WASHINGTON (CBS) — The owners of the only remaining coal-powered steamship on the Great Lakes call it an historical asset, but critics say it’s a major polluter.

WBBM Newsradio’s Regine Schlesinger reports the fight is playing out at the federal level.

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In 2008, the U.S. Environmental Protection Agency gave the owners of the S.S. Badger four years to find a solution to the ship’s pollution problems. For every trip it makes, the Badger dumps nearly 4 tons of toxic coal ash into the water.

LISTEN: WBBM Newsradio’s Regine Schlesinger reports

Now the Chicago Tribune reports the owners of the car ferry are asking the Badger to be declared a national historic landmark. Even just seeking such status might exempt the Badger from the more stringent federal pollution standards.

This past Friday, the U.S. House of Representatives approved an amendment to the Coast Guard budget that would allow the Bader to continue operating as-is for until it is taken out of service, the Muskegon Chronicle reported.

The amendment was sponsored by three Republican members of Congress; two from Michigan – Rep. Bill Huizenga (R-Mich.) and Rep. Dan Benishek (R-Mich.) and one from Wisconsin – Tom Petri (R-Wis.)

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On the House floor, Huizenga defended an exemption for the Badger, saying the small port cities in Wisconsin and Michigan would lose about $35 million without the ship, the Muskegon Chronicle reported.

Meanwhile, the owners of the ship are calling for landmark status in lieu of converting the ship to operate on another fuel. The owners say converting to oil would destroy part of the historic coal-delivery system and raise operating costs, while switching to diesel would leave the historic system intact, but not used, the Tribune reported.

The Web site for the Badger calls it a “national treasure” and touts its status as he only coal-fired steamship in operation in the country.

The 410-foot ship entered service in 1953, but stopped sailing in November 1990 as the need for car ferry service dried up. But the following year, businessman Charles Conrad put the Badger back into commission as a conveyance for leisure travelers and their cars, the Web site for the ship points out.

So now, the ship makes runs between Manitowoc, Wis., and Ludington, Mich., and dumps 509 tons of coal ash every year, compared to 89 tons of coal ash total for all 125 freighters on the Great Lakes together, the Tribune reported.

Coal ash contains toxic heavy metals such as lead and mercury, as well as arsenic and other poisons.

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Last year, the owners of the ship asked for federal stimulus money to convert the ship to diesel, the Tribune reported. A switch to natural gas has also been discussed, the newspaper reported.