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`r Third Quarter 2004 Groundwater Monitoring Report Boyett Petroleum,419 S.Main,Manteca,CA Page 2 well. The locations of the monitoring wells are shown in Figure 2, attached. 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. No floating product, sheen, or odors associated with petroleum hydrocarbons were observed in the groundwater inspection samples from the monitoring wells. Field observations are included on the Groundwater Monitoring Field Forms, attached. GROUNDWATER ELEVATIONS AND GRADIENT The average depth to groundwater was approximately 24.45 feet below the well measuring points, an increase of 1.84 feet since the previous monitoring event (June 2004). Groundwater elevation data are presented in Table 1,below, and historical groundwater elevation data are attached. Table 1: Groundwater Elevation Data(September 28,2004 Monitoring Well TOC Elevation' Screened Depth to Groundwater Interval b s) Groundwater Elevation MW-2 35.97 15-25 Dry Not Measured MW-3 36.18 15-25 22.63 13.55 MW-4R 35.21 10-25 24.40 10.81 MW-6 36.07 10-25 Dry Not Measured MW-7 36.42 10-25 DIX Not Measured MW-8 36.43 10-25 23.40 13.03 MW-9 35.95 40-50 25.18 10.77 MW-10 36.09 10-25 24.55 11.54 MW-11 36.15 29-39 25.44 10.71 . EW-1 36.23 29-39 25.55 10.68 'TOC Elevation:Elevations are referenced to NAVD88 datum,NGS Benchmark HS 4486. 'Groundwater Elevation:Elevations are measured from the top of the well casings and are referenced to the benchmark indicated above. All measurements are in feet. i A groundwater gradient was not calculated for the third quarter monitoring event. Only four shallow wells (MW-3,sufficient water for depth to water measurements. Three of the wells (M3, MW-4R, and MW-8) are aligned in a nearly straight line.MW-10 purged dry and did not recover. It is likely, therefore, that the water in the well was perched water and the depth to water measurement may not accurately reflect the groundwater elevation in the vicinity of MW-10. Groundwater elevation contours shown on Figure 3, attached, indicate the gradient was generally to the southwest during the third quarter monitoring event. Historical groundwater gradients reported for the Site have been highly variable (Table 2, on the next page, and Figure 4, attached). I i i 1 ;1� CONDOR