Construction of the new air quality control system (AQCS) at the coal-fired Big Stone power plant is about 27% complete and is on time and on budget, said Otter Tail Power in a Jan. 13 quarterly project update filed with the Minnesota Public Utilities Commission.
In January 2012, the commission approved this project. Actual construction commenced in March 2013. Examples of accomplishments so far include:
- All major concrete foundation work completed.
- Installation of the waste ash and pebble lime silos are complete. Waste ash silo approximately 50% insulated.
- Siding for the waste ash and pebble lime silo nearly complete. Electrical and mechanical installation well underway.
- Scrubber vessels have been erected. Baghouse and scrubber structural steel nearly complete. First baghouse modules have been put into place.
- Selective Catalytic Reduction (SCR) structural steel towers have been installed and truss work has started. Ground assembly of SCR has started.
As mentioned in the second quarter 2013 report, the overall project budget was reduced from $489m to $405m.
The EPA has issued the Mercury and Air Toxic Standards (MATS) rule, which 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,” the update noted. “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.”
The 475-MW Big Stone plant is located at Big Stone City in South Dakota, fires sub-bituminous coal and is majority owned by Otter Tail, with minority stakes held by NorthWestern Energy and Montana-Dakota Utilities. The full AQCS project is targeted for operation by early 2017.