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r in , Ripona Market Third Quarter Groundwater Sampling Report August 2004 Page: 2 Groundwater flow direction was to the east with a very shallow gradient (North 32 East/ 0 0006) similar to past monitoring events The groundwater elevations and groundwater flow direction are shown on Figure 2 Site Map/Groundwater Flow Groundwater Elevations 08-04-04 Well lCollar Elevation I DTW GW Elevation MW-1 6328 2779 3549 MW-2 6359 2808 3551 MW-3 638 283 355 MW-4 6352 2802 355 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 gasoline and aromatic hydrocarbons were detected in the deep well, MW4 Groundwater chemistry for the August 4, 2003 event is presented in Figures 3, 4, and 5 An Oxygen low is present at MW 1 with higher oxygen concentrations measured in the down gradient wells Dissolved oxygen distribution for the August 4, 2003 event is shown in Figure 6 LaboratoryGroundwater Sample Results Petroleum ComRounds 08/04/04 Sample I D I Gasoline I Benzene I Toluene I E-Benzene I Mens I MTBE I t-Butanol 1,2DCA I DO MW-1 <0 05 <0 3 <0 3 <0 3 <0 6 <0 5 <5 <0 5 668 MW-2 <0 05 <6 0 <6 0 <6 0 <12 0 450 <100 <10 179 MW-3 <0 05 <0 3 <0 3 <0 3 <0 6 <0 5 <5 <0 5 3 18 MW4 <0 05 10 70 10 49 <0 5 <5 <0 5 3 93 ND=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 witlun 2,000 feet of the point of release identified water well approximately 2000 feet from the former underground storage tanks The San Joaquin County Environmental Health Department requested submittal of revised groundwater elevation maps in a July 13, 2004 review letter of the "Vertical Groundwater Investigation and November 2003 Quarterly Monitoring Event" Revised groundwater elevation maps in attached as appendix C 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 a corrective action plan including recommendations for addition work or site closure is in preparation 0