Tom MacKay Storage Facility A Historic Tailings Facility
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TMSF Haul Road
k m MacKay Cree
TMSF North Dam Haul Road and Spur Road
TMSF North Dam
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The TMSF has safely managed tailings for more than 20 years underwater (sub-aqueous) as is being proposed for the Eskay Creek Revitalization Project.
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From 2001 to 2008, approximately 0.6 million tonnes (Mt) of tailings were subaqueously (underwater) deposited into the Tom MacKay Storage Facility (TMSF or “the Facility”) from the previous Eskay Creek mine.
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Little Tom MacKay Lake
Tom Mackay Creek Watershed
TMSF Spillway Outflow Channel
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6277000 Harrymel Creek Watershed
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Access Road
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TMSF East Diversion Channel
TMSF Southwest Diversion System
Supernatant Pond
Legend Pump
Reclaim Barge
Reclaim Pipeline Water Pipeline
Coulter Creek Watershed
Tailings
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Tailings Pipeline Contact Water Management Non-contact Water Management
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Facility Road
The expanded TMSF will be expanded with the construction of two main dams and a saddle dam.
Topsoil / Overburden Stockpile Dam
TMSF South Dam
Supernatant Pond
TMSF South Diversion Channel Skeena Gold + Silver Date: 29-Aug-2025
Eskay Creek Project
Tom MacKay Storage Facility Year 13 GA
TMSF Dams: Constructed with Safety, Focused on Sustainability Figure: -
Author: Skeena GIS
Skeena Mining Division - NTS 104B09 British Columbia, Canada
Tailings Waste Rock Scale: 1:20,000 Coord. System: NAD 1983 UTM Zone 9N 0
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S:\Projects\Eskay Creek\GIS\Workspaces\2025\250829_EC_TMSF_GA\250829_EC_TMSF_GA.aprx modified by dluo on 2025-08-29
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The TMSF North Dam will be developed in six stages and will reach a final height of 97 metres. The TMSF South Dam will be developed in five stages and will reach a final height of 50 metres. The east saddle dam will be 10 m in height at the end of the Project. All are being constructed on intact bedrock. The TMSF dams will be constructed using durable non-potentially acid generating (NPAG) and non-metal leaching material. A geomembrane liner and geosynthetic clay liner will be placed on the upstream face of each dam to manage seepage and minimize the potential for water infiltration through the dams.
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engage.eskay@skeenagold.com
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The TMSF is designed to contain a 1-in-1,000 year storm, managing the Probable Maximum Flood, and the dams are designed to withstand a 1-in-10,000 year seismic event via a spillway channel.
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The TMSF embankments and design criteria meet the Health, Safety and Reclamation Code for Mines in British Columbia.
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Governance of the facility include oversight by a Tailings Storage Facility (TSF) qualified person, design by a qualified Engineer of Record (EOR), technical review by a 3rd party independent reviewer, an independent tailings review board, dam safety reviews every 5 years, and an annual facility performance review by the EOR. September 2025
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The TMSF will also function as a primary contact water management facility from across the Project mine site. The water will be pumped to the TMSF prior to treatment and discharge into the receiving environment.
TMSF Stage 6 Spillway
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The existing TMSF will be expanded to permanently store potentially acid generating (PAG) materials generated by the Project, which will include approximately 39 Mt of tailings and 160 Mt of PAG waste rock and overburden.
PAG Waste Rock
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Expansion and Project Use
TMSF South Dam Haul Road