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Fourth Quarter,2001 Quarterly Groundwater Monitoring Report Canepa's Car Wash,Pacific Avenue,Stockton,CA January 14,2002 Page-2- Results Summary,October 2001: Current Phase of Project: Groundwater monitoring, additional groundwater and soil investigation Monitoring Frequency: Quarterly Free Phase Petroleum: Not noted as present Groundwater Gradient: Shallow—east at an approximate gradient of 0.003 ft/ft as measured between monitor wells MW-9 and MW-10 Contaminants of Concern: Gasoline constituents including gasoline oxygenates DISCUSSION FIELD OBSERVATIONS On October 25 and 26, 2001, Condor representatives made field observations at the 12 site monitor wells (MW-1 through MW-11 and MW-12d). Field observations included water level measurement, appearance of samples (color, clarity, and presence of petroleum product sheen or phase in samples), and collection of water quality field parameters(Table 1, on the next page). GROUNDWATER ELEVATIONS AND GRADIENT The locations and top of casing elevations of the monitor wells were re-surveyed on November 26, 2001. The well locations are referenced to the NAD 83 datum and the elevations are referenced to the NAVD 88 vertical datum from NGS benchmark JS1384. The survey indicated that six of the monitor well casing measurement points were approximately 2.02 feet greater in elevation than previously surveyed. This consistent difference appears to indicate that a different vertical datum was used for the previous well survey. The current survey also indicated that the casing measuring points for monitor wells MW-6 and MW-7 were 3.27 and 2.62 feet greater in elevation, respectively, than previously surveyed. The measuring point elevations for MW-6 and MW-7 determined by the previous survey, therefore, appear to have been erroneous (low) by approximately 1.25 and 0.60 feet, respectively, relative to the other wells. The incorrect (lower) elevations contributed to the appearance of a groundwater mound in the vicinity of monitor wells MW-1 and MW-2 by creating lowered water table elevations along the western and southwestern edges of the site. With the addition of groundwater elevation data from the new monitoring wells, and the corrected well casing elevations of monitor wells MW-6 and MW-7, the groundwater elevation contours now indicate a relatively uniform gradient to the east, and no groundwater mound as previously reported. Groundwater elevation contours for the shallow monitor wells are shown on Figure 3, attached (the contours exclude MW-12d because it is screened deeper than the other monitor wells). The groundwater gradient is approximately 0.003 ft/ft to the east as measured between monitor wells MW-10 and MW-9. A bydrograph of historic groundwater elevations is attached as Figure 3, and a 2001 hydrograph is attached as Figure 4 to provide an indication of the site-wide groundwater elevation trend and comparisons of the monitor well groundwater elevation trends, respectively. LABORATORY ANALYTICAL RESULTS The groundwater samples collected from the monitor wells were analyzed for benzene, toluene, ethylbenzene and total xylenes (BTEX), and methyl tertiary butyl ether (MTBE) by EPA Method 8020 and for total petroleum hydrocarbons, quantified as gasoline (TPH-G) by Method 8015m. The current groundwater sample analytical results (Table 1, on the next page) are generally consistent with �i CONDOR