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6.1.2 Chemical Degradation CRS® provides a soluble source of ferrous iron (Fe2+), which, in anaerobic conditions, can precipitate reduced iron sulfides, oxides, and/or hydroxides capable of destroying chlorinated contaminants via abiotic chemical reduction. The CRS® can potentially improve the efficiency of the overall reductive dechlorination process when injected with 3DME (Regenesis, 2017). 6.1.3 Pilot Test Injections and Monitoring The injections will be performed in the A-zone beneath the former north pond and adjacent to the load pad at the south tank farm. The injections beneath the former north pond will occur in three rows of four points. The rows will be 20 feet apart and oriented perpendicular to the groundwater flow direction.The injections near the south tank farm will occur in one row of five injection points. The proposed injection locations are depicted on Figure 8. The temporary injection points will be constructed using a truck-mounted direct push drilling rig. The drilling rods will be advanced in the A-zone to 65 feet bgs and then retracted to expose a screen extending to 45 feet bgs. The 3DME-CRS solution will be injected into the subsurface through the drilling rods and screen. After the injections are completed, the borings will be tremie grouted with neat cement through the drilling rods to the surface of the cap in accordance with San Joaquin County Standards and pursuant to discussions with the RWQCB. Based on the COC concentrations in groundwater below the former north pond, 5,200 pounds of 3DME and 2,000 pounds of CRS be mixed with tap water in accordance with the manufacturer's specifications to create an injection volume of 6,652 gallons (554 gallons per point). At the south tank farm, 3,200 pounds of 3DME and 1,200 pounds of CRS will be mixed with tap water to create an injection volume of 3,972 gallons (794 gallons per point). The solution will be injected into each point at flow rates up to 5 gallons per minute (gpm), and some points may be injected simultaneously. If needed, low pressure(10 to 40 psi)will be applied to each point using a specialized well cap and air compressor to ensure maximum distribution of the substrate to the subsurface without creating preferential flow pathways or flow up the drilling rods. New monitoring wells will be installed within and downgradient of the former north pond based on the pre-2012 and February 2017 flow directions (west to southwest). The wells will be used to determine if the injections enhance conditions for biodegradation and to monitor COC concentrations. Groundwater samples will be collected from the surrounding monitoring wells before and after the injections. 6.1.4 Performance Monitoring The enhancement of the environment for microbial degradation will be evaluated by measuring the parameters shown on Table 3. The groundwater monitoring and sampling program is summarized in Section 7. CPS Stockton, California 4 ;Q)"dt Pilot Test Work Plan