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1 <br /> First Quarter 2005 <br />' Thrifty#172 <br /> April 26, 2005 <br />' Page 3 <br /> analyzed for since it is a fuel additive at the site The SJCEHD further required that ethanol must <br />' be analyzed by EPA Method 8015 Ethanol was not detected using EPA Method 8015M <br /> dissolved lead was detected at 0 011 mg/L in well MW-11 The action level for lead in drinking <br /> water is 0 015 mg/L <br />' Possible New Release or Active Source <br /> The dramatic increases in TPHg (130,000 ug/L) and MTBE (122,000 ug/L) concentrations in <br /> well MW-3 may indicate that a new release may have occurred or an offsite active source is <br /> contributing dissolved hydrocarbons to the area of well MW-3 The TPHg concentration of <br />' 130,000 ug/L has not been detected in well MW-3 The highest historical TPHg concentration in <br /> MW-3 was 100,000 ug/L, detected on May 31, 1994 The TPHg concentration has steadily <br /> decreased in well MW-3 and has been non-detect (<15 or 50 ug/L) since August 1998 In <br />' addition, the highest previous MTBE in well MW-3 confirmed by EPA Method 8260B was 5 3 <br /> ug/L (2/21/2002) A possible reason for the increase in dissolved hydrocarbon concentrations in <br /> well MW-3 is the rise in groundwater elevation that occurred during the current quarter that <br /> may have brought the groundwater into contact with a pocket of hydrocarbon-affected soil This <br /> scenario is unlikely due to the remediation by vapor extraction conducted at the site since April <br /> 2001 In addition, the. groundwater elevation has been at the current-22 feet below mean sea <br /> level several times since Auzust 1998 with no correspondme increase in dissolved hydrocarbon <br /> concentration The close proximity of well MW-3 to the dispenser islands makes it possible that <br />' the source of the increased contamination in well MW-3 is a dispenser of perhaps a pipeline <br /> leak <br />' Thrifty will continue to monitor the dissolved hydrocarbon concentration in well MW-3 Thrifty <br /> believes that any additional assessment and/or remediation that are the result of the increased <br /> dissolved hydrocarbon concentrations in well MW-3 should be the responsibility of the current <br />' station operator <br /> Remediation Status <br />' Vapor Extraction System <br />' On April 26, 2001, a new Baker Furnace Thermal Oxidizer Unit was placed into operation with <br /> the hour meter reading at zero Presently, the remediation system is connected to soil vapor <br /> 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) <br />' as shown on Figure 6 <br />