By Susan Montoya Bryan, The Associated Press

ALBUQUERQUE, N.M. — Attorneys with the U.S. Justice Department are asking a federal judge to dismiss claims by New Mexico and the Navajo Nation that stem from a 2015 mine waste spill that fouled rivers in three Western states.

The Justice Department filed its motion Monday, following up on arguments first made by the Obama administration that the U.S. Environmental Protection Agency is protected by sovereign immunity and doesn’t fit the definition of a liable party.

Triggered by an EPA-supervised work crew, the spill sent 3 million gallons of toxic wastewater containing arsenic, lead and other heavy metals into the Animas River near Silverton, Colorado. The mustard-yellow plume reached rivers in New Mexico and Utah, setting off a major response by government agencies and private groups.

“This is not a case involving, for example, the alleged release of hazardous substances from a federal installation, or from an industrial site formerly owned or operated by a federal government agency,” the motion states.

The attorneys argue that the EPA was responding to ensure that contamination created by others does not endanger the public.

Similar immunity arguments were made last month when the EPA announced it would not repay dozens of claims totaling more than $1.2 billion for economic damages resulting from the spill.

Still angered by the earlier decision, New Mexico and Navajo officials have no plans to back down from the legal fight. New Mexico was the first to sue over the spill, targeting the EPA, the state of Colorado and the owners of two mines.

New Mexico has repeatedly argued that the federal government failed to take full responsibility for the spill and alleges in its lawsuit that the environmental effects were far worse than claimed by the EPA.

“I will continue to aggressively pursue litigation to obtain justice for our culturally unique population and damaged economy in order to protect New Mexico’s children and families for generations to come,” New Mexico Attorney General Hector Balderas said Tuesday in a statement sent to The Associated Press.

Navajo President Russell Begaye said the tribe remains deeply disappointed with how the EPA handled the spill and the aftermath, but he’s confident the court will hold the agency accountable.

“The U.S. EPA repeatedly assured the Navajo Nation that it would take responsibility for its actions and make all injured persons whole,” Begaye said. “Now they are attempting to avoid any responsibility or liability for their recklessness and misconduct.”

During the spill, water utilities shut down intake valves and farmers stopped drawing from the rivers as the plume moved downstream.

The EPA said water quality quickly returned to pre-spill levels. But New Mexico officials and others warn about heavy metals collecting in the sediment and getting stirred up each time rain or snowmelt results in runoff.

In the motion filed this week, government lawyers argue that the EPA responded to the contamination and most recently added the area that includes the Gold King Mine to its list of national cleanup priorities.