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Greg Lewicki And Associates, PLLC <br /> 3375 West Powers Circle Littleton, CO 80123 <br /> January 22, 2020 <br /> Colorado Division of Reclamation, Mining, and Safety <br /> 1313 Sherman St, Room 215 <br /> Denver, CO 80203 <br /> Detroit City Mine; DRMS File No. M-2017-003; Technical Revision <br /> Colorado Calumet Co. is filing a technical revision to address inspection items from the <br /> Division's August 29, 2019 of the Detroit City Mine site. These items are: <br /> 1. Provide an updated waste rock sampling plan. <br /> 2. Address surface water inflow at the portal entrance. <br /> 3. Provide chain-of-custody for material shipped offsite for disposal. <br /> Each item is addressed specifically below. Attachments can be found at the end of this document <br /> and are listed in a table for reference. <br /> 1. Waste Rock Sampling Plan <br /> In order to monitor waste rock from the mine workings that is shipped offsite to a landfill or <br /> other appropriate and approved destination,the following sampling plan will be implemented: <br /> 1) Rock generated from underground development is piled within the underground workings. <br /> From these piles, waste rock is transported to the surface for loading into trucks that take <br /> material offsite. <br /> 2) At the surface,the waste rock will be passed through a crusher and crushed to a size of two <br /> inches minus. This is the size that all material shipped offsite is crushed to. <br /> 3) The crushed rock output will be sampled using a five-gallon bucket. A sample will be pulled <br /> from the crusher output every five minutes until at least five buckets have been filled or all of <br /> the waste rock feed has been crushed, whichever is less. <br /> 4) These five gallon buckets will be mixed and split thoroughly. From this source, a fifteen <br /> pounds final sample will be taken. <br /> 5) The fifteen pound final sample will be sent to a certified laboratory for whole rock analysis <br /> and acid-base accounting. <br /> 6) A sample, as described above, will be taken from every 2000 cubic yards of waste rock that <br /> the mine ships offsite. At a minimum, one sample will be taken each calendar year that <br /> material is shipped offsite, e.g. if no waste rock is produced during a given year, no sample <br /> will be taken. <br /> 7) Sample results will be provided to the Division as part of the annual report. <br /> Detroit City Mine <br /> January 2020 <br /> G;eg I.ewicki and Associates.PIA A' <br /> 1 <br />