The EPA objection is over an air quality permit issued last November by the South Dakota Board of Minerals and Environment. At the time Big Stone II officials called the approval "a major step forward" for the plant. Now the EPA's Denver office is questioning whether the South Dakota air permit is adequate.
"We identified three key issues of the state's title five permit that we determined were not consistent with the requirements of the Clean Air Act," says the EPA's Carl Daly.
The agency wants South Dakota officials to revise the permit, he says.
Among the EPA objections to the permit are the sulfur dioxide and nitrogen oxide output limits and whether the permit sets up adequate monitoring of the plant's overall emissions, Daly says. Both gases contribute to acid rain.
South Dakota has 90 days to change the air permit to satisfy the EPA's objections. Daly expects South Dakota will be able to meet that deadline.
In a comment to the Associated Press, a member of the South Dakota Public Utilities Commission said the EPA's objections do not mean the end of the Big Stone II power plant project.
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Environmental groups are cheering the EPA action. They say the Big Stone coal plant would add to global warming problems. In a statement issued from its Washington, D.C. headquarters, the Sierra Club says the decision, "likely spells the end" of Big Stone II.
Other groups are not so sure. The EPA action is a big deal, but it doesn't necessarily mean the end of the power plant, according to Linda Taylor, with Fresh Energy in St. Paul.
"We'll have to wait and see what the revised permit says and whether that's adequate or not according to the EPA," says Taylor.
If the EPA accepts the new permit, Taylor says, the plant still faces another potential hurdle in Minnesota. The state Public Utilities Commission approved power lines in Minnesota associated with the power plant recently.
Big Stone II owners says they must have the power lines to build the plant. Taylor says the required changes in the South Dakota air permit will make the plant more expensive to build. Minnesota law requires that new power lines for a coal plant can only be approved under certain conditions, she says.
"The applicant, usually a utility, has to prove that that costs less than using renewable energy or energy efficiency or a combination of the two," says Taylor.
Her group will ask the PUC to reconsider its power line permit for Big Stone II. Taylor says the increased costs of the plant because of the air permit issue will be one of the issues the group raises. It's possible the plant's energy will cost more than renewables like wind power, she says.
The Big Stone Power II plant right now is projected to cost about $1.6 billion. The plant would generate enough electricity to supply about 400,000 homes.