The US Army Corps of Engineers must disclose the amount of pollutants its dams send into waterways for the first time in its history.

The decision is part of a settlement of a lawsuit brought by environmental groups, including Columbia Riverkeeper, against the “unchecked pollution”. It had previously described “dozens of oil spills and chronic oil leaks” at the dams.

As part of the agreement, the Army Corps must apply to the Environmental Protection Agency (EPA) for clean water permits for its dams and monitor the amount of pollution being discharged into the Columbia and Snake rivers in Oregon and Washington.

Columbia Riverkeeper praised the agreement as a key step in controlling oil leakages from machinery at eight dams operated by the Army Corps.

Brett VandenHeuvel, Columbia Riverkeeper’s Executive Director said: “This is a huge day for clean water. For years, the dams have discharged harmful oil pollution into the Columbia and Snake Rivers and finally that will stop.

“With the dams coming into compliance with the Clean Water Act, hopefully we will see an end to toxic spills and chronic seepage of pollutants that have been harming our community.”