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! 31 August 2000 AGE Project No 96-0232 ! Page 2 of 25 ! Environmental Health Division (PHS-EHD that three ground water monitoring wells (MW-1,MW-2 and MW-3)were installed at this time on-site to maximum depths of 24 feet bsg, well screens were between 9 and 24 feet bsg Dissolved petroleum hydrocarbons were ! not detected in initial ground water samples, however benzene was detected in samples collected from wells MW-1 and MW-3 during subsequent sampling events at concentrations as high as 9 4µg/l, general ground water flow direction was initially reported to be toward ! the north • 31 March 1995- According to PHS-EHD records, three 12,000-gallon gasoline USTs and ! one 12,000-gallon diesel UST were replaced at the site Laboratory analysis of soil and grab ground water samples detected total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d, respectively) beneath the former USTs and product lines AGE I has been informed by the PHS-EHD that monitoring well MW-3 was subsequently abandoned by grouting through the casing to the surface at the time the USTs were removed • 16 July 1996- One ground water monitoring well (MW-4) was installed on-site to a depth of 25 feet bsg Laboratory analysis of soil samples from MW-4 did not detect TPH-g,TPH-d, or BTEX compounds Laboratory analysis of ground water samples detected methyl tertiary butyl ether (MTBE) at a concentration of 0 74 ,ug/l from MW-4 and at concentrations of 310µg/1 and 3 7,ug/1 from MW-1 and MW-2, respectively The general ground water flow direction was reported to be toward the south-southeast at a gradient of 0 002 A report of findings (Closure Summary Report-February 1997, dated 30 April 1997) was prepared by AGE and submitted to the PHS-EHD and the RWQCB I9 23 August 1996- Ground water monitoring was performed on wells MW-I, MW-2 and MW-4 Laboratory analysis of ground water samples collected from MW-1 and MW-2 detected MTBE at concentrations of 380 yg/l and 4 6,ug/l, respectively, TPH-d was detected I in a water sample collected from MW-2 at a concentration of i 10µg/1 General ground water flow direction was toward the southwest at a gradient of 0 006 A report of findings (Closure Summary Report-February 1997, dated 30 April 1997)was prepared by AGE and submitted to the PHS-EHD and the RWQCB ' • 09 May 1997- Ground water monitoring was performed on wells MW-1, MW-2 and MW-4 General ground water flow direction was reported towards the northeast at a gradient of 0 009 Laboratory analysis of ground water samples detected MTBE from wells MW-1, MW-2 and MW4 at concentrations of 440µg/l, 5 5 µg/l and 2 7 ,ug/l, respectively A letter report of findings was prepared by AGE and subrrutted on 20 May 1997 to the PHS-EHD and the RWQCB • 19, 29 August and 05, 21 September 1997- Four soil borings (P1, P2, P3 and P4) were I advanced on-site to maximum depths of 70 feet bsg and one soil boring (P5) was advanced off-site at 14659 Thornton Road (Rocky's Restaurant) to a depth of 60 feet bsg MTBE was detected from the P1-35 foot soil sample at a concentration of 0 14 milligrams per kilogram Advanced GeoEnviranmental,Inc-