What are abandoned mines?

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    Abandoned mines are sites where mining activities occurred, but acceptable mine closure and reclamation did not take place or was incomplete. Abandoned mines contribute to the legacy of environmental degradation left by historic mining activities which occurred before mine closure regulations were developed. The environmental and social liability posed by abandoned mines in Canada has now been recognized, and regulators have initiated various programs to assess and remediate the abandoned mines within their jurisdictions.

    History of abandoned mines

    Mining is a temporary use of land, with the operating life of a mine lasting from a few years to several decades. Before the 1970s, it was common practice for mining companies to leave mine sites as they were when mining operations stopped, which was frequently in a state of excavation. [1] Current best practices in mine closure require the reclamation or rehabilitation of decommissioned mine sites, which involves returning the land and watercourses to an acceptable standard of productive use. [2] Reclamation activities often include removing or remediating any hazardous materials, reshaping the land, restoring topsoil, and planting native grasses, trees, or ground cover. [3]

    Abandoned mines may have been reclaimed to the standards of the day, but in some cases the methods used were inadequate for the prevention of environmental contamination and the mines are therefore considered to be improperly reclaimed by today’s standards. In addition, abandoned mines are frequently “orphaned” – mines for which the owners cannot be found or for which the owner is financially unable or unwilling to carry out the cleanup of the mine site. [4] As a result, governments are often left to close and rehabilitate orphaned and abandoned mines. [1]

    Reasons for mine abandonment

    Factors which contribute to the abandonment of a mine include: [1 p. 44, 5]

    • A lack of mine reclamation policies or regulations until the 1970s which meant there were no or few requirements to clean up mine sites
    • Ineffective enforcement of mine reclamation policies and/or minimal penalties for non-compliance
    • Economic events such as a decrease in the price of minerals or an unforeseen disaster could lead to the bankruptcy of the mining company, making it unable to complete the mine closure for financial reasons
    • No or inadequate financial assurance provided in case the mining company went bankrupt
    • National security issues in times of conflict which led to the rapid development of a number of mines with little consideration for the continuation of mining operations or closure requirements
    • Political unrest, social conflict, or political instability leading to the unscheduled halt of mining operations
    • Small-scale mining operations by artisanal or illegal miners are unlikely to undergo reclamation after the profitable mineral resources have been depleted

    A number of studies on the reasons for mine abandonment have been published by organizations including the National Orphaned/Abandoned Mines Initiative (Canada), the U.S. Environmental Protection Agency, and the United Nations, and they have also developed measures to prevent the creation of more abandoned mines. [1] Most jurisdictions now require mining companies to provide a mine closure plan and financial assurance to cover the costs of mine closure before a new mining project is approved, and there are growing expectations around the world that the preventative measures leading to adequate mine closure are always put in place. [1, 2] However, illegal small-scale mining continues to contribute to environmental concerns in some parts of the world. [1]

    Environmental mining legacies

    In many countries, including Canada, abandoned mines can be a health and safety, financial, and environmental liability for communities, the mining industry, and governments. [4] These liabilities are often referred to as a “negative legacy,” because they are passed on to the current generation of stakeholders by the previous mine owners who may no longer exist. [6] Mining legacies can also be positive, such as the provision of clean drinking water from dewatering operations, training opportunities for workers, re-use of mining infrastructure, or investment in the local economy. [6]

    The most serious environmental concerns at orphaned and abandoned mines are acid rock drainage from underground workings, open pit mine faces, waste rock piles, and tailings storage areas that were left exposed to the elements or inadequately reclaimed, resulting in the contamination of water with dissolved metals and acidity. [6, 7] Public health and safety hazards at abandoned mine sites can include accessible mine openings (i.e., unblocked pits, shafts, tunnels), hazardous mine wastes, abandoned infrastructure, and ground surface instability. [7]

    Abandoned mines vary in size and danger level, from shafts and test pits to large extensive sites. Each requires its own degree of rehabilitation. [7] The U.S. Bureau of Land Management has reported that of an estimated 100,000-500,000 small and midsize abandoned hard rock mine sites in the U.S., only 5-10% are considered to be a health and safety hazard, and 1-2% present an environmental risk, primarily in the form of water pollution. [1]

    Abandoned mines in Canada

    Canada has an estimated 10,000 abandoned mines. [5] The responsibility for orphaned and abandoned mines in Canada falls to the respective provincial or territorial government, although the federal government maintains most of the responsibility for mine sites in the north. [1] In response to emerging regulations or through voluntary and proactive initiatives, there has been a concerted effort over the last ten years by the Canadian federal, provincial, and territorial governments to address the abandoned mines that they have “inherited”. [7] In all the jurisdictions in Canada, abandoned mine sites are being assessed and prioritized, and those that have been identified as posing the greatest hazards have been or are being cleaned up. A few examples include:

    • Giant gold mine, NWT: Giant Mine officially opened in 1948, and was owned by several companies over the years. In 1990 it was bought by Royal Oaks Resources Ltd. Due to low gold prices in 1997-1998, the mine went bankrupt in 1999. [8] The courts transferred Giant Mine to Indian and Northern Affairs Canada, now Aboriginal Affairs and Northern Development Canada (AANDC) in 1999. [8] Giant was operated by Miramar Giant Mine Ltd until 2005 on the condition that Miramar would not be liable for the existing state of the mine. [8] As no financial assurance was required when the mine opened, and the previous mine owners no longer exist, AANDC and the Government of the Northwest Territories are sharing the costs of the cleanup. A new closure plan is being developed since the original closure plan approved in the 1950s is no longer viable due to the melting of permafrost. [8]
    • Britannia copper mine, BC: Operations began at Britannia in 1904, and continued until the mine was closed in 1974 due to low copper prices and high operating costs and taxes. [9] The mine was owned by a number of companies over its lifetime, and was closed according to the environmental standards of the day by then-owner Anaconda Mining Company. [10] However, the reclamation undertaken was not adequate to prevent extensive acid rock drainage (ARD) from occurring and the BC Government led a remediation campaign in 1997 to address the problem. [10] Funds were received from Anaconda and other past mine owners for the cleanup, which was managed by the BC Government. [10] The province took control of the majority of the mine site in 2003, and has since been operating a water treatment plant to treat the ARD. [10]
    • Kam Kotia copper and zinc mine, ON: The Kam Kotia Mine was developed in 1943 as part of the federal government’s War Minerals Program. [11] The mine was worked intermittently by a number of owners until 1972. [11] In 1988, the property was forfeited to the Crown without having undergone adequate closure or reclamation. [11] The Ontario provincial government began the cleanup of the site in 1999, and the rehabilitation work was completed in 2008. [12]
    • Gunnar uranium mine and mill site, SK: Mining operations began at Gunnar Mine in 1955, and the site was closed in 1963 with little decommissioning. [13] It is undergoing assessment and reclamation as part of Project CLEANS (Cleanup of Abandoned Northern Sites) jointly funded by the governments of Saskatchewan and Canada. [13]

    The future of abandoned mines in Canada

    The potential for creating new orphaned and abandoned mines in Canada is considered to be low due to the introduction of more stringent regulations, advances in reclamation techniques and technologies, and developments in best practices within the mining industry. [7] Mining related legislation is in place for mine closure and reclamation in all the provinces and territories in Canada, which require closure plans to be put on file before mine operations begin, and financial assurance to be provided for the proposed reclamation activities. [5] In the case where a mining company declares bankruptcy before the mine is closed, the responsible regulatory agency would use the security deposit to cover the eventual costs of repair, maintenance, cleanup, and closure of the mine’s site. [14]

    Partnerships between regulators and industry

    In 2002, the National Orphaned/Abandoned Mines Initiative (NOAMI) was established to encourage discussion between stakeholders, compile a database of abandoned mines, and identify challenges and solutions to addressing the abandoned mine problem. [7] The NOAMI Advisory Committee consists of representatives of the federal/provincial/territorial governments, the Canadian mining industry, environmental non-governmental organizations, and Aboriginal peoples and their communities. [15] The program has already produced a number of publications that have been internationally recognized, including studies on abandoned mine reclamation funding models, community involvement, legislation, and policies. [1].

    NOAMI activities are jointly funded by the federal, provincial, and territorial governments, the Mining Association of Canada, and the Prospectors and Developers Association of Canada, and administered by a secretariat at Natural Resources Canada. [7] In addition to their contribution to NOAMI, mining associations in Canada have voluntarily contributed funds and expertise to abandoned mine reclamation projects for a variety of reasons, such as improving the industry’s reputation in the area of environmental stewardship. In order to encourage this practice, some provinces, including Ontario and Québec, have “Good Samaritan” policies that encourage mining companies to help clean up abandoned sites without incurring liability from past operations. [7]

    iThe gold deposits found at Pueblo Viejo are in the form of sulphide minerals with a cap of oxide minerals. The oxide mineral cap was exploited from 1975-1991. Mining of the sulphide minerals began in 1991, but the existing infrastructure was not capable of effectively processing the sulphide ore, and operations closed down in 1999.
    iiThe Las Lagunas Gold Tailings Project will be using Xstrata Albion oxidation process technology with a standard carbon-in-leach (CIL) cyanidation plant.
    iiiDore (or Doré bar) refers to semi-pure bars made up of gold and silver that are normally created at the mine site and transported to a refinery for further purification.

    Case Study: Pueblo Viejo, Cotuí, Sanchez Ramirez, Dominican Republic

    Pueblo Viejo is a gold and silver mine located on the Caribbean island of Hispaniola, 15 kilometers west of the provincial capital of Cotuí in the Dominican Republic. [16, 17] The history of the Pueblo Viejo mining region dates back to the 1500s, when gold mining by Spanish explorers was recorded from 1505 to 1525 A.D. [18] Subsequent open pit mining was carried out by the state-owned company Rosario Dominicana between 1975 and 1999, producing 5.5 million ounces of gold and 25.2 million ounces of silver. [16] Mining operations largely stopped in 1991 due to low gold and silver prices, a change in the type of ore being minedi, and a lack of appropriate ore-processing technology, although selective mining of higher-grade ore by the company continued until the mine was shut down in 1999. [19]

    The mine was inadequately closed and reclaimed, resulting in the extensive formation of acid rock drainage (ARD), leading to a legacy of contaminated infrastructure, soil, and water at the site and surrounding area. Untreated and uncontrolled ARD resulted in the transport of high metal concentrations and acidity into local waterways such as the Arroyo Margajita and the Maguaca rivers. [20] Other environmental, health, and safety hazards identified at the site included rusting machinery, oil and gasoline-contaminated soils, mercury- contaminated materials, asbestos, and local groundwater contamination. [21]

    In 2001, tenders were invited by the government of the Dominican Republic to continue mining at the abandoned site, which would involve the remediation of the site and the construction of new infrastructure. [19] A 33-year contract was won by Vancouver-based company Placer Dome, which was acquired by Barrick Gold Corporation of Toronto in 2006. [19] Placer Dome had declined the rights to reprocess the existing tailings from the Rosario Dominicana operations stored in the Las Lagunas tailings impoundment facility. [22] In 2004, Envirogold (Las Lugunas) Ltd, a subsidiary of Australian mining company PanTerra, won the international tender and signed a contract with the Dominican State giving it the right to reprocess the tailings under a profit-sharing agreement with the government. [22]

    Las Lagunas Gold Tailings Project: Extracting gold and silver from waste

    The Las Lagunas Gold Tailings Project was designed to extract previously unrecovered gold and silver from the historic tailings. [18] The extraction process previously used by Rosario Dominicana (from 1991 to 1999) had a low recovery efficiency (30-50%) that left behind tailings still containing a relatively high concentration of gold and silverii. [18]

    The Las Lagunas tailings project is expected to recover 435,360 ounces of gold and four million ounces of silver over a period of six and a half years; it poured its first gold/silver doreiii July 2012. [23] The Las Lagunas project will use a process to detoxify cyanide, and will treat surface water affected by the existing tailings dams. This will ensure that the quality of water released into the environment will meet the water quality standards of the Dominican Republic government and the World Bank. [18] The tailings from the Las Lagunas tailings project will be re-deposited in the existing tailings dam which, upon the mine’s closure, will be buffered against further ARD production with limestone. [18] PanTerra has provided an environmental compliance insurance bond of US$ 168,000 for mine closure activities as required by their December 2006 Environmental Licence. [18]

    Pueblo Viejo Mine: Remediation before mining

    The main mine site at Pueblo Viejo is now owned by the Pueblo Viejo Dominicana Corporation (PVDC), which was formed jointly in 2009 by Canadian mining companies Goldcorp (40%) and Barrick Gold Corporation (60%), the latter of which is also the mine operator. [16] Barrick carried out studies to assess project feasibility, environmental and social impacts, baseline environmental and social indicators, and associated infrastructure. [19] PVDC will invest an estimated US$ 3 billion prior to beginning production, and the mine will be the largest project in the history of the Dominican Republic. [16]

    Before mine construction could begin, the abandoned mine site needed to be remediated. PVDC had originally agreed to provide cleanup on the mine site, with the Dominican Republic government responsible for cleanup costs outside the mine site. [24] However, PVDC went beyond this agreement and donated half of the government’s total cleanup cost (estimated to be $75 million) and provided financing to the government for their remaining half. [24] In addition, it is also spending $14 million on remediation of the mine site prior to beginning production. [25]

    Remediation of the abandoned mine site included the demolition of the old buildings, removal or bioremediation of contaminated soil, revegetation of exposed areas, construction of ARD capture infrastructure and a water treatment plant, and tailings dam reinforcement. [24] Biodegradable mats made by local women out of coconut fiber were used in the revegetation of exposed soil on slopes to protect the seeds from rain, birds, and other environmental factors. [25] Another corporate social responsibility (CSR) initiative that has been undertaken by Barrick is the inception of the Piedra Blanca Municipal Development Plan to assist with the management of mining revenues within the surrounding communities. [26]

    Pueblo Viejo Mine: Planning for closure

    A reclamation and closure plan for the new mining operation has been prepared by PVDC with the objective of returning the site to a suitable state which would support pre-mining land use activities such as small-scale agriculture, hunting, and artisanal forestry. [20] In addition, the intent of PVDC is to leave the site at closure with better water quality in the Margajita drainage system downstream than existed when the project was started. [20] The closure plan includes the long-term underwater storage of waste rock and tailing in the El Llagal storage facility; the decommissioning and removal of the metal processing plant facilities; the filling of the open pits with groundwater once dewatering is stopped; the covering and revegetation of disturbed areas with native seedlings grown in onsite greenhouses; and the collection and treatment of surface water and seepage from the mine site and tailings facility until the water quality meets the Dominican Republic and World Bank standards and can be directly discharged. [20] Water monitoring will be undertaken during mine operations and following mine closure. [20] An environmental compliance bond of US$ 16.4 million held in an offshore account was required by the mine’s Environmental Licence, and the amount is to be increased over the life of the mine. [20]

    An estimated 7,900 people were employed at the site during the construction of the mining facilities. [25] Forty per cent of these workers were from neighboring communities and the majority was from the Dominican Republic. [25] The mine started operations in August 2012, and is expected to employ 156 to 471 people and produce 24,000 tonnes of ore a day at full capacity. [19]

    Show References


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    2Dutta, 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.
    3Canada, 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/sites/www.nrcan.gc.ca.minerals-metals/files/files/pdf/abor-auto/mining-guide-eng.pdf.
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