It would be the 200th coal plant to shut down in the US.

The landmark settlement requires Alliant to phase out coal use or install pollution controls at all eight of its coal-fired power plants to comply with the Clean Air Act.

In a settlement announced this week by the US Environmental Protection Agency and the US Department of Justice, Alliant subsidiary Interstate Power and Light has agreed to install pollution control technology and meet stringent emission rates to reduce harmful air pollution from the company’s seven coal-fired power plants in Iowa.

The settlement also requires Interstate Power and Light to spend a total of $US6 million ($A8.13 million) on environmental mitigation projects, and pay a civil penalty of $1.1 million to resolve alleged violations of the Clean Air Act.

The state of Iowa, Linn County, Iowa, and the Sierra Club joined the US government as co-plaintiffs in the case.

The EPA’s Office of Enforcement and Compliance Assurance assistant administrator Cynthia Giles said that to serve the communities in which they operate, power plants must protect clean air for those living nearby.

“This case delivers on the goals of EPA’s national enforcement initiative to reduce air pollution from the largest sources. By installing new equipment and funding mitigation projects, Interstate Power and Light can help conserve energy and cut pollution in communities across Iowa,” she added.

Assistant attorney general John Cruden for the Justice Department’s Environment and Natural Resources Division said the settlement was “a victory for air quality and public health in Iowa”.

“This agreement will cover all of Interstate’s coal-burning facilities in Iowa, requiring new pollution cutting technology and environmental projects to enhance air quality in surrounding communities, among other lasting benefits,” Cruden said.

US Attorney Kevin Techau for the Northern District of Iowa said the emissions reductions required by the settlement would lead to cleaner air and significant environmental and public health benefits for Iowans.

“This settlement will eliminate thousands of tons of harmful air pollution each year significantly improving air quality in Iowa and throughout the Midwest,” he said.

“The agreement demonstrates the Department of Justice’s strong efforts, along with EPA, to bring large sources of air pollution into compliance with the Clean Air Act.”

Under the settlement, Interstate Power and Light will install and continuously operate new and existing pollution control technology at its two largest plants in Lansing and Ottumwa, and will retire or convert to cleaner-burning natural gas its remaining five plants in Burlington, Cedar Rapids, Clinton, Dubuque, and Marshalltown.

The new, state-of-the-art pollution controls required by the settlement are expected to cost about $620 million. EPA estimates that the settlement will reduce sulphur dioxide emissions by 32,500tpa and nitrogen oxide emissions by 3800tpa once the settlement is fully implemented.

The Sierra Club said the plants were emitting more pollution than was allowed by the company’s air permits, contributing to an estimated 32 deaths and 541 asthma attacks annually, and costing local residents $US15.3 million ($20.77 million) in healthcare bills each year according to the Clean Air Task Force’s plant-level 2010 estimates.

“Every step we take to reduce coal use helps Americans breathe easier, and the 200th coal plant to announce its retirement since the launch of the Beyond Coal Campaign is a great milestone for public health and for the environment,” said Michael Bloomberg, the UN secretary-general's special envoy for cities and climate change, who is also founder of Bloomberg Philanthropies which has committed $80 million to support the Beyond Coal campaign.

“Everyone who has worked hard to help the campaign succeed deserves a lot of credit. Less reliance on coal is the reason why the US has reduced its carbon footprint more than any other country since 2006.”

The Sierra Club said it, and its allies, have successfully phased out coal plants at a rate that has averaged one coal plant every 10 days since 2010; over the same period, the US has installed unprecedented wind and solar power generation capacity, the group said.

“As we make this transition to clean energy, it is essential to protect the livelihoods of workers and communities traditionally reliant on coal,” the Sierra Club said.

“In 2009, the pollution from the 200 coal plants now slated for retirement caused 6000 heart attacks, 60,000 asthma attacks and 3600 deaths each year. The plants emitted more than 188 million metric tons of carbon pollution, equivalent to the annual emissions of more than 39 million passenger vehicles.

“The coal plants also emitted more than 7600 pounds of mercury each year. Mercury, a potent neurotoxin, contributes to thousands of birth defects and neurological disorders, putting communities surrounding coal plants at higher risk.”

The Sierra Club claimed that as coal plants were retiring at “record rates”, states were also making major investments in wind and solar power, fuelling the transition to a clean energy economy.

“Iowa, for example, already generates more than a quarter of the energy powering homes and businesses from wind farms, ranking first in the nation in power generated by wind,” the club said.

“Nearly 7000 Iowans are now employed in the fast-growing wind energy sector, more than any other state, and Iowa has the potential to generate 100 times its current wind energy output.

“Iowa provides a model for neighbouring states to phase out coal and capitalize on clean energy, which can also be a cost-efficient and commonsense way to meet the US Environmental Protection Agency’s forthcoming Clean Power Plan requirements.”