Several optional routes are under consideration for the MSTI Project, a 350-450 mile-long, 500 kilovolt (kV) electric transmission line, but a preferred route has not been selected. Construction will not begin until NorthWestern Energy receives all necessary federal, state and local permits.
The proposed line would connect to a new substation near Townsend, Montana and run to the existing Borah or Midpoint substations located in southern Idaho. The Townsend substation will be adjacent to, and interconnect with, the two existing 500 kV lines between Colstrip and Garrison, Montana. The length of the proposed project will depend on the final route.
The line will be made up of lattice steel towers and tubular steel self-supporting towers that would range in height from 110 to 130 feet depending on the terrain. The line will require a 220 foot-wide right of way and have average span between structures of approximately 1,500 feet.
The map below illustrates the alternative routes and their corresponding numbers currently being considered for the proposed MSTI electric transmission line.
