A hearing will be held in May on Hyperion Resources' request for a state air quality permit for its proposed $10 billion oil refinery in extreme southeast South Dakota.

The state Board of Minerals and Environment set the hearing to start May 19 in Pierre and resume in late June. Additional days will be set as necessary.

The board also plans to hold a more informal meeting in April in Elk Point to get public comments, but no date has been set.

Lawyers for Hyperion asked for a hearing to be set soon so the project is not delayed. Lawyers for opponents wanted the hearing delayed until August to provide more time to study technical issues.

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