March 21, 2019

163-mile Big Stone South to Ellendale Transmission Line energized

On February 5 crews from co-owners Otter Tail Power Company and Montana-Dakota Utilities, Co., energized the 163-mile, 345-kV Big Stone South-Ellendale (BSSE) Transmission Line after eight years of planning and three years of construction. The $215 million line extends from the Big Stone South Substation near Big Stone City, South Dakota, to the Ellendale Substation near Ellendale, North Dakota.

"The team completed construction on time, under budget, and with a stellar safety record," said Project Manager Al Koeckeritz from Otter Tail Power Company. “I’d like to extend a special thanks to communities and residents throughout the project area. Your partnership has brought us to the finish line. Thank you.”

The project is one of 16 multi-value projects approved by the Midcontinent Independent System Operator, Inc. (MISO) and state regulatory agencies. “This portfolio was designed to improve reliability of the electric system and increase system capacity to address growth in demand, support public policy by enabling renewable energy to be integrated into the system, and boost regional economies by creating jobs, supporting local businesses, and contributing taxes,” said Otter Tail Power Company President Tim Rogelstad. “Congratulations to the project team and all those who touched this project.”

The project used local and regional contractors, including Webster-based Webster Scale, Inc.; Rapid City-based Brink Constructors, Inc.; and Sioux Falls-based Jacobsen Tree Experts.

High-voltage transmission lines, such as BSSE, allow access to diverse generation resources in a large geographic area. As the Regional Transmission Organization, MISO manages these high-voltage transmission lines and dispatches—or balances—generation resources to ensure all customers within MISO's 15-state footprint receive the reliable energy they need with the most cost-effective mix of resources available. MISO cost-allocation mechanisms allow recovering project costs from all customers who benefit from the line, so Otter Tail Power Company and Montana-Dakota customers will pay less than one percent of the project costs.

Otter Tail Power Company, a subsidiary of Otter Tail Corporation (NASDAQ Global Select Market: OTTR), is headquartered in Fergus Falls, Minnesota. With a balanced commitment to environmental, economic, and community stewardship, the company provides electricity and energy services to more than a quarter million people in Minnesota, North Dakota, and South Dakota. To learn more about Otter Tail Power Company, visit otpco.com. To learn more about Otter Tail Corporation, visit ottertail.com.

Montana-Dakota Utilities Co. distributes natural gas, generates, transmits and distributes electricity and provides related services in the northern Great Plains. The company serves approximately 143,000 electric customers and 274,000 natural gas customers in 262 communities in North Dakota, South Dakota, Montana and Wyoming. Montana-Dakota is a subsidiary of MDU Resources Group, Inc. (NYSE: MDU). For more information about Montana-Dakota visit www.montana-dakota.com. For more information about MDU Resources Group visit www.mdu.com.