COLORADO LEGACY LAND
<br /> pool,or possibly create other undesired effects(e.g.,increased concentrations of other constituents of environment as shown by the mine water pumped to the plant which is consistently reducing(less than 0 millivolts),which will
<br /> concern)?During the Division's last inspection of the site on September 14,2021,the operator mentioned have a continued effect on keeping the mine water fluctuations from increasing TDS.
<br /> plans to perform an additional in-situ treatment the first week of October.Was this treatment conducted?
<br /> If so,does the operator expect to observe similar results after this treatment as was observed after the last Yes,an in-situ treatment was conducted during the last week of September 2021:phosphoric acid was injected on 09/24/21 and
<br /> one? ethanol was injected on 09/29/21. CLL does not expect the 2021 treatment to produce results similar to the 2020 treatment:
<br /> different chemicals were used in the 2021 event and the in-situ injection will have a longer treatment period because CLL does
<br /> not expect tooperate the WTP again until the spring of 2022.
<br /> On page 20,the operator discusses"suspect"data for mine pool uranium and molybdenum concentrations Please see responses to specific comments below.
<br /> (shown on Figures E-3 and E-4) in the months preceding the 2017 in-situ treatment.The operator states
<br /> "these data are suspect because in the nearly 10 years of data shown on these figures, uranium
<br /> concentrations have not exceeded 25 mg/L and molybdenum concentrations have not exceeded 2 mg/L,
<br /> 16 with the possible exception of one sampling event in November 2017"and that"it is thought that there
<br /> might have been either a mix-up in the labeling of the samples(or)the samples were collected from the
<br /> wrong sample port".The operator then concludes"Regardless,the suspect data do not alter the conclusion
<br /> that the mine pool has been chemically stable for the last three years".The Division has the following
<br /> comments on these statements:
<br /> Nearly 10 years of data are not shown on Figures E-3 and E-4.While the earliest data shown is from mid- CLL has presented data that they have received.CLL was not involved with the mine at this point and cannot state for certain
<br /> 2012 (molybdenum)and late 2012/early 2013 (uranium),there is a small data gap between late 2014 and exactly what transpired during this period,e.g.,the data gaps in sampling the mine pool,but understands that the limited access
<br /> 16a mid-2015,a larger approximately 2 year data gap between late 2015 and late 2017,and an approximate 6- through White Ranch open space,and no access or limited access through Ralston Road while it was being rebuilt is a factor in
<br /> 7 month data gap between late 2019 and mid-2020.The Division estimates the data presented on these two the lack of data for the periods in question.In accordance with the permit,CLL collects mine pool sample once a quarter.
<br /> Figures represents less than 6 years of data total.Does the operator have an explanation for the data gaps
<br /> shown?
<br /> The"suspect"data appears to include 9-10 sampling events.It seems unlikely a labeling or sampling error As stated,mis-labelling the return samples as raw mine pool samples is as plausible an explanation as collecting the return
<br /> would have been repeated that many times.It may be more likely,especially given the elevated samples from the wrong sample port.Human error can easily be repeated if the action is thought to be correct,e.g.,collecting a
<br /> 16b concentrations observed around the same period but not included in the"suspect"data,the data in sample from the wrong port and going back to that same port because that is where the last sample was collected.Regardless,
<br /> question actually represents mine pool conditions during that time.If this is the case,does the operator there is not a reasonable explanation as to the anomaly.As shown in the data,the uranium and molybdenum concentrations
<br /> have an explanation for the significant uranium and molybdenum concentrations observed in the mine reported in the 2017 data did not occur before or after 2017.CLL was not performing the mine sampling at this point and cannot
<br /> ool in 2017? state for certain exactly what transpired during this period.
<br /> The operator believes the"suspect"data may be attributed to sampling or labeling errors.Please describe The suspect data included in AM-06 were collected by the previous operator Cotter. CLL can only infer or interpret the results,
<br /> 16c how the sampling procedure has been improved to prevent any such errors from reoccurring. and a labeling error/collecting samples from the wrong port appears to be the most plausible explanation.The CLL plant
<br /> operators are trained in the location and identification of the sample ports.
<br /> Please provide additional explanation of how the data presented in Figures E-3 and E-4 demonstrate the With the exception of the 2017 data,the uranium and molybdenum concentrations reported in 2012,as shown on the figures,
<br /> mine pool is chemically stable,given the data gaps on these figures,the"suspect"data for 2017,and the have only been approached in similar concentrations during periods of no treatments,except for the uranium concentrations,
<br /> overall higher uranium concentrations observed in the post-2015 data compared with the 2013-2015 which have been consistently below the 2012 concentrations.As stated for Figure E-4,the uranium concentrations(dissolved
<br /> data. and total)have maintained an average of approximately 12 mg/L with a slight positive slope.Although the trend indicates a
<br /> 16d slight positive slope,the majority of the uranium concentrations are in the 10 to 15 mg/L range.The molybdenum concentrations
<br /> (dissolved and total)have maintained an average of approximately 0.6 mg/L with a slight negative slope.
<br /> It is important to note that even though there has been variable mine chemistry during this time,it is always in the historical
<br /> range for TDS which is a bulk measure of chemical stabilization,and substantially below the historical range for the mine
<br /> chemistry concentrations for uranium.
<br /> On page 21,the operator refers to Figure E-5 which shows concentrations and linear regressions for Figure E-5 has been updated to include data collected since September 2020.CLL tried various regressions,e.g.,exponential,
<br /> uranium and molybdenum over three consecutive years. Please explain how the linear regression method power,logarithmic,polynomial,moving average.The results were that only the polynomial and moving average regressions
<br /> 17 was chosen for this analysis.Would another method be more appropriate for the type of data being differed dramatically from the rest and did not display an accurate relationship between the two variables,e.g.,time and
<br /> analyzed?Additionally,there appears to be an approximate 6-7month data gap between late 2019 and concentration.
<br /> mid-2020.Therefore,the analysis represented on Figure E-5 does not cover a full 3 year period.Please
<br /> include data collected since September 2020 in this analysis.
<br /> On page 21,the operator refers to Table E-2 which compares the pre-2017sample data mean(calculated Please see responses to specific comments below.
<br /> from mine pool data collected June 2000 to July 2007)to post-2017 sample data(calculated from mine
<br /> 18 pool data collected March 2018 to September 2020).The data presented in Table E-2 is meant to provide
<br /> further demonstration that chemical stabilization of the mine pool has been achieved for the last three
<br /> consecutive years.The Division has the following comments on Table E-2:
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