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CTCO109 CaI recti ILLS taco <br /> ' 1101 7`°street <br /> Modesto,Cahfornma 95354 <br /> (209)522-4119 1 Fax(209)5224227 <br /> ' REPORT <br /> ' Groundwater Monitoring <br /> 3rd Quarter 2004 <br /> ' Morita Brothers <br /> 814 E. Charter Way <br /> Stockton, CA <br /> 1 Project No 724 2 <br /> November 12, 2004 <br /> MEXECU'T'IVE SUMMARY <br /> This report summarizes the 3rd Quarter 2004 round of groundwater monitoring and testing <br /> ' that occurred on July 28, 2004 The laboratory analyses indicate that seven of the nineteen <br /> monitoring wells on tlus site remain impacted by gasoline range petroleum hydrocarbons <br /> The groundwater contamination plume appears to have migrated off site This can be seen in <br /> ' Figure 6 <br /> The average elevation of groundwater in the water table wells at the site was —23 04 feet <br /> ' MSL (below mean sea level) or approximately 38 feet below grade surface (Table 1) This <br /> project's 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 contammatnon <br /> Groundwater gradient calculations demonstrate that groundwater flow in the three-aquifer <br /> ' horizons investigated, water table, intermediate and deep wells, flowed in an easterly <br /> direction The historical groundwater gradients at this site consistently trend to the east The <br /> vertical flow component of shallow groundwater gradient was mixed for this quarter Well <br /> ' pair MW-41104 exhibited a downward flow that is consistent with past events <br /> The data from the wells that were installed at the site in December 2003 continues to indicate <br /> ' that the plume appears to extend to the east of the site It is not known whether or not <br /> contaminated properties to the northwest of the site may be contributing to the groundwater <br /> plume <br />