The upgrade, to take place in phases over 10 years, will improve the reliability of electric service to NorthWestern's customers in the area, including those served by electric cooperatives, and provide added capacity to meet electric load growth in the region.
The initial phase of the project will include substation upgrades and the construction of a new 100 kV transmission line from NorthWestern's existing Columbus-Rapelje substation to a new substation near Dean, in southern Stillwater County. The transmission line will be 45 to 55 miles in length, depending on the final route.
The first phase of the project, with an estimated cost of $34 to $39 million, is expected to begin early in 2013 with project siting and right-of-way acquisition. Construction is anticipated to begin in 2015.
Later phases of this project will include upgrades and rebuilding of existing transmission lines in the area.
NorthWestern Energy provides electricity and natural gas in the Upper Midwest and Northwest, serving about 673,200 customers in Montana, South Dakota and Nebraska.