Historical Timeline


  • Burwash Yellowknife Mines Ltd. stakes 21 claims, including the future Giant Mine


  • Yellowknife Gold Mines Ltd. acquires Burwash's assets, which become part of a subsidiary – Giant Yellowknife Gold Mines Ltd. (GYGML)


  • June 3: first gold brick is poured
  • Tailings deposited into Back Bay


  • Airborne arsenic emissions estimated at 7,500 kg/day


  • GYGML initiates first studies into arsenic in surrounding environment, leading to revised operations


  • Cold Cottrell Electrostatic Precipitator (ESP) installed to remove arsenic trioxide from roaster gases
  • Arsenic emissions drop to 5,500 kg/day
  • Arsenic trioxide dust pumped into mined-out storage chambers 80-250 feet below surface in permafrost


  • Mill processes 400 to 700 tons of ore per day


  • Tailings dam construction marks beginning of engineered tailings disposal


  • Hot Cottrell ESP installed to capture gold-bearing arsenic dust


  • Tailings dam #2 is built
  • Arsenic removal from tailings effluent commences


  • Mill processing rate increases to 1,000 tons per day
  • Dracco baghouse facility constructed to collect arsenic trioxide dust


  • Airborne arsenic emissions drop to 200 – 300 kg/day


  • Arsenic trioxide storage moves to mined-out stopes located in permafrost zone


  • Improved tailings effluent treatment circuit commissioned


  • Commissioner's Lands Act proclaims surface land transfers to the Government of the Northwest Territories (GNWT), including Giant Mine site


  • Open pit mining begins


  • New tailings effluent treatment plant commences operation


  • Koppers Corp. of Georgia, U.S.A. purchases 6,700 tons of arsenic trioxide dust from Giant Mine until the price drops ending Koppers Corp's purchases
  • Regular inspection of storage chambers begins


  • Northwest Tailings Pond built to accommodate re-processed tailings


  • Royal Oak Resources Ltd. gains control of Giant Yellowknife Gold Mines Ltd.


  • Royal Oak Mines Inc. formed

Black & white photos courtesy of the Prince of Wales Northern Heritage Centre
Aerial overview picture courtesy of Paul Vescei


  • Explosion during labour strike results in deaths of nine miners


  • Aboriginal Affairs and Northern Development Canada (AANDC) along with Royal Oak Mines, Environment Canada, the GNWT and the City of Yellowknife, co-host a technical workshop to discuss management of arsenic trioxide at Giant Mine


  • Royal Oak Mines goes into receivership and Giant Mine is transferred to AANDC
  • AANDC starts work on action plan to manage arsenic trioxide dust stored underground
  • AANDC sells Giant Mine assets to Miramar Giant Mine Ltd., a division of Miramar Mining Corporation. AANDC takes on role of caretaker for pre-existing environmental liabilities on the property, including arsenic trioxide dust stored underground


  • SRK Consulting wins international competition to become lead technical advisor to AANDC on the management of arsenic trioxide dust


  • Technical advisor completes report “Study of Management Alternatives – Giant Mine Arsenic Trioxide Dust”
  • Public technical workshop held to review report
  • Remediation work completed on former Back Bay tailings beach
  • Miramar Giant Mine Ltd. submits an abandonment and restoration plan to the Mackenzie Valley Land and Water Board


  • AANDC and community stakeholders appoint Independent Peer Review Panel to assess options for long-term management of arsenic trioxide dust
  • Tier 2 human health and ecological risk assessments conducted to assess risks of current arsenic releases from the mine site, as well as potential future releases under various arsenic trioxide management alternatives
  • Field testing initiated of deep thermosyphon


  • Independent Peer Review Panel tables its review of technical advisor's final report
  • Technical advisor tables its final report “Arsenic Trioxide Management Alternatives – Giant Mine” at a public workshop in January
  • AANDC initiates extensive public communications campaign regarding management alternatives for Giant Mine
  • Giant Mine Community Alliance is established and holds its first meeting
  • The Giant Mine Remediation Project teams hosts a workshop in May
  • AANDC seeks approval to proceed with project description


  • AANDC announces decision to proceed with the Frozen Block Method as the preferred long-term management alternative for storage of arsenic trioxide dust


  • AANDC and the GNWT sign a Cooperation Agreement to work together on surface and subsurface remediation of Giant Mine
  • Miramar terminates its obligations under the Reclamation Security Agreement. Giant Mine becomes an abandoned mine site
  • Deton' Cho Nuna Joint Venture wins a contract to assume responsibility for interim care and maintenance of Giant Mine


  • A Remediation Plan for the immediate and long-term cleanup of the mine is developed by AANDC's technical advisors and reviewed by independent experts


  • AANDC submits the Remediation Plan along with a water license application to the Mackenzie Valley Land and Water Board
  • Deton'Cho Nuna Joint Venture is awarded a multi-year contract for care and maintenance at Giant Mine


  • Mackenzie Valley Land and Water Board releases preliminary screening: Reasons for Decisions concluded that the Remediation Plan is not likely to be a cause of adverse environmental impact or public concern
  • City of Yellowknife refers project to environmental assessment under s.126(2)(d) of Mackenzie Valley Resource Management Act, citing potential adverse environmental impact within municipal boundaries
  • Mackenzie Valley Environmental Impact Review Board (Review Board) initiates Environmental Assessment


  • Review Board releases Terms of Reference for Environmental Assessment
  • Construction begins on freeze optimization study


  • A series of public meetings are held to discuss the components of the Remediation Plan and their possible impacts on the environment
  • Project Team submits Developer’s Assessment Report to Review Board


  • First Round of Information Requests completed as part of Environmental Assessment
  • Freeze optimization study becomes operational
  • Mackenzie Valley Land and Water Board and GNWT Municipal and Community Affairs issue Joint Determination on regulation of land use within City of Yellowknife
  • Review Board holds technical sessions as part of Environmental Assessment
  • Project Team removes claddiing from C-shaft headframe due to safety concerns
  • Project Team takes down conveyor gallery due to safety concerns


  • Second round of Information Requests completed as part of Environmental Assessment
  • Public meetings in N’dilo, Dettah and Yellowknife to discuss urgent work required at the site
  • Project Team applies for and receives Land Use Permit, MV2012S0019 for geotechnical drilling
  • Review Board holds public hearings as part of Environmental Assessment
  • Review Board public registry closes
  • Project Team applies to Mackenzie Valley Land and Water Board for water licence (MV2012L8-0010) for urgent work on site (Site Stabilization Plan)


  • Project Team proposes to treat minewater to drinking standard
  • Mackenzie Valley Land and Water Board issues water licence for Site Stabilization Plan
  • Work begins on roaster decontamination and deconstruction