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I� <br /> t1 Ii <br /> • 30 July 2003 <br /> AGE-NC Project No 01-0865 <br /> Page 5 of 6 <br /> • High concentrations of MTBE were detected in the samples from wells MW-2, MW-3, <br /> MW-6 and EW-1,the highest concentration of dissolved MTBE occurs in the area ofMW-2 <br /> and MW-3 Moderate to low concentrations ofMTBE were detected in the samples collected <br /> from MW-4,MW-5,MW-6,MW-9 and EW-1 MTBE was not detected in samples MW-7, <br /> MW-8 and MW-10 All detected MTBE concentrations exceeded California's MCLS or were <br /> above the Secondary MCLs <br /> • TAME was recorded this quarter in the samples from MW-2, MW-3, MW-6 and EW-1 <br /> • TPH-g were detected In the surface water samples collected from IDCW and IDCE at <br /> concentrations of 170 µg/1 and 130 µg/l, respectively MTBE was detected in the surface <br /> water sample collected from IDCW at a concentration of 160 �Lg/l <br /> • The northern and southern lateral extent of petroleum hydrocarbon-impacted ground water <br /> is not defined, the vertical extent is not defined except in the vicinity of MW-8,northeast of <br /> the AST system <br /> . 5.0. RECOMMENDATIONS <br /> Based on the findings of this investigation, AGE recommends <br /> • Continuation of the quarterly monitoring program, the next monitoring event should be <br /> performed in September 2003 <br /> • Monitoring well MW 1 at the top of the levee has been damaged and is currently unusable <br /> Between September 1997 and March 2001,the only analyte detected in the well was MTBE <br /> at less than 2 0 gg/l, in December 1998 and March 2001 Well MW-1 should be properly <br /> abandoned and replaced with another well at the former USTs location to help refine the <br /> hydraulic gradient and assess the concentration of contaminants in the ground water plume <br /> migrating eastward from the former UST area <br /> • Methanol and ethanol have not been detected at or above laboratory detection limits in any <br /> environmental activities a the site to date AGE proposes the discontinuation of the methanol <br /> and ethanol laboratory analysis at the site <br /> 6.0. LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> . environmental consultants practicing in this or similar localities The findings were based upon <br /> Advanced GeoEnvironmental,Inc <br />