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t <br /> URS <br /> Mr Harlin Knoll Page 2 of 5 <br /> San Joaquin County Environmental Health Department <br /> July 12, 2005 <br /> A pump and treat groundwater remediation system was operated at the site from 1992 until 1996 <br /> Post remediation groundwater monitoring showed increased MtBE concentrations at MW-2 and <br /> AMW-5 <br /> Depth to groundwater at the site currently ranges from 5 to 7 feet below ground surface (bgs) <br /> Groundwater flow direction beneath the site is to the northwest <br /> In a letter dated May 27,2005,SJCEHD directed ARCO to submit a workplan to conduct a vertical <br /> assessment of groundwater contamination beneath the site, and define the lateral extent of <br /> groundwater contamination downgradient of monitoring well MW-7 <br /> SCOPE OF WORK <br /> URS proposes to install two groundwater monitoring wells to Investigate the lateral and vertical <br /> extent of hydrocarbon-impacted groundwater encountered at the site One boring (MW-9) will be <br /> advanced to approximately 45 feet bgs on-sate in the downgradient groundwater flow direction for <br /> the installation of a deep groundwater monitoring well The second boring (MW-10S/MW-10D) <br /> will be advanced to approximately 45 feet bgs downgradient of MW-7 for installation of a dual <br /> completion groundwater monitoring well Proposed boring locations are presented on Figure 1 This <br /> workplan includes discussion of permitting, drilling and sample collection, monitoring well <br /> construction, groundwater monitoring well development, sampling, and surveying, and report <br /> preparation A site-specific health and safety plan (HASP) will be prepared and will be available <br /> onsite during field activities <br /> Permitting and Access Agreements <br /> SJCEHD requires that permits be obtained prior to the completion of soil borings and monitoring <br /> wells URS will submit the appropriate permit application(s) with fees to the SJCEHD prior to <br /> conducting field activities <br /> The proposed off-site monitoring well (MW-10S/MW-10D) is located on private commercial <br /> property An access agreement between ARCO and the proposed well location property owner must <br /> be obtained prior to conducting field activities <br /> Drilling and Sample Collection <br /> Boring locations will be clearly marked and Underground Service Alert (USA) will be notified a <br /> minimum of 48-hours prior to commencement of field activities A private utility locator will also <br /> • <br /> K 1Wprocess\J5 BP ARCOU 1194\2005 Well InstalA11194 Well Install WP 05 doc <br />