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M. Scott Mansholt - 2 - 12 November 2008 <br /> Chevron <br /> Mountain House Development Site #6 <br /> Fuel fingerprint evaluation determined that the crude oil present was consistent with <br /> • <br /> degraded San Joaquin Valley crude oil from the historical Chevron pipelines. <br /> ' SAICro osed 13 additional soil borings to continue to characterize the affected areas <br /> P P <br /> discussed above. Soil and groundwater samples will be collected for analysis in support of <br /> ' existing analytical data. <br /> Based on the review, Central Valley Regional Water Quality Control Board (Central Valley <br /> ' Water Board) staff has the following comments: <br /> • The lateral extent of affected soil and groundwater has not been adequately defined <br /> and additional characterization is needed. <br /> • With the exception of location J, Central Valley Water Board staff concurs with the <br /> additional soil boring locations. Two borings should be completed approximately 50 <br /> feet to the northwest and southeast, respectively from location J. <br /> • Where access issues may cause delay, proposed boring locations may be shifted to <br /> within the UPRR, West Byron Road, and/or existing pipelines right-of-way easements <br /> provided the purpose for the original location is accomplished and new locations are <br /> submitted for review. <br /> • When comparing non detect results with applicable Environmental Screening Levels <br /> and/or Preliminary Remedial Goals used for delineation or health risk assessment <br /> needs, applicable laboratory method detection limits should be used. <br /> Central Valley Water Board staff concurs with SAIC's proposal to conduct the additional <br /> investigation described above, provided our comments are addressed. <br /> By 1 May 2009, please submit the additional soil and grorandwater characterization report. <br /> If you have any questions or comments, please contact Dean Hubbard at (550) 445-5170. <br /> l 1 <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Engineering Geologist <br /> P.G. No. 6357 <br /> Attachment <br /> cc: Michael J. Infurna, San Joaquin County DEN, Stockton CA <br /> Hoanhi Foster, Tracy, CA <br /> ' Geoffrey Reeder. UPRR, Spring, TX <br /> Michael E. Jenkins, SAIC, Sacramento, CA <br />