STIBNITE GOLD PROJECT Valley County, Idaho REFINED PROPOSED ACTION MODPRO2 Midas Gold Idaho, Inc. PO Box 429 13181 Hwy 55 December 2020 Donnelly, ID 83615 STIBNITE GOLD PROJECT REFINED PROPOSED ACTION – MODPRO2 Summary This document describes Midas Gold Idaho, Inc.’s (Midas Gold’s) proposed further refinements of the Stibnite Gold Project (SGP) Plan of Restoration and Operations (PRO) (Midas Gold, 2016) and presents Midas Gold’s updated proposed action, the ModPRO21. The ModPRO2 was developed to further reduce potential environmental impacts of the SGP in alignment with Midas Gold’s Core Values as set out in the PRO (Section 2), Conservation Principles (PRO Section 2), its Sustainability Goals (PRO Section 2.4) and its Environmental Goals (PRO Section 6.2). Project refinements included in the ModPRO2: (1) are supported by udpated data and analysis that identify opportunities to reduce potential environmental impacts; (2) address persistent potential environmental impacts not sufficiently ameliorated or reduced by project refinements included in the original ModPRO; (3) are informed by public and reviewing agencies’ comments on the DEIS, and; (4) align with the National Environmental Policy Act (NEPA) and all applicable Federal, State and Local regulations and permit requirements. The ModPRO2 also aligns with the project development approach in Midas Gold’s Feasibility Study (FS) (M3, 2020). The ModPRO2 is presented in three sections and an appendix: • Section 1 describes the evolution of the ModPRO2 in the context of the original proposed action (the PRO) and alternatives evaluated in the SGP Draft Environmental Impact Statement (DEIS) including the ModPRO (DEIS Alternative 2). • Section 2 provides the justification and approach for refinements to components of the SGP that result in the ModPRO2. The technical basis for these refinements includes updated data and analyses that identify additional areas for reduced potential environmental impact. Additionally, recurrent themes in comments on the DEIS are addressed through further project improvements. • Section 3 provides a detailed description of the SGP ModPRO2 refined alternative. Each aspect of the mine is addressed from construction through operations, reclamation and post-closure. Also included in this description are connected actions relating to mine road access and transmission lines. Additional data and reports supporting this project description, including an updated GIS geodatabase, will be submitted subsequently. • Appendix A provides a tabular matrix comparing the alternatives analyzed in the DEIS to the ModPRO2. The ModPRO2 incorporates information derived from agency and public scoping for Midas Gold’s original proposed action (the PRO), the alternatives development process, baseline data collection and analysis, and predictive modeling (hydrologic, geochemical, water quality, stream temperature and air quality). It was also informed by Midas Gold’s interactions with the public; federal, state and local governments; Native American tribes; and other project stakeholders and considers comments submitted during the public comment period for the DEIS. The ModPRO2 presents a refined and improved project with a smaller footprint and reduced environmental impacts compared to the PRO and the first modification of Midas Gold’s proposed action, the ModPRO. Mining methods, ore processing, exploration activities, water management, and supporting features including structures, access and haul roads and infrastructure remain identical to the PRO and/or the ModPRO, or are slightly modified. In all cases, these proposed refinements address environmental concerns raised or identified by various sources or through the effects analysis of the DEIS, and are targeted at addressing them accordingly. These refinements align with the purpose and intent of the NEPA.The ModPRO2 represents a further refinement of Midas Gold’s proposed action and Midas Gold considers the it to be the best alternative for developing the SGP. 1 This is the second proposed modification to refine and improve the PRO; the first was referred to as the ModPRO (Brown andi Caldwell, 2019) Midas Gold Idaho, Inc. December 18, 2020 STIBNITE GOLD PROJECT REFINED PROPOSED ACTION – MODPRO2 TABLE OF CONTENTS SECTION PAGE INTRODUCTION ............................................................................................................................................. 1 1.1 BACKGROUND ..................................................................................................................................... 1 1.2 PURPOSE ............................................................................................................................................ 2 MODPRO2 DEVELOPMENT AND OVERVIEW .............................................................................................. 3 2.1 JUSTIFICATION AND APPROACH ............................................................................................................ 3 Updated Data and Analysis ................................................................................................. 3 Environmental Effects and DEIS Public and Agency Comments ........................................ 4 2.2 SUMMARY OF PROPOSED REFINEMENTS OF MIDAS GOLD’S PROPOSED ACTION .................................... 6 Hangar Flats Pit Footprint ................................................................................................... 6 Fiddle DRSF ........................................................................................................................ 6 Hangar Flats Pit Backfill ...................................................................................................... 7 Stream Temperature/Fisheries Habitat ............................................................................... 7 Tailings Arsenic Management ............................................................................................. 8 Ore Processing ................................................................................................................... 8 2.3 SUMMARY ........................................................................................................................................... 9 MODPRO2 DESCRIPTION ............................................................................................................................. 9 3.1 PROJECT LOCATION AND LAND MANAGEMENT ...................................................................................... 9 3.2 LIFE-OF-MINE SCHEDULE .................................................................................................................. 13 3.3 SITE ACCESS .................................................................................................................................... 13 Yellow Pine Route ............................................................................................................. 13 Burntlog Route .................................................................................................................. 13 Public Access .................................................................................................................... 14 Over Snow Vehicle Public Access .................................................................................... 15 State Highway 55 and Warm Lake Road Intersection ....................................................... 16 3.4 POWER TRANSMISSION AND COMMUNICATIONS SYSTEMS................................................................... 17 Power Transmission .......................................................................................................... 17 Communication and Repeater Sites .................................................................................. 18 3.5 OTHER OFFSITE INFRASTRUCTURE .................................................................................................... 18 Stibnite Gold Logistics Facility........................................................................................... 18 Burntlog Maintenance Facility ........................................................................................... 20 3.6 SITE PREPARATION AND SUPPORT INFRASTRUCTURE ......................................................................... 22 Overview ........................................................................................................................... 22 Growth Media Stockpiles .................................................................................................. 22 Mine Site Borrow Sources ................................................................................................. 23 Mine Support Infrastructure ............................................................................................... 23 3.7 MINING ............................................................................................................................................. 26 Mining Schedule ................................................................................................................ 26 Open Pits .......................................................................................................................... 26 Drilling and Blasting .......................................................................................................... 27 Loading and Hauling ......................................................................................................... 28 Mine Dewatering ..............................................................................................................