Mine Rehabilitation Objectives and Measures

One of the leading documents published on the topic of mine closure and rehabilitation is the Ontario Ministry of Northern Development and Mines' report entitled Rehabilitation of Mines, Guidelines for Proponents, published in 1995. The content provided in this section is based on information in Appendix B of that report and is intended to serve as a series of guidelines or checklists for mine closure.

Mining projects are typically divided into components or facilities during closure and rehabilitation planning. These components are typically things such as open pits, tailings facilities, underground features, rock piles etc. A series of rehabilitation objectives and measures have been summarized in table format for the the components listed below and discussed in the three broad categories of (1) Physical Stability, (2) Chemical Stability, and (3) Land Use.

Typical Mine Site Components Include:

The physical stability of structures such as crown pillars, pit slopes, underground openings, tailings dams, spillways, diversion structures, rock pile slopes etc. must be stable to eliminate any hazard to public health and safety.

Surface and groundwaters must be protected against adverse environmental impacts resulting from mining and processing activities.

In a closed out condition, the rehabilitated site should be compatible with the surrounding lands.

The general rehabilitation measures for each of the above mine site components aimed at achieving these objectives has been provided in a series of tables attainable by clicking on the specific component in the list above.


Return to Mine Closure Introduction Forward to Audits and Reviews

Underground Mines

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Openings to Surface Prevent inadvertent access
  • minimize number of openings
  • permanently plug or seal openings to surface
  • backfill shafts, raisses and slopes open to surface
  • vent water and gas pressures
Surface Disruption Prevent inadvertent access
  • use mining method resuting in stable surface
Surface and underground stabilization
  • stabilize surface
  • ditch/berm; fence and sign post unsafe areas until natural stabilization occurs
  • backfill surface openings, if practical
Surface Disturbance Subsidence

Stabilize surface
  • use mining method resulting in stable surface
  • re-contouring or diversion to re-establish drainage patterns
Barrier Pillars Stability

Prevent collapse and flooding of and/or stress transfer to adjacent mine
  • permanently support boundary pillar
  • ensure access to neighbouring mine and continued pumping
Chemical Stability Issues:
Acid Drainage and/or Leaching of Minerals or Contaminants

Seepage of Mill Reagents from Backfill
Meet surface water quality objectives by: controlling reactions and/or controlling migration; collect and treat
  • flood workings to control reaction
  • permanently plug workings and drillholes to control migration
  • collect and treat
  • drain oil containing equipment, motors, transformers, etc.
Land Use Issues:
Productivity and Aesthetics Return surface to original or approved use
  • backfill disrupted areas and openings where practicable
  • contour surface
  • revegetate

Open Pits

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Safety Restrict access to hasardous areas
  • ditch and berm
  • fence, and sign post, if necessary
  • slope stabilization
Emergency access to water
  • provide access to water
Slope Failure Prevent deep seated failure, if practical
  • stabilize by flattening slopes or constructing toe berm
Control sediment release, if necessary
  • restrict access with ditch/berm and, if necessary, fence and sign post
  • revegetate or place riprap on slopes
  • provide stable spillway and overflow channel
Chemical Stability Issues:
Acid Drainage and/or Leaching of Metals Meet water quality objectives by: controlling reactions and/or controlling migration; collect and treat
  • flood to control reactions
  • cover to control reactions and/or migration
  • collect and treat
Land Use Issues:
Productivity and Visual Impacts Return surface to original or approved use
  • backfill pit where practical and beneficial
  • flatten slopes
  • contour-blend with natural topography
  • revegetate slopes
  • rehabilitate for fish, waterfowl, wildlife habitat


Ore, Concentrate and Development of Rock Piles

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Slope Failure Avoid deep seated failure, large surface slumps and sediment release
  • site selection to avoid low strength foundations
  • construct in lifts to achieve flatter slopes
  • internal drains to prevent water table rise
  • covers and/or ditches to control water infiltration
  • doze crest if required, or construct toe berm to flatten overall slope
  • revegetate to establish riprap
Chemical Stability Issues:
Acid Drainage and/or Leaching of Metals, Mill Reagents or Contaminants Meet water quality objectives by: controlling reactions and/or controlling migration; collect and treat
  • underwater disposal to control reactions
  • pre-treatment-blending of alkali material to mitigate acid drainage
  • cover to control reactions and/or migration
  • segregation of deleterious materials for controlled disposal or cellular pile construction
  • detoxify by flushing with water or other solutions
  • regulate seepage quality to meet mine effluent objectives with covers and/or retention pond prior to release
  • collect and treat
Land Use Issues:
Productivity and Visual Impacts Return surface to original state or other approved use
  • contour-blend with natural topography
  • revegetate where practical



Tailings Impoundment Systems

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Tailings Surface Control dust migration, control water erosion
  • establish erosion resistant cover of vegetation, soil, riprap or water
Dams Factor of safey >1.5 for static conditions with erosion resistant overtopping protection
  • appropriate site selection and dam design
  • stabilize embankments by constructing toe berm to flatten overall slope
  • riprap, vegetation or soils cover to control erosion
  • increase freeboard and/or upgrade spillway to prevent erosion by overtopping in extreme events
Other Remove or establish long term stability of spillway, decant towers and pipes
  • remove or plug/backfill structures and decant lines through embankments
  • design and construct diversions and spillways for extreme events and long-term stability
  • define and provide for long-term monitoring and maintenance, avoid on-going operation where possible
Chemical Stability Issues:
Tailings and Pore Water Meet water quality objectives by: controlling reactions and/or controlling migration; collect and treat
  • flood to control reactions
  • pre-treatment removal of deleterious material for controlled dispersal elsewhere, or blending with alkali material to mitigate acid drainage
  • cover to control acid reactions and/or migration using inert material or bog
  • ditch to divert runoff
  • collect and treat
Dams, Structures Meet water quality objectives by: controlling reactions and/or controlling migration; collect and treat
  • do not construct with potential acid generating or leachable materials
  • decontaminate and/or remove acid generating or leaching materials
Land Use Issues:
Productivity of Land and Visual Impacts Return to original state or approved alternative use
  • rehabilitate by: flood, contour, cover, revegetate, wetland


Water Management

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Water Dams Ensure long-term stability with no overtopping
  • monitor/maintain embankment indefinitely or breach
Prevent erosion
  • protect erodible slopes
  • plug intake with concrete, plug decants and remove towers
  • maintain operating spillway preferably in durable rock
Ditches Adequate flood capacity, prevent blockage and overtopping
  • design for extreme events
  • construct from materials suitable for long-term stability
Prevent erosion
  • provide riprap protection
  • define and provide for long-term maintenance
Culverts Ensure maintenance free passage of water under design flood conditions
  • remove culvert and breach, otherwise upgrade for design flood
  • provide for long-term maintenance
Storage Tanks Remove
  • drain, remove, knockdown, fill and cover
Pipelines Remove surface and large shallow pipes
  • remove surface and large shallow pipes, plug pipes at depth
Chemical Stability Issues:
Contaminated Reservoirs Meet water quality objectives by: controlling reactions and/or controlling migration; collect and treat
  • drain, treat and discharge; or monitor and treat indefinitely
  • strip and dispose of contaminated soil in tailings basin or approved location
  • breach dam
  • revegetate
Land Use Issues:
Dams Restore drainage patterns
  • breach and restore to erosion resistant drainage patterns; or stabilize to maintain lake
Determine if alternative use exists
  • define means for transfer of ownership
Reservoirs Return to original or approved use
  • maintain lake and transfer ownership; or drain and revegetate
Ditches Restore drainage patterns
  • grade and establish vegetation

Buildings and Equipment

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Buildings, Equipment and Storage Areas Control inadvertent access
  • decontaminate if necessary, disassemble and remove all equipment and buildings
  • backfill excavations
  • remove buried tanks
  • restore natural drainage
Chemical Stability Issues:
Buildings, Equipment and Storage Areas Meet water quality criteria
  • contaminated soils assessed on a case-by-case basis, leave in place or excavated and disposed of in approved manner
Dispose of surplus chemicals off site
  • chemicals of all types to be recycled, returned to vendor, sold or disposed of in an approved landfill site
Land Use Issues:
Buildings, Equipment and Storage Areas Return to original or approved alternative use
  • contour
  • revegetate
  • break and bury concrete
  • restore natural drainage


Landfill and Other Wastes

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Landfill and Waste Storage Areas Control erosion
  • provide erosion resistant cover
  • stabilize slopes
  • upgrade diversion structures for appropriate maximum flood
Prevent inadvertent access
  • ditch/fence/berm and sign post where facilities which remain are hazardous
Chemical Stability Issues:
Landfill and Waste Storage Areas Meet water quality objectives by: controlling reactions and/or migration, collect and treat
  • divert runof with ditches or covers
  • relocate to controlled disposal facility
Land Use Issues:
Landfill and Waste Storage Areas Return to original or approved alternative use
  • where practical blend to match topography and revegetate


Infrastructure

After: Rehabilitation of Mines Guidelines for Proponents,
Ontario Ministry of Northern Development and Mines, 1995.

ISSUES REHABILITATION OBJECTIVES MEASURES
Physical Stability Issues:
Roads
Airstrips
Powerlines
Control erosion
  • remove culverts, all bridges, barricade approaches and stabilize
  • rip compact surfaces and establish vegetation
  • restore drainage patterns
Public safety
  • follow transportation regulatory authority specifications for maintenance and preventing inadvertent use
  • discharge and lock open all non-essential powerlines
Chemical Stability Issues:
Roads
Airstrips
Control releases to surface and groundwater from spills or erosion
  • contaminated soils assessed on a case-by-case basis; leave in place, or excavate, treat, dispose in approved manner
Land Use Issues:
Roads
Airstrips
Powerlines
Return to original or approved alternative use
  • transfer to new owners where appropriate
  • remove all elevated wires and poles
  • ground all buried wires