Opponents of the proposed $10 billion dollar Hyperion oil refinery are asking the South Dakota Supreme Court to strike down a state permit that would allow the project to be built in Union County.
Lawyers for three groups opposing the Hyperion Energy Center say the air quality permit approved last year by the Board of Minerals and Environment was flawed because an environmental study was not thorough enough.
Attorneys for the state board say there was no need to prepare a full-blown environmental impact statement, and board members took into account all relevant environmental issues.
Both sides made arguments in front of the high court Wednesday in Sioux Falls.
Hyperion's proposed refinery north of Elk Point would process 400,000 barrels of Canadian tar sands crude each day. The company declined to renew several thousand acres in land options in Union County this past week.
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