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II . . <br /> GeologicafTechnics Inc. <br /> 2741 River Road � <br /> i I3 .a <br /> _11odesto,Caftfornia 95351 <br /> (209)538-6424/1FaX"#538-5852 <br /> June 8, 2001 <br /> Project No.: 750.3 <br /> Project Name: City of Escalon <br /> Ms.Linda Sanborn <br /> State Water Resources Control Board <br /> 2014 T Street, Suite 130 <br /> P.O. Box 944212 <br /> Sacramento, CA 94244-2120 <br /> 1 <br /> RE: Cost Pre-Approval: Vadose Zone Remediation &`Groundwater Monitoring <br /> Location: Former Arco Gas Mini Mart, 1305 Escalo.n Avenue, Escalon,CA <br /> USTCFP: Claim No. 013929 <br /> i <br /> i� Dear Ms Sanborn: <br /> GTI has prepared the enclosed Remedial Design Plan and a budget to perform the vadose zone <br /> remediation, plus groundwater monitoring for a period of one year. <br /> The goal of the Remedial Design Plan is to protect public'health by: <br /> • Removing the contaminants in the vadose zone that are .leaching into the drinking water <br /> aquifer. <br /> • Help mitigate the BTEX plume in the groundwater by increasing the oxygen content of the <br />] capillary fringe, thus improving the natural attenuation process. <br /> i • Prevent these contaminants from impacting water wells. <br /> j Summary of Work Performed <br />' GTI performed a vapor extraction pilot test at the site in June of 2000. Field and laboratory test <br /> results showed that the site is conducive to remediation by vapor.extraction. The vapor <br /> extraction wells installed for the pilot tests are adequate for the remedial action project <br /> proposed here. <br />} Work performed to date is summarized below: <br /> • February 1999 - six boreholes were -drilled, soiland groundwater samples collected <br /> (including one groundwater sample from each borehole via hydropunch methods), samples <br /> tested for petroleum hydrocarbons. Analytical results show the presence of BTEX, TPH-G <br /> and oxygenated fuel compounds in the soil and groundwater: <br /> • April 1999 - One monitoring well and two vapor extraction wells were installed. <br /> • June 1999 - One monitoring well was installed. <br /> • July 1999 -.One monitoring well and two vapor extraction wells were installed. <br /> • April 2000 - A groundwater monitoring event revealsfthat MW-1 was impacted with BTEX, <br /> TPH-G and MTBE. Groundwater depth was approximately 56 feet below ground surface <br /> and flows to the west-northwest. <br />