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<br /> _�� COLORADO LEGACY LAND
<br /> to the Steve Level.Is this accurate?Lastly,please provide some discussion on whether the faults, Infiltration to the upper levels of the mine occurs seasonally during the spring and after periods of heavy rain.
<br /> pegmatites,and"Schwartz Trend"depicted on the figure are considered primary sources of groundwater During the majority of the year,however,the upper workings are dry. The chemistry of seasonal inflow to the
<br /> inflow into the mine,and whether any of these features might act as migration corridors for mine water upper mine levels is known from samples collected at five stations in May,1999.Sampling stations were located
<br /> downgradient of the site. on the Steve and Minnesota levels(Figure 1-1)and summarized in Table 9-9."
<br /> Yes,the CV Glory Hole connects to the Steve Level,as stated in the EPP,
<br /> "The Charlie and Minnesota levels,which are 119 and 226 feet above the Steve Level,respectively,intercept the
<br /> CVglory hole and represent the bulk of the upper workings(Figure 1-1)."
<br /> Yes,locally these are considered primary sources,as stated in the EPP,
<br /> "The inflow history of the mine indicates that the majority ofgroundwater flows are associated with localized
<br /> structural features including the West Rogers and Illinois Fault Zones and pegmatite dikes."This document
<br /> pro ides additional discussion about the groundwater inflow to the mine.
<br /> The slide titled"Historical Facilities"includes the waste rock piles and the mine pool.Would the fill placed The fill itself is not regarded as a"Historical Facility". However,the CSM has been revised by Ensero to include information about
<br /> 28q in the valley near the mine also be considered an"historical facility"with respect to potential contaminant the historical facilities in the valley(e.g.,previous water treatment plant,former mining operations and buildings)that
<br /> sources?Please update this slide as needed. contributed to the contaminated alluvium. These facilities have since been demolished in the course of reclamation work.
<br /> 28r Please update the second slide titled"Historical Waste Rock"to reflect the new diversion ditch constructed Revised as requested. Slides 13 and 14 discuss the North Waste Rock Pile Diversion Channel.
<br /> on the NWRP and the removal of all but one of the site sumps.
<br /> Please update the first slide titled"Mine Pool"to reflect current pump depths of the mine pool and any Slide 34,titled Mine Water,summarizes the pre and post in-situ treatment of these analytes.
<br /> 28s other constituents of concern elevated in the mine pool (the last revised EPP includes sulfate,antimony,
<br /> arsenic,iron,thallium,and radium 226; Section E.5.2.4 in Exhibit E of this application also includes
<br /> chloride).
<br /> The second slide titled"Mine Pool"includes information on the in-situ treatment test conducted in Slides 29-33,titled Mine Water-In-situ Injections,summaries the previous treatments. The analytical results of the in-situ
<br /> 2013.The Division is aware of at least three other in-situ treatments which have been conducted at the site treatment are presented on Slide 34.
<br /> since that time.Please update this slide to incorporate all results from the in-situ treatment program.In
<br /> Exhibit E,the operator indicates the mine pool may have reached equilibrium with respect to uranium Please see responses below for a discussion on the in-situ treatment viability.
<br /> concentrations and that fewer treatments may be needed moving forward.Please update this slide
<br /> accordingly.How long might the in-situ treatments be a viable option for reducing uranium concentrations The in-situ treatments remain a viable option for reducing uranium concentrations because the formation of a reducing
<br /> in the mine pool?Is there a point at which other undesired effects might occur with the continuation of this environment has resulted from all in-situ treatment occurrences.In fact,the in-situ treatments should lead to a sustained
<br /> program(e.g.,increased concentrations of other constituents of concern)? reducing environment,given other factors such as not pumping sump water into the mine,etc.A flooded mine at equilibrium has
<br /> the greatest chance of a sustained reducing environment. In-situ treatment is best considered as a way to reduce oxidation of
<br /> 28t rock within the mine workings that is in contact with mine water and stabilize the mine chemically.While in-situ treatment has
<br /> been discussed as a way to achieve removal of particular constituents (e.g.,uranium,molybdenum,etc.) it is the formation of
<br /> reducing anoxic conditions in the mine workings that provides a bulk water chemistry stabilization.This point is validated by the
<br /> demonstration that the mine is still at the same TDS range(2,850 mg/L in 2018-2021 vs.2,917 mg/L in 2000-2007),meaning
<br /> that the combination of(i) operation of the RO, (ii)performance of periodic in-situ treatment,and(iii)reducing airflow through
<br /> the mine by cutting off ventilation and filling mine voids results in a chemically stable mine.
<br /> CLL does not have a technical basis for believing that in-situ treatments are increasing concentrations of other metals(or COPC)
<br /> in the mine pool.However,field studies and published papers do not indicate any negative aspects to long-term in-situ
<br /> treatments.
<br /> Please update both slides titled"Groundwater Monitoring"to reflect the current approved groundwater Well logs indicate that MW-8 was drilled dry,which is why it was later replaced with MW-12.MW-14,MW-19,and MW-20
<br /> monitoring program.These slides state"a few of(the monitoring wells)are dry". Please specify which of contained very little water at the time of installation,but some water was observed during construction and/or well
<br /> the"dry"monitoring wells have been dry since installation,and which ones dried up after the mine pool development.
<br /> was dewatered.Please specify any background wells.Please specify any compliance wells (the last revised
<br /> 28u EPP states the original compliance well was MW-8,which was replaced with MW-12 in 2008).Were any As noted on the quarterly sampling report(provided to DRMS,City of Arvada,and Denver Water under separate cover),
<br /> numeric protection levels set for the compliance well?Please include the approved sampling frequency. depending on the water level elevation in the mine pool,some monitoring wells are dry. This can vary seasonally because CLL
<br /> only operates the water treatment plant for 6 months (or less)of the year.
<br /> CLL is not aware of any numeric compliance levels for the monitoring wells at the site. In their quarterly report to DRMS,
<br /> roundwater quality data are presented with respect to state criteria for comparison.
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