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' � t <br /> i logica I re,C`ntCS In C', <br /> ' 1101 7"Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)522-4227 <br /> 1 <br /> ' REPORT <br /> Groundwater Monitoring <br /> 4" Quarter 2003 <br /> ' Morita Brothers <br /> 814 E. Charter Way <br /> ' Stockton, CA <br /> Project No 724 2 <br />' February 3, 2004 <br /> EXECUTIVE SUMMARY <br /> This report summarizes the 4"' Quarter 2003 round of groundwater monitoring and testing <br />' that occurred on November 28, 2003 The laboratory analyses indicate that four of the ten <br /> monitoring wells on this site remain impacted by gasoline range petroleum hydrocarbons <br /> The groundwater contamination plume appears to be migrating off site as evident from <br />' detection in well MW-106 The contamination is present in well MW-106 at a depth of <br /> approximately 17 feet below the water table <br />' The average groundwater elevation in the water table wells at the site was —23 12 feet mean <br /> sea level (msl) and this corresponds to approximately 37 feet below ground surface (bgs) <br />' This project's historic low groundwater levels in the early 1990's were 20 feet lower than <br /> the current level This is part of the problem with trapped residual hydrocarbons below <br /> groundwater that act as a continuing source of groundwater contamination <br />' Groundwater gradient calculations demonstrate that groundwater flow in the water table <br /> wells MW-4 through MW-6 was S73°E at 0 018 ft/ft for the November 28, 2003 event The <br />' rose diagram shown in Figure 4A indicates that the water table groundwater gradients at this <br /> site consistently trend east to southeast A rose diagram was also constructed for the <br /> intermediate aquifer monitored by wells MW-1, MW-2, MW-3, MW-106 and MW-107 <br />' Figure 4B illustrates the historical intermediate aquifer gradients and the November 2003 <br /> gradient that was calculated to be S80°E at 0 002 ft/ft The vertical flow component of <br /> 1 <br />