Nucor accuses Big River of violating the federal Clean Air Act in the lawsuit. Nucor operates two steel mills outside of Blytheville and says pollutants from the Big River mill would negatively affect its workers productivity.
Nucor previously filed several objections to the mill during the approval process. An Arkansas environmental regulatory panel issued an air quality permit for the mill in April.
Big River Steel founder John Correnti calls the lawsuit "frivolous."