Problems with Closure of the Buckhorn Mine

The plans for mine closure have been written by the mining company in such a way that there is little to no accountability. Many years in the future, regulators and mining company personnel—who are not currently involved with the Buckhorn Mine closure process—will have to manage the mine and will base their actions on the directions provided in the closure documents (see Plans ). Ecology should ensure that the plans are clear, current, and contain the best information and guidance possible.
There is no plan to determine the pathways of mine contaminants that are currently escaping the capture and treatment system, so that pollution can be reduced and/or eliminated. The closure documents talk about working with Ecology but fail to provide specific actions that would mitigate the contamination escaping capture or any mechanism to determine if mitigation is effective.

The main activity of closure is recirculating water in the underground mine. This involves pumping polluted mine water from the mine through the treatment facility and discharging it back into the mountain. Over time, this would likely improve water quality; however, this activity would draw down the water table each year to accommodate the spring freshet. This runs contrary to the strategy that was analyzed and reviewed when the mine was originally planned. The Environmental Impact Statement states that the Gold Bowl Zone is expected to flood within a few years after cessation of mining, thus limiting exposure of the reactive rock that is already found in higher proportion there.

A portion of the waste rock from blasting the Buckhorn Mine was identified as Potentially Acid Generating (PAG), or capable of forming acid that can then leach metals and lead to degradation of aquatic resources. As a way of preventing the PAG rock from forming acid, it was placed in the Gold Bowl section of the underground mine, which will be allowed to flood, minimizing oxidation and preventing the sulfide rock from becoming acidic. Unfortunately, Ecology has approved a Closure Plan that includes lowering the water level in the mine each spring to accommodate spring runoff. The drawdown will expose PAG rock and release additional pollutants into the groundwater. Exposing PAG rock increases the risk of triggering acid mine drainage, which would further degrade water quality on Buckhorn Mountain.

The Closure Plan approval letter includes the prediction that five freshets will be adequate to return the site to natural hydrologic function. It states that Ecology expects the water treatment and recirculation facilities to remain functional during that time. Voicing agency expectations does not provide the public with protection. An expectation is not a requirement. Ecology should require a plan that the mining company will follow if water quality degrades, and should provide clear criteria for when the treatment facilities may be removed. The current approval letter implies that facilities could be removed after five freshets. What if the water still needs treatment at that time? The Closure Plan mentions using adaptive management, but there are no specific benchmarks, timelines, or actions. Adaptive management is a structured decision making process that takes into account the uncertainty inherent in natural resource management. There should be a Closure Adaptive Management Plan that outlines the steps that will be triggered by various potential outcomes. In addition to providing requirements, Ecology must define what natural hydrologic function means.

The Closure Plan uses water quality and groundwater levels to define the post-closure period; as a result, the actual timeframe for this period is fluid. Since groundwater in the region has significant seasonal variation, groundwater level is not an appropriate criteria. Water quality should be used — but needs adaptive management contingencies if water quality degrades.

Long-term water quality may be affected by seepage of poor-quality water from the Damaged Rock Zone located above the water table. This probability is not considered in the Closure Plan and is a significant, unacceptable omission.

The mine’s discharge permit requires various mine-related plans (adaptive management and hydrologic monitoring) be updated to reflect current conditions. Ecology must hold the mining company accountable for these updated plans.

Monitoring should continue until permit water quality is maintained continuously for 10 years.

Water Quality Contamination

Sulfates at the Buckhorn mine
Sulfates at the Buckhorn mine (NLF-3 wells)

The red dashed line in the above graph shows the allowable (2014 permit) level of sulfate. The other dashed lines show the general trend of sulfate levels in various monitoring locations.

These monitoring wells are located in a fault downgradient from the mine, just outside the capture zone, which is supposed to capture all mine contaminants. Sulfate concentrations in all these monitoring wells (MW) are still increasing. Many values in MW-14 and MW-2R even exceeded the State groundwater standard (250 mg/L — a much higher level than the 69.5 mg/L allowed by the permit). Although MW-14, which is closest to Gold Bowl Creek, had the highest peak concentrations, the recent overall trend in that well could be decreasing slightly.

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How Gold Mining Can Affect Water Quality

There are several ways in which gold mining can affect water quality. Some of the following information is taken from the Safe Drinking Water Foundation online article, “Mining and Water Pollution.” Local photos are displayed, pertaining to Buckhorn Mountain and the associated facilities.


A stream feeding the Nine Acre Wetland, located near the Buckhorn mining operation

Water is essential to life on our planet. A prerequisite of sustainable development must be to ensure uncontaminated streams, rivers, lakes and oceans.

Mining affects fresh water through heavy use of water in processing ore, and through water pollution from discharged mine effluent and seepage from tailings and waste rock impoundments. Increasingly, human activities such as mining threaten the water sources on which we all depend. Water has been called “mining’s most common casualty” (James Lyon, interview, Mineral Policy Center, Washington DC). There is growing awareness of the environmental legacy of mining activities that have been undertaken with little concern for the environment. The price we have paid for our everyday use of minerals has sometimes been very high. Mining by its nature consumes, diverts and can seriously pollute water resources.

Negative Impacts

While there have been improvements to mining practices in recent years, significant environmental risks remain. Negative impacts can vary from the sedimentation caused by poorly built roads during exploration through to the sediment, and disturbance of water during mine construction. Water pollution from mine waste rock and tailings may need to be managed for decades, if not centuries, after closure. These impacts depend on a variety of factors, such as the sensitivity of local terrain, the composition of minerals being mined, the type of technology employed, the skill, knowledge and environmental commitment of the company, and finally, our ability to monitor and enforce compliance with environmental regulations. One of the problems is that mining has become more mechanized and therefore able to handle more rock and ore material than ever before. Therefore, mine waste has multiplied enormously. As mine technologies are developed to make it more profitable to mine low grade ore, even more waste will be generated in the future.

Waste from the Mining Process

Ore is mineralized rock containing a valued metal such as gold…The ore is crushed into finely ground tailings for processing with various chemicals and separating processes to extract the final product.

Kettle River facilities

Types of Water Pollution from Mining

  • Acid Mine Drainage
    • Many of the metals being mined in North America, including the gold mined from Buckhorn, tend to be found in rock that contains sulfide minerals. When ore and surrounding rock are excavated during mining, the sulfides become exposed to water and air, and may form sulfuric acid. This acid in turn leaches metals and other substances from the rocks that can harm ecosystems. The acid will leach from the rock as long as its source rock is exposed to air and water and until the sulphides are leached out – a process that can last hundreds, even thousands of years. Acid is carried off the minesite by rainwater or surface drainage and deposited into nearby streams, rivers, lakes and groundwater. Acid mine drainage is considered one of the most serious environmental threats posed by mining, and it can devastate aquatic resources for generations.
  • Heavy Metal Contamination & Leaching
    • Heavy metal pollution is caused when such metals as arsenic, cobalt, copper, cadmium, lead, silver and zinc contained in excavated rock or exposed in an underground mine come in contact with water. Metals are leached out and carried downstream as water washes over the rock surface. Although metals can become mobile in neutral pH conditions, leaching is particularly accelerated in the low pH conditions such as are created by Acid Mine Drainage.
  • Processing Chemicals Pollution
    • This kind of pollution occurs when chemical agents (such as cyanide or sulphuric acid used by mining companies to separate the target mineral from the ore) spill, leak, or leach from the mine site into nearby water bodies. These chemicals can be highly toxic to humans and wildlife.
  • Erosion and Sedimentation
    • Mineral development disturbs soil and rock in the course of constructing and maintaining roads, open pits, and waste impoundments. In the absence of adequate prevention and control strategies, erosion of the exposed earth may carry substantial amounts of sediment into streams, rivers and lakes. Excessive sediment can clog riverbeds and smother watershed vegetation, wildlife habitat and aquatic organisms.
Drillpad exploration

Water Quantity

Mining can deplete surface and groundwater supplies. Groundwater withdrawals may damage or destroy streamside habitat many miles from the actual mine site. [end quote from the Mining and Water Pollution article]

Surface Remediation Well Underway, Fall 2018

Kinross began removing construction fill from the surface of the mine site and putting it underground even before they finished mining, but that has not reduced the pollution problem. Once mining was complete in 2017, Kinross rapidly began moving the rest of the construction fill into the underground mine shafts; even the fill that was under the treatment facility was moved. To do this, they dismantled the facility without authorization, leaving the mine site without a working treatment facility for a period of six months.

At this point, most of the buildings have been removed and the ground surface has been recontoured and seeded. On the surface, things are looking more natural. However, downgradient wells are still high in sulfates and other contaminants.

Waste Rock

Mitigation Obligations to be Met

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Reclamation Description

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Specific Problems with the Closure Plan

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2019 Permit Renewal

The Clean Water Act requires that the National Pollutant Discharge Elimination System (NPDES) permit be renewed every five years. The current permit was up for renewal in February 2019, but Ecology has administratively extended it. We can expect that Crown will try to pressure Ecology into making changes in the permit to make it less rigorous. Ecology has said that they do not expect to make substantial changes in the renewal. The 2014 permit appeal is under appeal to the Washington State Court of Appeals. Once the appeal is settled and a permit renewal is considered by Ecology, there will be a public comment period, and it will be important for concerned voices to be heard. OHA will let the public know when Ecology asks the public to comment so those who care about water quality on Buckhorn can speak up.

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Permit Needs Enforcement

Water quality at the Buckhorn Mine is regulated by the National Pollutant Discharge Elimination System (NPDES) permit, under the Clean Water Act. The continuous water quality permit violations at the Buckhorn Mine started shortly after mining operations began and have increased to the present day. The Washington State Department of Ecology (Ecology) has the responsibility to uphold and enforce the discharge permit. Over the past decade, OHA has regularly suggested corrective actions that would increase understanding of the contaminant flows at the mine site and lead to long-term solutions to the water quality problems.

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