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- s <br /> CleologccaC ! QG' cs (SLC. _ <br /> ' 1101 7`h streets <br /> Modesto,California 95354 <br /> (209)522-41191 Fax(209)522-4227 <br /> ' REPORT <br /> Groundwater Monitoring <br /> ' <br /> 1" Quarter 2006 <br /> Morita Brothers <br /> 814 E. Charter Way <br /> Stockton, CA <br /> ' Project No 724 2 <br /> April 25, 2006 <br /> MEXECUTIVE SUMMARY <br /> This report summarizes the I" Quarter 2006 round of groundwater monitoring and sampling <br /> ' that occurred on February 24, 2006 The laboratory analyses indicate that nine of the <br /> nineteen monitoring wells on this site remain impacted by gasoline range petroleum <br /> hydrocarbons The groundwater contamination plume appears to have migrated off site to the <br /> ' east This is evident in Figure 6 <br /> The average elevation of groundwater in the water table wells at the site was -2136 feet <br /> below mean sea level which corresponds to approximately 36 feet below grade 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 contamination <br /> ' Groundwater gradient calculations demonstrate that groundwater flow in the water table and <br /> deep aquifer wells flowed in a southeasterly direction The intermediate level wells displayed <br /> anomalous and variable gradients for the event The historical groundwater gradients at this <br /> site consistently trend to the east, ranging from northeast to southeast The vertical flow <br /> component of shallow groundwater gradient was negative for the MW-4/104 well pair Well <br /> parrs MW-6/106 and MW-7/MW-107 exhibited upward flow for the February 2006 event <br /> tThe highest levels of contamination found in the groundwater plume are in the MW-1081208 <br /> well pair to the northeast of the site- 98 3 and 1580 ug/1 TPH-G, respectively This suggests <br />