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Ie 1EC0 R z • Mr Harlin Knoll January 18, 2006 Page 2 Number of Detections Minimum Maximum Constituents above the MDL of the 4 Concentration in pg/L(Well ID) Concentration in Ng1L(well ID) Total Samples TPHd 2 X50 550-(MW-4) TPHg 1 X50 4 100(MW-4) Benzene 0 t0 5 <0 5 MtBE 2 <0 5 100(MW-3) ExNanation MDL=Method detection limit pg/L= Micrograms per liter Notes a = Laboratory report indicates the observed sample pattern is not typical of#2 fuelldiesel It elutes in the DRO range earlier than#2 fuel Groundwater monitoring well MW-1 is located next to the former waste oil tank At one time, groundwater samples collected from MW-1 did have detectable concentrations of oil • and grease However, oil and grease have not been detected in groundwater samples collected from this well in six consecutive sampling events No detections of TPHg have been reported In MW-1 since groundwater sampling began In May 1996 The most recent detection of TPHd occurred during quarterly monitoring in October 2004, at a concentration of 77 micrograms per liter (pg/L) The last TPHd detections prior to that monitoring event occurred in November of 1997 and 1998 SECOR has discussed the reported detections of TPHd with laboratory representatives During this discussion, the laboratory Indicated that the reported detections of TPHd could be caused by weathered gasoline, but they were unable to make a more accurate assessment without additional analyses MtBE has never been detected In MW-1 at or above its method detection limit (MDL) In almost 10 years of quarterly groundwater sampling Groundwater monitoring well MW-2 Is located downgradient, and to the north, of well MW-1 and the former underground storage tank (UST) pit Random, low level detections of TPHd have been reported well MW-2 over the past 10 years of quarterly groundwater monitoring, at a maximum concentration of 150 pg/L In July 2001 The reported detections of TPHd are qualified by a footnote in the laboratory analytical reports Indicating that the chromatogram is not representative of a typical TPHd chromatogram TPHg, benzene, toluene, ethylbenzene, and xylenes (BTEX) have never been detected in this well Sporadic detections of MtBE have occurred In this well over the past 10 years, but MtBE has never been detected in this well at or above Its primary maximum contaminant level (MCL) of 13 pg/L Additionally, MtBE has not been detected In this well at or above its MDL In nine • consecutive groundwater monitoring and sampling events N 1FdeslProjectslChevronlRetadl#9-82641Penodic Montor,ng1200514QMR0514Q2005 QMR doe