The federal government stepped in with a new order to help the cleanup underway for Gowanus Canal in Brooklyn.

Sunday marks 11 years since the Gowanus Canal was declared a federal Superfund site, meaning it's an area so polluted, it requires a long-term response to clean it up.

The Environmental Protection Agency ordered New York City to build two large retention tanks— an 8 million gallon at the head of the canal, and then another 4-million-gallon tank near the Department of Sanitation lot.

In November, the EPA started dredging the entire 1.8-mile-long Gowanus Canal. The agency pulled up a layer of what they called "black mayonnaise" that settled near the bottom, which they report was a mix of oil, coal, pesticides, sewage, chemicals and a mix of toxic metals.

The dredging process is hoped to be completed by 2023, but the entire cleanup could take up to a decade. The EPA says it might all be a waste of time without the tanks.

Federal officials say 360 million gallons of raw sewage and stormwater runs into the canal each year due to heavy rains. They say tanks are needed to catch and store this sewage, so the canal doesn't just get dirty again.

Walter Mugdan, the EPA's Acting Regional Administrator, says in a statement, "This order will ensure that EPA’s cleanup efforts will not be undermined by uncontrolled combined sewer overflow discharges that have contributed to the chemical contamination of this waterway and impacted this community for the past century and a half."

Federal orders in 2014 and 2016 had called on the city to find locations and designs for these tanks, but the federal government has accused the city of delaying construction. This new order tells the city that the tanks must be built by 2029.