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Third Quarter Groundwater Monitoring Report September 2063 Boyett Petroleum,419 S.Main,Manteca,CA Page 3 TABLE 1: Laboratory Analytical Results for MTBE and Groundwater Elevation Data {July 22, 2003} Monitor , Depth to Groundwater Well Sample I.D. MTBE(pg/L) TOC Elevation Groundwater Elevation MW-1 3761-MW1-7/22/03 3,900 36.16 22.04 14.12 MW-2 3761-MW2-7/22/03 220 35.97 21.65 14.32 MW-3 3761-MW3-7/22/03 X0.5 36.18 21.08 15.10 MW-6 3761 MW6-7/22/03 <0.5 36.07 22.52 13.55 MW-7 3761-MW7-7/22/03 6,800 36.42 21.44 14.98 MW-8 3761-MW8-7/22/03 <0.5 36.43 21.76 14.67 MW-9 3761-MW9-7/22/03 3.2 35.95 22.43 13.52 'TOC Elevation:Elevations are referenced to NAD83 datum,NGS Benchmark HS 4486. Groundwater Elevation:Flevations are measured fiom the top of the well casings and are referenced to the benchmark indicated above. All measurements are in feet, Unit Conversions: pg/L:parts per billion(ppb) Analytical: MTBE=methyl tertiary-butyl ether AUGUST 19, 2003 MONTHLY MONITORING EVENT On August 19, 2003, Condor representatives were on site to measure water levels and collect groundwater samples for MTBE laboratory analysis from monitor wells MWA through MW-9. Field observations included water level measurement (Table 2, on the following page), 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 purged from the monitor wells during the August 19, 2003 groundwater monitoring event. Clarity was good in the initial field inspection samples collected from the monitor wells; with the exception of MW-1 and MW-9, all the site monitor wells contained sandy sediment. Groundwater elevations fluctuated relative to the previous groundwater monitoring event conducted on July 22, 2003. The average groundwater elevation (13.55 feet) decreased with respect to the previous monitoring event by 0.77 feet. Groundwater elevation data for the August 2003 monitoring event are presented in Table 2, on the following page. The groundwater elevation contours (Figure 5, attached) estimated using depth to water measurements from monitor wells MW-1, MW-2, MW-3, MW-6, MW-7, and MW-8 and well survey data collected by Condor indicate a relatively steep groundwater gradient to the southwest. An estimated groundwater gradient of 0.0089 ft/ft towards the southwest was calculated using water level data from monitor wells MW-2, MW-6, and MW-8. The southwest gradient calculated for the August 2003 monitoring event is consistent with that calculated for the July 22, 2003, groundwater monitoring event. The groundwater samples were analyzed for MTBE by EPA Method 8260B by Argon. Laboratory analytical results for the groundwater samples collected at the site on August 19, 2003, indicated that MTBE was detected in the groundwater samnles collertPrl frnm N4W-1 ]v W-') NAYAT-7 �—A A ,AT o .rrt,o laboratory analytical results for the August 2003 monitoring event indicate a decrease in the concentration of MTBE detected in the groundwater samples collected from MW-1, MW-2, and MW-7, and an increase 4 CONDOR