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wood. Groundwater monitoring wells will be decommissioned by pressure grouting. Portland cement mixed with 3-5% bentonite gel (cement-bentonite grout) will be placed from the total depth of the well to the ground surface using a tremie pipe. Each well casing will then be capped and pressurized to a minimum of 25 pounds per square inch for at least 5 minutes. If after 5 minutes the grout column has dropped, additional grout will be added, and the casing will be pressurized for an additional 5 minutes. This process will continue until the grout column ceases to drop. Following pressure grouting activities at each groundwater monitoring well, the well box will be removed, and each well will be overdrilled to a depth of approximately three feet using a hollow-stem auger drill rig and augers at least one foot larger in diameter than the original boreholes in accordance with the San Joaquin County Well Standards (Environmental Health Department, 2005). An air knife or hand tools may be used to expand the diameter of the overdrilled borehole if augers of sufficient diameter are not available. Following overdrilling, cement-bentonite grout will be used to backfill the boring to approximately 1 foot below the ground surface. The upper 1 foot of each borehole will be backfilled with native material to match the surrounding ground surface. 5.0 GROUNDWATER MONITORING WELL INSTALLATION One 2-inch diameter groundwater monitoring well (MW-17) will be installed downgradient of the former ponds near MW-6 and will target the middle horizon groundwater zone. The well will be located as shown in Figure 2, final location may be adjusted in the field based on access or feasibility. The monitoring well will be constructed in compliance with the appropriate state (Department of Water Resources, 1991) and local well permitting requirements. Groundwater monitoring well installation methods are described in detail in Appendix A. The borehole will be advanced to at least 5 feet below ground surface (bgs) using hand auger equipment to clear potential subsurface utilities and, subsequently, to the target depth using hollow-stem auger drilling methods. Continuous soil core recovery will be attempted using either a split-spoon sampler or core-barrel sampling device. After reaching the targeted total depth, the well casing and screen, and the annular materials (filter pack sand, medium bentonite chip seal, and bentonite-cement grout seal) will be placed at depth within the augers to prevent bridging or borehole collapse. The final borehole depths and screen intervals will be determined by conditions in the field. Target specifications are as follows: https://woodpIc.sharepoint.com/teams/OlinTracy/Shared Documents/General/03.0 DocCtrl/2022 Decomm WP/Revised Decomm 3 WP/01_text/202207_Tracy_Wood_Decomm WP_text.docx