Following the recent decision, WPL will install a scrubber and baghouse system, which will reduce sulfur dioxide emissions from Unit 5 by about 90%.
WPL has plans to begin construction of the project in 2014 and put the plant in service in 2016.
The estimated project cost approved by the PSCW is about $410m, excluding AFUDC, while the project is expected to create more than 400 jobs during peak construction.
The three units at the 787MW Edgewater plant are located in Sheboygan, about 110 miles northeast of Madison.
Alliant said it plans to shut the 70MW Unit 3 at Edgewater by the end of 2015 or either convert to natural gas or shut the 308MW Unit 4 by the end of 2018.
Unit 3 entered service in 1951, Unit 4 in 1969 and Unit 5 in 1985.
WPL president John Larsen said Edgewater Unit 5 is a strong and efficient energy source for WPL customers.
"Installing these additional emission controls positions it to continue that service and deliver on our environmental commitment as we transition our generating fleet to meet our customers’ energy needs in a safe, reliable and cost effective manner," Larsen added.
