The coal-powered SS Badger pulls out of Ludington, Michigan's harbor as it heads towards Manitowoc, Wisconsin in August 2011. (Denise Stocker/Chicago Tribune/MCT via Getty Images)

The 2014 season for Lake Michigan's only coal-powered passenger and car ferry comes to a close Sunday, signaling the end of the controversial practice of dumping coal ash into the Great Lake. When the vessel resumes operations in 2015, it will no longer release the waste material into those waters.

The SS Badger, the last coal-fired steamship still operating in the United States, began service in 1953. From May to October, it ferries riders between Ludington, Michigan, and Manitowoc, Wisconsin. Until recently, it also dumped about 500 tons of coal ash per season into Lake Michigan. To put that into perspective, all other Great Lakes freighters combined discharge just 89 tons of coal, limestone and iron waste annually.

But as part of a 2013 Environmental Protection Agency consent decree, the ship reduced its ash output last year and, beginning in the 2015 season, will keep its ash out of the lake. A spokeswoman for Lake Michigan Carferry, which operates the Badger, told The Huffington Post that an ash retention system will be installed over the winter, and that the boat's next season will proceed as usual.

Lake Michigan Carferry last winter dropped $1.5 million to install a combustion control system on the ship. The pricey upgrade allows ash to be stored on board by reducing both the amount and temperature of the ash produced, according to the Chicago Sun-Times.

In an agreement with the EPA last year, Lake Michigan Carferry consented to reducing its coal consumption and cutting ash discharges by 15 percent this year. Prior to the agreement, however, the company lobbied to avoid EPA regulation entirely and pushed to get the ship designated as a National Historic Landmark, according to the Chicago Tribune. Shortly before the Badger's last permit expired in 2012, several congressmen attempted to pass legislation giving it a lifetime permit.

Many locals see the Badger as a historic treasure and a vital piece of the local economy. (The ship provides 200 jobs and brings a combined $35 million to the two port cities it connects.) Some were altogether opposed to new regulations for the ship; others favored compelling the Badger to stop dumping ash, as long as the EPA allowed Lake Michigan Carferry time to comply.

But detractors have long been concerned about the potential harm of coal ash, which contains mercury, arsenic, lead and other heavy metals.

“The SS Badger, the filthiest ship on the Great Lakes, has been given two more years to dump hundreds of tons of dangerous coal ash into Lake Michigan," U.S. Sen. Dick Durbin (D-IL) said in a statement when the EPA consent decree was lodged in 2013. "The millions of people who live, work and play in and around this beautiful lake should be outraged that this filthy ship will continue to operate."