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f T r Pombo Ranch Property Jul 2404 Third Quarter Groundwater Sampling Report Y Page; 2 0.5 feet higher than levels recorded in the May 14, 2004 event. Shallow groundwater flow was to the Northeast with a flat gradient (N30E / 0.008), similar to the groundwater flow observed in the May 14, 2004 event. A very slight downward vertical gradient was observed at the well pair MW5 and MW105. Wellhead elevations, depth to water measurements, and groundwater elevations are shown below. Groundwater elevations and flow direction are located on figure 2. Cumulative groundwater elevations are shown on a hydrograph in figure 6. Groundwater Elevations 07/14/04 Well lCollar Elevation DTW GW Elevation MW-1 53.47 10.57 42.9 MW-2 53.22 10.12 43.1 MW-3 55.02 10.75 44.27 MW-4 53.55 10.25 43.3 MW-5 53.46 10.38 43.08 MW-105 53.55 10.48 43.07 Gasoline petroleum hydrocarbons were not detected by the analytical laboratory in water samples collected from the monitoring wells. Volatile aromatic hydrocarbons were detected at very low concentrations in wells MW4 and MW5 located at and immediate down gradient from the former underground storage tanks. Fuel oxygenates were detected at very low concentrations in wells MW4. Laboratory analyses are located below and an Figures 3 and 4. Laboratory Groundwater Sample Results 07/14/04 Sample I.D. Gasoline Benzene I Toluene j E-Benzene I XyleneLi Oxygenates Dissolved 02 MW-1 <0.05 <0.3 <0.3 <0.3 <0.6 ND 0.69 MW-2 <0.05 <0.3 <0.3 <0.3 <0.6 ND 1.04 MW-3 <0.05 <0.3 <0.3 <0.3 <0.6 ND 1.25 MW-4 <0.05 7.5 <0.3 13 61 29 mtbe 0.80 MW-5 <0.05 1.5 <0.3 10 <0.6 ND 0.72 MW-105 <0.05 <0.3 <0.3 <0.3 <0.6 ND 1.16 ND=Non Detect NA=Not Analyzed Mg/L for gasoline&DO µg/L for BTEX,MTBE,and 8260 Oxygenated Compounds Dissolved oxygen measurements were collected as part of the groundwater monitoring to provide an estimate of the level of biologic activity in the groundwater. The dissolved oxygen was measured during this monitoring event in the field (and noted on the field logs), instead of in the , laboratory, using a down hole meter. Dissolved oxygen concentrations are presented in the above table and in figure 5.