Wild Border Watersheds

PROJECT: Kerr-Sulphurets-Mitchell

One of the world's largest undeveloped open pit mines, upstream from both Misty Fjords National Monument and the Nass Valley

Photo Credit: Mike Fay


Project Map CEA Project Status BCEA Project Status

Kerr-Sulphurets-Mitchell (KSM) is a proposed copper-gold-silver-molybdenum mine complex located 65 km northwest of Stewart, B.C., near the Canadian headwaters of Sulphurets Creek, a tributary of the Unuk River, upstream from Misty Fjords National Monument in Alaska. Seabridge Gold holds a 100% interest in the KSM property. The company proposes an underground and open pit mine operation, with at least three large open pits, processing up to 130,000 tons per day of ore, and generating over 2 billion tons of tailings waste. The proposed development would also include twin 23 km tunnels, drilled through the mountains to link the mine site to an ore concentrator plant and a 8x2 km tailings impoundment area between Treaty Creek and Teigen Creek, salmon bearing waters which drain into the Bell-Irving River, in the Nass River watershed, which is the third largest salmon producing system in B.C. 


Construction of the mine is estimated to cost $5.3 billion. Seabridge Gold’s corporate strategy is to obtain certificates and permits for the proposed mine, then sell the project to a bigger mining company. The Northwest Transmission Line would provide power to the mine. Ore concentrate would be transported by about 40 trucks per day to the deep-water seaport at Stewart, B.C., for shipment to an Asian smelter.


KSM poses the biggest single threat to rivers and salmon in the transboundary region. At the mine site, the mineralized rock has high sulfur content with a high probability for acid generation. Current plans for water treatment at the site are unprecedented in scale and rely on unproven technology. Potentially acid-generating waste rock would remain a long-term concern for the Unuk River, which provides spawning routes for Pacific salmon and steelhead trout, habitat for cutthroat and rainbow trout, char, and whitefish, and flows into Misty Fjords National Monument in Alaska. In Canada, more than 2 billion tons of tailings waste would be stored in two tailings impoundments between Teigen and Treaty Creeks – a part of the Nass watershed that provides spawning or other habitat for chinook, coho and sockeye salmon, steelhead, rainbow and bull trout, Dolly Varden char and mountain whitefish.


To access the mine site, new roads would be built through the Unuk and Sulphurets Creek valleys, along with the Bell-Irving drainage in the upper Nass watershed. The mine would pose a threat to water quality in two fish bearing river systems, fragment prime grizzly bear and mountain goat habitat, and greatly increase industrial truck and marine traffic in the region. Acid mine drainage and tailings contamination of fish habitat and water quality would be long-term concerns.

Related News

Kerr-Sulphurets-Mitchell Canadian Federal Environmental Assessment Process


CNSC or NEB is the Responsible Authority

CEA Agency is the Responsible Authority (45 days for screening)

No screening required. CEAA 2012 does not apply.

Regulatory EA process by CNSC or NEB
(public participation)

Public comments on whether an EA is required
(20 days)

Panel Review (2-yr limit). Public comments collected. "Interested parties" can participate in hearings

Standard Review
(1-year limit).
Public participation

Exempt from federal EA due to substitution or discretion

Exempt from CEAA 2012 due to equivalency


Kerr-Sulphurets-Mitchell British Columbia Environmental Assessment Process


Scope and
process for
determined by

(30-day public
comment period)


evaluated for
completeness by

Application review
(Public comment

Assessment report
prepared by EAO


Pre-application: no time limit

Completion evaluation: 30 days

Application review: 180 days

Decision: 45 days