Concepts and definitions of mine closure

Tommi Kauppila, Geological Survey of Finland, PO Box 1237, 70211 Kuopio, Finland; tommi.kauppila(at)

Acid base accounting (ABA) = An analytical screening procedure to measure the acid producing and acid neutralizing potential of a material (e.g. rock, mine waste, soil, etc.).

Acid consuming (AC) = Material that has greater neutralizing potential than acid generating potential such that when reacted in solution, solution acidity decreases.

Acid mine drainage (AMD) = Water that has been acidified by sulphuric acid as the result of interactions with sulphide minerals that have undergone accelerated chemical oxidation due to mining activity. AMD often has elevated metals concentrations as a result of both mineral oxidation and enhanced mineral dissolution by the acidic water itself. Often used interchangeably with ARD.

Acid potential (AP) = The maximum amount of acid that can be produced by a material as determined through ABA screening.

Acid rock drainage (ARD) = Water that has been acidified by sulphuric acid as the result of interactions with sulfide minerals that have undergone chemical oxidation. ARD often has elevated metals concentrations as a result of both mineral oxidation and enhanced mineral dissolution by the acidic water itself. Often used interchangeably with AMD.

Adaptive (resource) management = A planned and structured iterative process of environmental management which aims to improve (environmental) management practices by accruing information on the outcomes of existing measures and utilizing this to improve future management decisions.

Adit = A horizontal tunnel in an underground mine used either for travel within the mine or removing water from the mine.

Armouring = The accumulation of precipitate on reactive surfaces acting as a chemical barrier reducing reactivity at the surface site.

Autogenous mill = Where ore is ground by tumbling within a drum

Buffer = To lessen the change in pH resulting from the addition of acid or alkalinity, or the chemical constituent that induces said effect.

Care and maintenance = The process of maintaining a (temporarily) closed mine site safe, stable and suitable for recommencing operations should it become feasible in the future.

Closure issues = These are the issues that need to be addressed in mine closure. Listing of closure issues is one of the tools used in creating the Closure Management Plan (CMP).

Closure Management Plan (CMP) = An either conceptual or detailed plan for the communication and execution of mine closure. The plans provide contextual information on factors that affect closure, lays out the target outcomes and goals of the closure, and provides a detailed plan with actions, schedule, responsibilities, and verification showing how the goals will be reached. CMPs are updated regularly during the life of the mine and its level of detail increases as uncertainties are systematically addressed.

Concurrent rehabilitation = Rehabilitation actions taken during the operating period of the mine. Similar to, but narrower in scope than continuous closure.

Constructed impoundment = A basin designed to retain water, liquid waste and/or sediment and built using dams and/or excavation.

Continuous closure = Closure actions that are made during the operating period of the mine, before the final decommissioning phase. These actions are defined and scheduled in the CMP.

Cut and Fill = A method of mining in which ore is extracted horizontally or from a slight incline and waste rock, tailings and/or sand is used to fill the void left by the ore

Environmental risk assessment (ERA) = A combination of ecological and human health risk assessment. A systematic procedure for predicting potential risks to human health or the environment of specified activities or inaction.

Flocculent = Used here as a general term to describe accumulated material precipitated from solution.

Flotation = A process in which minerals are separated on the basis of physical and chemical properties, generally using a reagent to capture specific mineral types within a froth while other minerals are allowed to settle out.

Gap analysis = One of the tools to guide the review and updating of the CMP is a systematic analysis of knowledge gaps surrounding closure issues. Action plans of the CMP contain actions aimed at reducing the identified uncertainties.

Glory Hole = A general expression for surfacial mine openings and can be used to describe the point at which underground mine shafts open to the surface, or where collapsed mine shafts have caused a surface depression or opening.

Hardpan = A dense soil layer with low permeability generally formed from precipitation of minerals from solution

Internal stakeholders = Internal stakeholder to mine closure are organizational levels, divisions, teams and key personnel within the mining company (mine operator) who provide inputs to the mine closure process itself or whose designs and day to day decisions affect the outcomes of the closure process.

Inert = Not chemically reactive.

Leach bed = Used here to refer to a pond filled with substrate designed to alter pond water chemistry. The altered pond water is put in hydraulic connection with either a pollution point source, or waters impacted by a pollution source to counter impacts of pollution.

(Final) Mine closure = The actions performed at a mine site upon and following the permanent ending of the mining operations, with the aim of achieving the aims of good mine closure.

Mine water = All water emanating from active, abandoned or closed surface or underground mines.

Neutralizing potential (NP) = The amount of alkalinity within a material available for acid neutralization as measured by acid titration.

Open pit = A surface mine open to the surrounding environment.

Ore = Material containing a mineral or mineral assemblage of value, often mixed with non-valuable rock materials collectively referred to as gangue.

Ore concentrate = The marketable mineral product after ore processing

Portal = The entrance to underground mine workings.

Post Closure Management Plan (PCMP) = Similar to CMP but for the post closure period. An official PCMP may be required in certain jurisdictions.

Reclamation = Reclaiming the mine site to new sustainable uses after mine closure.

Reclamation and closure plan (RCP) = See Mine closure plan

Rehabilitation (ecol.) = Partially restoring the original biological communities in cases where complete restoration is not feasible.

Restoration (ecol.) = Restoration of the original biological communities and ecosystems.

Source control = A general principle of mine operation and closure stating that contamination and environmental impacts are best avoided by controlling and managing the sources of contamination rather than capturing and treating the emissions.

Tailings = Generally sand to clay sized waste material consisting of gangue minerals, unrecovered minerals, and process water which remains after minerals of value have been extracted from ore.

Tailings beach = The portion of tailings material within a tailings pond exposed to air, situated between inundated tailings and the impoundment wall. The beach forms from the coarser fraction of tailings that settle from the tailings slurry discharged to the pond.

Underground workings = All of the underground openings constructed for the purpose of underground mining.

Waste rock = Rock material extracted with ore that has insufficient concentrations of ore minerals to warrant further processing.

Water breaks = Structures designed to minimize wave action by reducing area of the contiguous water surface.