INDIANAPOLIS (AP) – Opponents of the Interstate 69 extension through southern Indiana have filed another lawsuit trying to stop construction.

The Hoosier Environmental Council and the grassroots group Citizens for Appropriate Rural Roads have filed a complaint in U.S. District Court in Indianapolis seeking to overturn an Army Corps of Engineers permit for the $3 billion project.

The Indianapolis Business Journal reported Wednesday the complaint alleges the permit violates the Clean Water Act because it allows about 225,000 cubic yards of fill material to be dumped into wetlands and streams in Greene and Monroe counties without considering less-damaging alternatives. It involves a section of the highway southwest of Bloomington now under construction.

A spokeswoman for the corps’ office in Louisville,   says the agency doesn’t comment on pending litigation.