HAMMOND | Environmentalists are taking another swing at BP's new Whiting plant air permit, this time by suing the company in federal court.

The Natural Resources Defense Council filed a suit Wednesday against BP in federal court in Hammond for violations of the Clean Air Act, according to the group.

The group's lawsuit focuses primarily on three new flares -- the large torch structures used to relieve pressure in the refinery -- planned as part of the refinery's $3.8 billion expansion.

The NRDC has alleged BP's air permit does not account for increased pollution from the flares, and has criticized the Indiana Department of Environmental Management for being too lax in BP's permitting.

BP and IDEM have defended the permit as legal and protective of the environment. The U.S. Environmental Protection Agency last month upheld the IDEM-backed permit, allowing BP to continue building its expansion.

A BP spokeswoman said she could not comment on the lawsuit until the company has fully reviewed it.

"We care about Lake Michigan and the water and air our employees and neighbors drink and breathe, and we are listening to people's concerns and working hard to minimize the environmental impact of this project," BP spokeswoman Sarah Howell said.

"This project has and will continue to undergo intense regulatory scrutiny and will comply with state and federal regulations governing protection of human health and the environment," Howell said.

The lawsuit alleges that BP did not properly calculate emissions of some pollutants and did not account for all emissions that would result from the refinery's construction. In doing so, BP did not implement the best available pollution prevention technology, a violation of the Clean Air Act, according to the suit.

Emissions expected under the new permit will cause severe public health and environmental problems around the refinery, the suit alleges.

NRDC's appeal comes on the heels of the group's victory appealing an air permit for an expansion of the ConocoPhillips refinery in Roxana, Ill. An EPA appeal board upheld a challenge, led by the NRDC, arguing that ConocoPhillips had not properly controlled its flare emissions.

In a statement, NRDC senior attorney Ann Alexander said of the BP suit, "Flares are enormous sources of pollution. That pollution may be a little harder to count than some other types of pollution, but you still have to do it. It's not an option for BP and IDEM to stick their heads in the sand and act like the problem does not exist."

Alexander continued: "The failure of Indiana and BP to take the public interest and the law seriously has forced the issue and required that this case be brought before the federal courts."

The NRDC is assisting other groups that have filed appeals of the air permit with the Indiana Office of Environmental Adjudication.