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1� Second Quarter 2005 Thnfty#172 July 21, 2005 Page 3 Possible New Release or Active Source In the 1st quarter of 2005, Thrifty noted dramatic increases in TPHg (130,000 ug/L) and MTBE (122,000 ug/L) concentrations in well MW-3 that may indicate that a new release occurred or an offsite active source is contributing dissolved hydrocarbons to the area of well MW-3 In the current quarter, TPHg and MTBE concentrations in well MW-3 declined to 1,010 ug/L and 59 ug/L, respectively However, the benzene concentration in well MW-3 increased from non detect(<22 ug/L) to 265 ug/L Concentrations of toluene, ethylbenzene, and xylenes also increased from non-detect to71 ug/L, 72 ug/L, and 73 ug/L, respectively This scenario where MTBE is detected f rst followed by a rise in concentrations of BTEX compounds follows the pattern of a new release Thrifty will continue to monitor the dissolved hydrocarbon concentration in well MW-3 and will provide a detailed evaluation regarding the possibility of a new rlease in its 3rd quarter status report Remediation Status • Vapor Extraction System On April 26, 2001, a new Baker Furnace Thermal Oxidizer Unit was placed into operation with the hour meter reading at zero Presently, the remediation system is connected to soil vapor extraction wells VW-1, VW-2 (A,B), VW-3, VW-4 (A,B,C), VW-5 (A,B,C), and VW-6 (A,B,C) as shown on Figure 6 As of June 27, 2005, a total of 142,407 pounds of hydrocarbons have been removed by the VEU (Table 3) Field Status Reports are included in Appendix C and air analytical results are provided in Appendix D A historical summary of hydrocarbons removed by vapor extraction is presented in Table 3, vapor sample analytical results for the individual wells sampling are presented in Table 5 Groundwater Treatment System The groundwater treatment system was started in conjunction with the vapor treatment system on April 26, 2001, and the flow meter started at zero Presently, the remediation system is connected to groundwater well MW-11 A down-well pneumatic pump draws water into a 150- gallon polyvinyl tank, which then transfers the water through two (2) one thousand-pound granular activated carbon canisters in series Dunng the reporting period, the system was shut down for quarterly sampling on May 9 and restarted on May 16, 2004, and for carbon change out from May 31, 2005 and restarted on June