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First Qua:ter 2005 Groundwater Monitoring Report Boyett Petroleum,419 S.Main,Manteca,CA Page 2 petroleum odor was 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 Groundwater elevation data collected during the first quarter 2005 monitoring event indicate an average groundwater elevation at the Site of 17.80 feet, an increase of 2.90 feet since the previous monitoring event (December 2004). Groundwater elevation contours based on the depth to water measurements collected on March 22, 2005, indicate a gentle gradient to the northeast. Groundwater elevation data are presented in Table 1, below, and historical groundwater elevation data are attached. Previous quarterly monitoring reports produced by Condor have included a figure with both groundwater elevation contours and a gradient that was calculated with a three-point problem using the groundwater elevations for MW-2, MW-6, and MW-8. The calculated gradient direction frequently varied from the gradient direction indicated by the groundwater elevation contours. It is Condor's opinion that the groundwater elevation contours more accurately represent the gradient at the Site, so Condor is no longer using a three-point problem to determine the gradient in quarterly monitoring reports for the Site. 'fable 1: Groundwater Elevation Data March 22, 2005) Monitoring Well TOC Elevation' Screened Depth to Groundwater Interval(b s) Groundwater Elevation' MW-2 35.97 15-25 17.99 1798 MW-3 36.18 15-25 19.33 16.85 MW-4R 35.21 1 10-25 17.29 17.92 MW-6 36.07 10-25 18.04 18.03 • MW-7 36.42 10-25 18.52 17.90 MW-8 36.43 10-25 18.53 17.90 MW-9 35.95 40-50 18.71 17.24 MW-10 36.09 10-25 18.24 17.85 MW-1 1 36.15 29-39 17.95 18.20 EW-1 36.23 29-39 18.07 1 18.16 1 T'OC 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. LABORATORY ANALYTICAL RESULTS The groundwater samples collected from the monitoring wells were analyzed for benzene, toluene, ethyl benzene, total xylenes (BTEX), and selected gasoline oxygenatesladditives by EPA Method 8260B, and for total petroleum hydrocarbons quantified as gasoline (TPH-G) by EPA Method 8015M by Argon Laboratories of Ceres, California. The selected oxygenates/additives included MTBE, ethanol (EtOH), tertiary-butanol (TBA), di-isopropyl ether(DIPE), ethyl tertiary-butyl ether(ETBE), tertiary-amyl methyl ether(TAME), 1,2-dichloroethane(1,2-DCA), and 1,2-dibromoethane(EDB). The laboratory analytical results for the first quarter 2005 quarterly groundwater monitoring event are presented in Table 2, on the next page. A map presenting MTBE isoconcentration contours in groundwater is included as Figure 4, aitached. i 11 a CONDOR