2021-06-14_REVISION - M2012032 (3)

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Ouray Silver Mines Inc. Technical Revision 15 May 24, 2021 room area, it will flow to a sump,where it will be pumped back to the 18,000 gallon process water tank or reagent mixing tanks depending on the material spilled. The maximum amount of chemicals to be on site at any one time are listed in Table 2. Reagents are stored in the reagent room located on the east side of the mill filter building except the lime day tank of 9200 gallons. Chemical SDS sheets for the chemicals above have been included in Appendix 2, which was included as part of TR-14. The mill filter building houses two large 18,000 gallon tanks; one is for tailings slurry and the other is for process water. The area where these tanks are housed was used as a reagent room by previous operators and the environmental controls have remained the same. The 18,000 gallon tanks sit on a 6"concrete slab with a sump and vertical curbs that was coated with an epoxy for secondary containment. There is an additional protection against spills leaving the mill filter building area,which is a concrete apron of 78 feet long and 9-10 feet wide. The thickness of the reinforced concrete is 6 inches. A swale was formed in this concrete which is 6"to 8"deep and leads to a sump on the east side of the building. A level-controlled pump of 300 gpm capacity has been installed in this sump to automatically pump any liquids or slurry back to the thickener or 18,000 gallon slurry tank. The apron captures leakage from the garage door as well as the 2 doors where the fine tailings are dropped from the filter presses into the two filter cake bays. This concrete apron was approved as part of TR-05. In the mill area,portable spill kits have been placed, which can be used to clean up spills in the area. Employees assigned to the mill are trained in Standard Operating Procedures(SDP's) which address inspection of pumps,piping, chemical containers and the epoxied berm for leaks, cracks or other malfunctions. They area also trained in the use of the spill kit and reporting procedures. 7 Tailing Chemistry and Water Quality at the Tailings Storage Facilities Tailings from the milling process have a size range from approximately 100 mesh to below 200 mesh. After the metal sulfides are extracted in the flotation cells,the tailings slurry is then pumped to the thickener across the bridge where a large portion of the water is extracted. The remaining slurry is then pumped back to the 18,000 gallon tailings tank in the filter building, where it is then pumped to the filter presses where remaining water is squeezed out,and the tailings drop into either one of two filter cake bays,which are separated by a concrete wall. A backhoe or small loader is used to enter the filter bays and load them into trucks which haul the tailings to either the Revenue Tailing Storage Facility(immediately west of the mine portal)or the Atlas Tailing Storage Facility,which is on the west side of Atlas Creek and is currently being constructed. The trucks must utilize County Road 26 to reach the Atlas Tailing Storage Facility. Prior to removal from the filter bays,tailings will be checked to see if they have the proper moisture content to allow compaction in the piles. In 2015„ samples of the tailings were sent to CTL Thompson in Denver for gradation, moisture/compaction, as well as triaxial shear and cohesion. The results of the tests are provided in Appendix 3. Using these parameters, slope stability tests were performed which confirm that Page 11 of 12