Slide 1: SGP: Fish Tunnel
S G P : F I S H T UN N E L Ju n e 2021 TSX :P P TA N A SDA Q:P P TA PERPETUA RESOURCES C r i t i c a l R e s o u r c e s . R e s p o n s i b l e M i n i n g . E n v i r o n m e n t a l R e s t o ra t i o n . www.perpetuaresou rc e s.c om
Slide 2: Presentation Outline
PRESENTATION OUTLINE 1. Stibnite Gold Project Site Overview 2. Present and Future Fish Passage 3. Fishway Design 4. Q&A
Slide 3: Stibnite Gold Project
STIBNITE GOLD PROJECT Coeur d’Alene Stibnite Gold Project Perpetua Resources Au-Sb 3
Slide 4: Historical Stibnite Mining District
1890s The Thunder Mountain gold rush brings mining to the area 1900-1930 The town of Stibnite is established HISTORICAL STIBNITE 1938 Mining at Yellow Pine pit stops salmon migration upstream 1941-1950 The town of Stibnite booms when antimony & tungsten were declared critical & strategic minerals MI
Slide 5: Legacy Conditions
YELLOW PINE PIT HISTORICAL The East Fork of the South Fork dumps into a legacy mine pit. Currently, ~80 feet of sediment has collected at the bottom LEGACY FISH PASSAGE Fish migration After 100+ years of mining activity, many environmental legacies remain. is blocked by the Yellow TAILINGS & SPENT O
Slide 6: Yellow Pine Pit Restoration
YELLOW PINE PIT RESTORATION CURRENT INTERMEDIATE RESTORATION The East Fork of the South Fork of the A 0.9-mile tunnel fishway will allow fish to Backfilling the Yellow Pine pit will Salmon River flows into the abandoned swim back to historical spawning areas allow reestablishment of a natural Yellow
Slide 7: Fish Passage
FISH PASSAGE 8 1%, . ‘= ¢ eh) =, " Sees, ae FOLD ie, \ We *. ae
Slide 8: During Mining
DURING MINING DURING MINING Interim Fish Passage • Tunnel, 0.9-mile long • Fish re-connected to native spawning grounds for the first time in over 80 years. 8
Slide 9: Relationship of Tunnel to Ultimate Pit
RELATIONSHIP OF TUNNEL TO ULTIMATE PIT Proposed Yellow Pine pit vs. Temporary EFSFSR Tunnel Alignment Tunnel Tunnel EFSFSR Proposed Yellow Pine pit extents 9
Slide 10: Backfill and Restoration Beginning in Year 7
BACKFILL AND RESTORATION BEGINNING IN YEAR 7 10 10
Slide 11: Tunnel Fishway Design
TUNNEL FISHWAY DESIGN 11
Slide 12: Key Design Considerations
KEY DESIGN CONSIDERATIONS Jump-start Population Recovery Geotechnical / Tunneling Conditions Run-of-river facility • Must accommodate a wide flow range Upstream passage of adults ~12-15 years before permanent passage solution Downstream passage of juveniles (stream/floodplain restoration) is complet
Slide 13: Geotechnical Considerations
GEOTECHNICAL CONSIDERATIONS CONSTRUCTABILITY AND STABILITY • Soft ground near portals • Broken rock and faults • Mostly Idaho Batholith intrusives • Gradient ~4% overall • Profile adjusted slightly to improve tunneling conditions • 15’x15’ tunnel 13
Slide 14: Tunnel Structure
TUNNEL STRUCTURE ROBUST REINFORCEMENT • 5 rock support types – shotcrete, bolting, and steel sets • Heaviest reinforcement at fault zones • Probing and pre- grouting • Scour protection • Spile or pipe canopy in legacy dumps, till, near portals • Soil nail walls at portals 14
Slide 15: Hydrology Considerations
HYDROLOGY CONSIDERATIONS 15
Slide 16: Hydrology Considerations
HYDROLOGY CONSIDERATIONS PIT tagged Adult Chinook & Steelhead Detections East Fork South Fork Salmon River near Parks Creek 60 13 miles downstream of Project [adjusted 1 week later] 250 (2009-2017) • Run timing by species 50 200 • Originally optimized for late Chinook (n=1,306) Chinook (pink)/bull t
Slide 17: Precedents and Alternatives
PRECEDENTS AND ALTERNATIVES Precedent for Successful Tunnel Passage Identified precedents for tunnel fish passage in literature search Screened fishway design alternatives (11 variations) on various metrics: • Technical feasibility • Passage performance • Constructability • Schedule • Capital and op
Slide 18: Testing Fishway Hydraulics
TESTING FISHWAY HYDRAULICS Computational Fluid Dynamics (CFD) Models to Simulate KEY LOCATIONS KEY FLOWS • Fishway exit and control weir • Low/high passage flows for 3 species • Fishway and tunnel accessway at 4.5% (overall range 8 to 239 cfs) • Tunnel slope transition to 1.5% • 500-year flood event
Slide 19: Fishway Hydraulics
FISHWAY HYDRAULICS 4.5% Tunnel Velocity Results at Middle Weir at Qtotal (fishway + access way) = 54 cfs, Qfishway = 29 cfs 5% exceedance flow for Chinook salmon / bull trout (passage design high flow) 19
Slide 20: Fishway Hydraulics
FISHWAY HYDRAULICS 4.5% Tunnel Velocity Results at Middle Weir at Qtotal = 54 cfs Average velocity of 6.5 fps at weir is less than bull trout burst speed and well under Chinook/steelhead sustained speeds at 54 cfs. 20
Slide 21: Fishway Hydraulics
FISHWAY HYDRAULICS 4.5% Tunnel Velocity Vector Results between the Middle and Last Weir at 54 cfs A Note slack water and recirculation, throughout B water column = fish resting area. C Horizontal Section View Plan Views at Each Section 21
Slide 22: Fishway Hydraulics
FISHWAY HYDRAULICS Results at Headworks at Max. Fish Passage Flow 5% exceedance for adult steelhead Qtotal = 239 cfs Qfishway = 52 cfs First Fishway Weir Resting/Orientation Pool Second Fishway Weir Velocity at fishway weirs equals bull trout burst speed (6.6 fps), and still well under steelhead sus
Slide 23: Fishway Details
FISHWAY DETAILS DOWNSTREAM TO UPSTREAM – North Portal Downstream Portal Fishway at Preliminary 1.5% Slope Rendering Access to Tunnel Portal Structure Juvenile Orientation Pool Adult Exclusion Barrier Fishway Entrance Adult Resting Pool Weir 23
Slide 24: Fishway Details
FISHWAY DETAILS DOWNSTREAM TO UPSTREAM – Tunnel Fishway Fishway Details • 2’ high fish weir within 4’ weir • 5’ divider wall • Weir anchored to bedrock/tunnel lining • Divider wall similarly anchored • Weir spacing 22’ @ 4.5% and 66’ @ 1.5% 24
Slide 25: Fishway Details
FISHWAY DETAILS DOWNSTREAM TO UPSTREAM – South Portal Preliminary South Portal Portal Structure Rendering Tunnel Access Control Weir with Pickets Access for Sediment Fishway at Debris Barrier Removal 4.5% Slope Fishway Exit Bedload / Resting/Orientation Pool Sediment Additional Sediment Collection S
Slide 26: Yellow Pine Pit Restoration Summary
YELLOW PINE PIT RESTORATION SUMMARY Fish Access, Habitat Restoration and Water Quality Solutions Built Into Project: ACCESS: • Immediate and long-term solutions for access to minimum 3.4 miles of additional habitat, jump-starting recovery EFSFSR Tunnel Passage Key Points: • East Fork of the South Fo
Slide 27: Thank You
THANK YOU. w w w. p e r p e t u a r e s o u r c e s . c o m 27
Slide 28: Webinars
WEBINARS www.perpetuaresources.com/connect/virtual-events