The U.S. Department of Justice has announced that the city of Duluth has cleaned up its act after millions of gallons of sewage overflow spilled into Lake Superior, ending a decade-old order that forced the city to deal with the problem.

U.S. District Judge John R. Tunheim lifted the regulatory consent decree last Thursday that had required the city and the Western Lake Superior Sanitary District to follow federal instructions to cap sewage overflows by 2016. The city met the federal guidelines ahead of schedule.

Mayor Don Ness said this is a significant environmental accomplishment for the city.

“Protecting Lake Superior is our most important responsibility as Duluthians, and we were failing in that responsibility,” he said. “It was difficult and expensive for a city of our size to deal with the problem.”

In 2009, the city and the district had agreed to pay a fine of $400,000 and spend more than $130 million to fix its sewage problems and protect Lake Superior. Six years later, the cost for improvements has reached roughly $160 million.

Between 1999 and 2004, the U.S. Environmental Protection Agency found that about 250 sewer overflows in Duluth led to 47 million gallons of sewage seeping into the St. Louis River and Lake Superior. In 2001, the city saw 8.1 million gallons of overflow seep into Lake Superior.

The city has not had an overflow in more than three years. Duluth has corked overflows caused by heavy rains by raising sewer rates, repairing private lines and improving old and leaky sewage infrastructure. The city also upgraded and added new pumps as well as built eight storage basins to hold more sewage.

Before the sanitary district was created by the Minnesota Legislature in 1971, Duluth was experiencing overflow into Lake Superior. For years, water from rain and snow would infiltrate into sanitary sewer systems through cracks or illegal drainage systems. Those pipes and pump stations would fill up, and sewage would overflow and leak out. The EPA took notice of the problem in 2003 and six years later the consent decree was signed.

The sanitary district, which serves 17 communities, formed a historic partnership with the city of Duluth to deal with the widespread overflow problem, said Daniel Fanning, a city spokesman.

Jack Ezell, the sanitary district’s manager of planning and technical services, said the joint effort helped both groups come up with the best solutions to cease overflows.

Although a lid has been put on the overflow issue for now, Fanning said the city will continue its same course to stop future overflows.

“We want to be vigilant going forward and stay a step ahead,” he said.