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Extraction Well Installation Summary Report and Injection ARCADIS Well Installation Work Plan Former Occidental Chemical Corporation Facility Lathrop, California • visual observation indicated an improvement in the water clarity, • water-quality indicators stabilized after a minimum of 10 well casing volumes had been removed, and • no additional improvement in specific capacity was seen from development activities. The well development log is included in Appendix B. Extraction well EW-12B abandonment activities were conducted from March 18 to 22, 2013.The EW- 12B abandonment log is included in Appendix B. EW-12B was abandoned by pressure grouting the sump and screen interval(170 to 205 feet bgs)with neat cement grout followed by over-drilling from the surface to 170 feet bgs.The interval from the surface to 170 feet bgs was drilled with an HSA drill rig utilizing 12.25-inch-diameter augers to remove the PVC casing, sand pack, and grout installed in the original boring. The borehole was then sealed with neat cement grout under pressure from the bottom of the borehole to the surface. Installation and abandonment procedures were conducted in accordance with SJCEHD standards. 2.2.4 Well Survey The top of casing elevation, ground surface elevation, latitude, and longitude for the new wells will be surveyed using the same datum as previous investigations at the Site after well head completions have been installed.Well survey information for the newly installed wells will be included in a subsequent report summarizing the conveyance line piping installation. 2.2.5 Groundwater Sampling Following well development, a grab groundwater sample was collected from each newly installed well using a bailer on March 19,2013 and analyzed for sulfolane according to APPL SOP ANASULF to obtain baseline water quality data. Laboratory analytical reports for these samples are presented in Appendix C. Following installation and connection to the treatment system,the extraction wells will be sampled per monitoring and reporting programs No. R5-2004-0800 and No. R5-2012-0106 on a quarterly basis for a minimum of four quarters, after which,the sampling frequency will be reevaluated. Tabulated analytical data from grab groundwater samples collected on March 19,2013 are provided in Table 2. Sulfolane concentrations in the new extraction wells ranged from less than the reporting limit (20 micrograms per liter[pg/Ll)in wells EW-14A, EW-15A, and EW-17 to 4,600 pg/L at EW-12B(R). EW-10 was re-sampled on March 25, 2013 after completing an approximately three-volume purge of lathmp.ell installation mport_final_(04-29-13).do 6