How ballast works, from the International Maritime Organization.
The federal government has agreed to develop more stringent national regulations governing the discharge of ship ballast water, which has been a major source of troublesome invasive species in California and other states.
Under a settlement filed Tuesday in the D.C. Circuit Court of Appeals, the Environmental Protection Agency will rewrite a permit system challenged by a coalition of environmental groups in a long-standing legal battle.
The agency must issue a new permit by late next year, although it would not take effect until the current one expires in December 2013. The lag time is intended to give the maritime industry time to develop systems to treat the ballast before releasing it overboard.