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SI Fourth 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 December 28 2005 Monitoring pH Specific Dissolved Oxygen Oxidation-Reduction Well Conductance S (mglL) Potential (relative mV) MW-2 7.98 772 2.73 -46.4 F MW-3 7.58 816 2.41 12.0 MW4R 7.90 954 1.16 15.7 MW-6 6.26 766 2.95 -15.8 MW-7 7.94 909 2.27 1.5 MW-8 7.99 1,014 3.62 40.9 MW-9 7.90 772 1.15 -21.5 MW-10 7.83 1,051 2.79 27.7 MWA 1 7.67 743 1.39 13.1 EW-1 7.70 712 1.42 -56.3 GROUNDWATER ELEVATIONS AND GRADIENT Groundwater elevation data collected during the fourth quarter 2005 monitoring event indicate an average groundwater elevation at the site of 18.19 feet, an increase of 1.60 feet since the previous monitoring event (September 2005). Shallow groundwater elevation contours based on the depth to water measurements collected on December 28, 2005, indicate the groundwater gradient at the site is generally to the north. Groundwater elevations in MW-9, MW-11,and EW-1, which are screened below a clay unit, are generally higher than the elevations in nearby shallow wells, indicating there may be an upward • vertical gradient at the site. Groundwater elevation data are presented in Table 2, and historical groundwater elevation data are attached. Table 2: Groundwater Elevation Data December 28, 2005 Monitoring Well TOC Elevation Screened Depth to Groundwater Interval h s Groundwater Elevation MW-2 35.97 15-25 17.74 18.23 MW-3 36.18 15-25 18.03 18.15 MW4R 35.21 10-25 17.03 18.18 MW-6 36.07 10-25 17.87 18.20 MW-7 36.42 10-25 18.27 18.15 MW-8 36.43 10-25 18.30 18.13 MW-9 35.95 40-50 17.67 18.28 MW 10 36.09 10-25 17.96 18.13 MW-11 36.15 29-39 17.90 18.25 EW-1 36.23 29-39 18.01 18.22 '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. 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 _,,__ L .a L -« i .1- rTbLI !1\ L , VD A 11Ao4.1. A Qf1t C11 f 1- A---- ivt w�at ParclCum. tty&W-C bons. :t-w: 1-44cd as �uooauav "..4i -1 _> ---- a.avwava. --_'i v> ,-E,_ Laboratories of Ceres, California. The selected oxygenates/additives included MTBE, ethanol (EtOH), 4M I.1) CONDOR