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l s ' Pombo Ranch Property Second Quarter Groundwater Sampling Report April 2006 Page; 2 • SUMMARY FINDINGS Shallow groundwater was measured at depths of 12.15 to 13.17 feet below grade during the April 13, 2006 groundwater monitoring event. Water levels were approximately 0.6 to 0.8 feet higher than levels recorded on January 10, 2006. Overall shallow groundwater flaw was to the northeast with a very flat gradient (N54E / 0.0046 Ft/Ft). Moderate downward vertical groundwater movement (0.024 Ft/Ft) was observed in 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 04/13/06 Well Collar Elevation DTW T GW Elevation MW-1 53.47 12.38 41.09 MW-2 53.22 12.15 41.07 MW-3 55.02 13.27 41.75 MW-4B 54.26 13.17 41.09 MW-5 53.46 12.52 40.94 MW-105 1 53.55 13.63 39.92 Gasoline petroleum 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 the contaminate distribution displayed on Figures 3, 4, and 5. Laboratory Groundwater Sample Results 0411310 Sample I.D. Gasoline Benzene Toluene E-Benzene X lens Oxygenates Dissolved 02 MW-1 <0.05 <0.3 <0.3 <0.3 <0.6 ND 1.95 MW-2 <0.05 <0.3 <0.3 <0.3 <0.6 ND 2.01 MW-3 <0.05 <0.3 <0.3 <0.3 <0.6 ND 2.90 MW-4B <0.05 <0.3 <0.3 <0.3 <0.6 1.2 mtbe 1.26 MW-5 0.06 <0.3 <0.3 <0.3 <0.6 ND 1.58 MW-105 <0.05 <0.3 <0.3 1 <0.3 <0.6 ND 4.18 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 down gradient of the former underground storage tanks and remedial excavation indicating increased biologic activity is occurring in the area of the excavation. Dissolved oxygen concentrations are presented in the above table and in figure 6. i