Mystic 50 kV transmission line rebuild project




NorthWestern Energy will rebuild about 5.3 miles of one of the two parallel 50 kV transmission lines from the Mystic Lake Dam powerhouse to the Line Creek switchyard.

The transmission line is in the Custer Gallatin National Forest and generally runs along West Rosebud Road.

Existing wooden power poles will be replaced with steel poles and new power line will be installed.



Preparation work started in mid-April. New poles will be installed beginning in May and the project is expected to be complete in 2022 when reclamation work will take place.


Construction work

The view from above looking down at Mystic Powerhouse and the West Rosebud drainage.

Construction work

The work requires heavy equipment and helicopters. NorthWestern Energy is working with the Custer Gallatin National Forest and other stakeholders to ensure the safety of the public and crews during the project.

Campers, hikers, anglers, kayakers and other recreationalists and users of the area will experience traffic delays along West Rosebud Road. Signs will direct traffic throughout the project and flaggers will be present at times for longer delays.

Helicopters will be used to transport supplies and place the steel power poles in area.

The Mystic 50kV transmission line rebuild project will replace poles and line that are near the end of their useful life. The rebuild will enhance reliability for NorthWestern Energy’s customers served by the transmission line and harden the infrastructure system.

About Mystic Dam

Two hikers take in the view of Mystic Lake.

About Mystic Dam

The dam is at the foot of Mystic Lake, in the West Rosebud Creek drainage in the rugged Beartooth Mountains, about 75 miles southwest of Billings.

A spectacular waterfall at the foot of Mystic Lake, the largest in the Beartooths, provided the basis for a hydroelectric operation launched in 1924. The first electricity flowed out of the Mystic Dam powerhouse in March of 1925, carried by transmission line east to Red Lodge. In the early days, Mystic supplied electricity to Billings and as the transmission system was expanded, it helped power area mines. Today, it has a generating capacity of about 12 megawatts.

The foot trail from the powerhouse offers a popular path to Mystic Lake and the high country of the Absaroka-Beartooth Wilderness. It’s also the start of one of several routes to Granite Peak, at 12,799 feet, the highest point in Montana.