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C000agical rec%iics W. <br /> 1101 7v'Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)522-4227 <br />' REPORT <br />' <br /> Groundwater Monitoring <br /> 4th Quarter 2004 <br />' J.M. Equipment Company <br /> 1245 West Charter Way <br />' Stockton, California <br /> Project No 507 2 <br />' February 22, 2005 <br /> EXECUTIVE SUMMARY <br /> This report summarizes the results of the 4t' Quarter 2004 groundwater monitoring and <br /> sampling event that took place on December 29, 2004 For this event, the average <br /> groundwater elevation at the site was —1173 feet below mean sea level (msl) and the <br />' groundwater flow was N58°E at 0 003 ft/ft A vertical groundwater gradient calculation for <br /> wells MW-9 & 109 show that groundwater is flowing downward at a slope of 0 0060 ft/ft <br /> The analytical results of groundwater samples show that detectable concentrations of gasoline <br /> range hydrocarbons were present in four of the site's groundwater monitoring wells for this <br /> event Well MW-6 could not be monitored because it was under several inches of storm <br /> water on day of sampling The magnitude of the contamination in the wells is consistent with <br /> historical site data The fuel oxygenate compound MTBE was detected in four monitoring <br /> wells <br />' Moderate to strongly negative Oxidation-Reduction Potential (ORP) measurements show that <br /> eight of ten monitoring wells are within the halo of reaction depleted water caused by <br />' biodegradation of the contamination plume The ORP values are slightly more positive for <br /> wells MW-7 &MW-10 <br /> GTI submitted our June 10, 2003 "In-Situ Remediation Pilot Test" work plan for an in-situ <br /> hydrogen peroxide injection pilot test The SJC E111) issued approval of the work plan in <br /> their September 10, 2003 letter The injection process began on March 19, 2004 and report <br />