A state board is scheduled to decide Thursday whether to approve an air quality permit for a $10 billion oil refinery that Hyperion Resources wants to build in southeastern South Dakota.

The Board of Minerals and Environment has held hearings over the past few months. Lawyers for Hyperion and opponents of the project will give closing arguments before the board votes on the air quality permit.

Hyperion argues the oil refinery will be a clean, modern plant that can help the nation reduce its dependence on foreign oil.

Opponents say the refinery would cause too much pollution and would not meet federal air quality standards.

The refinery near Elk Point would process 400,000 barrels of Canadian tar sand crude oil each day.