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Pombo Ranch Property Third Quarter Groundwater Sampling Report July 2005 Page; 2 ti•. SUMMARY FINDINGS Shallow groundwater was measured at depths of 10.7 to 11.5 feet below grade during the July 20, 2005 groundwater monitoring event. Water levels were approximately 0.1 to 0.5 feet higher than levels recorded in the May 10, 2005. Shallow groundwater flow was to the northeast with a very flat gradient (N59E / 0.009 Ft/ft). A very slight down vertical gradient (0.0002 Ft/ft) 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 directions are shown on figure 2. Cumulative groundwater elevations are shown on a hydrograph in figure 7. Groundwater Elevations 07/20105 Well lCollar Elevation DTW GW Elevation MW-1 53.47 10.73 42.74 MW-2 53.22 10.71 42.51 MW-3 55.02 11.47 43.55 MW-4B 54.26 11.48 42.78 MW-5 53.46 10.95 42.51 MW-105 53.55 10.99 42.56 Gasoline petroleum and volatile aromatic hydrocarbons were detected at very low concentrations in well MW5 located down gradient from the former underground storage tanks. Fuel oxygenates were detected at very low concentrations in well MW4B. Laboratory analyses are shown below and on Figures 3, 4, and 5. Laboratory Groundwater Sample Results 07/20/05 S le I.D. Gasoline I Benzene Toluene E-Benzene I Xylenes Oxygenates Dissolved 02 MW-1 <0.05 <0.3 <0.3 <0.3 <0.6 ND 3.67 MW-2 <0.05 <0.3 <0.3 <0.3 <0.6 ND 4.29 MW-3 <0.05 <0.3 <0.3 <0.3 <0.6 ND 4.61 MW-4B <0.05 <0.3 <0.3 <0.3 <0.6 2.4 mtbe 2.06 MW-5 0.58 0.8 <0.3 3.6 1 <0.6 ND 2.60 MW-105 <0.05 1 <0.3 <0.3 <03 <0.6 ND 4.05 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), using a down hole meter. A distinct oxygen low is present in the area of the former underground storage tanks and remedial excavation indicating increased biologic activity is occurring. Dissolved oxygen concentrations are presented in the above table and in �� figure 6.