• What happens to mine sites after a mine is closed?

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    Mining is a temporary activity, with the operating life of a mine lasting from a few years to several decades. Mine closure occurs once the mineral resource at a working mine is exhausted, or operations are no longer profitable. Mine closure plans are required by most regulatory agencies worldwide before a mining permit is granted, and must demonstrate that the site will not pose a threat to the health of the environment or society in the future. Depending on the site, the mine may be repurposed for other human uses or restored to its pre-mining use following closure. Financial assurance is increasingly required by regulators as a guarantee that the funds required for mine closure will be available in the event that the responsible company is unable to complete the closure as planned.

    Mine closure

    Mine closure is the process of shutting down mining operations on a temporary or permanent basis. Mines have a limited lifetime which is determined by the size and quality of the mineral deposit being extracted. Mines are closed when the supply of ore runs out or the commodity prices drop, making the mine uneconomical to operate. [1] It typically takes two to ten years to shut down a mine, but it can take longer if long term water monitoring or treatment is required. [1]

    Mine closure process

    Mine closure activities typically consist of several steps: [1, 2]

    • Shut-down: Once production stops, the number of workers is reduced, and only a small labour force is retained to permanently shut down the mining equipment. In some cases, the mining company may provide re-training or early retirement options to their workers before the mine is closed.
    • Decommissioning: Small crews or contractors decommission or take apart the mining processing facilities and equipment. Pipelines are drained, equipment and parts are cleaned and sold, buildings are repurposed or demolished, warehouse materials are recovered, and waste is disposed of.
    • Remediation/reclamation: The objective of reclamation is to return the land and watercourses to an acceptable standard of productive use, ensuring that any landforms and structures are stable, and any watercourses are of acceptable water quality. Reclamation typically involves a number of activities such as removing any hazardous materials, reshaping the land, restoring topsoil, and planting native grasses, trees, or ground cover. It is described in further detail in the mine closure plan section below.
    • Post-closure: Monitoring programs are used to assess the effectiveness of the reclamation measures and to identify any corrective action that may be needed. In addition, mines may require long-term care and maintenance after mine closure such as ongoing treatment of mine discharge water, periodic monitoring and maintenance of tailings containment structures, and monitoring any ongoing remediation technologies used such as constructed wetlands.

    Although the mine closure steps are listed above in a linear fashion, mining operations often begin closure and remediation during active operations.

    Mine closure regulations and requirements

    Mine closure planning is relatively new to the mining industry and has evolved since it was first developed as understanding and awareness of mining’s environmental legacy increased, more stringent regulations were introduced, and mining companies became financially liable for reclamation. Prior to the introduction of mine closure requirements and best practices beginning in the 1970s, mines were often abandoned without being adequately decommissioned or reclaimed by today’s standards. [3] Abandoned mines have the potential to be safety or environmental hazards where infrastructure is left (buildings, open mine shafts), contamination is not addressed, or acid rock drainage is being formed. Over the last forty years, environmental concerns over abandoned mines and the cost to taxpayers for their cleanup have led governments to tighten regulatory controls on mine closure. [2]

    Mine land reclamation and closure plans are now required by regulatory agencies around the world, and are often a component of the environmental impact assessment process practiced in over 100 countries. [4, 5] Mine site rehabilitation has been integrated into the early planning process, even preceding the start of mine operations, and is now an ongoing consideration throughout the mine’s lifetime both from a technical and a financial standpoint. [6]

    Financial assurance requirements

    There are a number of cases where the owner of a contaminated site has been financially unable to complete the cleanup of the site due to unforeseen circumstances such bankruptcy or corporate dissolution. [7] In order to prevent mine abandonment for such reasons, mining companies are increasingly required to provide financial assurance in the form of a deposit or bond to governments and communities as a guarantee that the resources to meet closure requirements will be available. [8] The bonds can range from a few thousand to over 100 million Canadian dollars for a larger mine. [1]

    Different agencies have diverse requirements for the amount of financial assurance to be provided for mine closure. For example, many jurisdictions in Australia determine the financial assurance required on a case-by case basis, and in Texas, the financial assurance required is determined by the mine’s permit conditions. [10] India requires a fixed sum per hectare of mine site, and Suriname and Botswana require funding for closure as an ongoing expense. [10] The jurisdictions of Arkansas, New Brunswick, and Ontario require financial assurance covering the complete cost of mine cleanup, while Québec requires funds covering 70%, Nevada requires 40%, and Ghana requires 5-10% of the estimated cleanup costs to be provided. [10]

    Although the adoption of financial assurance programs is relatively new and has yet to be optimized and practiced in all jurisdictions, cost recovery and enforcement of environmental cleanup have been directly improved by financial assurance requirements. [7] Many of the unrecovered environmental obligations in the U.S. are a result of the failure of past rather than current regulations, and government officials surveyed in Canada, South Africa, and the U.S. reported their current financial assurance policies to be generally effective. [7, 10]

    Mine closure in Canada

    In Canada, the provincial and Yukon governments regulate the mining industry, and have all developed and enacted legislation and regulations for the administration of mining activities and mine closure. [1, 3] The federal government has also developed acts and regulations that govern mine closure, and is responsible for mine reclamation and closure in Nunavut, the Northwest Territories, and on First Nation Reserves. [1] Co-management boards share responsibility with the federal government in Nunavut and the Northwest Territories. [1] All the jurisdictions require that closure plans are put on file and funds for the cleanup and reclamation are provided by the mining company before mining operations can begin. [1] Reclamation is done according to the approved closure and reclamation plan, which must be continuously updated by the mining company and approved by the responsible government agency. [1]

    All the provincial, territorial, and federal governments have legislation in place to provide financial insurance for reclamation in the event the mine operation is unable to do so. [3] If a mining company declares bankruptcy before the mine is closed, the responsible government agency would use the security deposit to cover the eventual costs of repair, maintenance, cleanup and closure of the mine’s site. [4] If the mining company conducts the proper cleanup and site reclamation, the financial security deposit is returned to the company. [4]

    Mine closure plans

    Mine closure plans are specific to each mine, and include details on how the mining company will close the mine site, how environmental protection will be achieved, and how the site will be returned to an acceptable state for a pre-arranged land use. [1] The terms reclamation, remediation, rehabilitation, and restoration are all used to describe mine closure activities that attempt to alter the biological and physical state of a site. [11] The terms are sometimes used interchangeably, and are closely linked, but refer to distinct steps in the preparation of the site for another use: [11, 12]

    • Remediation: The cleanup of the contaminated area to safe levels by removing or isolating contaminants. At mine sites, remediation often consists of isolating contaminated material in pre-existing tailings storage facilities, capping tailings and waste rock piles with clean topsoil, and collecting and treating any contaminated mine water if necessary.
    • Reclamation: The physical stabilization of the terrain (dams, waste rock piles), landscaping, restoring topsoil, and the return of the land to a useful purpose.
    • Restoration: The process of rebuilding the ecosystem that existed at the mine site (where applicable) before it was disturbed. The science of mine reclamation has evolved from simple revegetation activities to a discipline which involves using native plants to mimic natural ecosystem development over an extended period of time. [13]
    • Rehabilitation: The establishment of a stable and self-sustaining ecosystem, but not necessarily the one that existed before mining began. In many cases, complete restoration may be impossible, but successful remediation, reclamation, and rehabilitation can result in the timely establishment of a functional ecosystem.

    Technical audits and reviews of mine closure plans and activities are often completed by professional specialists, government agencies, and review committees in order to review the safety, stability, and environmental risks at mine sites. [14]

    Potential uses of mine sites following mine closure

    Mine sites are usually returned to their pre-mine uses, which, for the majority of mines in Canada, is wildlife habitat or forestry. However, the new concept of economic sustainability and its growing inclusion in mine closure plans has resulted in the collaboration of mining companies, regulators, land-use planners, investors, and citizens to identify the most beneficial use of a mine site, leading to the creative and successful re-use of a number of decommissioned mines sites around the world. Repurposing mine sites can take advantage of existing infrastructure and contribute to the local economy after the mine has closed down. [12] Former mine sites have been used as:

    • Museums or education centres
    Britannia Mine Museum, Squamish, British Columbia
    Bellevue Underground Coal Mine, Crowsnest Pass, Alberta 
     
    • Visitor attractions
    Wieliczka Salt Mine, Cracow, Poland has 300km of galleries with works of arts carved in the salt, and has been designated a UNESCO World Heritage Site
    The Eden Project at a disused clay mine in Cornwall, U.K., is an ecosystem biome project, educational centre, and concert venue
       
    • Scientific centres
    The Sudbury Neutrino Observatory was built in INCO’s Creighton Mine near Sudbury, Ontario
       
    • Recreational areas
    Gotland Ring, Sweden, is a world-class car racing track situated in an old limestone quarry
    Kőbánya, Budapest, Hungary, is a limestone quarry which has been flooded, and is now a popular scuba diving destination
      
    • Gardens or parks
    Butchard Gardens, Victoria, British Columbia used to be a limestone quarry mined for making concrete
    Wheal Jane tin mine in Cornwall, U.K. features wetlands and recreational trails
      
    • Fish farms
    • The AngloGold Ashanti Homase mine in Ghana has started aquaculture in disused mine pits
      
    • Agriculture
    • The Big Hole at the Kimberley Mine is being used to grow oyster mushrooms
    Tatum Lignite Mine in East Texas was reclaimed to productive farmland and wetland areas
     

    Case Study: Island Copper Mine, Port Hardy, British Columbia, Canada

    Island Copper Mine is located adjacent to the Rupert Inlet approximately 14 kilometers south of Port Hardy on northern Vancouver Island. [15] The mine began production in 1971, and was the third largest copper mine in Canada when it was closed in 1995 due to resource depletion. [15] An estimated 1.3 million tonnes of copper, 31,000 tonnes of molybdenum, 31.7 tonnes of gold, 336 tonnes of silver, and 27 tonnes of rhenium were extracted over the lifetime of the mine. [16] More than a billion tonnes of material was excavated, which produced an oval-shaped pit with a depth 400 metres below sea level. [15]

    During mining operations, the excavated ore was ground up and processed in a slurry by floatation to remove the copper and molybdenum. [15] Waste rock (rock with no economic value) was dumped in piles on site and along the shore, and the tailings produced from the copper processing operations were placed on the seabed in the Rupert Inlet. [15] The underwater tailing disposal system at Island Copper was one of the first in the world, and was considered to have less of an environmental impact than an equivalent on-land disposal system. [16, 17]

    In response to concerns about the impacts of the tailings on the health and diversity of marine life in Rupert Inlet, a comprehensive oceanographic monitoring program was developed and implemented in 1970, and was overseen by a committee of university professors appointed by the federal and provincial governments. [15] By 1985, no long term impacts on marine life as a result of the tailing disposal system had been identified. [18] However, in 1986, acid rock drainage (ARD) from the waste rock dumps was observed, and considerable effort was put into monitoring and evaluating stream flow volumes and dissolved metal content. [18] A water management program was implemented to control runoff and drainage water from the waste rock dumps and recycle it through the metal processing plant. [15]

    Planning for mine closure began before the mine was constructed in 1969, and the final closure plan was developed and submitted to the provincial regulatory authorities in 1994. [15] The mine closure plan was updated several times in order to incorporate changes in mine production, post-closure land use, and developments in reclamation technologies. [15] In addition to the environmental components, the closure plan incorporated considerations for the economic sustainability of the Port Hardy community, and the mine owners BHP Minerals Canada Ltd. were instrumental in attracting and supporting entrepreneurs to purchase the buildings and dock facilities and establish wood processing and aquaculture operations. [15] The 90 hectare ore processing plant site was remediated to government standards for the proposed land use, and was the first mine site in B.C. to participate in the contaminated sites regulation process and receive a Certificate of Conditional Compliance. [19] The buildings, operating machinery, and mobile equipment were sold, and any structures which were not sold were dismantled. [15]

    A further 480 hectares of disturbed land was converted back to productive woodland and wildlife habitat. [15] Replanting had been continuous since the beginning of mine operations, and over 600,000 alder and lodgepole pine seedlings were planted over the years. [15] The land dumps were reclaimed with grass and legume seed mix, red alder and pine seedlings , and the waste rock beach dump in Rupert Inlet was sculpted into six bays to create marine habitat. [18] The revegetation strategy used plants which were native to the area, and the site is expected to eventually return to the cedar-hemlock forest common to the region. [20]. The revegetation has been successful so far, with forest productivity on the waste dumps equivalent to or better than forest growth in the surrounding area. [20] The site has already attracted a relatively large number of deer, bears, and Canada geese. [20]

    The decommissioned open pit was flooded with seawater from Rupert Inlet in 1996, creating a 330 metre deep lake covering 215 hectares. [15] Flooding the pit stabilized the pit walls and provided an effective receiving environment for passive treatment of the ARD, which is collected in two ditch systems and discharged into the lake via two polyethylene pipes at a depth of 200 metres. [15] The lake is layered or stratified, with a salt water, anoxic (oxygen-free) layer on the bottom, and a largely freshwater layer on the top from rainfall and surface water runoff. [18] In the anoxic layer, sulphur-reducing bacteria produce hydrogen sulphide, which reacts with the metals in the ARD to form a stable metal-sulphide precipitate that settles to the bottom of the lake. [18] The passive treatment system is considered to be an effective long-term treatment option for the ARD. [18]

    The water quality at the mine site has been monitored before, during, and following mining operations, and has consistently been considered acceptable. [20] Monitoring of marine life from 1970 to 1998 showed the number and diversity of bottom-dwelling animals in the mine tailings at the bottom of Rupert Inlet to have returned to pre-mining levels, as have the populations of juvenile salmon, dogfish shark, rock cod, and crab. [15] Environmental monitoring of the reclamation will continue until it has been clearly demonstrated that the replanted forest is sustainable, at which point the property will be returned to the provincial government. [15] An environmental performance bond of four million Canadian dollars remained in effect in 2000. [15] The reclamation of the Island Copper Mine has received a number of environmental performance awards from the B.C. Technical and Research Committee on Reclamation, the Mining Association of B.C., and a national award from the Prospectors and Developers Association of Canada for environmental and social responsibility. [15] Pictures of the Island Copper mine in 2005 are available here.



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    References

    1 Canada, Natural Resources Canada. 4. Mine Closure, Mining Sequence: Mining Information for Aboriginal Communities, 2011 [cited 2012 July 13]; Available from: http://www.nrcan.gc.ca/minerals-metals/aboriginal/mining-information-kit/4179.
    2 Champigny, N. International Survey of Mine Reclamation and Funding, Proceedings of the 15th Annual British Columbia Mine Reclamation Symposium, 1991 [cited 2012 July 20]; The Technical and Research Committee on Reclamation. Available from: https://circle.ubc.ca/bitstream/handle/2429/12528/1991%20-%20Champigny%20-%20International%20Survey%20of%20Mine%20Reclamation.pdf?sequence=1.
    3 Mackasey, W.O. Abandoned Mines in Canada, 2000 [cited 2012 July 20]; Prepared for MiningWatch Canada]. Available from: http://www.miningwatch.ca/sites/www.miningwatch.ca/files/Mackasey_abandoned_mines_0.pdf.
    4 Noble, B.F., Introduction to Environmental Impact Assessment: A Guide to Principles and Practice, 2006, Don Mills, Ontario: Oxford University Press.
    5 Sassoon, M. Financial Surety: Implementation of Financial Surety for Mine Closure, 2009 [cited 2012 July 31]; World Bank Oil, Gas, and Mining Policy Division. Available from: http://siteresources.worldbank.org/INTOGMC/Resources/7_eifd_financial_surety.pdf.
    6 Minalliance, 100 Innovations in the Mining Industry, 2012, PDAC and The Mining Association of Canada.
    7 Boyd, J. Financial Responsibility for Environmental Obligations: Are Bonding and Assurance Rules Fulfilling Their Promise?, Discussion Paper 01-42, 2001; Resources for the Future. Available from: http://www.rff.org/rff/Documents/RFF-DP-01-42.pdf.
    8 International Council on Mining & Metals. Projects: Mine Closure and Legacy, 2011 [cited 2012 July 23]; Available from: http://www.icmm.com/our-work/projects/mineclosure.
    9 Cowan, W.R., W.O. Mackasey, and J.G.A. Robertson. The Policy Framework in Canada for Mine Closure and Management of Long-Term Liabilities: A Guidance Document, 2010 [cited 2012 July 20]; National Orphaned/Abandoned Mines Initiative. Available from: http://www.abandoned-mines.org/pdfs/PolicyFrameworkCanforMinClosureandMgmtLiabilities.pdf.
    10Miller, C.G. Financial Assurance for Mine Closure and Reclamation, 2005 [cited 2012 July 31]; International Council on Mining and Metals. Available from: http://www.icmm.com/page/1158/financial-assurance-for-mine-closure-and-reclamation.
    11 Finger, S.E., S.E. Church, and P.v. Guerard. Chapter F: Potential for Successful Ecological Remediation, Restoration, and Monitoring, Integrated Investigations of Environmental Effects of Historical Mining in the Animas River Watershed, San Juan County, Colorado, 2008 [cited 2012 July 20]; U.S. Geological Survey Professional Paper 1651. Available from: http://pubs.usgs.gov/pp/1651/downloads/Vol2_combinedChapters/vol2_chapF.pdf.
    12 Dutta, S., R. Rajaram, and B. Robinson, Chapter 5: Mineland Reclamation, in Sustainable Mining Practices -- A Global Perspective, V. Rajaram and S. Dutta, Editors. 2005, A. A. Balkema Publishers, a member of Taylor & Francis Group: Leiden, The Netherlands. p. 179-191.
    13 Errington, J.C. History and Future of Mine Reclamation in British Columbia, Proceedings of the 16th Annual British Columbia Mine Reclamation Symposium, 1992 [cited 2012 July 20]; The Technical and Research Committee on Reclamation. Available from: https://circle.ubc.ca/bitstream/handle/2429/14193/1992%20-%20Errington%2c%20History%20and%20Future%20of%20Mining%20Reclamation.pdf?sequence=1.
    14 Robertson, A. and S. Shaw. Mine Closure, InfoMine E-book, 2002 [cited 2012 July 23]; Available from: http://www.infomine.com/publications/docs/E-Book%2002%20Mine%20Closure.pdf.
    15 Welchman, B. and C. Aspinall. A Sustainable Legacy: Utilizing Mine Assets Post-Closure Island Copper Mine, Proceedings of the 24th Annual British Columbia Mine Reclamation Symposium, 2000 [cited 2012 July 20]; The Technical and Research Committee on Reclamation. Available from: https://circle.ubc.ca/bitstream/handle/2429/9546/2000%20-%20Welchman%2c%20Aspinall%20-%20A%20Sustainable%20Legacy.pdf?sequence=1.
    16 Rescan. Island Copper Mine, Projects, 2011 [cited 2012 July 23]; Available from: http://www.rescan.com/projects/rs_projects3.php.
    17 Polling, G.W., Chapter 11: Postclosure Rehabilitation and Assessment of Inlet System, in Underwater Tailing Placement at Island Copper Mine 2002, Society for Mining, Metallurgy, and Exploration, Inc: Littleton, Colorado, USA. p. 161-165.
    18 Horne, I.A. The Development of a Closure Plan for Island Copper Mine, Proceedings of the 17th Annual British Columbia Mine Reclamation Symposium, 1993 [cited 2012 July 20]; The Technical and Research Committee on Reclamation. Available from: https://circle.ubc.ca/bitstream/handle/2429/11056/1993%20-%20Horne%20-%20The%20Development%20of%20a%20Closure%20Plan.pdf?sequence=1.
    19 North, R.H.J. The First Certificate of Compliance For a Mine Site in British Columbia: BHP Minerals Canada Lts. Island Copper Mine, Proceedings of the 23rd Annual British Columbia Mine Reclamation Symposium, 1999 July 23]; The Technical and Research Committee on Reclamation. Available from: https://circle.ubc.ca/bitstream/handle/2429/9621/1999%20-%20North%20-%20The%20First%20Certificate%20of%20Compliance.pdf?sequence=1.
    20 Polster, D.F., B. Welchman, and C. Hanks. Revegetation Strategy at the Island Copper Mine, Proceedings of the 25th Annual British Columbia Mine Reclamation Symposium, 2001 [cited 2012 July 20]; The Technical and Research Committee on Reclamation. Available from: https://circle.ubc.ca/bitstream/handle/2429/10599/2001%20-%20Polster%2c%20Welchman%2c%20Hanks%20-%20Revegetation%20Strategy.pdf?sequence=1.

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