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k4 KLEINFELDER f { 0 DIPE by EPA Method 8260B [non-detect<0.50 µg111; • ETBE by EPA Method 8260B [non-detect<0.50 µg111; and TAME by EPA Method 8260B [non-detect<0.50 µg/1]. For a summary of analytical data for the analytes listed above, please see Table 2 behind the "Tables" tab of this report. 5.3 SOIL GAS MONITORING 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 (HDD) 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/catalytic 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. During this quarter, the groundwater remediation system has undergone extensive upgrades. Flounnated Ethylene Propylene (FEP) tubing was installed within the HDD conduit and replaced the former tubing due to slight failures. The FEP tubing is even more conducive to ozone applications. A venturi injector system was also designed and installed to help reduce ozone pump pressures needed to inject the ozone in the air stream. During the fourth quarter the vapor extraction operation was shut off at wells (VE-2 —VE-5) due to the high concentrations found at VE-1 (centrally located over the former UST locations). Photo-ionization detector (PID) samples were collected from VE-1 each month during the Fourth Quarter 2004 and ranged in concentrations of 950 to 1500 ppm (before PID termination). Air inlet sampling was conducted at the main manifold of the catalytic oxidizer on November 11 and December 21, 2004. TPH-G was detected at a concentration of 310 ppmv and 730 ppmv respectively. The destruction efficiency of the thermo/catalytic oxidizer was calculated at 98%. ! I � 1 ! t 12280.M0N/ST05RI73/JZ:1v Page 9 of I I 02005,Kleinfelder, Inc. February 11,2005