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COLORADO LEGACY LAND
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<br /> would re-establish a hydraulic gradient away from the creek in the permit area,and reduce the exposure of
<br /> wall rock to oxygen in order to minimize uranium oxidation in the workings.At the time,the mine
<br /> workings were flooded to the creek level,so the efficacy of the proposed dewatering level had not yet been
<br /> validated.Now that the mine pool has been maintained below the 150 foot limit for some years,the efficacy
<br /> of this limit can be evaluated based on data collected over this period.Please provide additional
<br /> information demonstrating that maintaining the mine pool below 150 feet below Steve Level establishes a
<br /> hydraulic gradient away from the creek.In accordance with Rule 3.1.6(1),this demonstration must address
<br /> potential interaction between the mine pool and the creek not only within the permit area,but also
<br /> down radient of the permit area between the mine site and Ralston Reservoir).
<br /> One of the arguments made by Cotter Corporation,the former operator,against the initial 500 foot As noted by the reviewer,dewatering the mine pool is a balance of objectives. CLL does not have a technical basis for believing
<br /> dewatering limit,was that pumping the mine pool down to such a deep level would expose a lot of wall that dewatering the mine pool to—400 ft below Steve has produced a less chemically stable environment.A comparison of the
<br /> rock to oxidation,thus increasing uranium concentrations in the mine pool.The modified 150 foot mine pool water quality from CLL's operations (2018 to present)to data collected from 2000-2007,i.e.,during the mine refilling
<br /> dewatering limit was meant to reduce the exposure of wall rock to oxidation.However,in recent years,the period,is provided in Table E-2. During CLL's operations the mine pool was dewatered to below the regulatory limit. In 2000
<br /> water treatment plant operation strategy has consisted of pumping the mine pool down much deeper than Cotter ceased mining operations and the underground was allowed to flood. Data from the dewatered mine(2018 to present)
<br /> 5b the 150 foot limit(to approximately 400 feet below Steve Level)to support seasonal operation of the plant. are generally of better quality than data from the flooded mine workings(2000-2007).Bulk TDS of the mine water has not
<br /> This strategy results in the repeated exposure and flooding of hundreds of vertical feet of mine workings. changed when comparing the last 4 years with the initial flooding period,meaning the mine is definitely chemically stable
<br /> Please explain how this operating strategy is"reducing the exposure of wall rock to oxygen,which
<br /> minimizes uranium oxidation in the workings"as stated.Would maintaining the mine pool at a consistent CLL's management approach to reduce oxidation of the mine workings has been to seal up the mine workings by refilling the
<br /> level year-round result in a more chemically stable environment? open hole and other mine workings,not operating the mine ventilation system,and maintaining the mine pool in a biochemically
<br /> reducing state.Maintaining the mine pool at a consistent year-round level would not result in a chemically stable environment
<br /> more than what is achieved by taking these steps in the current management approach.
<br /> On page 15,the operator states"The WTP has been operating approximately 50%of the time for the last Yes.Table E-3 has been updated with data from the 2021 operating season which validates that the plant has been operating on
<br /> three consecutive years".However,according to Table E-3,the plant has operated for 50%or less of the average at less than 50%of the time since CLL has taken over the mine site while gaining more than 200 feet of storage during
<br /> 6 time only in 2018 and 2020.In 2019,the plant operated for 66%of the year.Therefore,the data provided this time.Accounting for the increased storage that has been achieved,this less than half-time operating has resulted in increased
<br /> does not demonstrate the plant has been operating 50%of the time for the last three consecutive years. storage each year.
<br /> Does the operator have additional data which supports this statement?
<br /> On page 15,the operator mentions a malfunction with the 60-hp pump that occurred in April 2020,during Due to the remote nature of the site and long lengths of power cable,prior to an upgrade in power supply that was completed in
<br /> which time,the 25-hp pump was brought into operation to dewater the mine pool.Please explain the cause 2020,the plant and mine pump has at times experienced surges in supplied power.The malfunction of the 60-hp pump was
<br /> of the malfunction,and what was done to correct this issue.Has the operator modified the mine pool attributed to over voltage or inconsistent voltage to the motor of the pump due to the long length of cable from the Variable-
<br /> 7 dewatering program and/or infrastructure to help prevent this issue from occurring again?Does the Frequency Drive(VFD)to the motor.To prevent this in the future,a sine-wave filter was installed on the load side of VFD to
<br /> operator intend to maintain the 25-hp pump in the Steve Adit as a back-up? provide smooth sine wave voltage and prevent excessive voltage spikes and prolong the life of the motor.The 25-HP pump
<br /> remains in the mine pool to serve as a back-up.In the event of a maintenance issue,the operator would use the wench on the
<br /> headframe to remove the 60-HP pump and make the necessary repairs as was performed in April 2020.
<br /> The current mine pool dewatering program includes shutting down the water treatment plant and pump Every winter,the water treatment plant is shut down and precautions are taken to prevent equipment damage.The shortest
<br /> 8 for a portion of the year.In an emergency situation,what is the shortest amount of time it would take to amount of time to bring the plant online in the spring,or in the event of an emergency,would be four days.The four days would
<br /> safely brin-2 the plant/pump plant/pump back online to re-initiate mine dewatering? be used to prepare equipment and operate the plant in recirculation in order to ensure smooth operation before discharging.
<br /> On page 15,the operator discusses entering the mine in October 2020 to verify the mine pool elevation and CLL is not aware of the previous operator's transducer calibration records.
<br /> to calibrate the transducer used to measure the mine pool elevation.During this time,it was discovered the
<br /> mine pool had been dewatered to 22 feet lower than the elevation of the transducer,which caused The transducer provides real-time data(by the second) of the mine pool elevation and records elevations every 30 minutes.
<br /> inaccurate measurements to be recorded.The transducer was then lowered to 354 feet below the Steve These data are monitored remotely by CLL. In the event of a transducer malfunction or misreading,operators would know
<br /> 9 Level and recalibrated.When was the last time (prior to 2020)the mine pool elevation was verified and the within the hour. CLL's operating strategy of dewatering the mine pool well below the 150-foot regulatory level allows the
<br /> transducer calibrated?Is this something that must be done on a regular basis?When was the current operator ample time to respond to maintenance issues.
<br /> transducer installed in the mine?Given the importance of keeping the mine pool lowered below a specific
<br /> elevation,has the operator considered installing an additional transducer or implementing other Monitoring the water levels in MW-18 provides good indication of water elevations in the mine pool.CLL is willing to install a
<br /> redundancies to ensure accurate measurements of the mine pool level are being recorded? transducer in this well to provide a secondary indication of mine water levels.
<br /> Please describe the cone of depression created when pumping down the mine pool with the 60-hp pump. The 60 HP pump is used to dewater the flooded mine workings;for which the groundwater recharge zone captured by mine
<br /> Where is the transducer installed relative to the pump intake?Is there a chance the outer edges of the mine workings is illustrated on Figure 8-11 of the EPP(Technical Revision 23,Attachment B Schwartzwalder Mine Environmental
<br /> 10 pool(outside of the pump capture zone) could be at levels higher than the regulatory limit even when the Protection Plan [Whetstone Associates Inc.,2016])and the capture zone associated with the mine pool is shown on Figure E-2.
<br /> transducer readings indicate the mine pool is below this limit? The 60-HP pump is located within the Jeffery Air Shaft. The transducer is installed through the Steve adit bulkhead and hangs in
<br /> the mine pool in Shaft 2.Because the mine pool is located in open mine voids,the mine levels rise and fall across the entire
<br /> workings,the edges do not have any impediment to drainage when the mine pool drops,or impediment to storage when the
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