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3 a'C'fa <br /> S E C 0 R <br /> • Mr Harlin Knoll <br /> March 30, 2006 <br /> Page 3 <br /> Number of Detections Above Minimum Maximum <br /> Constituents the MDL Concentration in pg/L Concentration in pg/L <br /> Total Samples Collected=8 (Well ID) (Well ID) <br /> TPHd 5 <50 320'(MW-1) <br /> TPHg 2 <50 130(MW-3) <br /> Benzene 3 <0 5 8(MW-2) <br /> MtBE 4 <0 5 140(MW-3) <br /> Explanation <br /> MDL=Method detection limit <br /> /rg/L= Micrograms per liter <br /> TPHd=Total petroleum hydrocarbons as diesel <br /> TPHg=Total petroleum hydrocarbons as gasoline <br /> MtBE=Methyl tert-butyl ether <br /> Notes <br /> a=Laboratory report indicates the observed sample pattern is not typical of#2 fuel/diesel It elutes in the DRO range <br /> one earlier and one later than#2 fuels <br /> CONCLUSIONS <br /> • Groundwater monitoring well MW-1 is located downgradlent of the former waste oil and <br /> underground storage tank (UST) excavations Concentrations of TPHd and MtBE have <br /> Increased this quarter when compared to the data from the previous two quarters, which <br /> reported the constituents were below method detection limits (MDLs) Despite the Increase <br /> In MtBE from non-detect to a concentration of 12,vgIL, Its present concentration is below Its <br /> maximum contaminant level (MCL) of 13 NgIL <br /> Monitoring wells MW-2, MW-3, and MW-5 are southeast of well MW-1 and downgradient of <br /> the former UST area and dispenser Islands In well MW-2, the constituents TPHd, TPHg, <br /> benzene, and MtBE have decreased In concentration from the previous quarter However, <br /> in well MW-3 the constituents TPHd, TPHg, benzene, and MtBE have Increased in <br /> concentration from the previous quarter In well MW-5, TPHd has Increased while TPHg, <br /> benzene, and MtBE remain below MDLs when compared to data reported from the <br /> previous quarter <br /> Monitoring well MW-4 Is located in the planter to the southwest and across from the former <br /> UST area and dispenser Islands The constituents TPHd, TPHg, and MtBE are all below <br /> MDLs and have been for the past three quarters Benzene has increased In concentration <br /> from below MDL to 2,ugIL, which is just slightly above its MCL of 1 Ng/L <br /> r <br /> Groundwater monitoring wells MW-6A and MW-6B are located downgradlent and to the <br /> • northwest of well MW-1 and the former UST excavations In well MW-6A, TPHd and TPHg <br /> continue to remain below MDL, while the MtBE concentration decreases No petroleum <br /> a <br /> N IFiles\ProjectslChevronlRetaill#9-86321Penodic Monitonng1200611 QMR2006 doe <br /> K <br />