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1 <br /> Geological TeCAW ics inn. <br /> ' 1 101 7"Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)522-4227 <br /> ' REPORT <br /> Groundwater Monitoring <br /> ' 2"d Quarter 2003 <br /> ' Morita Brothers <br /> 814 E. Charter Way <br /> Stockton, CA <br /> ' Project No 724 2 <br /> August 11, 2003 <br /> EXECUTIVE SUMMARY <br /> This report summarizes the 2"d Quarter 2003 round of groundwater monitoring and testing <br /> ' that occurred on June 30, 2003 The laboratory analyses indicate that five of the ten <br /> monitoring wells on this site reinam 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 43 feet mean <br /> sea level (ms]) and this corresponds to approximately 36 feet below ground surface (bgs) <br /> ' Protect 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 S45°E at 0 0071 ft/ft for the June 30, 2003 event The rose <br /> diagram shown in Figure 4A indicates that the water table groundwater gradients at this site <br /> 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 413 illustrates the historical intermediate aquifer gradients and the June 30 gradient <br /> that was calculated to be SWE at 0 0014 ft/ft <br /> 1 <br />