4.1. Driving forces for remedial work
The fundamental reason to remediate tailings piles is to reduce the level of hazards and thus lessen the risk of significant impacts upon human health and the environment, or to reduce ongoing levels of impact where effects are already apparent. Whilst the objective may be altruistic, that is the work is undertaken because of a concern for human and environmental well-being, the objective typically is also based upon concerns about the potential cost of not undertaking remedial works. These costs may be in the form of:
Compensation payments, where a case is made that inadequate or improper measures were taken to safeguard people or the environment;
Lost productivity from contaminated and quarantined land or fisheries;
Development costs for constructing water wells or sophisticated water treatment plant to replace water previously supplied from now contaminated surface and ground water resources;
The larger financial consequences from greater areas of contaminated land and water resources and continued contamination or air sheds should the remedial work not be undertaken.
Regulatory and legal frameworks pose significant potential (financial) risk to organizations holding liabilities in the form of current or past mine, mill and waste storage facilities.
Increased knowledge of the harm caused by and the potential risks associated with such facilities, more open arrangements to access information and to challenge responsible agencies, greater accountability required of government and private enterprises, and increased
public concern, combine to provide powerful incentives for reducing current and potential future liabilities through design and execution of remediation works.
4.2. Remedial work undertaken
The incentive for remedial work to be undertaken by the private sector is to comply with regulatory requirements. Examples of remediation of historic sites by the private sector are limited. Many of the mines concerned, which began operations in the 1940-1950s, were operated by government agencies or were subject to tight government control through to their closure. A few continued operating through to the 1970s and later, when regulations requiring remediation of tailings piles were in place in some Western countries. Therefore upon closure the private operator was compelled to conduct remedial works consistent with the regulations of the day. The number of private sector entities, where liabilities to remediate historic uranium mill sites could be identified, was however further reduced owing to many going out of business during the years of low uranium prices in the 1980s. Examples of remediation of historic sites by the private sector include the Beaverlodge area in Saskatchewan, and Mary Kathleen in Australia.
The Eldorado Beaverlodge operation was shut down in 1982 after 29 years. Decommissioning objectives were set by a panel of regulators in radiation protection, safety and environment.
Physical decommissioning at Beaverlodge, which included a number of satellite mines, was done in three years. Monitoring continues to this day and is undertaken by government agencies. When stable conditions are evident, the company will apply to relinquish the leases and turn the property over to the government [63].
At the Mary Kathleen mine in Queensland Australia, mining and milling took place in two periods between 1954 and 1982. By the time operations ceased, regulations requiring remediation of the tailings pile had come into force, and the operator was required to design and complete remedial works consistent with these requirements [68].
Several governments around the world in the last twenty years have implemented major remedial works. The timing and type of programme has been influenced by several different factors. These include access to information on health and environmental effects, changes in government agencies’ attitudes towards making information available to the public, access to sufficient funds, and the type and extent of operations, and their impacts on the environment.
Funding is not necessecarily an impediment in Western countries, provided that the problems translate into political debate and pressure. However, some other countries have been unable to implement remediation owing to lack of funding or political willingness. The breakdown of the Soviet Union made public discussion on impacts from uranium mining and milling possible for the first time in many countries. German unification led to sufficient funding for dealing with the impacts from uranium mining and milling in the former GDR. Plans for extension of the European Union to include Central and Eastern European (CEE) countries led to development of a funding scheme for remediation planning and execution in those countries under the PHARE programme [69]. Similar assisstance is being given be the EU to former Soviet Republics under the TACIS (Technical Assisstance to the Commonwealth of Indipendent States) programme. Some examples of government remediation programmes are given in the following subsection.
4.3. Examples from the USA
A suggested link between leukaemia rates and uranium mill tailings in Grand Junction, Colorado was the driver for development of legislation for the Uranium Mill Tailings Remediation Programme (UMTRA) [18]. The UMTRA programme in the USA focussed specifically on uranium tailings piles accumulated at 22 sites mainly in the central western states [70]. In many places tailings had been placed in unbounded or poorly bounded piles on level to gently sloping ground. Several piles were within city limits and along or close to river banks. Dust dispersion of the tailings, and re-use by the community as construction sand and fill, gave rise to significant health risks. The programme resulted in tailings being moved from the remnant piles, and reclaimed from thousands of urban sites, for relocation in purpose-designed and built repositories. The repositories generally consisted of lined storage cells with rock-armoured embankments designed to last at least 1000 years. Capping to minimise the risk of exposure of the tailings and reduce radon flux was placed on top. The containment designs were based on extensive research funded for the purpose by the US Government.
4.4. Examples from France
Milling residues were stored at 22 locations across France, and their remediation is part of a programme to rehabilitate mines, mills and waste storages in accordance with regulations under the Mining Code, Registered Facilities for Environmental Protection, and general regulations dealing with water, air, water, noise and landscape protection [71]. Except for the Forez site (where residues are stored under water), the tailings are above ground level, covered with clean waste rock from the site to provide mechanical protection, resist erosion and intrusion, and to reduce radiological flux and exposure. Drainage works are included, to minimise the volume and concentration of contaminated surface water.
4.5. Examples from Germany
Remediation of the WISMUT sites in the states of Saxony and Thuringia entails a range of stabilization measures, such as mine flooding, reshaping and covering of waste rock dumps, pit backfilling and in situ consolidation of the tailings ponds [72]. Owing to the climate, intensive land use and regulatory conditions, the water pathway is most important in the evaluation of remediation options. The goal is not to stop all releases of contaminants, but to reduce loads to levels that fall within the natural assimilative capacity of the surrounding environment.
4.6. Examples form the Czech Republic
Uranium mining and milling are controlled by the state in the Czech Republic. Due to declining needs, increases in production cost, and low world market prices a step-wise reduction of uranium production was decided at the end of the 1980s. The state-owned enterprise DIAMO is now responsible for a large scale closure programme, including technical, social, and environmental aspects. The first decommissioning and remediation works of exhausted mines were undertaken in the 1950s, but these works are sometimes considered inadequate, resulting in ‘legacy sites’. As part of the policy of continuing improvement of the environment, the government is funding the remediation of such ‘legacy sites’ [206]. Between 1993 and 1997 an inventory of these ‘legacy sites’ was drawn up. A respective remediation project was initiated in 1998, and by its completion in 2007 is estimated to have cost 232.3 M CZK (8.3 M USD). Overall, the DIAMO remedial activities concern conventional as well as in situ leaching sites, tailings ponds, and long term water treatment facilities. Environmental activities will have to continue until about 2040 and are
estimated to cost above 60.0 bill. CZK (2.2 bill. USD). The predominant part (> 90%) of these activities is being funded through the state budget of the Czech Republic.
4.7. Examples from Australia
The Rum Jungle mining area was operated by a private company under contract to the government and remained unrehabilitated after milling ceased in 1972. A small clean up programme in 1977 dealt mainly with aesthetic matters, but failed to prevent occasional breaches of the dam and continued releases of tailings and liquor to the Finniss River. The government funded a remediation programme aimed at reducing hazards in 1985–86, in which tailings and contaminated soil were placed in one of the open pits without any preparation. The tailings were covered with a geomembrane and a 1 m rock blanket, then alternating layers of contaminated subsoil and copper heap leach material. The area was then covered with topsoil and revegetated, and drainage diversions installed [22]. Hazard reduction works were also undertaken in the South Alligator region, where tailings were removed for reprocessing for gold, and the tailings pad ripped and revegetated.
Concerns over the continued hazards posed in these areas — mainly from open pits and waste rock piles, and requests from indigenous land owners for improved access and use — has lead to funds being provided for studies into performance of the existing remedial works and options for improvement. The tailings areas may be further remediated as part of this programme.
4.8. Evaluation of the remedial works at historic tailings piles
Many remediation programmes of historical tailings piles are not yet complete, or have not been completed long enough to enable meaningful assessments of their effectiveness to be made. A few qualitative assessments are available for some sites, and high level assessments of cost and effectiveness (in terms of lives saved) have been made.
At Rum Jungle in Australia, the post 1982–86 remediation programme monitoring regime indicates that aquatic life has returned to the Finniss River in the 15 km stretch downstream of the tailings pile, which had been killed as a result of copper and uranium contamination.
Results from the groundwater monitoring programme suggest that it will take another 15 years before contaminant concentrations leaving the waste heaps drop significantly [7].
However, the level of environmental protection afforded generally by the 1980s remediation works is considered inadequate by today’s standards, and funding has recently been provided by government for planning further remediation work. One aspect requiring attention will be landform design and capping design to reduce the impacts of natural erosive and vegetation processes. The present design requires annual removal of vegetation to avoid capping degradation through root penetration. Clearly this high-maintenance approach is not consistent with objectives for long term stability and reliable stewardship.
Monitoring at Port Pirie in South Australia, where tailings were covered by a 1.5 m layer of zinc slag, indicates that the level of dust generation has been reduced very significantly, and that radon emanation has dropped to below limits recommended by the USEPA for rehabilitated uranium tailings piles [7].
Design of containments built to accommodate tailings relocated by the UMTRA Programme in USA was initially based on steady state equilibrium conditions with covers constructed to limit infiltration into the pile to no greater quantity than seepage rates out of it. However, revised water quality standards required more emphasis on limiting infiltration in order to
avoid or minimise groundwater contamination. Other considerations requiring revision of early design concepts and standards were redesign of covers that beneficially exploit ecological changes on and in the cover over time, instead of concentrating solely on physical design parameters that are liable to degrade over time as a consequence of natural erosional, climatic and vegetative processes (see Annex XI).
Attempts have been made to evaluate the effectiveness of remedial work done to date in terms of expected environmental impacts and conditions arising from closed out uranium mine and mill facilities by relative cost and calculated lives saved. An attempt in 1997 to collate such information for the medium to long term was of very limited success [31]: only eight countries responded to this survey question. The information provided was quite different from country to country, and no comparisons or overall conclusions were possible.
Relative costs of remediation of mines, mills and ancillary facilities including tailings piles are reported for individual countries or remedial programmes in various articles, and information has been recently tabulated for a wide range of types of mine and mill and ancillary facilities around the world (Tables 2,3,4 in [7]). The tabulated information does not discriminate costs of tailings remediation from other operational components, but it does indicate which remedial programmes included tailings piles as part of the works conducted.
These comprise sites in eight countries (Australia, Canada, Czech Republic, France, Germany, Spain, Sweden, and the USA). The discussion points out that a comparison based on aggregated cost figures would not be objective, because the scope and extent of works will vary considerably for several reasons, even for similar sites and projects. Observations made on the data compilation for mines and mills are equally valid for tailings piles. The costs vary greatly as a factor of the amount of planning and preparation done for remediation and closure during the operational phase, local climate, condition of the tailings pile, degree and area of contamination, population density in the area, land use, labour costs, standards and objectives for remediation, etc. The single undisputable conclusion is that the costs of remediation are very significant, and place a significant budgetary burden on governments.
For this reason an assessment of the effectiveness of remediation in terms of benefits to society is warranted. A good example is the assessment of lives saved as a result of reduced public doses related to removal of tailings in the UMTRA programme [51] [73]. Whilst the basis for calculation may be subject to discussion, this sort of analysis presents information of a type readily understood by government officials and decision makers.
5. PRESENT DAY PRACTICES