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Geological Technics Inc. <br /> 1 101 711 Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)522-4227 <br /> REPORT <br /> ' Groundwater Monitoring <br /> 4t'' Quarter 2002 <br /> ' Morita Brothers <br /> 814 E. Charter Way <br /> ' Stockton, CA <br /> Project No 724 2 <br /> ' March 11, 2003 <br /> EXECUTIVE SUMMARY <br /> ' This report summarizes the 4" Quarter 2002 round of groundwater monitoring and testing <br /> that occurred on December 20, 2002 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 19 feet below the water table <br /> The average groundwater elevation in the water table wells at the site was --21 36 feet mean <br /> sea level (msl) and this corresponds to approximately 36 feet below ground surface (bgs) <br /> Project historic low groundwater levels in the early 1990's were 20 feet lower than the <br /> 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 561°E at 0 0042 ft/ft for the December 20, 2002 event <br /> The rose diagram shown in Figure 4A indicates that the water table groundwater gradients <br /> at this site are consistently towards the east A lose diagram was also constructed for the <br /> interinediate aquifer monitored by wells MW-1, MW-2, MW-3, MW-106 and MW-107 <br /> Figure 413 illustrates the historical intermediate aquifer gradients and the December 20, <br /> 2002 gradient that was calculated to be S890E at 0 0014 fUft <br /> r <br />