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Extraction Well Installation Summary Report and Injection ARCADIS Well Installation Work Plan Former Occidental Chemical Corporation Facility Lathrop, California with extraction well EW-12B(R).Abandonment and replacement of EW-12B was approved by the RWQCB in an email to ARCADIS dated March 4,2013. The following activities were conducted prior to abandoning EW-12B and installation of EW-12B(R): • A well abandonment and boring permit was obtained from the SJCEHD.A copy of the permit is provided in Appendix A. • The current property owner, Simplot,was contacted to discuss the presence of utilities in the vicinity of the proposed work. • Underground Service Alert was contacted in accordance with local notification requirements. • A private utility locator was contracted to assess the presence of potential underground utilities in the vicinity of the boring location. • EW-12B(R)was cleared to a depth of approximately 5 feet bgs using an air knife. EW-12B(R)installation activities were conducted from March 6 to 8,2013.A borehole was advanced with mud rotary drilling methodology using a 12-inch bit from the ground surface to the total depth of 203 feet bgs. Following advancement of the 12-inch bit,the drilling mud used to hold the borehole open was thinned to a target viscosity of approximately water and the well materials were placed in the borehole.Well construction details are summarized in Table 1. EW-12B(R)is screened from approximately 150 to 180 feet bgs and consists of a 6-inch-diameter 5-foot-long Schedule 80 PVC blank sump,followed by a 6-inch-diameter stainless steel well screen with 0.010-inch slots. Blank 6- inch-diameter Schedule 80 PVC casing was installed from the top of the screen to approximately the ground surface.After the screen and casing were placed in the open borehole, a sand pack consisting of#2112 Monterey sand was placed in the borehole to approximately 7 feet above the screen; 5 feet of time release bentonite pellets were placed above the sand pack to prevent grout from entering the sand pack.The borehole was then sealed with neat cement grout to 5 feet bgs.The well was left with a temporary well box and is awaiting vault construction associated with the future expansion of the groundwater treatment system.The original proposed screen interval(170 to 200 feet bgs)was adjusted to 150 to 180 feet bgs due to a layer of clay encountered from 180 to 195 feet bgs. The EW- 12B(R)well construction log is presented in Appendix B. EW-12B(R)was developed from March 12 to 14, 2013 by brushing, surging, airlifting, bailing, and pumping to remove fine-grained sediment and drilling fluids from the sand pack.Temperature, pH, conductivity,turbidity, and volume removed were monitored during development. Development activities continued until all of the following were true: latfimp yell installation reportfiml_(0420,13)d= 5