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Mr. Nam Baek 2 — 21 March 2008 1 <br /> Occidental Chemical, Lathro <br /> 3. We are concerned about the persistence of elevated concentrations of constituents of <br /> concern in WS-1 at all depth intervals, despite its proximity to several extraction wells. <br /> Field parameters in WS-1, such as conductivity and pH, tend to be different from those for <br /> the conventionally completed wells (as shown in Appendix H); is it possible that <br /> representative samples cannot be collected from these sampling points because of the <br /> way the well is constructed? Please provide an in-depth analysis of the well construction, <br /> performance, and chemistry and recommendations for obtaining representative sampling <br /> results. If the well's integrity is shown not to influence chemical results, we request <br /> OxyChem propose corrective measures to reduce concentrations of sulfolane and DBCP <br /> at this location. <br /> 4. Based upon the the Annual Report, the OxyChem groundwater extraction and treatment <br /> system's capture zone appears to encompass the J.R. Simplot site's potential release <br /> areas (the treatment ponds and the UN-32 tank area). It is possible that OxyChem's <br /> pumping is partially pulling nitrate releases in groundwater from J,R. Simplot. We strongly <br /> recommend that OxyChem work with J.R. Simplot to evaluate available data and initiate a <br /> dialogue to define a cooperative arrangement for management of the site cleanup. <br /> If you have any questions regarding this correspondence, please contact me by telephone at <br /> (916) 464-1588 or by email at kdominic@waterboards.ca.gov. <br /> Kathryn L. Dominic <br /> Engineering Geologist <br /> cc: Mr. Mike Anderson, Glenn Springs Holdings, Inc., Dallas, TX <br /> Mr. Mike Mateyk, CRA, Waterloo, ON <br /> Mr. Tom Royse, CRA, Stockton <br /> Mr. Tim Van Domelen, J.R. Simplot, Lathrop <br /> Ms. Debbie Schecter, SFD72 Site Cleanup Branch, USEPA Region No. 9, <br /> San Francisco, CA <br /> Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, <br /> Stockton, CA <br /> Mr. Paul Horton, The Source Group, Inc., Walnut Creek, CA <br />