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115 N a ��s� - , C) a Data validation was performed by URS, consisting of a review of: • data completeness; • holding times; • blanks; • system monitoring compounds (surrogates); • laboratory control samples; • matrix spike/matrix spike duplicates; and • compound identification and quantification. The results of the data validation are included in the Data Validation Summary (Appendix B). The data validation found all results to be acceptable and useable for their intended purpose with the no limitations: GROUNDWATER ELEVATIONS AND GRADIENT A contour map of groundwater elevations for September 20, 2007, is provided as Figure 2. Current and historical water level elevation data fof all wells are included in Table 2. The depth to water ranged from approximately 44 to 45 feet below ground surface,'or approximately -27 feet with reference to mean sea level datum (MSLD). A hydrograph of groundwater level elevations in DMW71 (Figure 3) shows that water levels are currently in a rising trend, superimposed on a seasonal variation of about.5 to 7 feet. Historically, water level elevations rose about 30 feet during the 1990's to a high of '18 feet-MSLD in May 2000, and subsequently declined approximately 10 feet through 2003. Between 2003 and 2006 water levels rose by approximately 7 feet. In September 2007 the groundwater gradient was 0.003 feet per foot to the northeast. Historically, the gradient has been primarily to the north-northeast. GROUNDWATER ANALYTICAL RESULTS A historical summary of analytical,results for groundwater samples collected through September 2007 is included in Table 3. Results for tetrachloroethene (PCE) and 1,2-dichloroethatne (1,2-DCA) for samples collected during September 2007 are presented on Figure 4. Time versus concentration plots of 1,2-DCA in monitoring well samples are presented in Figures 5 and 6. TPH-diesel Total petroleum hydrocarbon (TPH) reported as diesel was not reported for any samples collected in September 2007. Volatiles and Oxygenates by EPA Method 8260B 1,2-Dichloroethane (1,2-DCA) was reported in samples collected from DMW-2 (0.64 gg/L), DMW-5 (7.7 µg/L), DMW-6 (18 µg/L), and DMW-9 (22 µg/L). The California Department of Health Services (DHS) Maximum Contaminant Level(MCL) for 1,2-DCA is 0.5 ltg/L. Tetrachloroethene (PCE) was not reported in any of the samples collected in September 2007. Chloroform was reported at concentrations ranging from 1.0 gg/L to 2.8 pg/L in samples collected from DMW-1, DMW-4, and DMW-8. The highest concentration of chloroform was observed for DMW-4. The DHS MCL for chloroform is 100 gg/L. Carbon tetrachloride was reported in the sample collected from URS Corporation 2870 Gateway Oaks Drive,Suite 300 Sacramento,CA 95833 Tel:916.679.2200 Fax:916.679.2900