Under the deal, BP agreed to a new system to reduce the flaring of refinery gas, new controls and practices to lower emissions throughout the refinery, and other environmental upgrades

The settlement imposes some of the lowest emission limits in refinery settlements to date, enhancing controls on wastewater containing benzene. It also requires the refinery to spend $9.5 million on projects to reduce greenhouse gas emissions, the EPA said.

BP also will install equipment to monitor emissions of benzene, sulfur dioxide and other pollutants and to post the data online.

Nicole Barker, executive director of the regional environmental group Save the Dunes, another partner to the agreement, said the pollution reductions will benefit residents of northwest Indiana and the Lake Michigan ecosystem.

"The refinery sits in the midst of one of the most unique ecosystems in the world and that needs to be protected too," Barker said.

The Indiana Department of Environmental Management issued a statement saying it was pleased with the outcome of the consent decree.