The Obama administration is ordering an ambitious cleanup of the Chicago River, a dramatic step toward improving an urban waterway treated for more than a century as little more than an industrialized sewage canal.

In a letter obtained Wednesday by the Tribune, the U.S. Environmental Protection Agency demands that stretches of the river must be clean enough for “recreation in and on the water,” a legal term for recreational activities including swimming and canoeing.

Read the complete Chicago Tribune story, “Feds demand Chicago River cleanup.”