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Lewicki & Associates <br /> ENGINEERING I GEOLOGY I ENVIRONMENTAL <br /> August 9, 2022 <br /> Colorado Division of Reclamation, Mining, and Safety <br /> 1313 Sherman St, Rm 215 <br /> Denver, CO 80203 <br /> Delivered Via Email <br /> RE: Gold Hill Mill, Permit No. M-1994-117 <br /> Technical Revision—TimesNVynona Mine Bulkhead Design <br /> To Whom It May Concern <br /> The Colorado Milling Company is adding to plans/designs to the Gold Hill Mill permit as part of <br /> satisfying the approval stipulation from AM-01. This stipulation requires a mine water drawdown <br /> plan or some other method to reduce the hydraulic pressure behind the current Times Mine <br /> Bulkhead to appropriate levels. To address this stipulation, a preliminary dewatering plan and a <br /> new bulkhead design have been developed. Both options are being integrated into the currently <br /> approved permit with this technical revision. These plans affect the operational components of <br /> the Gold Hill Mill only; the reclamation plan remains unchanged. <br /> Both proposed plans will accomplish the same goal: removing the risk of a bulkhead failure that <br /> causes uncontrolled water discharge from the Times adit. Dewatering and then puncturing the <br /> bulkhead removes the hydraulic pressure that exists on the bulkhead, ensuring no bulkhead <br /> failure. Installing a new bulkhead that can handle the full range of hydraulic pressure will ensure <br /> that there is no bulkhead failure. <br /> No operations will take place at Gold Hill Mill until either the new bulkhead is installed or the <br /> dewatering plan has taken place. <br /> 1 . Times/Wynona Mine Preliminary Dewatering Plan <br /> As an alternative to the proposed bulkhead in this technical revision, CMC may dewater the <br /> Times/Wynona Mine and remove the top of the Times bulkhead to make it inoperative. This <br /> dewatering plan will consist of three primary components: <br /> 1. Assembly onsite of at least 370,000 gallons of water storage capacity. <br /> 2. Pumping down the Times/Wynona Mine to below the top of the Wynona Winze. <br /> 3. Removal of the top 1-ft of the Times bulkhead. <br /> Prior to executing this dewatering plan, a technical revision will be filed with CDRMS outlining <br /> the following: <br /> 1. The water storage devices used to provide at least 370,000 gallons of water capacity <br /> including ponds, tanks, in-mill storage, or any other water storage to be used. <br /> GHM Q1 2022 <br /> July 2022 1 Lewicki&Associates <br />