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Mr. Jeff Wong San Joaquin County Environmental Health Department May 8, 2023 Page 4 deeper than the installed well depth, then the well will be overdrilled to the total depth of the original borehole. The diameter of the auger will be based on the diameter of the original borehole (the minimum auger diameter will be the diameter of the borehole). A guide rod will be inserted in the well casing prior to drilling. On the nested wells the guide rod will be placed in the deeper (`B") well casing. Once the well is overdrilled, the borehole will be backfilled with Type I/II cement grout mixed at a ratio of 6 to 7 gallons of water per 94 pounds of cement, or in accordance with SJCEHD requirements. The auger will not be completely removed from the boring prior to grouting. No more than five feet of unsupported boring may be exposed at any time to avoid loss of borehole integrity. The grout will be placed inside the augers using a tremie pipe lowered to the bottom of the borehole and will be filled from the bottom up to the ground surface. The tremie pipe will be kept submerged in the grout mixture and periodically raised as the borehole is filled in one continuous operation. Any groundwater produced will be containerized and disposed and handled per applicable laws. Once the borehole is filled with grout, the augers will be removed from the borehole. Additional grout may be added to the borehole until the grout fails to drop any further. Upon completion of grouting and the grout material has set, 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. Any deviation from this method will require approval of the appropriate SJCEHD representative. Handling and Disposal of Investigation -Derived Waste: Destruction activities will result in the generation of soil and equipment decontamination (decon) water, and potentially groundwater displaced from well casings that will require treatment and/or disposal. The investigation -derived waste (IDW) will be containerized in 55 -gallon, DOT -approved drums with lids and appropriately labeled and stored on the Site pending disposal. Disposal of the IDW will be documented in RDM's well destruction report. Upon the completion of drilling, RDM will collect one, 4 -point composite soil sample from the stockpiled soil for laboratory analysis. The composite soil sample will be analyzed for: • Full List VOCs by EPA Method 826013; • Total petroleum hydrocarbons as diesel (TPHd) by EPA Method 8015M; • Total petroleum as hydrocarbons as gasoline (TPHg) by EPA Method 8015M; • Total petroleum as hydrocarbons as motor oil (TPHmo) by EPA Method 8015M; • Semi -VOCs by EPA Method 8270C; • Polychlorinated Biphenyls (PCBs) by EPA Method 8082*; and • LUFT 5 Metals (cadmium, chromium, lead, nickel, and zinc) using EPA Method 6010. *If PCBs are detected then analyze sample for dioxins. Based on the laboratory analytical results and following evaluation of disposal options, the drummed soil will be hauled off-site to an appropriately licensed disposal facility. A copy of the disposal manifest or bill of lading will be included in RDM's well destruction report. Any water (decon and groundwater) generated during the well destruction activities will be containerized on-site in 55 -gallon, DOT -approved drums and appropriately labeled. If required by the disposal facility, a composite water sample will be collected and analyzed for: • Full List VOCs by EPA Method 826013; • TPHd by EPA Method 8015M;