Otter Tail Power told the Minnesota Public Utilities Commission in a July 13 quarterly update that the Big Stone Air Quality Control System (AQCS) project, approved by the commission in 2012, is now over 99% complete.
The project entered a new phase with the shut down of the Big Stone Plant on the evening of Feb. 27 for the start of the outage to “tie-in” all of the AQCS equipment. The outage also signals the start of the large amount of boiler work that is part of the AQCS project. The outage was scheduled to be completed and the unit back on line by June 9. Because of problems found with the plant’s High Pressure (HP) turbine during routine inspection (nearly all ten rows of HP turbine blading and the control stage baldes were found in need of replacement because of cracking), the outage has been extended.
The current expected time for Big Stone to return to service is early August, an approximate nine-week extension from the original schedule.
The project budget was reviewed in early 2013 and then again in early 2014. Following both reviews the projected budget was reduced. The original project budget was $491 million. It was reduced in 2013 to $405 million and again reduced to $384 million in 2014. Because of the outage extension, the project budget will be negatively impacted but should finish on or under budget, the report said.
The 475-MW Big Stone plant is located in South Dakota, and is majority owned by Otter Tail Power, with minority shares held by NorthWestern Energy and Montana-Dakota Utilities. The AQCS project includes a scrubber and selective catalytic reduction.
Otter Tail Power, a subsidiary of Otter Tail Corp. (NASDAQ Global Select Market: OTTR), is headquartered in Fergus Falls, Minnesota. It provides electricity and energy services to more than a quarter million people in Minnesota, North Dakota, and South Dakota.