Slide 1: Perpetua Resources
Ju ly 2021 TSX :P P TA N A SDA Q:P P TA Not for further distribution 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: Agenda
AGENDA ✓ The Stibnite Gold Project ✓ Baseline Surface and Groundwater Quality ✓ Geochemical Characterization for Predictive Modeling ✓ Objectives – Protect and Improve WQ ✓ Water and Waste Management Plans ✓ Water Treatment ✓ Tailings Management ✓ Summary ✓ Discussion 2
Slide 3: Water Quality
WATER QUALITY 3
Slide 4: Water Quality Today: Water quality monitoring program
WATER QUALITY TODAY Water quality monitoring program Baseline groundwater and surface water monitoring program initiated in 2011 and is ongoing • CERCLA and NEPA compliant data QA/QC • 32 perennial stream surface water monitoring locations • 23 surface water seeps, adit seeps and other mining featur
Slide 5: Water Quality Today
WATER QUALITY TODAY Bradley Dumps Meadow Creek, circa 1940s West End Pit Upper Meadow Creek Tailings “Bradley Tailings” Yellow Pine Pit Smelter Meadow Construction Site Creek Mine Heap Leach Pad On/Off Pads Smelter Area YP-T-22 5 S.O.D.A
Slide 6: Water Quality Today
WATER QUALITY TODAY Bradley Dumps Bradley Pit, circa 1940s West End NW Pit Bradley Dump Yellow Pine Pit Meadow Bradley Pit Creek Mine On/Off Pads Smelter Area YP-T-22 6 S.O.D.A
Slide 7: Water Quality Today: Summary of findings
WATER QUALITY TODAY Summary of findings • Arsenic and antimony are key COIs • Arsenic and antimony concentrations generally show inverse • Meadow Creek and Bradley Pit reach are significant relationship with discharge sources of arsenic and antimony • WQ data from non mining impacted areas show elev
Slide 8: Meadow Creek Valley
MEADOW CREEK VALLEY Surface water impacts Historical placement of spent ore over Bradley Panoramic View of Meadow Creek Valley looking west Tailings (SODA) South North Former Spent Blowout Mill and SODA Ore Creek Smelter SMI Leach Hecla Heap Leach Bradley Pads Tailings YP-T-22
Slide 9: Meadow Creek Water Quality
MEADOW CREEK WATER QUALITY Upstream and downstream Bradley tailings and SODA Meadow Creek below Keyway Marsh 36.0 µg/L As mean 6.1 µg/L Sb mean Arsenic and antimony 2.0 ng/L Hg mean concentrations increase substantially adjacent to and downstream of Bradley tailings and SODA Meadow Creek Meadow Cree
Slide 10: Hangar Flats Area
HANGAR FLATS AREA Surface water quality Modest changes in metal concentrations in Meadow Creek Meadow Creek below Leach Pads 36.2 µg/L As mean 8.2 µg/L Sb mean 8.7 ng/L Hg mean Meadow Creek below Keyway Marsh 36.0 µg/L As mean 6.1 µg/L Sb mean 2.0 ng/L Hg mean 10
Slide 11: East Fork South Fork Above YP Pit
EAST FORK SOUTH FORK ABOVE YP PIT Surface Water Impacts Southeast Southwest Photo Upper EFSF Meadow Creek Legacy Camp dumps adjacent to EFSF DMEA Dump MGI Facilities East Fork Dumps YP-SR-8 EFSF Valley looking south
Slide 12: East Fork South Fork Through YP Pit
EAST FORK SOUTH FORK THROUGH YP PIT Surface Water Impacts Photo Midnight Hennessey Creek Creek YP-SR-6 Bradley Pit Smelter Waste Repository YP-SR-6 Bradley Pit EFSFSR Northwest Bradley Dump YP-SR-4 EFSF Valley looking south Bradley Dumps looking south along the EFSF
Slide 13: Water Quality
WATER QUALITY EFSFSR EFSFSR Downstream of Yellow Pine Pit 67.2 µg/L As mean 31.3 µg/L Sb mean 4.14 ng/L Hg mean EFSFSR Upstream of Yellow Pine Pit 31.6 µg/L As mean 19.5 µg/L Sb mean 3.99 ng/L Hg mean 13
Slide 14: Surface Water Dissolved Constituent Loading Estimates – 2014
WATER QUALITY TODAY Surface Water dissolved constituent loading estimates – 2014 • Discharge estimates used for each sampling location to calculate constituent loads • 2014 data generally representative and captures peak runoff Adits 1% Tributaries Adits 7% 1% Tributaries Sugar 13% Creek 8% Meadow C
Slide 15: Water Quality Today: Groundwater
WATER QUALITY TODAY Groundwater downgradient of legacy mining impacts frequently exceed water quality guidelines for As, and Sb, as well as Mn, Fe, and Al Keyway Dam Post 1970 fill Airstrip Box Culvert SODA Tailings GESTRIN Bradley Valley Fill Tailings Sediments Meadow Creek Valley Cross Section Loo
Slide 16: Natural Background Water Quality
NATURAL BACKGROUND WATER QUALITY Water in mineralized areas is naturally elevated in metals Yellow Pine & West End Perpetua Resources Exploration Sampling of soils and stream sediments delineates a broad region of naturally occurring mineralization with elevated arsenic, antimony, sulfur and mercury
Slide 17: Natural Background Water Quality
NATURAL BACKGROUND WATER QUALITY Natural Background Natural Background Water in mineralized areas is naturally Conditions in Conditions in ID chronic criterion for elevated in metals Groundwater Seepage from aquatic life; Mineralized Areas (150 ug/L Arsenic) 300 Site Characterization studies prepare
Slide 18: Geochemical Characterization
GEOCHEMICAL CHARACTERIZATION 18
Slide 19: Geochemical Characterization Study
GEOCHEMICAL CHARACTERIZATION STUDY Data collection to support mine planning and impact assessment MATERIAL SAMPLING • Development Rock and Ore: 425 Drillcore Samples • Legacy Mining Wastes: 349 Auger Samples • Future Mill Tailings: 6 Metallurgical Test Composites • Additional Phase 2 sampling based
Slide 20: Acid Rock Drainage?
ACID ROCK DRAINAGE? WHAT IS ACID ROCK DRAINAGE? Acid rock drainage is a naturally occurring process of Pyrite (Fe2S) + Water (H2O) + Oxygen Acid (H+) + Carbonate Minerals (CaCO 3) (O2) = Sulfuric Acid (H2SO4) + soluble Fe = bicarbonate (HCO3) + Ca2+ sulfide minerals oxidizing, combining with water a
Slide 21: Geochemical Characterization Study: Humidity Cell Test Results
GEOCHEMICAL CHARACTERIZATION STUDY Phase 1 humidity cell test results – circum-neutral leachates 10 Phase 1 and Phase 2 humidity cell Quartz Monzonite (HC-2) • Quartz Monzonite (HC-3) programs showed neutral to alkaline Quartz Monzonite (HC-24) conditions (pH 6.5 to 9) for all cells 9 Quartz Monzoni
Slide 22: Geochemical Characterization Study: Static Test Results
GEOCHEMICAL CHARACTERIZATION STUDY Static test results – low probability of ard Acid Base Accounting Results by Gold Grade 1000 Non Acid • The majority of development rock is Generating likely to be net-neutralizing and NNP > 20, NPR > 3 presents a low risk for acid generation 3 eq/t) eq) 800 Majori
Slide 23: Geochemical Characterization Study: Neutral Metal Leaching
GEOCHEMICAL CHARACTERIZATION STUDY Phase 1 humidity cell test results – neutral metal leaching 10 Quartz Monzonite (HC-2) • Arsenic and antimony were Quartz Monzonite (HC-3) consistently released at Steady state arsenic Quartz Monzonite (HC-24) concentrations above some release from most cells Quart
Slide 24: Integrated Environmental Modeling
INTEGRATED ENVIRONMENTAL MODELING 24
Slide 25: ASAOC Staff Update
ASAOC Staff Update 2021-04-15
Slide 26: Remove Waste
REMOVE WASTE FROM NEAR EAST Photo looking south along the EFSFSR from confluence with Sugar Creek FORK SOUTH FORK NW Bradley dumps SALMON RIVER Relocate 100,000 tons of waste from toe of NW Bradley dump to top of dump Bradley On/Off Man Camp On/Off Remove Pads Pads 200,000 tons of waste at Bradley M
Slide 27: Lower Meadow Creek Tailings Removal and Stream Restoration
Lower Meadow Creek Tailings Removal AND Stream Restoration TAILINGS DISTRIBUTION • Former tailings ponds along lower Meadow Creek and EFSFSR below confluence
Slide 28: Lower Meadow Creek Tailings Removal: Alternative 1
Lower Meadow Creek Tailings Removal AND Stream Restoration ALTERNATIVE 1: LOWER MEADOW CREEK • 5000 CY tailings and 18000 CY alluvium • Upstream to downstream sequencing
Slide 29: Lower Meadow Creek Tailings Removal: Alternative 2
Lower Meadow Creek Tailings Removal AND Stream Restoration ALTERNATIVE 2: FORMER TAILINGS PONDS • 22500 CY tailings and 5000 CY alluvium • Targets schoolhouse tailings ponds and remnants from 2005 restoration
Slide 30: Lower Meadow Creek Tailings Removal: Field Investigations
Lower Meadow Creek Tailings Removal AND Stream Restoration FIELD INVESTIGATIONS • Test Pit Excavations • Geoprobe drilling • Temporary bridge for access to east side of MC • Additional water sampling site • Water elevation monitoring in existing wells
Slide 31: Bradley Man Camp Dumps Removal Action
BRADLEY MAN CAMP DUMPS Southeast Southwest REMOVAL ACTION Upper Meadow EFSF Creek DUMPS ADJACENT TO EFSFSR • Appx 2500 x 200 feet and 9 feet thick DMEA MGI Dump • Appx 137,000 CY of mine wastes Facilities • Materials to be placed in on-site East Fork repository Dumps EFSF Valley looking south
Slide 32: Bradley Man Camp Dumps and Onsite Repository
BRADLEY MAN CAMP DUMPS AND ONSITE REPOSITORY REMOVAL SEQUENCE • Access along old Haul Road (2 way traffic) • Upstream to downstream excavation sequence • Removal of access road on retreat downstream to upstream • Four to six 40 Ton articulated trucks and excavator • 10-12 Weeks
Slide 33: Bradley Man Camp Dumps and Onsite Repository
BRADLEY MAN CAMP DUMPS AND ONSITE REPOSITORY DUMP FIELD INVESTIGATIONS • Test Pit Excavations • Reopen access road on old haul road • Additional water sampling sites
Slide 34: Onsite Repository
ONSITE REPOSITORY REPOSITORY DESIGN • Appx. 150,000 CY storage capacity • 25,000 tons of tailings from Meadow Creek • 200,000 tons from EFSFSR Man Camp Dumps • Appx. 1500 x 200 feet and 25 feet tall • Minimum 18” vegetated cover of clean fill
Slide 35: Borrow Source Development
BORROW SOURCE DEVELOPMENT ON-SITE MATERIALS FOR TCRA CONSTRUCTION • Floodplain backfill and bank armoring materials • Stream diversion bedding and rip-rap materials • Repository cover materials (general fill, drainage media, liner bedding, etc) • Excavator/Loader and Dozer with ripper • Mobile scree
Slide 36: Borrow Source Investigation
BORROW SOURCE INVESTIGATION • Excavate Test Pits • Bulk geotechnical samples ON-SITE MATERIALS FOR TCRA CONSTRUCTION • Metals analyses with XRF/lab assays Hennessey Creek Fiddle Blowout
Slide 37: Bradley Dumps and Hennessy Creek
BRADLEY DUMPS AND HENNESSY CREEK SOLUTIONS: EARLY ACTIONS • Dumps composed of ~4.5 MT of sulfide altered waste • Inflows through EFSFSR reach that spans pit and dumps rock and overburden account for up to half of EFSFSR arsenic load depending • Hennessy Creek currently diverted upslope of dumps on s
Slide 38: DMEA Waste Rock Dump Area
DMEA WASTE ROCK DUMP AREA SOLUTIONS: EARLY ACTIONS • DMEA Adit and Waste Rock Dump • Located on USFS-managed land Reduction in water • Arsenic load in DMEA interacting with dump Water conveyed creek increases from upstream to downstream around dump in pipe or lined ditch Significant of dumps reducti
Slide 39: DMEA Waste Rock Dump Area
DMEA WASTE ROCK DUMP AREA *DMEA = Defense Minerals Exploration Administration
Slide 40: Meadow Creek Valley & Smelter Site
MEADOW CREEK VALLEY & SMELTER SITE SOLUTIONS: EARLY ACTIONS • Buried mill and smelter remnants and pond- deposited tailings • High arsenic and antimony in seeps and springs adjacent to area Water conveyed around mill site and tailings in pipe A or lined ditch A A’ Reduction in water interacting with
Slide 41: Adit Study
Bailey Tunnel Outlet Bonanza Adits ADIT STUDY Conduct baseline studies of Mine Influenced Water at five adits. Cinnabar Tunnel Adit Adits include: • Bailey Tunnel • DMEA Adit • Bonanza Adits DMEA Adit • Cinnabar Tunnel • Meadow Creek Mine Meadow Creek Undertake baseline studies to inform the design
Slide 42: Perpetua Resources 2021 Technical Committee Meeting: ASAOC Status Update
Perpetua Resources 2021 Technical Committee Meeting ASAOC STATUS UPDATE May 11, 2021 Austin Zinsser, CERCLA Project Manager
Slide 43: ASAOC Milestones to Date
ASAOC Milestones to Date Project Progress to date Contractors • January 15th signing of ASAOC • EH&S Plan (CERCLA HASP) Guidance & strategy • Approval of Site Characterization report outline • Project Schedule • Work Plan approach presentations • Contractors brought on-board and approved CERCLA docu
Slide 44: ASAOC Looking Forward
ASAOC Looking Forward May Draft wetland assessment workplan Agency Comments on Initial 3 Work Plans and QAPP, EMP, FSP Initial Construction Contractor Engagement June Agency Site Visit Draft site characterization report and data uploads July Final lower Meadow Creek tailings removal workplan Final m
Slide 45: ASAOC Strategies
ASAOC Strategies Communication, collaboration and engagement with agencies Targeted content on site conditions Site Visit with agencies and contractors Technical Workshops with agencies Legal support and expert engagement Strategic technical planning Legal coordination Anticipation of technical hurd
Slide 46: Lower Meadow Creek Tailings Removal and Stream Restoration
Lower Meadow Creek Tailings Removal AND Stream Restoration ALTERNATIVE 1: LOWER MEADOW CREEK CLEANUP AND RESTORATION • 5000 CY tailings and 18000 CY alluvium • Upstream to downstream sequencing DEMONSTRATION PROJECT • Remove 25,000 tons of tailings and contaminated alluvial materials • Place materia
Slide 47: Bradley Man Camp Dumps
BRADLEY MAN CAMP DUMPS DUMPS ADJACENT TO EFSFSR • Appx 2500 x 200 feet and 5-20’ feet thick • Appx 137,000 CY of mine wastes • Materials to be placed in on-site repository REMOVAL ACTION • Upstream to downstream excavation sequence • Removal of access road on retreat downstream to upstream • Four to
Slide 48: Onsite Waste Repository
ONSITE WASTE REPOSITORY REPOSITORY DESIGN • Appx. 150,000 CY storage capacity on historical leach pads • 25,000 tons of tailings from Meadow Creek • 200,000 tons from EFSFSR Man Camp Dumps • Appx. 1500 x 200 feet and 25 feet tall • Minimum 18” vegetated cover of clean fill
Slide 49: Stream Diversion Project
STREAM DIVERSION PROJECT Designs utilize geosynthetic lined channels rather than pipes HENNESSEY CREEK DMEA CREEK SMELTER FLATS Alt 1: Lined channel along Alt 1: Remove dump Single alternative existing route • Assumes upgrading of entire • Relocate majority of DMEA • 1500’ Lined channel with 2900 ft
Slide 50: NW Bradley Dump Removal
NW BRADLEY DUMP REMOVAL WORK PLAN IN PROGRESS RISKS AND OPPORTUNITES • Relocate 100,000 tons of legacy dump • Potential for excavation of saturated material from EFSFSR materials below water table • Place material on top of Bradley Dumps • Floodplain excavation and revegetation • 2.5:1 cut slopes AL
Slide 51: Preliminary Cost Estimates
PRELIMINARY COST ESTIMATES INITIAL COSTS ESTIMATES FOR MULTIPLE ALTERNATIVES • First principle build up and vendor quoted costs estimates Alternatives Base Cost Sub Total Total Perpetua Agency Equipment, Labor & Incl Mobilization, Camp, Includes 25% Project Alternative Proposed Preferred? Supplies E