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i ' 04 November 2002 i AGE-NC Project No 97-0301 Page 4 of 5 t • Ground water elevation generally decreased at the site an average 0 30 feet between the March 2002 and the June 2002 ground water monitoring events,the ippregse of ground water elevation is probably due to seasonal fluctuation 43&1r - ' • The ground water elevation at the site was generally within or approximately 1 foot above the screened intervals of wells MW-1 through MW-4, MW-6 and MW-7, which should yield samples fully representative of shallow ground water conditions, however, the water level in well MW-5 was approximately 50 feet above the screen interval and yielded a sample more representative of deeper ground water conditions ' ' • The core of the dissolved petroleum hydrocarbon plume appears to be located in the area of wells MW-1 and MW-7, analysis of ground water samples collected from MW-1 and MW-7 suggest the core of the plume is impacted by TPH-g, TPH-d, TPH-k, BTEX and 1,2-DCA ' Substantial concentrations of dissolved TPH-mo have previously been detected in water samples collected from well MW-4(screened 30 to 50 feet bsg)and from well MW-5(screened 80 to 90 feet bsg), indicating that there is a limited area impacted with TPH-mo in the area t assessed . BTEX and 1,2-DCA concentrations in ground water samples MW-1 and MW-7 were ' substantially above their respective Maximum Contaminant Levels in drinking water • Very low concentrations of MTBE,EDB and TBA have been detected at MW-1 indicating that ' there is only a minor impact of these components • The vertical extent of dissolved petroleum hydrocarbons is not fully defined at the site, the ' lateral extent of the dissolved petroleum hydrocarbon plume is not fully defined toward the southeast, east and northeast of the current area bound by wells MW-1 through MW-7 1 5.0. RECOMMENDATIONS ' Based upon data collected during June 2002, AGE recommends • Continued ground water monitonng utilizing wells MW-1 through MW-7 The next quarterly ' ground water monitoring event should be performed concurrently with the Califonua Tank-Line Inc site (3105 South El Dorado Street) ' A Work Plan for installation of three multi-level wells was submitted to the SJCEHD on 09 April 2002 and approved by the SJCEHD by letter on 22 April 2002 Because two of the multi-level wells are ' proposed in San Joaquin County right-of-way,encroachment permits are necessary prior to scheduling field work AGE is in the process of obtaining a"Faithful Performance Bond"for each of the proposed 1 Advanced GeoEnvironmental,Inc I 1