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5.2 Well MW-6RR Replacement The pH levels in the groundwater from monitoring well MW-6RR since its installation in 2020 have been between 10 and 12. These pH levels are potentially lethal to denitrifying and dechlorinating bacteria. The pH levels in wells previously located in the vicinity of well MW-6RR (wells MW-2, MW-6, MW-6R and MW-7)were between approximately 6 and 7.5. The abnormally high pH levels in well MW-6RR suggests there may be issues with the construction of the well. Well MW-6RR will be replaced with well MW-9 at the location shown on Figure 4. If the pH levels exceed 9 standard units and the 1,2,3-TCP concentrations are similar to those in well MW-6RR, a lactic or citric acid solution will be injected into the groundwater to create an environment that supports denitrifying and dechlorinating bacteria. After the pH has been reduced to a safe level, a carbon source solution will be injected to facilitate EISB. 5.2.1 Monitoring Well Permits Monitoring well destruction and installation permits will be obtained from the San Joaquin County Environmental Health Department (EHD). Rubik will notify the EHD and RWQCB at least 3 days prior to the start of field work. 5.2.2 Monitoring Well Destruction Well MW-6RR will be destroyed in accordance with San Joaquin County requirements. The wells will be destroyed by removing the concrete well pad and over drilling the well casing to 1 foot below the installed depth (approximately 66 feet bgs). The boring will be tremie grouted with neat cement to approximately 5 feet bgs. The remaining annulus will be filled with soil obtained onsite from a non-operational area. 5.2.3 Monitoring Well Installation The well will be installed using a hollow stem auger drilling rig. During drilling, soil cores will be collected every 5 feet and logged in the field using the Unified Soil Classification System. The monitoring well will be drilled to approximately 65 feet bgs. After reaching the maximum extent of drilling, the augers will be removed in stages as the annular space is backfilled with the well construction materials. The well will be constructed of 2-inch diameter Schedule 40 polyvinyl chloride (PVC) casing with 20 feet of 0.010-inch slotted screen installed between 50 and 70 feet bgs. The annular space between the borehole wall and the well screen will be backfilled with a silica sand filter pack to approximately 2 feet above the top of the well screen. A 2-foot thick hydrated bentonite pellet seal will be installed above the filter pack. A sanitary seal comprised of neat cement will be installed from the top of the bentonite seal to approximately 2 feet bgs. The well will be completed with an aboveground monument and the remaining annular space will be backfilled with concrete. Field conditions will dictate whether the aboveground monument will be a flush mount or stove pipe design. Construction details for both options are presented on Figure 5. 5.2.4 Well Development In accordance with the California Well Standards (DWR, 1991), the wells will be developed a minimum of 48 hours after installation by a combination of bailing, surging, and pumping. The Nutrien Vernalis, California 3 p Pilot Test Work Plan