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was injected into the groundwater beneath the former evaporation pond at the northern corner of the Site. Concentrations of nitrate and 1,2,3-TCP declined following the injections. In 2007, HRC-Xe, a longer lasting form HRC®,was injected into the groundwater at the former evaporation pond and upgradient of offsite well MW-5. After the injections, concentrations of 1,2,3-TCP declined in offsite well MW-5 and in MW-6 downgradient of the former pond. The injections didn't appear to have an effect on the nitrate concentrations either well. Since 2013, COC concentrations in the on and offsite monitoring wells have fluctuated but generally declined. Nitrate concentrations exceed the MCL in onsite well MW-3 have been below the MCL in offsite well MW-5 for three consecutive sampling events. Concentrations of 1,2,3-TCP exceed the MCL in well MW-6RR. Concentrations of 1,2,3-TCP in offsite, downgradient well MW-5R since March 2022. Concentrations in well MW-6RR have also declined since 2005, but still exceed the MCL by an order or magnitude. The August 2023 groundwater sampling analytical results are shown on Figure 5. Graphs showing the COC concentrations over time are included as Appendix A. Historical COC concentrations in groundwater are summarized on Table 3. 5.0 PILOT TEST A carbon source will be injected upgradient of well MW-3R and possibly near the northern corner of the site to determine if nitrate concentrations in the groundwater can be reduced through EISB. The injection locations are shown on Figure 4. Offsite monitoring wells MW-5R and MW-8R will be used as the compliance wells and well MW- 4R will be used as the background well to fulfill the requirements of RWQCB General Waste Discharge Requirements (WDR) Order No. R5-2015-0012. 5.1 Remediation Technology EISB consists of creating conditions in the groundwater that are favorable for the COCs to be consumed during cellular respiration. Cellular respiration, or biodegradation, is a process where carbon and an electron acceptor(the COCs) are utilized by microbes to generate cellular energy, thereby stimulating microbial growth and reproduction. Increased microbial respiration following the addition of carbon results in depletion of dissolved oxygen (DO) and lowering of the oxidation reduction potential (ORP) due to the release of hydrogen. As conditions become anaerobic, nitrate, manganese, iron, then sulfate sequentially replace oxygen as the most energetically favorable electron acceptors. Once conditions are sufficiently anaerobic and the other electron acceptors have been depleted, 1,2,3-TCP can be degraded through biodegradation, abiotic reduction, and/or reductive dechlorination. A solution consisting of water and RNAS Remediation Product's (RNAS) Newman Zone will be injected into the groundwater at the locations on Figure 4. Newman Zone is comprised of fermentable carbon sources (lactic acid and fatty acids) that stimulate microbial growth in an anaerobic environment.A product information sheet for Newman Zone is included in Appendix B. Nutrien Vernalis, California 2 p Pilot Test Work Plan