Mining Impacts and Remediation Overview

Overview

Lecture on mining impacts, tailings, environmental risks, remediation, and policy/community issues, with examples from Canada, the U.S., and Brazil.

Tailings: ground-up rock from ore processing or overburden removal; large volumes require storage.
Example stratigraphy (Ring of Fire): peat layers, Paleozoic limestone, underlying Shield rocks with ore.
Tailings often barren of vegetation despite surrounding plant growth; recolonization can be slow.
Sudbury nickel-copper tailings pile from 1980s remains unvegetated; monitoring by authorities.

REEs needed primarily for magnets in motors, not batteries.
High-tech systems can contain large REE masses (e.g., jets); specific elements not recalled.
Co-occurring hazardous elements include arsenic, radium (with uranium), and thorium; radiological risks.
Worker safety and environmental exposure must be managed during REE ore handling and processing.

Mercury naturally present in organic soils; disturbance mobilizes it.
Mining does not add mercury in Canada, but soil disturbance increases mercury movement.
Methylmercury issues can arise with dams and wetland alterations.
Any excavation in organic-rich northern soils must plan for mercury mobilization.

Pyrite (FeS2) is reduced iron and sulfur; “fool’s gold” with metallic luster.
AMD: oxidation of pyrite produces strong acidity; one mole pyrite can yield 14 moles acidity.
Acidic conditions accelerate further pyrite breakdown; chain reaction effect.
Sulfide ores often host Cu, Ag and other metals; economic viability fluctuates with metal prices.

Profitability changes daily with commodity prices; operations can rapidly downsize.
Example: abrupt layoffs at a uranium company due to falling uranium prices.

Victor Goldschmidt grouped elements: lithophile (silicate-loving), siderophile (iron-loving), chalcophile (sulfur-loving), atmophile (gas).
Framework guides ore discovery and environmental mobility understanding, though categories can overlap.

Historic copper mine discharging extremely acidic waters (pH down to -1).
Ongoing acid generation expected for centuries; management focuses on limiting oxidation and treating effluent.

Historic gold mine produced ~260,000 tons arsenic trioxide, ~200 tons of gold.
Arsenic emitted to air historically; severe local toxicity events recorded.
Current plan: freeze arsenic trioxide underground indefinitely until better solution emerges.

Early 1900s silver boom fueled development in southern cities; “hinterland vs heartland” dynamic.
Historical rush saw extreme labor practices to retain workers en route to lumber camps.
Long-term arsenic contamination persists a century after mining ceased.
Emphasis on preserving mining history and addressing environmental liabilities.

Mining since late 1970s; only ~0.1% of ~1,000 km² mined area certified reclaimed.
Bitumen coats sand and clay; extraction uses heat and sodium hydroxide, dispersing fines.
Tailings ponds have persistent suspended solids; prohibited discharge to Athabasca River; leakage concerns.
Two tons of ore yield one barrel of oil, generating roughly double the waste material.
Water recycling improved (about 20% makeup), but saline groundwater and residual toxics complicate treatment.

True restoration (pre-disturbance state) is not feasible; peatlands took millennia to form.
Constructed salt marshes may be more realistic given saline conditions, but biodiversity remains low.
Challenges: contaminants, salinity, low biomass, limited topographic complexity; aim for landscape integration.

Key goals: minimize water leakage, control dust, anticipate site-specific risks in boreal vs temperate zones.
Dust can transport nutrients and toxins; often overlooked in impact assessments.
Fast-tracking approvals must include robust reclamation and restoration planning.
Stringent regulations can shift mining abroad; balance competitiveness with environmental protection.
Support for local communities critical; modern mines may be short-lived with rapid build-out and closure.

Trails, BC: smelter emissions killed vegetation; arsenic trioxide stockpiles remain an issue.
Constructed anaerobic bioreactors: gravity-fed wetland cells immobilize arsenic; local materials used.
Achieved ~15 ppb arsenic; regulatory change to 10 ppb ended system; media recovered and smelted for metals.
Brazil tailings dam: lime drain neutralized acidity; near-complete arsenic removal in seepage.
Dam stability concerns required rapid embankment reinforcement; study sites buried.

Second largest continuous wetland; extensive organic deposits.
Numerous mining claims (nickel, copper); proposed road and concentrate transport required.
Baseline studies (water, soil, wetlands) essential to distinguish future impacts from natural background.

Proposed rare earth mine (northern Labrador) intersects caribou migration; concentrate transport and processing planned offsite.
Junior miners often propose new projects; fewer cash reserves and higher bankruptcy risk than majors.
Need for strong financial assurance and adherence to environmental standards.

REE demand must be prioritized across applications; defense vs energy transition trade-offs.
Voting and public policy influence resource use and environmental safeguards.

Tailings: Finely ground waste from ore processing or overburden material requiring storage and management.
Overburden: Soil and rock overlying an ore body; removed during mining.
Rare Earth Elements (REEs): Elements used largely in high-strength magnets for motors and electronics.
Acid Mine Drainage (AMD): Acidic water formed by oxidation of sulfide minerals, mobilizing metals.
Pyrite (FeS2): Iron sulfide mineral; oxidation generates acidity.
Reclamation: Returning land to a usable state with altered ecosystem structure.
Restoration: Returning land to pre-disturbance ecological conditions (often not feasible).
Tailings pond: Containment for liquid-solid waste from mineral processing.
Baseline study: Pre-disturbance environmental measurements to define natural conditions.

Incorporate dust assessment in environmental impact studies for mines.
Require baseline environmental data collection before northern and wetland mining.
Tie fast-tracked approvals to equally fast-tracked, funded reclamation plans.
Ensure financial assurance from junior miners to cover long-term liabilities.
Develop and validate wetland designs suited to saline, contaminated substrates for oil sands regions.
Expand community monitoring and support mechanisms near active and legacy mine sites.