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Addendum to the Well Installation and <br /> Hydraulic Testing Report and Additional <br /> ARCADIS Well Installation Work Plan <br /> Former Occidental Chemical Corporation <br /> Lathrop, California <br /> Summary <br /> The purpose of the proposed extraction and injection well network expansion is to expedite the <br /> treatment of COC-affected groundwater and decrease COC concentrations within the current footprint. <br /> Proposed extraction wells were placed in areas of high concentrations of sulfolane, DBCP and/or EDB. <br /> Operating flow rates for the new extraction wells are within the range of flow rates that have been <br /> shown to be sustainable yields for other on-site wells.The placement and flow rates of treated <br /> groundwater injected within the footprint of the plume at INJ-11 and INJ-12 were determined based on <br /> modeling simulations to be captured by the nearby extraction wells(Appendix B and C). Extraction <br /> wells EW-03 and EW-04 are located along the outer edge of the plume, making them candidates for <br /> conversion to injection wells INJ-13 and INJ-14.Treated oxygenated groundwater injected into wells <br /> INJ-13/EW-03 (shallow and intermediate zones) and INJ-14/EW-04 (intermediate and deep)would <br /> stimulate in-situ biodegradation of sulfolane and be captured by EW-05(intermediate and deep), and <br /> EW-04A(deep). Modeling results indicate that the proposed extraction and injection system will reduce <br /> concentrations of sulfolane, DBCP and EDB within the current plume footprint(Appendix C). <br /> 7. Schedule <br /> ARCADIS is prepared to proceed with well installation activities upon receiving approval of the scope of <br /> work summarized in the Report and Work Plan and supplemented in this Addendum.Additional wells <br /> may be installed as needed during subsequent phases of well network optimization. <br /> 8. References <br /> ARCADIS U.S., Inc. (ARCADIS). 2011. Soil Excavation Report, Former Occidental Chemical <br /> Corporation Facility, Lathrop, California. December 21. <br /> . 2012.Well installation and hydraulic testing report and additional well installation work plan. <br /> Former Occidental Chemical Corporation Facility, Lathrop, California. February 28. <br /> . 2012b. Supplemental investigation in the AgChem Area: Summary Report and Well Installation <br /> Work Plan. Former Occidental Chemical Corporation Facility, Lathrop, California.April 30. <br /> California Regional Water Quality Control Board—Central Valley Region (RWQCB). 2004. Monitoring <br /> and Reporting Program, Former Occidental Chemical Corporation Facility, Lathrop, San Joaquin <br /> County. February 11. <br /> . 2012. Review of well installation and hydraulic testing report and additional well installation work <br /> plan, Former Occidental Chemical Corporation Facility, Lathrop, San Joaquin County. August 6. <br /> 2012-09-13 addendum well install work plan_hy test rpt.docx 14 <br />