SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Mr. Timothy VanDomelen - 3 - 17 September 2009 IR. Simplot, Lathrop 6. In Figures 14 through 16, the Explanation shows a "line of [constituent] in soil at TDL, in feet above mean sea level." The note should be revised to read, "area of soil [constituent] concentrations that exceed calculated TDL." 7. Impacted soil areas (as shown in Figures 14 through 16) are not sufficiently delineated to make an accurate estimate of costs or determine the feasibility of achieving the remedial goals. Please prepare a Work Plan for further delineation of soils in order to better define the locations and estimate the total volume of soils requiring cleanup. 8. In Section 6.2.3, text states that an estimated 30% of soil, that would require excavation in order to meet the proposed cleanup goal, is inaccessible. Inaccessibility of soils is an assumption used to support the selection of the no-action alternative for soils. The FS does not explain options for dealing with impacted soils that are left in place — e.g., monitoring, in-situ treatment, etc. Please provide this information in an addendum to the FS. 9. The duration of operation of any groundwater treatment system, and therefore the costs of a groundwater remedy, would be significantly reduced if your remedy includes both .reduction of contaminant mass in soils and methods for prevention and detection of future leaks from the ponds and associated piping. The annual plant shutdown in late summer is an opportunity to conduct source reduction/removal operations and pneumatic testing of the piping that connects the process water ponds to the plant. We request that the addendum to the FS include the costs for conducting testing and developing a monitoring protocol for annual confirmation of pond and piping integrity. 10. Geomatrix indicates in the FS that a significant amount of mass of inorganic constituents is present in the water table zone (10-27 feet below ground surface) but do not state whether the chemical concentrations are being affected by GHSI's groundwater extraction, and/or if there is an ongoing release to the groundwater. The site conceptual model on which the FS and future cleanup are based should clearly state an interpretation of the pollutant source and factors affecting the fate and transport based on the data. If there is uncertainty about how to interpret these data, then J.R. Simplot should propose to collect more data to address this uncertainty. 11 . In Section 2.3, Geomatrix stated that the groundwater extraction and treatment system at the former Occidental Chemical site, ,operated by Glenn Springs Holdings, Inc. (GHSI) "is currently operated for about half of each year." Since June 2008 the Occidental Chemical system has been operating continuously. Please make this correction and any necessary changes to the hydraulic model calculations presented in Appendix D.