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Third Quarter 2005 Groundwater Monitoring Report Boyett Petroleum,419 S.Main,Manteca,CA Page 2 . observations are included on the Groundwater Monitoring Field Forms, attached. Groundwater monitoring field measured parameters are presented in Table 1. Table 1: Groundwater Field Measured Parameters Se te><nber 30 2005 Monitoring pH Specific Dissolved Oxygen Oxidation-Reduction well Conductance(AS) (mg/L) Potential(relative mV) MW-2 6.38 979 3.53 68.5 MW-3 6.61 910 4.81 76.5 MW-4R 6.78 1,297 3.00 73.4 MW-6 6.34 849 5.77 91.8 MW-7 6.66 1,244 3.81 51.7 MW-8 6.67 1,301 4.59 56.3 MW-9 7.28 893 1.21 36.9 MW-10 6.50 1,255 3.72 58,9 MW-11 6.72 894 2.58 39.9 EW-1 7.21 1,131 4.35 73.0 GROUNDWATER ELEVATIONS AND GRADIENT Groundwater elevation data collected during the third quarter 2005 monitoring event indicate an average groundwater elevation at the Site of 16.59 feet, a decrease of 0.87 feet since the previous monitoring event (June 2005). Shallow groundwater elevation contours based on the depth to water measurements collected on September 30, 2005, indicate the groundwater gradient at the Site is to the southwest. The groundwater elevation for deep well MW-9 is approximately one foot higher than the groundwater elevation in the other deep wells (MW-11 and EW-1). It is possible the sampling techniciAn made an error • of one-foot in reading the tape of the depth to water meter. Groundwater elevation data are presented in Table 2, and historical groundwater elevation data are attached. Table 2: Groundwater Elevation Data(September 30 2005 Monitoring Well TOC Elevation Screened Depth to Groundwater Interval b s Groundwater Elevation MW-2 35.97 15-25 19.42 16.55 MW-3 36.18 15-25 19.63 16.55 MW-4R 35.21 10-25 18.65 16.56 MW-6 36.07 10-25 19.64 16.43 MW-7 36.42 10-25 19.89 16.53 MW-8 36.43 10-25 19.89 16.54 MW-9 35.95 40-50 18.51 17.44 MW-10 36.09 10-25 19.56 16.53 MW_11 36.15 29-39 19.74 16.41 EW-1 36.23 29-39 19.84 16,39 ITOC 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 oxygenates/additives by EPA Method 8260B, and for totai petroieum hydrocarbons quantified as gasoline (TPH-G) by EPA Method 6_05.5 by Argon Laboratories of Ceres, California. The selected oxygenates/additives included MTBE, ethanol (EtOH), tj„� CONDOR