Air emissions project at Big Stone coal plant is about 86% complete

Otter Tail Power told the Minnesota Public Utilities Commission in a Jan. 14 quarterly update that the Big Stone Plant Air Quality Control System (AQCS) project, approved by the commission in January 2012, is getting close to completion.

Actual construction on the project is now approximately 86% completed. Considerable progress was made this last quarter; however the early arrival of winter in early November has been challenging for the outside construction work, the report noted. Examples of accomplishments include:

  • Structural steel to support the ductwork into the scrubber is now all in place. Th eductwork is being fabricated and placed and should be completed in January.
  • Inlet ductwork for the induced draft (ID) fans is all in place and outlet ductwork for B fan is complete until the tie-in outage work. Insulation on the ductwork and fans continues.
  • Baghouse is complete structurally. Piping insulation, siding, electrical and instrumentation is all being worked on. Commissioning has started checking out systems in the lower baghouse area. A few systems, such as building heating, are being put into service.
  • Selective Catalytic Reduction (SCR) installation is complete. Weld out is almost done. Siding, roofing, piping and electrical is all well underway structurally. The catalyst will begin arriving in early January for placement inside the reactor boxes.
  • Ammonia system unloading facilities are substantially complete, while piping to the control skids and then to the distribution grid are being worked on.
  • Preparation for the tie-in outage has begun. Numerous planning sessions have taken place and wiring and site preparation has begun for the boiler contractor that will mobilize to the site in January.
  • The fourth quarter of 2014 began with approximately 425 construction workers onsite. In late November, the parties passed the peak staffing and the number has declined to approximately 370 at the end of the fourth quarter. The number will slowly drop for the next month and then start to pick up again as the tie-in outage nears.

The update noted: “As described in previous quarterly reports, the project budget was reviewed in early 2013 and then again in early 2014. Following both reviews the projected project budget was reduced. The original project budget was $491M; it was reduced in 2013 to $405M and again reduced to $384M in 2014.”

The filing added: “The EPA has issued the Mercury and Air Toxic Standards (‘MATS’) rule, also known as the utility Maximum Achievable Control Technology (‘MACT’) rules, which require control of hazardous air pollutants. While the final rule has been issued, several petitions for review have been filed in United States Court of Appeals for the D.C. Circuit which could ultimately delay its effective date. The rule as issued requires the Big Stone Plant to reduce mercury emissions, which can be controlled by adding Activated Carbon Injection (‘ACI’) to the project. The estimated cost to add ACI as a standalone project is $5M. Because of the synergies of installing the system at the same time as the AQCS, the owners have decided to include the ACI system as part of the scope of the AQCS Project; we have only increased the projected cost of the AQCS Project by $2.1M to account for the ACI system. Although the standard MATS rule compliance date is April 16, 2015, on August 27, 2013 the South Dakota Department of Environment and Natural Resources granted a one year compliance extension for Big Stone Plant, such that the new compliance date is April 16, 2016.”

Big Stone is a 475-MW coal plant, located at Big Stone City, South Dakota, that is co-owned by Otter Tail Power, NorthWestern Energy and Montana-Dakota Utilities.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.