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f KLEINFELDER in NP-70' and NP-80' appears to be from a lifting effect as seen in the past caused by.the air sparging and soil vapor extraction remedial action on the source area of the plume as evidenced by the decreasing concentrations in NP-90'. Most downgradient wells (MW-DIS-9, MW-DIS-I ls, MW-DIS-1 ld, MW-DIS-12, MW-DIS-13, MW-DIS-14s, MW-DIS-14d and MW-DIS-15) all showed decreasing concentrations of 1,2- DCA and non-detectable concentrations of BTEX compounds, EDB, and oxygenates. Only i MW-DIS-lls showed an increased concentration of TPH-g and 1,2-DCA. The 1,2-DCA I concentration in MW-DIS-14s continued to show a decreasing trend during the 2004 monitoring period (down to 2.0 ug/l from 3.4 ug/1). It should be noted that the concentration of 1,2-DCA reported for MW-DIS-15 Glacier Court was the lowest since monitoring this location began (2.1 ug/1). Based upon the screened depth intervals of the monitoring wells, which range from as shallow as 65 feet to 85 feet and as deep as 154 feet to 164 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 shallower screened zones of the monitoring wells during the treatment process. The 1,2- DCA increases are anticipated as the lifting effect, and consequential resonation in concentrations, that is occurring at the front of the plume (downgradient of the source area) continues until the deep contamination at the source area is more 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 site) by means of AS/SVE utilizing a thermal oxidizer unit. Continual operation of the thermal oxidizer began in June 2003, In July 2003, the AS/SVE unit was converted from a thermal oxidizer to catalytic oxidizer thereby optimizing the efficiency through fuel uptake. The ozone injection system began consistent operation within the downgradient portion of the plume in September 2003. The system has only been inoperable during periods of system maintenance and enhancements. c 1 Photo Ionization Detector (PID) samples were taken from the five vapor extraction wells (VE-1 through VE-5) each month in during the Third Quarter 2004. Extraction wells VE-2 through VE-5 averaged approximately 35 ppm for the three months during the Third Quarter. VE-1 (located in the former tank area) ranged from approximately 950 to 1100 ppm (before PID termination). Air inlet sampling was conducted at the main manifold of the catalytic oxidizer on June 2, 2004. TPH-G was detected at a concentration of 460 ppm, showing an increase from the i previous (March 22, 2004) sampling event of 28 ppm, still below the 1,400 ppm detected during ++ the September 2003 sampling event. 1 12280.M0N/ST04R1610/JZ:Iv Page 2 of 13 0 2004,Kleinfelder,Inc. December 10,2004