What You Need To Know About Kensington Mine’s Proposed Expansion

Written by Sarah Davidson

December 10, 2020

Photo by Kenneth Gill of Gillfoto

Kensington Mine has applied to the Forest Service for an expansion. Read on to learn about the mine’s plan, why we’re concerned, public meeting information, and how to submit substantive comments to the Forest Service.



The Forest Service is hosting a virtual public meeting on Thursday, Dec. 10, 2020, from 5:30-7:30 p.m. Alaska Time. This meeting is a great opportunity to hear from the Forest Service, ask questions, and share your concerns.


The deadline for submitting public comments has been extended to Monday, Jan. 4, 2021. Comments may be submitted to Matthew Reece:

  • What is the mine doing? Make sure the Forest Service provides a clear explanation for the expansion and press them on any points that are vague or don’t make sense.
  • How many additional years will the expansion allow the mine to operate? Make sure the Forest Service provides a clear and exact timeline.
  • Do you anticipate an additional expansion in the future? If so, why are you not analyzing for a longer life-of-mine now? The analysis of impacts should include all possible impacts including reasonably foreseeable future expansions..
  • This expansion requires increasing the height of the tailings dam by 36 feet, making it taller than the Federal Building — the tallest building in Juneau Will it last forever? If it fails, how much of the tailings will reach Berners Bay?
  • What additional measures will you require to prevent the current dam from leaking or failing altogether? The tailings dam uses similar technology that failed in the 2014 Mt. Polley mine disaster. Will these protections go on forever?
  • How are you incorporating considerations for climate change into your analysis of the proposed expansion plan? The current draft, supplemental environmental impact statement (DSEIS), conducted over 15 years ago, does not include any climate change considerations.
  • Which alternatives to raising the dam exist in the draft supplemental EIS? Storing tailings in water requires the dam to last forever in order to prevent devastation downstream.  It is considered a dangerous and outdated technology by mining experts. The Kensington Mine is located in an area prone to torrential downpours, earthquakes, and landslides, and it doesn’t make sense to increase the risk of failure by raising the existing dam.
  • How do you enjoy Berners Bay? This is important to include so the Forest Service can take your “use” into account during the environmental analysis.
  • The Forest Service must ensure that the proposed expansion does not impact other users of the Berners Bay Watershed.
  • Everyone should be concerned that using another natural waterbody for dumping tailings could become standard practice for other mining proposals such as Herbert Glacier or in the Chilkat Valley.
  • Any violations or reporting or water quality standards by the mine need to be addressed and measures to prevent them from happening again put in place before an expansion with the potential for even more violations is approved. The risk analysis in the SEIS must consider past performance.
  • The Forest Service must consider alternatives that do not rely on the integrity of dams and permanent water covers as recommended by the Mt Polley Expert Panel.
  • The Kensington underground gold mine is owned by Coeur Alaska, a subsidiary of Coeur Mining Inc. and has been operating since 2010.
  • The mine sits above the northwest side of Berners Bay at the foot of Lions Head Mountain, a sacred site for the Auk Kwaan Tlingit people.
  • Berners Bay is heavily used by many Southeast Alaskans for recreation, sport, and subsistence hunting and fishing. It provides spawning and rearing grounds for herring and hooligan, feeding opportunities for marine mammals and migratory birds, and intact habitat for mountain goats, brown bear, and moose. Berners Bay was designated an Aquatic Resource of National Importance by the EPA during the Clinton Administration and is considered one of Southeast Alaska and the nation’s most valuable public resources.
  • The Kensington Mine is unique in the United States. It is the only mine that was allowed to dump tailings into an existing natural lake by a Supreme Court decision. The lake, Lower Slate Lake, was re-designated as a “tailings treatment facility” at the time of the decision. All life that once existed in Lower Slate Lake has been extinguished.
  • Currently 4.5 million tons of tailings are held back by an 88-foot dam comprised of waste rock that is supposed to last forever.
  • The demand for gold that drives this mine is based on vanity and fear. Between 74-78% of all gold mined is used only for jewelry (vanity). Most of the rest is only for investment purposes to hedge against falling stock markets (fear). Only 4.5% of gold mined is necessary for technology and dental uses. Vanity and fear are poor excuses to threaten fragile ecosystems.
  • In 2019, Coeur Alaska submitted an amended Plan of Operations (POA1) to the Forest Service in order to double the amount of tailings stored there and allow another 10 years of operational capacity. The Forest Service has thus begun the National Environmental Policy Act (NEPA) process to amend the current Plan of Operations with the proposed expansion.
  • The current waste storage capacity for tailings and waste rock will be reached by the year 2023.
  • The purpose of the expansion is to extend the mining time period for approximately 10 more years by adding more storage capacity for waste.
  • The expansion would allow the disposal of an additional 4.0 million tons of chemically-treated tailings into Lower Slate Lake and 4.5 million additional tons of waste rock.
  • This is about same amount of tailings authorized in 2004, thereby doubling the amount of tailings dumped in Lower Slate Lake.
  • This proposed expansion will also require raising the tailings dam for a fourth time, bringing the final dam height to 124 feet — taller than Juneau’s tallest building, the 9-story, 110-foot Federal Building.
  • The increase of lake depth will require construction of a 40-foot tall dam to separate Upper Slate Lake from the contamination. The plan calls on allowing the tailings facility to flood Upper Slate Lake and some of its tributaries — all natural and pristine waterways.
  • Coeur Alaska also seeks to expand three waste rock disposal areas and construct a new waste rock pile above the Lynn Canal side of the project area.
  • Coeur is also seeking permission to increase the milling capacity by one-third from 2,000 tons per day (tpd) to 3,000 tpd. The associated effects of increasing mill capacity, such as increased fuel and chemical storage and transport, increased road traffic, and shorter life-of-mine will not be reviewed by the Forest Service.
Instability of Tailings Dams:
  • Kensington Mine employs a similar type of tailings technology that failed at the Mt. Polley Mine in 2014, the worst mine disaster in Canadian history.
  • After the Mt. Polley failure, the Canadian government convened an Expert Panel to avoid a similar failure in the future. The Expert Panel concluded that submerged tailings technology needs to be discontinued.
  • In describing the future mining industry, the Expert Panel defined Best Management Practices (BMPs) as “filtered, unsaturated, compacted tailings and reduction in the use of water covers in a closure setting.”
  • This type of tailings technology results in two-five major failures each year, worldwide. This is more than two orders of magnitude higher than the failure rate of conventional water storage dams.
  • This proposal to raise the dam 36 feet and expand Lower Slate Lake to hold another 4.0 million tons of toxic waste essentially doubles the ticking time bomb sitting above Berners Bay.
  • The Forest Service must consider safer alternatives than the out-of-date technology of permanent water covers behind earthen dams. This type of tailings treatment is failing worldwide at unprecedented rates.
Noncompliance with Environmental Regulations:
  • On Aug. 8, 2019, the U.S. Environmental Protection Agency (EPA) fined Coeur Alaska over $500,000 for more than 200 permit violations, unauthorized discharge of acid rock drainage, multiple sampling violations, failure to conduct required monitoring, assessments, inspections and trainings, failure to use proper sample handling and analysis procedures, and failure to report releases of nitrate compounds from 2013 to 2017 among other violations.
  • The EPA noted that mine water discharges that are not properly controlled and treated can harm water quality and aquatic life.
  • The most recent compliance data show that acute copper standards are still routinely exceeded in Johnson Creek. Other exceedances include: acute copper standards exceeded in Slate Creek in 2018, manganese that exceeded the human health consumption of water and aquatic life standard in November 2018 and continues to do so, exceedances in the acute water quality standards for copper in both January and November 2018 in Sherman Creek, and exceedances of nitrate, sulfate and total dissolved solids during 2018 in Ophir Creek with similar exceedances in previous years. Additional exceedances occurred in Lower Slate and Johnson Creeks.
  • A recent check with EPA Enforcement and Compliance shows that Coeur Alaska is still out of compliance by its continued failure to maintain proper records and submit required reports.
  • It is important for the Forest Service to make sure that each of these documented exceedances have been addressed before allowing the mine to expand its adverse impact.
Failure to Consider Cumulative Impacts:
  • The mine will likely last much longer than the 10-year expansion, but the company is trying to limit the analysis of environmental affects by only asking for authorization in 10 year increments.
  • Protecting ecosystems that have evolved over thousands of years cannot be effectively managed under short-sighted 10-year incremental plans.
  • The Forest Service must base all risk analysis on the ability to predict the effects of climate change which will impact all possible outcomes. If the Forest Service cannot accurately predict the impacts of climate change (and they cannot because uncertainty is high), then they must employ the precautionary principle and err to the side of protection.
  • The Forest Service must consider the cumulative impacts beyond 10 years, understanding that no mine walks away from a project while there is still profit to be made.

You May Also Like…