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DMAV-8 at a conccn.tration of 1.7 Etg!L. The DHS MCL for carbon tetrachloride is 0.5 pg;.L. No other volatile organic compounds were reported. Plots of 1,2-I)CA concentrations versus time were prepared for the four monitorinI� wells in which that constituent has been consistently reported. `I-hese plots are presented as Figure 9 (DMW-2 and DMW-3), and Fi(?ure 10 (L)MW-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 = tnx b, where m is the slope of the line. A negative slope to the trendline is statistically indicative of declining concentrations. The regression analysis shows a declining trend for DMW-2, DMW-3, and D.MW-6. While the last ten quarters of data for DMW-9 Show a declining trend, overall the data indicate a rising trend. CONCLUSIONS The following conclusions may be made from the data collected during March 2007, as well as the overall historical data for the site: • Groundwater elevations have been rising for the last three years. Groundwater levels were approximately 45 feet below ground surface in September 2007. • The groundwater gradient in September 2007 was approximately 0.003 feet per foot to the northeast, which is consistent with the average groundwater gradient at the site. • With the exceptions of the reported detections for the fourth quarter 2006, TPH has not been reported in any of` the satnples Since June 2004, and has been reported only sporadically since approximately December 2001. • 1,2-DCA was reported for four wells during September 2007 at concentrations ranging up to 22 which was slightly lower than the maximums reported during 2005 and 2006. The highest concentration was observed in the sample collected from DMW-9. PCE was not reported in any (if the samples collected in Sep[tember 2007. • The overall historical trend of concentrations of 1,2-DCA is downward for all wells with the exception of DMW-9. However, the trend of 1,2-DCA concentrations in DMW-9 over the last ten quarters has been downward.. • The lack of detections of 1,2-DCA in DM W-8 compared to the shallower well DM W-9 suggests a lack of',ertical migration for that constituent. If you have any questions or need additional information, please do not hesitate to call me at (916)679-2293. Sincerely, URS Corporation _ (1, Anthony M indling, K.G. Enclosures URS Corporation 2870 Gateway Oaks Drive, Suite 300 Sacramento,CA 95833 Tet: 916.679,2200 Fax 916 679.2900