Public Comments of Al Gedicks, executive director, Wisconsin Resource Protection Council
DEQ Public Meeting in Stephenson, MI – January 9, 2019

TAILINGS DAM FAILURES

The proposed Back Forty tailings waste storage uses the “upstream” dam construction method. According to the 4 th World Landslide Forum in Slovenia in 2017, “Several examples of recent tailings dam failures involved dams constructed by the upstream method, where
the new embankments are founded on tailings, causing the dam to become progressively more dangerous as its height increases.” According to Aquila’s mine plan, waste rock will be used to build the embankment around the tailings dam.

Based upon the record of historical failures, two distinct failure mechanisms seem to be dominant. The first mechanism is related to the development of progressive failure in a weak soil layer in the dam foundation. Appendix A of the Golder Report states that the project site is typically covered with topsoil underlain by a variable thickness of silty sand overburden soil of very loose to loose relative density.

The second dominant failure mechanism is related to static or dynamic liquefaction of loose tailings material at a critical state. Static liquefaction is the sudden loss of strength when loose soil, typically granular material such as tailings sands, are loaded and cannot drain. Loading and deformation produce a tendency for the materials to contract and develop excessive pore pressure faster than drainage systems can relieve the pressure. Static or dynamic liquefaction of loose tailings may occur at a critical condition, where a rapid (undrained) small increase in the shear strain results in a large increase in pore pressure, reduced effective stresses and a dramatic reduction of shear strength. Typical for these types of failures is that they occur rapidly with no warning, so it is an extremely dangerous phenomenon. Although it is called static liquefaction, a triggering event usually causes the rapid strength loss.

There are many potential triggers, including:

• vibrations from construction equipment
• rise in water pressure in a slope
• stress increase due to a dam raise
• stress concentrations due to a higher dam
• loss of horizontal confining stress due to lateral strains in
  the foundation or dam

Source: Klohn Crippen Berger, “Static Liquefaction and Strength Loss in Tailings Dams,” posted on April 11, 2018. Available at https://www.klohn.com/blog/static-liquefaction-strength-loss-tailings-dams/

Static liquefaction and strength loss of tailings dams due to undrained failure has become a major concern in tailings management following the Mariana, Brazil and Mount Polley
tailings dam failures. At both Mount Polley, British Columbia and the Samarco mine in Brazil, the companies’ failure to act on warnings and prepare for possible disasters points to an alarming corporate practice of putting production and profit ahead of safety concerns.

Source: Judith Marshall, “Tailings dam spills at Mount Polley and Mariana: Chronicles of Disasters Foretold,” Canadian Centre for Policy Alternatives, August 2018. Available at https://www.policyalternatives.ca/tailings-disasters

CAUSES OF TAILINGS DAM BREAKAGE

The causes of tailings dam breakage are numerous. Apart from construction problems, poor maintenance or unusual weather are cited in a review of tailings dam failures in Geotechnical News Magazine in December 2010.

Aquila’s amended permit application minimizes the potential for external erosion of the tailings dam from the runoff of rainwater by using 18-year-old data on the severity of storms. It is not sound science to predict the safety of tailings dam storage on such old data.

According to the chief scientist at Climate Central, “Across the board, the United States has seen an increase in the heaviest rainfall event, and the Midwest specifically has seen an increase of almost 40 percent.” In August 2018, in Wisconsin’s Coulee Region–and Vernon County in particular–was hammered by heavy rains that cause two dam failures and damaged at least five more dams.

The public needs information on the potential volume of tailings release, the chemical composition of the tailings release, and the flow of tailings release to the Menominee River and wetlands under both dam-break and dam-failure scenarios.

AQUILA’S FINANCIAL ASSURANCE PLAN

Aquila has proposed a financial assurance plan for the Back Forty Project that is clearly inadequate to administer reclamation, remediation, and post-closure monitoring. The indirect cost estimates for the Back Forty financial assurance are less than that recommended by most sources.

One of the often-quoted public sources of guidance is the U.S. Forest Service’s “Training Guide for Reclamation Board Estimation and Administration.” The Forest Service recommends indirect costs at a minimum of 39%, ranging up to 128% of the direct cost of reclamation and closure. The amount of indirect cost proposed for the Back Forty financial assurance is 10%. This amount is clearly inadequate.

Source: Dave Chambers, “Review of Aquila’s Back Forty mine proposal,” Center for Science in Public Participation, February 24, 2016.

Aquila’s total financial assurance cost estimate for the end of construction operating period and the Life of Mine (LOM) operating period is $130.5 million. Compare this with the $544 million financial assurance to protect taxpayers from future cleanup costs at Polymet’s proposed mine and processing site near Babbitt and Hoyt Lakes, Minnesota–if the company went bankrupt or couldn’t do the work itself.

The amount of financial assurance is calculated to cover the cost of closing and reclaiming the mine, in addition to long-term water treatment needed to meet state and federal pollution standards.

Source: Dan Kraker, Minnesota Public Radio, “Polymet offers state $544M if it couldn’t pay for mine cleanup,” December 15, 2017.

The calculation of direct cost for reclamation involves a significant amount of detailed analysis. Aquila can offer its estimate of the financial assurance, but it is the responsibility of the DEQ to carefully check these calculations for their accuracy. There is significant financial incentive for Aquila to make optimistic assumptions about the cost of individual items of the financial assurance, in order to keep these costs to a minimum. However, it is always less expensive for the mine proponent to conduct reclamation activities than it is for the DEQ to contract and oversee these same activities.

If the DEQ does not have the expertise internally to check the assumptions and calculations made by Aquila in its financial assurance calculations, then it should retain the services of a qualified contractor to review Aquila’s financial surety bond.

Such reviews can and often do result in millions of dollars in increases in the financial assurance, which is of major significance to the public, since this is a potential financial liability. After Minnesota’s review, Polymet’s new financial assurance plan provides about $200 million more than the initial estimate included in its first mine permit application.

ENVIRONMENTAL IMPACTS

In the 900 pages of Aquila’s Mining Permit Amendment Application, there is a systematic dismissal of the potential for pipeline spills, tailings spills, tailings impoundment failures, and other releases of hazardous materials. The economic and environmental costs of these releases are not covered in either state or federal financial assurance programs—even though they commonly occur at metallic sulfide mines.

In a recent report,* Earthworks reviewed state and federal documents and a federal database for fourteen copper-sulfide mines, representing 89% of copper production in 2010—the most recent data available from the U.S. Geological Survey. These mines provided a representative view of the types of environmental impacts resulting from the development of copper-sulfide deposits, focusing on pipeline spills, tailings failures and water collection and treatment failures.

The report found that:

• ALL OF THE MINES (100%) experienced pipeline spills or other accidental releases.
• At 13 of the 14 mines (92%), water collection and treatment systems failed to control contaminated mine seepage, resulting in significant water quality impacts.
• Tailings spills have occurred at nine operations, and a partial failure of the tailings impoundment occurred at four out of fourteen mines (28%). The total costs for just 7 of these large failures was $3.8 BILLION DOLLARS, at an average cost of $543 million per failure.
• These losses, according to dam committee reports and government accounts, are almost ALL the result of failure to follow accepted practice.

According to the report, these failures are a direct result of the increasing prevalence of tailings storage facilities with greater than a 5-million cubic meter total capacity—necessitated by lower grades of ore and the higher volumes of ore production required to attain or expand a given tonnage of finished product.

In Aquila’s mine permit application, they proposed to store 5.1 million cubic meters of tailings, thereby increasing the risk of a tailings spill, according to the scientific literature.

In Aquila’s amended application, they propose to store 4.9 million cubic meters of tailings, despite the increased size of the tailings dam. How is it physically possible to have a larger tailings dam with a smaller volume of tailings?

Regardless, whether it is 5.1 million cubic meters or 4.9 million cubic meters, the large volume of tailings poses a serious risk for a tailings dam failure—which is ENTIRELY OMITTED in Aquila’s amended permit application.

* Source: Earthworks, “U.S. Copper Porphry Mines: The Track Record of Water Quality Impacts Resulting from Pipeline Spills, Tailings Failures and Water Collection and Treatment Failures,” July 2012. Available at: https://www.earthworksaction.org/files/publications/Porphry_Copper_Mines_Track_Record __8-2012.pdf

Aquila’s amended application states that the project will generate a total of 61.56 million tons of waste, including 48.81 million tons of waste rock, 8.95 million tons of tailings, and 3.80 million tons of overburden. All of this waste must be safely stored and contained in the tailings storage facility in perpetuity. According to the International Commission on Large Dams: “Tailings facilities are probably the largest man-made structures on earth.” They also contain some of the most toxic metals that threaten human health–such as arsenic, lead, and mercury.

Aquila’s public statements about the Back Forty Project have admitted that “Mining worldwide hasn’t always effectively managed environmental impacts” and this has been unfortunate. However, according to Aquila, “Today’s practices and regulations are meant to address these issues.”

However, if we look at the evidence on catastrophic mine waste, a new study reveals that catastrophic mine waste failures are increasing in frequency, severity, and costs—all around the world. The study by Bowker and Chambers* found that nearly half of all recorded “serious failures” happened in modern times, between 1990 and 2010. It calculated an average cost of $543 million for the most serious spills, with some climbing well above $1.3 billion. Since 1990 a dozen spills even resulted in the loss of lives–over 380.

These losses, according to dam committee reports and government accounts, are almost all the result of failure to follow accepted practice. These failures are a direct result of the increasing prevalence of tailings storage facilities with greater than a 5-million cubic meter total capacity, necessitated by lower grades of ore and the higher volumes of ore production required to attain a given tonnage of finished product.

Aquila’s original plan was to store 5.1 million cubic meters of tailings. The amended application proposes to store 4.9 million cubic meters of tailings.

The study projects 11 very serious failures between 2010-2020, at a total unfundable public cost of $6 billion. “There is no organized industry attempt to cover these losses in a risk-management loss-prevention program, and no political jurisdiction issuing permits is large enough to prefund a low-frequency, high-consequence loss of this scale. The inevitable result is either ‘government pays,’ or the damages go uncompensated.”

Aquila’s tailings storage facility is a disaster waiting to happen.

Source: Risk, Public Liability & Economics of Tailings Storage Facility Failures by Lindsay Newland Bowker & David M. Chambers, Washington, D.C., Earthworks, 2015.