The Navajo Nation is preparing for a legal battle against President Obama's Environmental Protection Agency (EPA).

The tribe contends that the EPA's Aug. 5 accident in Colorado, which made national headlines after turning portions of the Animas River bright yellow, also leaked hazardous substances into the San Juan River — one of the Navajo Nation's primary water sources.

Now, they've hired law firm Hueston Hennigan LLP to represent them in what some are predicting could be a multibillion-dollar lawsuit expected to be filed in the coming weeks, as lawmakers on Capitol Hill prepare for a round of hearings examining the issue.

And heading their legal team is powerhouse attorney John Hueston, who was the lead prosecutor in the 2006 case against former Enron executives Kenneth Lay and Jeffrey Skilling, who were found guilty of fraud and conspiracy.

Russell Begaye — president of Navajo Nation, which totals roughly 300,000 people — also sent a letter to Federal Emergency Management Agency (FEMA) officials on Monday, calling on them to appoint a FEMA official to coordinate their efforts in the response to the spill.

"This expansion into Navajo lands via the San Juan River has critically impacted the River and its dependent ecosystems including wildlife, fish populations, and the land base adjacent to the River," Begaye wrote in the letter, first obtained by The Hill.

He said that "the nature of this toxic chemical spill will acutely and chronically impact the River and dependent ecosystem if immediate and effective corrective actions and remedies are not taken."

Navajo Nation Attorney General Ethel Branch said in a statement that the hazardous-material spill "has been devastating to our culture and economy, as well as to the peace of mind of our people.

"With unknown amounts of this fine sediment in our water we now face the risk of reliving this nightmare with every major increased water flow event affecting the river,” she said in a statement.

EPA officials have previously announced that they've launched an internal investigation into the spill.

Navajo leaders say EPA officials accidentally released about 3 million gallons of water contaminated with arsenic, lead and cadmium after officials were inspecting a mine.