CHICAGO (CBS) — A coalition of environmentalists joined U.S. Sen. Dick Durbin on the lakefront Monday morning to call for tighter environmental controls on a famous coal-fired car ferry.

WBBM Newsradio’s John Cody reports Durbin said the S.S. Badger is the filthiest ship on Lake Michigan, and he wants changes to a federal agreement that allows it to keep dumping coal ash into the lake through the end of 2014.

Howard Learner, president of the Environmental Law & Policy Center, said the Badger dumps 500 tons of coal ash into the lake every year, more than the total from every other ship on the lake.

“That’s more coal ash coming from this one ship, S.S. Badger, than 125 other large ships that operate around the Great Lakes,” he said.

Joel Brammeier, president and CEO of the Alliance for the Great Lakes, said coal ash contains several toxic chemicals that don’t belong in the lake.

“What they’re dumping contains all sorts of trace elements that are nasty stuff; arsenic, mercury, things you don’t want in the world’s largest source of fresh surface water,” he said.

Brammeier and Learner joined Durbin in trying to rally public support for stiffer U.S. Environmental Protection Agency controls on the Badger. The ship’s owners received a two-year reprieve last month on a deadline to stop dumping toxic pollution into the lake, under an earlier deal with the EPA.

“No more extensions, no more delays. No more extensions, period,” Learner said.

Durbin said other ships operate profitably without polluting the lake, and the Badger must find a way to do the same.