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URS GROUNDWATER ELEVATIONS AND GRADIENT Contour maps of groundwater elevations for September 30 and December 23, 2004 are shown in Figures 3 and 4, respectively Current and historical water level elevation data for all wells are included in Table 2 Water levels measured September 30, 2004 were between 52 and 54 feet below ground surface, or approximately -36 feet with reference to mean sea Ievel datum (MSLD) Water levels measured December 23, 2004 were between 49 and 52 feet below ground surface,or approximately-32 feet MSLD A hydrograph of groundwater level elevations in DMW-1 (Figure 5) show that water levels were rose from a low of approximately-52 feet MSL in July 1991 to a high of approximately -18 feet MSL in May 2000, and have since declined to the current elevation of approximately-32 feet MSL in December 2004 The September 2004 water level data indicate an irregular groundwater gradient The December 2004 water level data indicate a groundwater gradient of 0 02 to the northwest GROUNDWATER ANALYTICAL RESULTS A historical summary of analytical results for groundwater samples collected through December 2004 is included in Table 3 Results for tetrachloroethene (PCE) and 1,2-dichloroethatne (1,2-DCA) for samples collected in September and December 2004 are presented on Figures 6 and 7 Time versus concentration plots of 1,2-DCA in monitoring well samples are presented in Figures 8 and 9 TPP-DIESEL Neither total petroleum hydrocarbon (TPH) reported as diesel or unknown hydrocarbon (UH) were identified in groundwater samples collected during the third and fourth quarters of 2004 Volatiles and Oxygenates by EPA Method 8260B Por samples collected on September 30, 2004 (third quarter of 2004), 1,2-dichloroethane was reported in samples collected from DMW-2 (19 micrograms per liter [µg/L)), DMW-5 (15 µg/L), DMW-6 (27 pg/L), and DMW-9 (21 pg/L) Chloroform was reported to sample collected from DMW-I (1 0 µg/L) PCE was reported in the sample collected from DMW-9 (7 1 �Lg/L) Chloroform was reported in the samples collected from DMW-1 (1 4 µg/L) and DMW-8 (0 93 gg/L) The only other EPA Method 8260B constituent reported for the September round was carbon tetrachloride at concentrations of 0 55 µg/L for DMW-1, and 0 77 µg/L for DMW-8 For samples collected on December 23, 2004 (fourth quarter 2004), 1,2-DCA was reported in samples collected from DMW-5 (2 5 pg/L), DMW-6 (21 gg/L), and DMW-9 (25 gg/L,) Chloroform was reported in samples collected from DMW-1 (1s 7 µg/L), and DMW-4 (0 68 gg/L) PCE was reported in only in the sample collected from DMW-9 at a concentration of 3 4 µg/L, which is below the California Environ- mental Protection Agency(Cal/EPA) maximum contaminant level (MCL)of 5 }ig/L The only other EPA Method 8260B constituent reported for the December round was carbon tetrachloride at concentrations of 0 93 µg/L for DMW-1,0 97 pg/L for DMW-5, and 14 µg/L for DMW-$ Plots of 1,2-DCA concentrations versus time were prepared for the four monitoring wells in which that constituent has been consistently reported These plots are presented as Figure 8 (DMW-2 and DMW-3), and Figure 9 (DMW-6 and DMW-9) Trend lines, based on a linear regression analysis, are shown on these plots, together with their equation in the form of y = mx +b, where in is the slope of the line A negative slope to the trendline is statistically indicative of declining concentrations For ail of the plots, concentrations of 1,2-DCA are declining or level,based on the regression analysts • 0 U0B1AFP\Quarterly1Q404WQ04AFP—rev01 doc