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Ripona Market Fourth Quarter Groundwater Sampling Report February 2005 Page: 2 • Groundwater flow direction was to the northeast with a very shallow gradient (North 20 East / 0 002) similar to past monitoring events The groundwater elevations and groundwater flow direction are shown on Figure 2 Site Map/ Groundwater Flow Groundwater Elevations 02/03/05 Well lCollar Elevation I DTW I GW Elevation MW-1 6328 2548 378 MW-2 6359 258 3779 MW-3 638 2602 3778 MW-4 6352 2576 3776 The analytical laboratory reported groundwater contamination by MTBE in well MW-2, located at the edge of the tank basin Trace concentrations (below drinking water standards) of aromatic hydrocarbons were detected in the deep well, MW4 Groundwater chemistry for the November 1, 2004 event is presented in Figures 3 and 4 An Oxygen low is present at MW 1 with higher oxygen concentrations measured in the down gradient wells Dissolved oxygen distribution for the November 1, 2004 event is shown in Figure 5 Laboratory Groundwater Sample Results Petroleum Com ounds 02/03/05 • Sample 1 D I Gasoline I Benzene I Toluene I E-Benzene I Xylenes I MTBE t-Butanol I 1,2DCA I DO MW-1 <0 05 <0 3 <0 3 <0 3 <0 6 <0 5 <5 <0 5 7 73, . MW-2 <0 05 <1 2 <12 <1 2 <2 4 126 <20 <2 0 190 MW-3 <0 05 <0 3 <0 3 <0 3 <0 6 <0 5 <5 <0 5 348 MW-4 <0 05 <0 3 <0 3 <0 3 <0 6 <0 5 <5 <0 5 662 Nil=Non Detect NA=Not Analyzed Mg/L for gasoline&Dissolved Oxygen µg/L for BTEX,MTBE,and 8260 Oxygenated Compounds The lateral and vertical extent of MTBE, the contaminant of concern has been defined laterally and vertically to be restricted to the immediate vicinity of the former underground storage tanks A survey of potential contamination plume receptors within 2,000 feet of the point of release identified a water well approximately 2000 feet from the former underground storage tanks It appears that the release does not pose a risk to the identified water wells in the vicinity of Ripona Market Quarterly monitoring of all wells will continue An evaluation of the potential long term threat of the impacted groundwater and corrective action plan was submitted on October 28, 2004 to the San Joaquin County Environmental Health Department