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Stantec Wel/Destruction Work Plan Stockton Charter Way Commingled Plume August 12, 2011 3.2 Permitting Prior to performing the well destruction activities, necessary permits will be obtained from the SJCEHD. 3.3 Preliminary Field Activities Well locations will be marked or cleared of underground facilities prior to well destruction activities. As required by the California Government Code 4216, Underground Service Alert (USA) North and 811 will be notified at least two working days before excavation/drilling activities. Well locations will be marked with white paint to indicate the area of excavation/drilling. This will allow USA North members, including local utility companies, to identify and mark the horizontal path of their underground facilities located within the area of excavation/drilling. The area will be cleared if no underground facilities are found. In conjunction with USA North and 811, a private utility locating company will be utilized for clearing proposed well boring locations for underground utilities. 3.4 Over-Drilling SMW-7 Stantec will oversee a C-57-licensed contractor over-drill SMW-7 in accordance with the California well standards. The SMW-7 well borehole will be air-knifed to approximately 8.1 ft bgs to investigate that no underground facilities exist within the area of drilling. Prior to over- drilling activities, the well casing will be inspected for obstructions; if obstructions are found, they will be removed. Well SMW-7 will be over-drilled using a 12-inch diameter sonic drill rig to remove material within the original borehole including the well casing, filter pack, and annular seal. The borehole will then be grouted with neat cement using a tremie pipe system forming a grout cap/surface seal from the bottom of the borehole to two ft bgs. If groundwater is expelled during the grouting process, it will be properly contained, characterized, and disposed. The borehole locations will be backfilled and resurfaced with appropriate materials to match the existing grade. 3.5 Pressure-Grouting SMW-18-80 and SMW-18-120 Stantec will oversee a C-57-licensed contractor pressure-grout CMT wells SMW-18-80 and SMW-18-120 according to the manufacturer's suggested procedures for decommissioning CMT wells (Appendix D). Prior to CMT well decommissioning activities, each channel will be inspected for any obstructions or debris; if obstructions or debris are found, they will be removed or cleaned out. According to the manufacturer, a quarter-inch diameter tubing will be used as a tremie and will be set at the bottom of each channel. Clean water will be utilized first through the pump and tremie system to verify that the flow is continuous and consistent. Grout pumping will begin once continuous flow is verified. As recommended by the manufacturer, a variety of grout compositions will be tested prior to actual CMT well grouting to determine how well the variety of grout compositions will set and how easily the grout can be pumped through the quarter-inch diameter tubing. Grout consisting of 2:1 and 3:1 water to cement ratio with the addition of plasticizer at approximately 4% by weight of cement will be tested. Grout composition will be considered acceptable/appropriate if continuous grout pumping is observed through the tremie tubing and if the grout does not cure Stockton Charter Way Commingled Plume Well Destruction Work Plan.doc 4