The lawsuit is over what's known as the Pollution Diet -- the Environmental Protection Agency's plan to restore the Chesapeake Bay by asking states to reduce agricultural and urban runoff and sewage in rivers and streams that flow into the bay.
In January, the American Farm Bureau Federation sued the EPA, arguing the agency was overreaching its authority and using faulty science in the cleanup plan. Agricultural groups and other critics also say the plan burdens both states and farmers with onerous costs.
The Chesapeake Bay Foundation and other groups want to join the suit on the side of the EPA. They say the EPA has all the authority it needs to enforce the program under the Clean Water Act, an executive order, and several legal settlements. They point out that federal funds have been made available to help farmers.
"The Chesapeake Bay has been called the crown jewel of America's estuaries," says Will Baker, head of the Chesapeake Bay Foundation. "It's been called America's bay. It can be saved. In our lifetimes, for our children and for our grandchildren."
A federal judge will decide whether the environmental groups can join the suit.