Steel Dynamics Inc., one of the largest U.S. steelmakers, struck a deal with environmentalists that will encourage regulators to approve a pending pollution permit for the company's new $1.9 billion mill near the Texas coast.

Steel Dynamics Inc. agreed to create a special marsh -- known as a constructed wetland -- to filter the mill's wastewater beyond what's required in the state's environmental permit, according to a joint statement by the company and The Aransas Project, a prominent green group that was pressing regulators to deny the permit.

The manufacturer's Sinton mill northwest of Corpus Christi is slated to open in mid-2021 and will add at least 200,000 tons of steel a quarter.