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Pombo Ranch Property <br /> Quarterly Groundwater Sampling Report April 2003 <br /> Page: 2 <br /> measurements, and groundwater elevations are shown below. Groundwater elevations and <br /> flow direction are located on figure 2. <br /> Groundwater Elevations 04-25-03 <br /> Well lCollar Eleva-t-io-n-T DTW TGW Elevation <br /> MW-1 43.45 11.16 32.29 <br /> MW-2 43.44 11.12 32.32 <br /> MW-3 45 11.65 33.35 <br /> Gasoline petroleum hydrocarbons and volatile aromatic hydrocarbons were not detected <br /> by the analytical laboratory in water samples collected from the monitoring wells. MTBE <br /> was detected at a concentration of 0.9 ug/l in well MW2, located down gradient from the <br /> area of former underground storage tank. No other fuel oxygenates were detected. <br /> Laboratory analyses are located below and on Figure 3. <br /> Laboratory Groundwater Sample Results 04-25-03 <br /> Sample I.D. I Gasoline Benzene TToluene E-Benzene I Xylenes I Oxygenates 02 <br /> MW-1 <0.05 <0.3 <0.3 <0.3 1 <0.6 ND 2.8 <br /> MW-2 <0.05 <0.3 <0.3 <0.3 1 <0.6 0.9 mtbe 2.9 <br /> MW-3 <0.05 <0.3 <0.3 <0.3 1 <0.6 ND 4.3 <br /> ND=Non Detect NA=Not Analyzed <br /> Mg/L for gasoline µg/L for BTEX,MTBE,and 8260 Oxygenated Compounds <br /> Dissolved oxygen measurements were collected as part of the groundwater monitoring to <br /> provide an estimate of the level of biologic activity in the groundwater. A slight drop in <br /> oxygen concentrations is present down gradient of the former underground storage tank <br /> compared to the concentrations present in the up gradient well. This suggests a slight <br /> increase biologic activity in the area of the release. Dissolved oxygen concentrations are <br /> shown on figure 4. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Shallow ground water flow was to the North Northeast with flat gradient. The detected <br /> contaminant was MTBE at 0.9 ug/l below the current action level of 13 ug/l. A slight <br /> decrease in dissolved oxygen concentrations is present in down gradient off the former <br /> underground storage tank indicating biologic activity associated with the release is <br /> occurring. Quarterly monitoring will continue to confirm the breakdown of the remaining <br /> contaminants. <br /> • <br />