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. 31 January 2005 AGE-NC Project No 96-0232 Page 8 of 9 City Chevron had effectively reduced influent MTBE concentrations to levels below 20 µg/l,which could be argued were levels that could potentially warrant a site closure However, a `spike' in the influent MTBE concentration was reported in the July 2004 influent sample (47 [.g/1 ), which may be attributed to the Banner Avenue MTBE-impacted ground water plume being drawn towards the Flag City Chevron extraction wells Since start-up of pump-and-treat operations, MTBE concentrations sampled from Flag City Extraction wells EW-1 through EW-10 all generally declined to either non-detectable(EW-1,EW-2, EW-3,EW-6,EW-7,EW-10)or near non-detectable levels(EW-4,EW-5,EW-8,EW-9),which also could be argued were levels that could potentially warrant a site closure However, a general trend of significant `spikes' was evident between March and June 2004 from wells EW-5, EW-7, EW-8 and EW-10(northern trench line)and from well EW-9(fuel dispenser island area) The March-June 2004 `spikes' may be attributed to the above referenced third MTBE-impacted ground water plume being drawn towards the Flag City Chevron extraction wells AGE has interpreted the data collected to date to represent a third,separate MTBE-impacted ground water plume that migrated from the First Zone near Banner Avenue to the First Zone/Second Zone near the northern Flag City Chevron property boundary, influenced by the pump-and-treat cone of depression, the third MTBE-impacted ground water plume converged at the north trench-line of ground water extraction wells (EW-5, EW-7, EW-8 and EW-10) 5.0 RECOMMENDATIONS Based upon data collected from the site, AGE recommends • A separate subsurface investigation of the Banner Avenue MTBE plume AGE believes that a separate investigaton is warranted and should be directed by either the San Joaquin County Environmental Health Department or by the RWQCB • Recision of Cleanup and Abatment Order (C&A) 5-00-700 Because the Banner Avenue MTBE plume encroached onto the Flag City Chevron property and has essentially interfered with the on-going cleanup efforts,the status of Cleanup and Abatement Order(C&A) 5-00- 700 should be modified AGE is of the opinion that all the prior conditions of C&A order 5- 00-700 order have been diligently met, and that Flag City Chevron should not be held to the C&A order for the cleanup of the Banner Avenue MTBE plume Furthermore, it is our understanding that the primary reason for the issuance of the C&A Order was because of the MTBE-impact to the domestic drinking water well formerly located at the Rocky's Restaurant Since the Rocky's domestic well has been abandoned and is no longer a threat for contamination impact, the C&A Order is unnecessary Advanced GeoEnvironmental,Inc