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Toxicity In an email dated January 27, the County inquired about the toxicity of the process water. On February 3, Simplot replied, stating that historical sampling of the process water in the North Pond (the source of the January spill) indicates elevated ammonia as nitrogen, nitrate as nitrogen, sulfate, and TDS. These constituents are not listed in Appendix X (22 OCR Div. 4.5, Ch. 11, App. X) as chemicals that create a presumption that a waste is hazardous waste. Typical water quality of process water in the lined ponds can be found in Simplot's Waste Discharge Requirements for Class ll Surface Impoundments, Order R5-2019- 0010. The excavated solids have not been characterized beyond the data provided, which includes total metals (CAM 17), VOCs, pH, and TPH (TPH for offsite portion of May 2021 spill event only). Waste Characterization While it is expected to find trace metals in the process water due to the potential for trace metal content from raw materials used in our processes, there is no further introduction of metals in the process. Since the water is recycled in the process, it is not considered a waste and as such, waste analysis (such as STLC or TCLP) is not conducted. However, in the rare cases of a process water spill, the waste (composed of a mixture of the process water and backfill/soil materials), is characterized using a total metals analysis confirming generator knowledge regarding toxicity from metals in the process water. None of the total metals results exceeded "20X the TCLP limit" for RCRA hazardous waste characterization (D Code listing); therefore, TCLP analysis, which would determine if a toxicity characteristic for the RCRA 8 metals was applicable, was not conducted. Similarly, the results from a TTLC analysis are used to determine if an STLC test is required. In the laboratory report, no STLC analyses were "triggered" or recommended by the lab (see results table footnotes). Due to the likely presence of fertilizer constituents, the waste was disposed of as Non- RCRA Hazardous. Summary The excavation efforts on this spill response were conservative (high solids to spill ratio, as noted above; disposed of as Non-RCRA Hazardous) and coordinated with the County. All follow-up information was provided as requested, including waste characterization lab results and pH readings of soils left in place. Simplot will provide copies of the hazardous waste manifests/disposal records (soils were transported on April 18) to the County when received. Simplot is confident that this spill was addressed adequately. For future spills, Simplot will request that the County approve of excavation efforts shortly after the excavation is completed. Sincerely, 1.41rldryllvvirvirvilrJr.L.A.4.4.41,4r 4.41,49,11riv4r4wiri. irvarimir.41,14,4•47,41. irmirvar