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t Fourth Quarter,2002 Quarterly Groundwater Monitoring Report Canepa's Car Wash,Pacific Avenue,Stockton,CA Page 2 FIELD OBSERVATIONS . On October 14 and 15, 2002, Condor representatives made field observations at the 12 site monitor wells (MW-1 through MW-11 and MW-12D), and at one soil vapor extraction (SVE) well (SV4). Field observations included water level measurement (Table 1, below), appearance of samples (color, clarity, and presence of petroleum product sheen or phase in samples), and collection of water quality field parameters. Field observations are included in the field forms, Attachment D. GROUNDWATER ELEVATIONS AND GRADIENT Groundwater elevation contours estimated for the shallow monitor wells (MW-1 through MW-11) on October 14, 2002, indicate that the groundwater gradient is to the northeast and is generally consistent with previously estimated groundwater gradients (Figure 2, attached). Monitor well MW-12D was not used in groundwater elevation contouring due to the well's deep screen interval. An estimated groundwater gradient of 0.005 ft/ft towards the northeast was measured using water level data from monitor wells MW-5 and MW-6. The average depth to groundwater measured in the 12 monitor wells at the site increased by approximately 3.61 feet since July 1, 2002. A hydrograph of historic groundwater elevations is attached as Figure 3. It should be noted that well screens for shallow monitor wells MW-1 through MW-8 were drowned. Table 1 Groundwater Elevation Data (October 14,2002) Well Casing Well Collar Depth to Groundwater WELL Screen Elevation Water Elevation Interval feet feet-b s (feet) (feet) (feet) MW-1 50-70 15.48 37.49 -22.01 MW-2 50-70 15.29 37.08 -21.79 MW-3 50-70 15.53 38.03 -22.50 MW4 50-70 15.83 38.24 -22.41 MW-5 50-70 14.71 37.37 -22.66 MW-6 45-65 14.89 36.38 -21.49 MW-7 45-65 15.80 37.47 -21.67 MW-8 45-65 15.31 37.54 -22.23 MW-9 25-45 14.84 37.48 -22.64 MW-10 25-45 14.72 36.39 -21.67 MW-11 25-45 15.12 36.82 -21.70 11 MW-12D 100-110 14.99 36.80 -21.81 LABORATORY ANALYTICAL RESULTS The groundwater samples collected from the monitor wells and SV-4 were analyzed for BTEX, TPH-G, and MTBE by Excelchem Laboratories, Inc. of Roseville, California (Exccichem). The current monitor well groundwater analytical results presented in Table 2, on the following page, are generally consistent with the historical results (Attachment Q. The groundwater analytical results for SV-4 are generally consistent with the previous groundwater analytical results reported for SV-4 during the July 2002 monitoring event. Benzene and MTBE isoconcentration contour maps are included as Figure 4 and Figure 5, respectively, in Attachment A. The highest concentrations of BTEX constituents, MTBE and TPH-G were detected in the samples from SV-4, and a broken petroleum sheen was noted in the groundwater . purged from SV-4. The groundwater sample analytical results from well MW-12D continue to indicate a trend of lower contaminant concentrations since the initial sampling event for this well.conducted on 4M �� CONDOR