2025-06-23_REVISION - M1980244 (23)

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Docusign Envelope ID:45B9721C-FDE2-4821-B686-80BBC79CA6DD 40. Within Section 4.3.3,the design states VLF1 Phase 6 PSSA utilizes the existing VLF1 Phase 4 and VLF1 Phase 5 as its northern and southern boundaries, respectively, and will • require geomembrane to be installed on the re-sloped sides of these facilities. This is depicted on Drawing A024. Please provide details how re-sloped spent ore will achieve the subgrade specifications required for the facility. Please also provide examples where spent ore has previously been used as structure fill on-site as a part of VLF construction. The spent ore will be regraded, moisture conditioned and compacted to provide a firm surface for geomembrane deployed, in the same manner as previously done for the VLF1 Phase 5 PSSA along Phase 4 slope and for the VLF1 Phase 4 PSSA over the Phase 3 slope. 41. Section 4.4.1 discusses the construction of the VLF1 Phase 6 PSSA Embankment. The embankment will be 120 feet high, 1,275 feet long with a minimum crest width of 25 feet. It also states that the Structural Fill for the Embankment will be placed and compacted in accordance with the Technical Specifications included in the Exhibits of the Report however no Technical Specifications specifically addressing the PSSA Embankment were included. Please provide the Technical Specifications to be used in the construction of the PSSA Embankment. The specifications should include but are not limited to, materials selection, materials source, lift thickness,compaction requirements,field testing as well as QA/QC testing and reporting requirements. The VLF1 Phase 6 PSSA embankment will be constructed using Structural Fill. The Structural fill specifications are in Specification Number 02200 Earthworks if a contractor is to construct the embankment, and Specification Number 02200-1 Earthworks if the owner is to construct the embankment. Previously, for the construction of other PSSA Embankments, the same material and placement specification has been used. 1111 42. Section 4.4.2 states VLF1 Phase 6 PSSA is sized to hold maximum storage required as determined from the water balance discussed in Section 6. Section 6 discusses further information on the water balance can be found in Appendix F of the Report.Appendix F provides a recommendation that the facility's storage capacity be at least 27 million gallons. Figure 5- PSSA Filing Curve shows the Top of PSSA (9840') holds 145,689,971 gallons.As this appears to be the only mention of the total capacity of the proposed VLF1 Phase 6 PSSA facility, please update the Section 4.4.2 narrative with these details. Revised the first paragraph of section 4.4.2 to read: "The VLF1 Phase 6 lined PSSA Basin is located upstream of the VLF1 Phase 6 PSSA Embankment and is sized to hold 132.8 million gallons, which exceeds the minimum storage required as determined from the water balance of 27 million gallons, as discussed below in Section 6.0." 43. Please update Section 4.4.3. High-Volume Solution Collection Recovery System to discuss the installation of a PSSA pond level piezometer which will be placed away from the HVSCS for monitoring the 80% capacity compliance limit without being affected by the draw down from the pumps. Further assessment is required to better understand the drawdown behavior associated with the existing pump installation, in order to determine suitable and viable locations for piezometer placement. We remain committed to installing an additional piezometer, contingent upon feasibility. 44. Section 4.6.2 discusses the VLF2 Phase 4 Infiltration Gallery. Please address the following items: a. Please provide details on how this system will function during freezing conditions. • The infiltration gallery is designed to be passive in operation. During normal operation, the wells and piping should be empty, so there is no risk from freezing temperatures. If temperatures reach freezing SSR Mining Inc. PAGE 11/19