is occurring at the front on the plume may continue until the deep contamination at the source area is significantly mitigated. GROUNDWATER TREATMENT SYSTEM OPERATION The soil vapor extraction system installed by CH2M Hill was replaced by Kleinfelder during 2003 with an air sparging (AS)/high vacuum soil vapor extraction (SVE)/ozone injection system. The AS/SVE system consists of a network of two air sparging wells (shallow/deep) and a vapor extraction well positioned at five distinct locations, totaling fifteen wells. The ozone injection system consists of a horizontally directional drilled conduit for ozone/air transmitted to a system of wells triple-nested at three different depths below-groundwater, at five separate locations, equaling fifteen wells. Active remediation began in May 2003 in the source area (actual Disco i site) by means of AS/SVE utilizing a thermal oxidizer unit. Continual operation of the thermal 12280.MON 1 ST04R397 Page 2 of 13 ®2004,IUeinfelder,Inc May 11,2004