The Nation has asked a judge to stop the federal government from allowing a sewage treatment plant to be built on Syracuse's South Side before an environmental impact study is conducted. In a friend of the court brief, the Nation charged that the U.S. Environmental Protection Agency hadn't fully investigated whether the treatment plant next to Onondaga Creek would disturb ancient tribal villages and burial sites. EPA ruled the county did not need to conduct a broader environmental study. The brief enters the Nation into a suit filed against the EPA March 13 by Atlantic States Legal Foundation, Syracuse United Neighbors and others opposing the plant, a part of a $380 million cleanup plan for Onondaga Lake.