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u <br />Dawe Plafa P'gjeet <br />ar R.anQ w.1Q Q.arlr <br />I.0 SUMMARY OF SIGNIFICANT FINDINGS <br />The results of the fourth quarter water quality analyses for the Dowe Flats project show no <br />significant changes from the first, second, or third quarter results. Elevated concentrations of <br />benzene and acetone were detected in one surface water and two groundwater samples. These <br />compounds were detected at concentrations above the EPA practical quantitation limit (PQL), <br />but also were present in the laboratory blanks. The occurrence of these compounds in the <br />laboratory blank suggests a contaminant source within the laboratory and does not reflect <br />groundwater and surface water quality at Dowe Flats. <br />Inorganic analyses also are generally similar to the results of the analyses of the first three <br />quarters. Surface water and groundwater quality is interpreted to be representative of <br />background conditions. Major ion balance calculations indicate that some of the fourth quarter <br />water analyses are not within an acceptable error range. <br />2.0 INTRODUCTION <br />• The fourth quarter sampling event was performed on March 7, 1991. The first quarter sampling <br />event was performed by Western Technologies Inc. (WT) on June 8, 1990 and on August 2, 1990. <br />The second quarter sampling event was performed on September 18 and 20, 1990 and the third <br />quarter sampling event was performed on December 27, 1990. Evergreen Analytical, Inc., of <br />Wheat Ridge, Colorado provided analytical laboratory services for each quarterly sampling event. <br />• <br />Water samples were collected from four groundwater monitoring wells and three surface water <br />locations. In addition, a trip blank labeled DFSW-4 was submitted to the lab as a QA/QC <br />measure. A laboratory trip blank also was present during the sampling. Plate 1 contains a map <br />of the monitoring locations. Table 1 summarizes all water quality data collected to date. Copies <br />of the chain of custody and laboratory results for the fourth quarter sampling event are provided <br />in the Appendix. <br />Pnojsl N®6e: 769-9J-lNZ <br />Apa 18, 1991 <br />Page 1 <br />