Opponents of a proposed $10 billion oil refinery in southeastern South Dakota on Wednesday asked the state Supreme Court to strike down a state permit that would let a Texas company to begin construction.

Gabrielle Sigel, an attorney for three groups fighting the Hyperion Energy Center, said the Board of Minerals and Environment erred when it approved an air quality permit last year because its study did not include a full-blown environmental impact statement.

Sigel said the refinery would be the largest industrial project in state history and that the preparation of an impact statement should involve other agencies and evaluate a project's broader effect. State officials abused their discretion by bypassing that process, she said.

Attorneys for Hyperion and the board countered that an environmental impact statement is not required by state law that and board members took into account all relevant environmental issues when issuing the air quality permit.

The state Department of Environment and Natural Resources can require an impact statement but decided it wasn't necessary. "The board agreed," said Rick Addison, a Dallas-based attorney representing Hyperion.