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COVERS FOR MINE WASTE DISPOSAL FACILITIES

COVERS FOR MINE WASTE DISPOSAL FACILITIES. By Andy Robertson and Shannon Shaw. Review of Cover Purpose. Access Physical Isolation Erosion Protection Vegetation Establishment Oxygen (oxidation) Control Infiltration (leaching) Control. Soil Covers. Types of Covers: Simple

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COVERS FOR MINE WASTE DISPOSAL FACILITIES

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  1. COVERS FOR MINE WASTE DISPOSAL FACILITIES By Andy Robertson and Shannon Shaw

  2. Review of Cover Purpose • Access • Physical Isolation • Erosion Protection • Vegetation Establishment • Oxygen (oxidation) Control • Infiltration (leaching) Control

  3. Soil Covers • Types of Covers: • Simple • Permeability depends on grain size • Compaction • Oxygen diffusion depends on moisture content • Compound • Complex • Variable • Multi-layered waste low density high density moisture waste

  4. Grey Eagle Tailings Cover

  5. Trends in Cover Design • Infiltration barrier design for wet climates (water barrier) • Evaporation enhancing designs for dry climates (water balance/store and release) • Thick HDPE geomembrane covers to resist disruption

  6. Typical comparison of alternative covers

  7. Typical comparison of alternative covers

  8. mm

  9. Oxygen Control Migration Control Simple Covers Soil covers Complex Covers Multiple soil “Cefyl” Clay layered Geomembrane* * Perpetual replacement @ 50 year intervals ~22% of present value hence long term fund $0.40-0.60/tonne $2 - $6/m2 or $0.03-0.10/tonne waste rock $20 - $30/m2 Or $0.33-0.50/tonne waste rock Dry Cover Costs

  10. Water Cover Costs • New Rock Waste • In natural water bodies • Haulage costs • In man-made impoundments • $0.25 - $1.50 + haulage costs • Old Rock Waste • With treatment of storage products • >$2.75 - $4.00/tonne

  11. Suitability of Cover Types

  12. High Risk Elements of Cover Performance

  13. Minimizing Risk of Cover Failure 1. Materials • Maximize use of natural, durable materials • Minimize use of geosynthetics which deteriorate • Rip-rap control of erosion in dry climates 2. Climate • In dry climates: • consider evaporative cover designs • increase use of rip-rap for erosion protection • provide for sedimentation control • In wet climates: • consider infiltration cover designs • consider water covers

  14. Minimizing Risk of Cover Failure 3. Biota • Beaver (beaver control or wide channels) • Burrowing animals (bio-intrusion layers) • Ants & insects (bio-intrusion layers) • Anthropogenic activity (institutional control) • Roots (control vegetation species) 4. Monitoring & Maintenance • Erosion • Settlement • Sedimentation (& Glaciation) • Biotic factors (fauna, flora, man)

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