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C,e0logica I reChAks In C. <br /> 1 101 7'h Street <br /> Modesto,California 95354 <br /> (209)52241 19/Fax(209)522-4227 <br /> r REPORT <br /> ' Groundwater Monitoring <br /> 1" Quarter 2004 <br /> Valentine (Castle Motors) <br /> 231.5 N. El Dorado St. <br /> ' Stockton, CA <br /> Project No 723 2 <br /> June 15, 2004 <br /> EXECUTIVE SUMMARY <br /> This report summarizes the I" Quarter 2004 round of groundwater monitoring and testing <br /> that took place on March 21, 2004 The event marks the first time that three new multi- <br /> chambered tubing (CMTTM) wells were sampled The CMTTM wells were installed in <br /> ' November 2003 in an effort to further define the extent of the gasoline groundwater plume <br /> at the site <br /> The laboratory results indicate that detectable concentrations of the aromatic hydrocarbon <br /> compounds (BTEX) and gasoline range petroleum hydrocarbons (TPH-G) are present in all <br />' six shallow/intermediate monitoring wells on site On site deep wells MW-l O 1/MW-201 <br /> did not contain contamination above the laboratory reporting limits which supports a <br /> conclusion that the initial contamination detected in the wells was a drilling artifact <br />' Trace BTEX constituents were detected in well set MW-7/107/207 located to the north of <br /> the site All three intervals of the down gradient well set MW-8/108/208 contained BTEX <br />' and TPH-G All three intervals of the up gradient well set MW-9/109/209 did not contain <br /> contaminant concentrations above the laboratory reporting limits <br /> The groundwater elevation averaged —23 66 feet mean sea level in the wells and this <br /> corresponds to about 33 5 feet below grade surface (bgs) This elevation is an increase of <br /> approximately 3 42 feet since the November 2003 monitoring event Groundwater gradient <br />