Three environmental groups sued the U.S. EPA yesterday to force the agency to control the dumping of ballast water into bays, rivers, and lakes. More than 21 billion gallons of ballast water are discharged into U.S. waters each year, introducing exotic species and chemical contaminants that damage native ecosystems. Concerned about the damage, the environmentalists want the EPA to repeal a rule exempting ballast water from regulation under the Clean Water Act. An EPA scientist studying the problem of exotic species says the agency has prepared a report on invasive species that it may make public soon.