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and extent of it. If water in flow is encountered that cannot be stopped by grouting or a similar <br /> source control method, the Division will be notified in writing within 30-days. <br /> Groundwater inflows are defined as any instance where water flows steadily into the mine from <br /> the surrounding rock at any location that is more than 100 feet underground. <br /> 2.3 Portal Reclamation—Water Control <br /> When mining is complete at the Detroit City Mine,the entrance will be backfilled to a depth of <br /> at least 40 feet. The portal sump will be filled with local talus material and the tunnel ditch <br /> graded out. All inflows to the portal sump will thus occur naturally and be allowed to flow <br /> through the talus as it had done prior to and during mining. <br /> Prior to backfilling,the operator will install a two-foot-tall berm across the tunnel floor. This <br /> berm will be installed with slopes sufficient for equipment travel. It will be made of compacted <br /> crushed waste rock. It will be installed 100 feet into the tunnel from the mine surface. This berm <br /> is to prevent any surface water flows from the portal of flowing back into the deeper mine <br /> workings. <br /> 3. Offsite Disposal—Chain of Custody <br /> Attached to this technical revision is a chain of custody for all shipments of waste rock from the <br /> Detroit City Mine to authorized disposal facilities. Detroit City Mine transported material to two <br /> locations: a Pueblo, CO facility operated by Waste Connections and a facility operated by Twin <br /> Enviro Services in Penrose, CO. Only 4000 tons of rock have been hauled from the Detroit City <br /> Mine. Roughly 125 tons to the Pueblo facility and the remainder to the Penrose facility. <br /> Colorado Calumet will provide a chain of custody document similar to those attached as part of <br /> each annual report, beginning with the 2020 annual report. <br /> Table 1 -Attachments <br /> DocumentsMaps <br /> Chain of custody documents <br /> _ HASP exchange contract <br /> �A water commissioner correspondence <br /> Please contact me if you have any further questions or concerns. <br /> Sincerely, <br /> Ben Langenfeld, P.E. <br /> Greg Lewicki and Associates <br /> Detroit City Mine <br /> January 2020 3 Creg 1—wki and As iwt VLL( <br />