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Additional comments• • ' As presented in Figure 1 and Table 2, MTBE was detected during this monitoring event in well VEW3 at a concentration of 30,300 micrograms per liter (µg/L) MTBE was not detected at or above EPA Method 8260 reporting limits in groundwater samples collected from this well in either ' February or March 2001 As VEW3 is located within approximately 15 feet of the existing underground storage tanks(USTs),this recent dramatic increase in MTBE concentrations from non- detectable to 30,300 gg/L may indicate that a new, unauthorized release associated with the current USTs has occurred ExxonMobil has not operated the station since December 1995 ExxonMobil installed MW7 in 1994 in a location that is upgradient of onsite source areas and ' approximately 60 feet downgradient of the neighboring 7-Eleven facility No 14117 MW7 did not contain detectable concentrations of hydrocarbons until August 2000, when MTBE was first detected MTBE has been detected in MW7 at concentrations as high as 260 Ag/L Tertiary butyl ' alcohol (TBA) was detected in MW7 at a concentration of 16 1 gg/L during this most recent sampling event,which is more than six years after ExxonMobil transferred the property to New West ' Petroleum As presented in the Report on Additional Site Assessment and Recommendations, prepared by The IT Group in December 2001 for the neighboring 7-Eleven Store#14117,MTBE and TBA have been detected at concentrations of up to 36,000 and 98,000 µg/L, respectively, at this ' upgradient 7-Eleven facility These data suggest the MTBE and TBA detected in MW7 are from offsite sources ' ExxonMobil has not operated at the site since December 1995 The recent detection of 30,300µg/L in VEW3 (located within 15 feet of the existing USTs) and the recent detection of MTBE and TBA in upgradient well MW7, which is downgradient of the neighboring 7-Eleven facility #14117, ' indicate that new, unauthorized releases have occurred which are not the responsibility of ExxonMobil As such, ExxonMobil respectfully requests that additional responsible parties be named I ADDITIONAL ACTIVITIES PERFORMED AT SITE ' No additional activities were performed at the site ' WORK PROPOSED FOR NEXTQ UARTER ' Groundwater will be monitored in accordance with the attached groundwater monitoring plan ' ETIC Engineering, Inc is currently assessing the potential migration of petroleum hydrocarbons and MTBE from offsite sources onto this site I g\proJects17370BVrimierlwp\90302L3706text doe 2