Proposed Mine a Ticking Time Bomb
Mine on Wisconsin border would use approach that has resulted in 46 catastrophic failures in last 20 years.
Tailings are the waste material left over from the crushing, grinding and chemical processing of mineral ores. Shock waves from the collapse of the Brazilian tailings dam continue to affect global investors and industry associations. Yet Michigan regulators gave the design that Brazil banned preliminary approval. The proposed mine would be a mere 150 feet from the Menominee River, which borders Michigan and Wisconsin and flows into Lake Michigan. A failure of the proposed Back Forty mine tailings dam would threaten residents’ health and safety, drinking water supplies in the area and the waters of Lake Michigan.
To advance the goal of zero catastrophic incidents, the expert review panel has invited the public to offer their suggestions in an online consultation that will be open for six weeks from November 15 to December 31. If the draft proposals are adopted, it would require mining companies to identify and address the rights of local, indigenous and tribal peoples who may own, occupy or use land or natural resources at or near tailings facilities, or downstream areas that may be affected by a failure. This would include the land within the footprint of the proposed Michigan mine where the creation story of the Menominee Indian Tribe of Wisconsin took place about 10,000 years ago.
Tailings Dam Failures Are Increasing
Catastrophic mine failures are not isolated events. There have been 46 in the past 20 years. A recent study reveals that mining waste failures are increasing in frequency and severity because lower ore grades have necessitated larger, open pit mines for economies of scale. As mines grow bigger, they generate larger volumes of waste, stacked into higher tailings dams.
According to Dr. David Chambers, an internationally recognized expert on tailings dam failure, “These dam failures are not limited to old technology or to countries with scant regulation. Previous research indicates that most tailings dam failures occur at operating mines and 39 percent of such failures worldwide occur in the United States, significantly more than in any other country.”
Following the disaster, a group of 96 institutional investors, controlling more than $10 trillion in assets, wrote to over 600 publicly listed mining companies, demanding they reveal the safety records of their tailings waste facilities. The Church of England Pensions Board estimates there are 18,000 tailings storage facilities worldwide, 3,500 of which are active. However, less than half of the companies responded, leaving an incomplete picture of the true global situation.
Those companies that responded indicated that 10 percent of tailings dams have had some issues related to the stability of the dam. However, this estimate means very little if no one is actually assessing stability or even doing inspections. According to Lindsay Newland Bowker, Executive Director of the World Mine Tailings Failures organization, “our analysis suggests a high level of potential risk in the USA tailings portfolio. 42% of the 12.2 billion cubic meters of accumulated tailings in the United States are in 295 tailings facilities rated as ‘high potential hazard’ in the event of failure. Only 8% (93) of these have Government reported or ‘known to Government’ inspections since October 1, 2015. Governments across the country had no inspection information on 57% (168) ‘high hazard potential’ facilities containing 57% of accumulated tailings volume.”
Dam Safety Permit Suspended in Mines
In September 2019 the Minnesota Court of Appeals ordered a temporary stay of a dam safety permit until the Minnesota Department of Natural Resources (DNR) does a full-scale review of the connection between the Brumadinho dam collapse and PolyMet’s proposed dam for a metallic sulfide mine in northeast Minnesota. The court said that the DNR failed to adequately consider “the massive failure of a tailings basin dam at an iron ore mine in Brazil that shares design characteristics with the dam PolyMet plans to build to store mine waste.”
The design characteristic at issue is known as the “upstream dam” construction method. It is the lowest cost dam design but also the most prone to failure, according to experts. About 76 percent of the tailings dam failures worldwide are related to the upstream construction method. Paula Maccabee, an attorney with Water Legacy, an environmental group opposing PolyMet, raised the obvious question in a story by the Wall Street Journal: “Why is an upstream construction method good enough for Minnesota, when Brazil has found this design so unacceptable that old upstream dams must be decommissioned as well as new ones prohibited?”
Michigan Regulators Postpone Aquila Resources’ Dam Safety Permit
Michigan regulators at the Department of Environment, Great Lakes, and Energy (EGLE), have responded to widespread public concerns about this same tailings dam design next to the Menominee River. They have requested additional information on the tailings dam from Aquila Resources, owner of the Back Forty metallic sulfide mining project. EGLE specifically asked for a “risk assessment to the environment or public health and safety associated with potential embankment failure of the Contact Water Basin and Tailings Management Facility (TMF) and the response measures that shall be followed for such an event. This analysis should include an assessment of likelihood of the various failure modes as well as flooding and environmental impact associated with failure of these facilities.”
Climate Change and the Risk of Tailings Dam Failure
EGLE has informed the company that their review of the dam safety permit will be postponed until further hydrogeological (water balance) data has been collected at the mine site. According to the International Commission on Large Dams, the lack of control of the water balance within impoundments is one of the most common causes of tailings dam failure. “All impoundments and their retaining dams need to be able to accommodate extreme hydrologic events, up to the Probable Maximum Flood.”
However, according to Stephen Hoffman, an environmental scientist who reviewed Aquila’s mine permit application for the Menominee Nation, Aquila assumed a water balance based upon 18 year old weather data. “Given the fact that due to climate change, the severity of storms have become more severe and the amount of precipitation can exceed records, it is not sound to use old data to base fluid capacity designs for the contact Water Basin or for the Tailings Storage Facility.”
Extreme weather events could cause serious damage to a tailings dam. James Kuipers, a mining engineer consultant with the EPA on tailings dams, told Bloomberg that a heavy downpour can rapidly increase the weight of the material inside the dam and liquefy relatively dry mine waste that can then spill out, overwhelming and drowning people in its path
Upstream Tailings Dam Design is Vulnerable to Heavy Rainfall
In July 2019, a fierce storm near the proposed Back Forty mine site hit Marinette County, Wisconsin and Menominee County, Michigan. Strong winds of up to 80 miles per hour were reported and thousands of trees fell, often damaging buildings and taking power lines with them. “It really was an unprecedented weather event,” said Jenny Short, community relations leader for Wisconsin Public Service, told the Eagle Herald. “We haven’t seen anything with this magnitude.” Heavy rain has been implicated in 25 percent of global and 35 percent of European tailings dam failures.
The EPA emphasizes the extreme vulnerability of the upstream dam construction method to sudden failure in areas of heavy rainfall. “A tailings pond that is expected to receive high rates of water accumulation (due to climatic and topographic conditions) should be constructed using a method other than upstream construction” the agency has recommended.
Aquila’s Amended Contingency Plan for their tailings dam boldly asserts that “Impacts from high precipitation are reversible and off-site impacts are not expected to occur.” The plan goes on to claim that the project is located in “a remote, sparsely populated area; therefore, an unlikely release of contact water to the environment would have a minimal affect (sic) to local residents.” There is no evidence to support this claim.
According to the United Nations Environment Program, “Despite many good intentions and investments in improved practices, large storage facilities, built to contain tailings can leak or collapse. These incidents are even more probable due to climate change effects. When they occur, they can destroy entire communities and livelihoods and remain the biggest environmental disaster threat related to mining.”
Tailings Dam Safety Requires Strict Governance Standards
In the aftermath of the Brazilian tailings dam failure, Tom Butler, president of the International Council on Mining and Metals (ICCM), the industry trade group, recently told Reuters that “The engineers know what they’re doing with these things but the implementation and the management and the change in management, that all involves humans. Therefore it involves governance and that’s where there’s potential for things to go wrong if the governance is weak or the right hand is not talking to the left.”
While the immediate causes of tailings dam failures are physical, such as excessive rainfall or erosion of the dam structure, a recent study of four tailings dam failures in countries with a strong mining tradition (Los Frailes in Spain, Mt. Polley in Canada, Samarco and Brumadinho in Brazil) showed that production had been increased and/or cost cutting measures had been put in place before the accidents. The study suggests that the management compensation packages which reward cost cutting and increasing production so as to increase their annual bonuses are playing a role by encouraging managers to risk serious long-term accidents.
The Political Movement to Achieve Zero Catastrophic Failures
The ICCM is now looking at ways to require the mining industry to adopt so-called dry-stack tailings, where water is removed from the slurry before tailings are stored, thus increasing a dam’s stability. However, this is the most expensive technique, costing as much as 10 times the cheapest method.
The draft recommendations of the Global Tailings Review are an important first step in addressing how increasing volumes of mine waste can be safely stored. The success of this challenge to the mining industry will depend upon investor demands for greater regulatory oversight, corporate transparency and strict governance of tailings facilities. It will also require the free, prior and informed consent of local and indigenous peoples affected by mine waste facilities. Unless the mining industry begins to rank safety over costs, the list of catastrophic failures will continue to grow. “If mining waste cannot be disposed of responsibly, we need to evaluate whether that mine should continue to be in operation or should be built in the first place,” says Payal Sampat, mining program director at Earthworks, a mining industry watchdog in Washington, DC.
Post-script: On December 12, 2019, Aquila informed Michigan’s EGLE that it was withdrawing its dam safety permit application prior to a December 31, 2019 deadline for submission of a completed application. Aquila will gather additional information requested by EGLE and resubmit a dam safety permit application in 2020. This will restart the dam safety permit review process from the beginning, including new opportunities for public review and comment. Aquila will not be able to begin mine construction until EGLE has approved all permits, including the dam safety permit.
Al Gedicks is emeritus professor of environmental sociology at the University of Wisconsin-La Crosse and executive secretary of the Wisconsin Resources Protection Council.