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Geosyntec oo consultants will be grouted using tremie pipe or equivalent from the bottom up with a bentonite and neat cement mixture to between four to five feet below grade, followed by clean earth fill to surrounding grade.3 Sealing materials shall be placed in one continuous operation, and Geosyntec will coordinate with SJCEHD, as necessary, so that verification by a SJCEHD representative can be made to determine that an adequate seal has been installed. 4.3 Installation of Monitoring Wells MW-5C and MW-7C A C-57 licensed drilling contractor (PeneCore Drilling of Woodland, California) will be subcontracted by Geosyntec to install two new replacement monitoring wells, MW-5C and MW-7C. Geosyntec will be present during the monitoring well installation activities to direct and document the work. Each new well will be installed at a location within 15 feet of the well being replaced. Geosyntec staff will make the final determination on exact locations based on field observations. The locations of monitoring wells MW-513 and MW-713 are presented in Figure 2, and MW-5C and MW-7C will be offset to the east of the phytoplantation along the access road, where tree roots are anticipated to be less dense. Monitoring wells MW-5C and MW-7C will be installed and developed in the manner described below. 4.3.1 Borehole Completion The drilling contractor will advance the borings using hollow stem auger methodology with 10-inch diameter augers. Soil samples will be collected continuously from ground surface to final depth for logging purposes only (no samples will be collected for laboratory analysis). All soil samples will be collected using macrocore liners prior to advancing the auger. Soil cores will be logged by Geosyntec staff under the direction of a California Professional Geologist or Civil Engineer using the Unified Soil Classification System. Borings will be advanced until reaching final depth at approximately 26 feet bgs and 28 feet bgs for well MW- 5C and MW-7C, respectively (defined as one foot below the bottom of the target screen interval); however, final depths may be adjusted by Geosyntec based on the results of the continuous soil sampling. 3 Grouting to four to five feet below grade,with clean earth fill to surrounding grade,was required by the CRWQCB for previous well destructions at the Site,as it allows future earth work activity to occur at the Site while minimizing the potential to disturb the grout seal.This protocol was described in the CRWQCB's March 6, 2013 letter, Conditional Concurrence With Well Destruction Work Plan, Oxychem Stockton, 1904 Charter Way,Stockton,San Joaquin County. OxyChem-Stockton MW Replacement Work Plan 7.18.25 4 2025.07.18