The Navajo Nation is expected to sue the Environmental Protection Agency Tuesday for the toxic spill the agency caused in Colorado last year that sullied the waterways of three states.

The one-year anniversary of the spill was on Aug. 5, and the agency reiterated on that day that it takes full responsibility for the spill that poured 3 million gallons of toxic sludge from the Gold King Mine in Silverton, Colo., into the Animas River.

The anniversary was also marked by a decision from the EPA inspector general and the Justice Department to launch a criminal probe into the spill, which may have spurred the Navajo to sue.

The Navajo Nation became involved when the toxic plume reached its lands along the San Juan River in New Mexico, causing the state to issue water quality warnings that interrupted farmers' harvest well into the fall.

Navajo Nation President Russell Begaye told the Washington Examiner in an exclusive interview last September that the toxic spill ruined livelihoods of many of his nation's farmers while creating a "culture of distrust" between his people and the Obama administration.

Begaye said back then that the nation was preparing to sue the agency.

The decision to sue the EPA became clear, Begaye said, "especially [after] I got a report that they knew about it. That they knew this was about to happen, [but] they did nothing."

"We are going after EPA. They are going to pay for it," he said, recalling what he told a tribal committee after learning that the agency was clearly at fault. "We are going to make them pay."

Begaye will hold a news conference Tuesday from a bridge overlooking the San Juan River in Shiprock, N.M. He will announce they have directed their counsel, Hueston Hennigan LLP, to file a lawsuit "regarding the unprecedented environmental disaster arising from the Gold King Mine spill," according to a statement.

Other senior officials with the nation will join Begaye at the press conference, including Ethel Branch, the nation's attorney general.