2021-06-14_REVISION - M2012032 (3)

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Ouray Silver Mines Inc. Technical Revision 15 May 24,2021 5.3 Thickener There have been no changes made to the tailings thickener. The thickener is 26 feet in diameter and 8 feet deep. The total height of the thickener from the ground is 15 feet. The volume of the thickener is a maximum of 4400 cubic feet of slurry. The concrete containment is bigger than the thickener itself and will handle a minimum of 110%of the full volume of the thickener. The thickener has a 6 inch thick reinforced concrete containment. Based on the footprint area of 1693 sq. ft, as measured from the site inspection and using a minimum wall height of 3.0 feet,this results in a containment volume of 5079 cu. ft. Since there is approximately 200 cu. ft. of structures in the containment,the actual volume of containment is 5079—200=4879 cu. ft,which is 111%of the tank volume. The plans correspond to the designs presented in TR-05. In the case of a rupture of the thickener tank or piping,a slurry pump is located at the low point of the thickener containment,which would then pump the slurry back to the 18,000 gallon tailings tank located in the filter building. In this way,no tailings will be allowed to leave the area. The slurry will be transported from the filter building to the thickener by overhead HDPE process water lines of 8"diameter. A return slurry line for concentrated slurry and a return waterline is installed on the bridge. The bridge consists of a steel truss structure of 6 feet width and 100 feet long. An airline and electric cable are also suspended in the same bridge. The bridge is 18 feet high to allow clearance and there will be two support structures; one at the filter building end of the overhead truss and the other at the thickener end, and the distance between them is 100 feet. The truss supports at both ends are steel supports in a foundation which is separate from both the thickener and the filter building. 5.4 Reagent Room See discussion below on Chemical Handling Systems and Containment. 6 Chemical Handling Systems and Containment Chemicals will be mixed in the reagent room-a separate partition of the mill filter building expansion. As stated in TR 14,chemicals arrive in secured sacks,metal drums or plastic totes, which have a protective metal mesh around them. The chemical list was revised in TR 9 and is included below in Table 4 for convenience. The floor of the Reagent Room area is 6"reinforced concrete slab sealed with an epoxy layer to prevent damage to the concrete should a spill occur. There are no under drains or liners. The reagent room will contain,at a maximum, 12,730 gallons of reagents. The secondary containment volume is 28,019 gallons including the sump volume of 268 gallons. A telehandler or skidsteer is used to transfer new chemicals into the reagent room. Sumps are located throughout the reagent room. If water, slurry or liquid chemical is spilled in the reagent Page 10 of 12