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COLORADO LEGACY LAND $CHWARTZWALDER MINE a reducing environment is being achieved to form insoluble uranium species that precipitate out of the mine pool. As shown on Figure E-4, dissolved molybdenum concentrations indicate a consistent pattern of decreasing concentrations with the in-situ treatments followed by an increase in concentrations. The dissolved molybdenum concentrations decreased from approximately 1.5 mg/L before the first in-situ treatment in 2013 to a minimum of approximately 0.04 mg/L, an approximate 97% reduction in concentration. There was a rebound in dissolved molybdenum concentrations in 2014, which decreased again after the injections of MicroC®and molasses in 2015.The dissolved molybdenum concentrations again rebounded to a maximum of approximately 6 mg/L before the second in-situ treatment in 2017 followed by a decrease to a minimum of approximately 0.05 mg/L,an approximate 99%reduction in concentration,after which dissolved molybdenum concentrations started increasing.The decreasing dissolved molybdenum concentrations is another indication of a reducing environment. As shown on Figure EA the molybdenum concentrations increased in 2018 following the in-situ treatment in 2017, decreased after the in-situ treatment in 2020, and started to increase until the last sampling event in September 2020. The pattern of increasing and decreasing molybdenum concentrations with in-situ treatments is consistent. As shown on Figure E-3, there was not a significant decrease in uranium concentrations after the 2020 in-situ treatment as was seen in the previous in-situ treatments.There may be several factors for the absence of the significant decrease as follows: • The natural population of SRB in the mine pool might be at a steady-state condition from the 2017 in-situ treatment and not actively biocycling sulfur. • The mine pool uranium concentrations in 2020 were nearly the same as in 2018 and these concentrations may indicate that there was a rate limiting factor in the creation of a proper reducing environment conducive to the reduction of U(VI) to U(IV), combined with other factors discussed herein. • The addition of sump water to the mine pool during treatment may not have occurred at a regular frequency for the previous in-situ treatments, as indicated by available data. During the period the mine pool pump was off after the in-situ treatment began in January 2020 until the mine pool pump was turned on in April 2020, the sump water pumped into the mine an average of 5 gpm with a maximum during this period of approximately 18 gpm.Thus,oxygenated water was entering the mine pool and may have disrupted the creation of a sufficient reducing environment. A red circle is shown on Figures E-3 and E-4 to signify suspect data in the months preceding the 2017 in-situ treatment. These data are suspect because in the nearly 10 years of data shown on these figures, uranium concentrations have not exceeded 25 mg/L and molybdenum concentrations have not exceeded 2 mg/L,with the possible exception on one sampling event in November 2017. The sudden increase in uranium and molybdenum concentrations does not fit with historical data and there is no plausible explanation to the increase. However, while a definitive explanation is not available to rule out this anomaly, it is thought that there might have been either a mix-up in the labelling of the samples the samples were collected from the wrong sample port. For example, treated water, which has a higher concentration of uranium and molybdenum is returned to the mine pool. Mislabelling the return samples as raw mine pool samples is as plausible an explanation as collecting the return samples from the wrong sample port.Regardless,the suspect data do not alter the conclusion that the mine pool has been chemically stable for the last three years. JUNE 2021 20 AMENDMENT 6