In the short term, a three-year, $627 million construction project at the Columbia Energy Center near Portage is expected to bring as many as 500 construction jobs to the area.
In the long term, the project is designed to lessen, by 90 percent, the amount of mercury that the power plant's two coal-fired units emit into the atmosphere, as well as reduce sulfur dioxide emissions.
The Public Service Commission of Wisconsin on Thursday approved the construction of an emissions control system at the Columbia plant, located in the town of Pacific outside of Portage. The plant - whose two units generate a total of 1,023 megawatts of electricity - recently was cited in a report from the environmental group Wisconsin Environment as spewing more mercury than any other coal-burning power plant in Wisconsin. The report said that, by the power plant's self-reported figures, it emitted 627 pounds of mercury in 2009, though Alliant Energy figures showed that, in 2010, the plant's mercury emissions had been lowered to 482 pounds.
The project was in the works long before the Wisconsin Environment report, titled "Dirty Energy's Assault on our Health: Mercury," was released earlier this month.
The three-member PSC's approval Thursday means that the project can begin soon, though a construction date has not been set, said Alliant Energy Spokesman Scott Reigstad.
However, because the state has set a January 2015 deadline for the plant to reduce its mercury emissions by 90 percent, the work will have to start soon because it will take about 36 months to complete, he said.
This would be, by far, the largest project of its kind in Wisconsin, he said, dwarfing a similar project now going on near Sheboygan, valued at about $150 million.
About 500 construction workers probably will come into the Portage area for the project, Reigstad said.
"It should be a great economic development boom for the Portage area," he said. "These are people who will shop in Portage stores and eat in Portage restaurants."
When the work starts, Reigstad said, there is likely to be an abundance of steel and other building materials coming in to the area near the plant, by truck and by rail.
The project, basically, consists of an activated carbon injection system, in which exhaust coming from the plant would be injected with carbon particles, then channeled into a baghouse, where it would be collected in a series of cloth bags. In the bags, the carbon would absorb the mercury before the exhaust is released into the atmosphere.
When the project is completed, there will be a new structure at the power plant, but outward changes in the plant's appearance are not likely to be noticeable to people casually driving by the plant on Highway 51, Reigstad said.
The sulfur dioxide control system was proposed to go in at the same time.
The Citizens Utility Board had asked that the PSC approve only the mercury control system, because new federal standards governing sulfur dioxide emissions are expected soon. But all three PSC members voted to approve both systems together, because separating them might add to the cost.
Reigstad said the three entities that own the Columbia plant are splitting the cost, with Alliant paying about $290 million, Wisconsin Public Service paying $197 million and Madison Gas and Electric paying $140 million.
The Wisconsin State Journal contributed to this story.