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Geosyntec'' consultants in accordance with the DTSC and CVRWQCB approved Groundwater Monitoring Work Plan(GMWP), and I"Addendum to the GMWP (Geosyntec 2018, 2019). 2.3 Destruction of Wells The well destructions will be conducted by a C-57 licensed drilling contractor working under the supervision of a California licensed professional geologist. Each well that is destroyed will be overdrilled using the hollow stem auger(HSA)drilling method' to the total well depth using an auger diameter greater than the original well borehole and the well materials removed from the subsurface. Once the well materials have been removed,the borehole will be tremie grouted with Portland cement grout under inspection by SJCEHD from the bottom of the borehole to 5 feet bgs. In accordance with the California Well Standards, the top 5 feet bgs will be backfilled with native soil (California Department of Water Resources [DWR], 1991). The soil cuttings and well casing removed from the ground as part of the well destruction activities will be stored in drums or bins, the soil cuttings will be sampled and profiled, and the material will be transported off-site for disposal at an appropriate disposal facility. The disposal facilities that will accept the soil cuttings will be dependent on the analytical results of the soil sample collected for waste profiling during fieldwork. It is anticipated that if the soil is characterized as non-hazardous, it will be accepted and disposed of at Forward Landfill in Manteca, California (a permitted Class II and III landfill), and if the soil profiles as hazardous,it will be accepted and disposed of at the Kettleman Hills Facility in Kettleman City, California(a permitted Class I and III landfill). 2.4 Replacement of Monitoring Wells Replacement monitoring wells will be installed using the HSA drilling method by a C- 57 licensed drilling contractor working under the supervision of a California licensed professional geologist. The wells will be installed in accordance with the DTSC and CVRWQCB approved Well Installation Standard Operating Procedures(SOP,Appendix B). The SOP was previously included in the GMWP (Geosyntec, 2018). All new monitoring wells installed at RRI since 2018 have been installed in accordance with the SOP, and design details in the SOP were based on the conceptual site model (CSM) and 1 DTSC and CVRWQCB will be notified if an alternative drilling method will be used. 2 DTSC and CVRWQCB will be notified if an alternative drilling method will be used. Rail Line Well Destruction Work Plan 2 April 27,2021