2022-02-09_PERMIT FILE - M2021046

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P.O. Box 326, Canon City, CO 81215 angela@ envalternatives.com 719-275-8951 . 3 Feb 9, 2022 Tim Cazier CO Division of Reclamation Mining and Safety 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Dawson Gold Mine, Permit No. M-2021-046 Dear Mr.Cazier, On behalf of Mr. David Felderhof, please accept the following response to the Division's October 14, 2021 Preliminary Adequacy Review. RULE 3.1 RECLAMATION PERFORMANCE STANDARDS 3.1.6 Water—General Requirements 1. The underground workings will be developed in rock similar to the development rock samples tested as part of the tailings characterization program. A schematic of the underground is shown below Figure 1. The unmodeled space is composed of granites. The brown feature in the hanging wall is the sulfide zone. As can be seen in Figure 1,the majority of the workings are in the granitic host rock and do not expose the sulfide zone. The granitic rock, as described in the tailings characterization report, is non-potentially acid generating and metal content similar to the typical crustal abundance of granite. The underground workings do pierce the sulfide zone in selected areas. These are shown in Figure 2. The area of exposed surface area in the sulfide zone is small relative to the exposed surface area within the granite. It is reasonable to expect the exposed sulfide zone to produce acidity locally, however,the lag period to do so is unknown at this time. The granitic host rock does provide carbonate neutralization that would neutralize acid production. At closure,the mine will be allowed to flood,at which time anoxic conditions will be re- established and oxidation will essentially cease. For a period of time after flooding,secondary oxidation products will solubilize and diffuse into the groundwater until the inventory of secondary oxidation products is consumed. in the long term, it is expected groundwater quality within the mine workings will return to background levels.