Teck Resources Limited Class A · TSX:TECK.A
Teck Resources Limited Class A — Corporate Update (December 2025)
51 slides from Teck Resources Limited Class A's corporate update, Dec 3, 2025
Slide 1: Tulsequah Chief Mine Information Webinar
TULSEQUAH CHIEF MINE INFORMATION WEBINAR December 3, 2025
Slide 2: Thank you for joining our information session
Thank you for joining our information session on remediation planning for the Tulsequah Chief Mine. In this webinar, we will share how Teck Resources and the Taku River Tlingit First Nation (TRTFN) are collaborating to develop a remediation plan for the site. You will learn about the progress made s
Slide 3: Send Your Questions
SEND YOUR QUESTIONS Go to teck.pigeonhole.at Enter passcode TCMR Teck - Internal/Interno Teck
Slide 4: Meet the Team (Teck – TRTFN) Steering Committee
MEET THE TEAM (TECK – TRTFN) STEERING COMMITTEE Rodger Thorlakson, Gideon Kyei Matthew Taylor, Jackie Caldwell, Lands and Serbeh, Mining Mining Resources Consultant for Coordinator, Technician, Manager, TRTFN TRTFN TRTFN TRTFN Chris Sergeant, Stephanie Research Deborah Read, Tissot, Scientist, U. of
Slide 5: About the Tulsequah Remediation Team
ABOUT THE TULSEQUAH REMEDIATION TEAM 5
Slide 6: About Teck Resources
ABOUT TECK RESOURCES Teck is a leading Canadian critical minerals company focused on responsibly providing metals essential for global development and the energy transition. 100+ years of history as a Canadian company headquartered in Vancouver, B.C. 6 total operations in Canada, the U.S., Chile and
Slide 7: About TRTFN
ABOUT TRTFN The Taku River Tlingit First Nation is located in Atlin, BC, a small remote community of approximately 400 people. We represent our Citizens on all matters that could affect our Territory that covers over 40,000 sq/km. Our Territory contains high mountains, expansive forests rich with wi
Slide 8: Collaborative Governance
COLLABORATIVE GOVERNANCE Objective: work together in the development of a final remediation plan for the mine site. Teck and TRTFN meet regularly to plan and discuss remediation planning and field activities. Steering Committee: • Guides decision-making. • Supports alignment on priorities and progre
Slide 9: Collaborative Governance: Memorandum of Understanding
COLLABORATIVE GOVERNANCE Objective: work together in the development of a final remediation plan for the mine site. Memorandum of Understanding (MOU) between TRTFN, Teck, and BC: •Signed: September 17, 2024. •Purpose: Joint development of a closure and reclamation plan for the Tulsequah Chief Mine.
Slide 10: The Tulsequah Chief Site - Location
THE TULSEQUAH CHIEF SITE - LOCATION The mine is located approximately 100 km south of Atlin, British Columbia, on the Taaltsux̱éi Héen. The mine is approximately: • 10 km upstream of where the Taaltsux̱éi Héen flows into the T'aakú Héeni. • 30 km from the US border • 50 km NE of Juneau 10
Slide 11: The Tulsequah Chief Site - Overview
THE TULSEQUAH Historic underground CHIEF SITE - copper, lead, and zinc OVERVIEW mine, operated from 1951- 1957 Objective: Teck and TRTFN working on a final remediation plan for the mine site Ownership: Teck does not own the site or facilities and does not hold mining rights Teck is voluntarily fundi
Slide 12: Timeline of the Tulsequah Chief Mine
TIMELINE OF THE TULSEQUAH CHIEF MINE Teck voluntarily conducts remediation planning. Remediation discussions with Teck, BC, and TRTFN, including current efforts focused on long- Mine site entered term permanent into receivership remediation of the site 2015 2023 to today… 1947-1958 1987-2014 2018-20
Slide 13: Site Layout
SITE LAYOUT Upper and lower mine workings, airstrip, camp, lime sludge pit waste rock, WTP (not functional), lime sludge pit, exfiltration pond barge landing, barge camp, fuel storage 13
Slide 14: Mine Workings Cross Section
MINE WORKINGS CROSS SECTION ground surface 6500 Level Upper workings 6400 Level 5900 Level (blocked at 90m) tunnels Lower workings 5400 Level mined out cavity 5200 Level (dam at 390m) Current remediation concept - Secure all portals to prevent human entry - Plug 5200, 5400 to prevent acid mine drain
Slide 15: Mine Workings
MINE WORKINGS Upper Workings Two Open Shafts fe @ 6500 Level 6400 Level $400 Levet $900iLevel
Slide 16: , Poe Blas
, Poe Blas ar, cant 5400 Level ie + Wasie Rock Ore Storage icv A SS -NORPAG Bedrock —2 at 7) hy Welty 4 ae H PAG, Bedrock Waste.Rock Fuel Storage Hazardous Wastes A onc 5200 Level & " ‘ * a J 3 Exfiltration Pond and Spillway
Slide 17: Water Quality
WATER QUALITY • Water from UG and waste rock dumps is acidic • High concentrations of Al, Cd, Cu, Fe, Zn. • Elevated concentrations of As, Pb, SO4 Impact: 5400 • For some metals, higher concentrations than background seen up to 3km downstream • Monitoring by USGS and DEC to date shows concentrations
Slide 18: Tulsequah Chief Overview
TULSEQUAH CHIEF OVERVIEW Complicating factors to planning and remediation: • Critical Infrastructure in disrepair or not functioning at all • Bridges and culverts, airstrip, WTP, historic camp • Isolated site location • Air access only (Twin Otter, Caravan, Helicopter) • Barging may be option in fut
Slide 19: Tulsequah Chief Mine Remediation Planning
TULSEQUAH CHIEF MINE Remediation Planning • Shared Priorities: TRTFN, Teck, and Province of BC agreed on key priorities for a detailed remediation plan and formalized in a Memorandum of Understanding (MOU) signed in September 2024. • Collaborative Work Plans: Teck and TRTFN worked together to prepar
Slide 20: Progress Made During 2024 and 2025 Field Seasons
PROGRESS MADE DURING 2024 AND 2025 FIELD SEASONS Water Safe Underground Management Mined Rock Environment Waste Access (U/G) and Monitoring Maintain safe, Clean up and Install temporary Remove reliable access Secure assess existing sediment control Quantify waste some historic to site underground wa
Slide 21: Safe Access
SAFE ACCESS Challenging Site Access The remote mountainous terrain limited access to the mine, requiring air transport via helicopters and fixed-wing aircraft. Airstrip Maintenance - Cleared large stones and debris - Cut brush - Compacted Weather station Footnote if requ ired 21
Slide 22: Safe Access
SAFE ACCESS Temporary Accommodation Setup 2024 investigation revealed that the historic Shazah Camp was: - Heavily impacted by mould - Not compliant with electrical and camp codes A temporary 20-bed camp was established in 2024 and 2025 to support field activities after the historic camp was deemed
Slide 23: Safe Access
SAFE ACCESS Safety and Infrastructure Improvements Helipads constructed at upper portals to allow access. Loose rocks scaled and removed from slopes near portals, camp, and work areas. Infrastructure Maintenance: • Two rotting bridge decks replaced to allow access to southern end of site. 23
Slide 24: Bridge Repair
BRIDGE REPAIR Mine workings Potential riprap and cover material 24
Slide 25: Before After
Before After Teck Teck - Internal/Interno
Slide 26: Underground
UNDERGROUND Mine Safety Enhancements Teck improved safety by: • clearing debris, • replacing timber, and • reinforcing key mine levels to prevent cave-ins and hazards. Footnote if requ ired 26
Slide 27: Mine Workings
MINE WORKINGS Upper Workings Two Open Shafts fe @ 6500 Level 6400 Level $400 Levet $900iLevel
Slide 28: Underground
UNDERGROUND 2024 and 2025 Drone Surveys: • Conducted in 5200, 5400, 5900, and 6400, and 6500 Levels. • 5200 Level dam observed retaining water but past design life—potential safety risk. • Data will inform engineering for safe access. Footnote if requ ired 28
Slide 29: Sludge depth estimated to be 45 cm
Sludge depth estimated to be 45 cm 29
Slide 30: 5200 L Portal Dam at 392m
5200 L Portal Dam at 392m IN FLIGHT | UPTIME || ASSIST) 341 SIS ||sPoRT X: 310m Y¥. 236m | Z: 235m D:3924m H: 355° Kd <1 (TP) prisceed < 100 >
Slide 31: Underground
UNDERGROUND 2025 Underground Stabilization Work: • 5400 Level: Debris cleared, timber replaced. • 5900 Level: Reinforced with timber and bolts. • 6400 Level: Loose rock removed. Footnote if requ ired 31
Slide 32: May 2025 August 2025
: 4 ; i q : a i is ¢ May 2025 August 2025 Teck Teck - Internal/Interno
Slide 33: Teck - Internal/Interno
33 Teck - Internal/Interno Teck
Slide 34: Mined Rock
MINED ROCK Quantify waste rock at surface - 2024 Surface drone survey Footnote if requ ired 34
Slide 35: Water Management
WATER MANAGEMENT Clean and inspect existing temporary water treatment plant Assessed potential refurbishment requirements Sediment control Aquatic Monitoring Program Footnote if requ ired 35
Slide 36: Water Treatment Plant (WTP)
WATER TREATMENT PLANT (WTP) CLEARING WTP REMOVING BLACK MOULD 36
Slide 37: Water Treatment Plant Assessment
WATER TREATMENT PLANT ASSESSMENT ASSESSING PIPING ASSESSING PLC PANEL 37
Slide 38: Water Management and Monitoring
WATER MANAGEMENT AND MONITORING Sediment Control: • Fencing and straw wattle installed at portals to reduce sediment load to river while underground work occurring. • Fencing removed post-season to prevent spring runoff impact. 38
Slide 39: Water Management and Monitoring
WATER MANAGEMENT AND MONITORING Sampling: 2024: AEMP (Water quality, sediment, benthic invertebrates, slimy sculpin) 2025: Monthly water quality sampling at 36 valley locations. Sediment samples collected in June and September. TRTFN participated in 2024 and 2025 Footnote if requ ired 39
Slide 40: Aquatic Effects Monitoring
AQUATIC EFFECTS MONITORING Kick Netting Water Sampling 40
Slide 41: How Does the Mine Affect Salmon in the Taaltsuxéi Héen?
HOW DOES THE MINE AFFECT SALMON IN THE TAALTSUX̱ÉI HÉEN? Acidic Water Formation: • Sulphide-bearing rocks + air + water = acidic water in mine tunnels. • Acidic water dissolves metals (i.e., copper, iron), which is carried downstream. • Most water flows to water management pond, overflows into river
Slide 42: How Does the Mine Affect Salmon in the Taaltsuxéi Héen?
HOW DOES THE MINE AFFECT SALMON IN THE TAALTSUX̱ÉI HÉEN? Results from Environmental Monitoring • Elevated Metals: higher metal levels in water and sediments up to 3 km downstream, beyond that, conditions normalize. • Salmon: • Adult salmon migrating past the mine unlikely to accumulate metals. • Hab
Slide 43: How Does the Mine Affect Salmon? Future Trends
HOW DOES THE MINE AFFECT SALMON IN THE TAALTSUX̱ÉI HÉEN? Future Trends • Glacier retreat – river becomes warmer, clear, more vegetated; better salmon habitat. • Mine remediation will benefit current & future salmon populations. 43
Slide 44: Environment
ENVIRONMENT Bat Monitoring: • Equipment installed at portals to detect bat roosting/hibernation. • Monitoring to continue for about 18 months to inform planning for remediation of underground. Climate Change Studies • Focused on future temperature, rain, and snow trends. • Results expected end of 20
Slide 45: Environment
ENVIRONMENT Soil Sampling: • Conducted from airstrip to barge landing to assess possible contamination from historic mine activities. Footnote if requ ired 45
Slide 46: Waste
WASTE 2025 Legacy Waste Removal: • 253 fuel drums • 106 vehicle batteries • 28 bags of bottles/cans 2024 and 2025 Waste: All newly generated waste removed from site. 46
Slide 47: 2026 Proposed Plans
2026 PROPOSED PLANS Water Safe Underground Management Mined Rock Environment Remediation Access (U/G) and Monitoring Planning Maintain safe, Assess options for Draft Quantify the Understand reliable access Secure mobile water Remediation geochemistry of aquatic risk to to site underground treatment
Slide 48: Next Steps & Concluding Remarks
NEXT STEPS & CONCLUDING REMARKS Teck and TRTFN will continue collaboration on remediation planning: • Plan 2026 field season • Review information from technical reports • Renew regulatory approvals • Advance community engagement efforts 48
Slide 49: Send Your Questions
SEND YOUR QUESTIONS Teck Go to teck.pigeonhole.at Enter passcode TCMR Teck - Internal/Interno 49
Slide 50: Stay Connected
STAY CONNECTED Thank You for Joining Us We appreciate your participation in today’s webinar and hope the information shared was valuable. For questions on remediation planning, field For questions on regulatory approvals, bonding, and activities and collaboration between Teck & provincial consultati
Slide 51: Thank You
Teck THANK YOU