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Mr. Jeff Whitworth % - 2 - % 15 July 2008 <br /> Regional Water Board staff concurs with the CPT borings, discrete depth groundwater <br /> sampling, and water supply well field survey proposed in the Work Plan. The Regional Water <br /> Board notes that although the three water supply wells identified so far are potentially located <br /> cross gradient (northwest) from the site investigation area based on the inferred groundwater <br /> flow direction (northeast), they appear to be located in close proximity to the former pipeline <br /> alignment, which also trends in the cross gradient direction (northwest to southeast). This <br /> section of the former pipeline located northwest of the site has not been investigated for <br /> potential releases. Furthermore, groundwater contamination where investigated extends to <br /> depths that would overlap with the gravel pack interval depths of the identified water supply <br /> wells. Therefore, Shell should sample these and any other water supply wells identified by the <br /> field survey for the site constituents of concern or explain why any of the wells need not be <br /> tested. <br /> The results of the investigation, completed sensitive receptor survey, and water supply well <br /> testing are to be submitted by 30 September 2008. Provide the Regional Water Board at <br /> least 10 days notice prior to any field activities including water supply well sampling. If you <br /> have any questions regarding this letter, you may contact me at (916) 464-4665 or <br /> ncasebeer@waterboards.ca.gov. <br /> Aathanebeer, P.G. <br /> Engineering Geologist <br /> Private Sites Cleanup Unit <br /> cc: Mr. Michael Hurd, Scientific Applications International Corporation, Oakland <br /> Mr. Mike Infurna, San Joaquin County Environmental Health Department, Stockton <br /> Ms. Eileen Nottoli, Allen Matkins Leck Gamble & Mallory LLP, San Francisco <br /> Ms. Ileana Rhodes, Shell Global Solutions (US) Inc., Houston, TX <br /> Mr. David Corliss, Golden State Developers, Walnut Creek <br /> NEC/VV:\slit dodWustin Staff\Nathan\Shell-Hansen&Schulte Rd\6-6-08 Investigation Work Plan.doc <br />