BSSE Transmission Line


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About the project

Construction of the Big Stone South to Ellendale 345-kV Transmission Line began in 2016. It will extend 163 miles from Big Stone City, South Dakota to Ellendale, North Dakota. Otter Tail Power Company and Montana-Dakota Utilities Co. own this project that's estimated to cost $240 million to $300 million. We expect to energize the line in 2019.


Improved reliability of the regional electrical system.

Increased system capacity to address growth in regional demand.

Supports public policy by enabling renewable energy to be integrated into the system.

Boosts regional economies by creating construction jobs and supporting local businesses.

2008-2012: Planning

The Midcontinent Independent System Operator, Inc. (MISO), an independently governed organization tasked with ensuring transmission network reliability and efficiency in the Midwest, conducted planning studies to determine the need for upgrades and changes to the transmission grid. For more than 10 years, MISO studied and incorporated the BSSE project into planning models.

2012-2014: Environmental review and permitting

Following the identification of a preferred route, Montana-Dakota Utilites Co. and Otter Tail Power Company filed applications with the apporpriate regulatory commissions.

  • In August 2013 the project filed a Facility Permit Application with the South Dakota Public Utilities Commission.
  • In October 2013 the project filed a combined Corridor Certificate and Route Permit Application with the North Dakota Public Service Commission.
  • On July 10, 2014, the North Dakota Public Service Commission approved the project and a final route.
  • On August 22, 2014, the South Dakota Public Utilities Commission issued Final Decision and Order; Notice of Entry.
2012-2016: Engineering design and right of way

We began initial engineering and design early in project development. In spring 2016 we finalized engineering and design.

Land agents continue to coordinate with landowners along the final route.

2016-2019: Construction

In summer 2016 construction began. To prepare for construction, we finalized easement agreements with landowners and completed the line's design.

Check out the interactive construction map.

2019: Line in-service

We expect the BSSE transmission line to be in service in 2019.

©2018 Otter Tail Power Company and Montana-Dakota Utilities Co.