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Mr. Jeff Wong San Joaquin County Environmental Health Department May 8, 2023 Page 3 • MW -5 and MW -5B — East Main Street • MW -10 and MW -11 —South Windsor Avenue Traffic Control: RDM will subcontract a traffic control company to prepare a traffic control plan and provide traffic control during the destruction of the wells MW -5, MW -513, MW -10, and MW -11 which are located in the City of Stockton right-of-way. Well Destruction Permits: A well destruction permit(s) will be obtained from the San Joaquin County Environmental Health Department (SJCEHD) prior to beginning field activities. A sealing ("grout") inspection will be scheduled with SCEHD a minimum of two working days prior to drilling. Destruction of Groundwater Monitoring Wells by Blast Perforating: RDM proposes destroying all the monitoring and remediation wells associated with the Site by blast perforating. Tylor McMillan Well Service of Bakersfield, California will be subcontracted by either RDM or RDM's subcontracted driller, Gulf Shore Exploration of Shingle Springs, California to perform the blast perforating. Prior to destruction, the depth to groundwater and total depth of each well will be measured to ensure there are no obstructions. If there is an obstruction in the well an attempt will be made to clear up the obstruction. If the obstruction cannot be cleared, the well will need to be overdrilled instead of blast perforated. Assuming there are no obstructions, the work site will be cleared of all unessential personal. The tremie pipe will then be lowered to the bottom of the well casing and the blasting charges will be placed in the well. The blasting charges will be aligned with the screened section of the well. The sealing material (Type 1/II cement grout (grout), mixed at a ratio of 6 to 7 gallons of water per 94 pounds of cement, or in accordance with SJCEHD requirements) will be placed in the well casing using a tremie pipe and the well casing will be filled from the bottom up to the ground surface The grout will be pumped through the tremie pump using an appropriate grout pump to displace any encountered groundwater. Any groundwater produced will be containerized and disposed and handled per applicable laws. Once the well casing is removed, the tremie pipe will be removed. The blast area will then be checked and cleared, and a blast warning will be sounded. The charges (explosives) will then be armed, and a final blast warning will be sounded. The charges will then be detonated. The well will then be checked by the blaster and an all clear notification will be sounded. Additional grout will then be added to the well casing if necessary, until a mushroom cap is formed over the top of the well casing. Copies of Tyler McMillan Well Service's Blasting Safety Plan and Standard Operating Procedures are included in Enclosure D. McMillan Well Service will also prepare individual blast plans for each well and they will be onsite during the well destructions and can be provided to SJCEHD in advance of the well destructions if requested. Following completion of the grouting the well casing, the surface completion (well box/manhole cover) will be removed and well casing and borehole will be either overdrilled or hand excavated to a depth of at least 18 -inches below the ground surface and the well casing will be cut off 6 inches above the bottom of the excavation and removed. The excavation will be filled with clean backfill material (soil and/or aggregate base rock) and the ground surface will be repaired with material (asphalt, concrete, native soil, gravel, bark, etc.) to match the existing surface grade. For wells MW -10 and MW -11 which are located in the paved shoulder of the street, the asphalt will be patched in accordance with the City of Stockton requirements which may require hot patch of a larger section of asphalt. Any deviation from this method will require approval of the appropriate SJCEHD representative. Destruction of Groundwater Monitoring Wells by Overdrilling: If any of the wells require overdrilling due to a blockage in the casing they will be overdrilled. If the original borehole depth was