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Brennan Linsley, Associated Press
Water flows through a series of sediment retention on Aug. 14, 2015, The ponds were built to reduce heavy metal and chemical contaminants from the Gold King Mine wastewater accident, in the spillway about a quarter-mile downstream from the mine outside Silverton, Colo.

SALT LAKE CITY — Utah Attorney General Sean Reyes said contractors, mine operators and others working at the Gold King Mine in Colorado nearly two years ago committed a series of negligent steps, leading to the massive release of contaminated sludge that despoiled key Utah waterways.

In a lawsuit filed in federal court Monday, Reyes asserts the contractor, subcontractor and mine owner — Delaware-based Sunnyside Gold Corp. — failed to take a host of proper precautions to avoid the disastrous breach near Silverton that released 3 million gallons of metals-laden sludge.

The Utah Department of Environmental Quality is continuing to take water samples from the San Juan River, which was impacted, and Lake Powell, where most of the sludge was deposited.

While Utah agencies and other entities, such as San Juan County, were compensated by the U.S. Environmental Protection Agency $464,000 for costs related to the initial response, Reyes' suit asks for punitive damages for the ongoing environmental impacts, stigma associated with the spill and interference with the public's ability to enjoy the waterways.

The suit asserts the EPA's on-site team:

• Assumed that because the mine was draining it was not under pressure from the contaminated water behind it

• Didn't believe it was necessary to test the level or volume of contaminated water from the blockage

• Did not take a measurement to determine the pressure of the water against the blockage of the adit, or horizontal mine entrance

Additionally, Reyes' suit says the on-site team failed to take the precaution of installing a secondary containment system to prevent large quantities of toxic wastewater from reaching the Animas River and did not develop or implement an emergency response plan.

Although the Occupational Safety and Health Administration, as well as EPA, requires a health and safety plan in conjunction with hazardous waste site operations, the plan in place failed to meet those requirements, the suit asserts.

On Aug. 5, 2015, the day of the spill, the EPA's on-site team was performing work on the Level 7 adit, where none of the proper measurements or precautions were taken, according to the lawsuit.

"Members of the EPA on-site team have given conflicting reports regarding their work. Some believed the objective was to excavate the adit to create an opening. Others believed the objective was to use a backhoe excavator to scratch the earth around the adit," the suit reads. "On information and belief, this conflict was caused by miscommunication among the EPA on-site team."

The suit says the mine blowout continues to pose environmental, economic and other damages to Utah that are not inconsistent with a "national contingency plan," that will require additional investigation and remediation that will include soil and water testing.

Although the defendants named in the lawsuit should have known the Gold King Mine presented a "high risk of significant harm to the state of Utah and other downstream communities," they acted in disregard of those risks, the suit says.

New Mexico and the Navajo Nation brought lawsuits against the EPA for the spill, and New Mexico also sued Colorado, asserting negligence.

In late June, the U.S. Supreme Court refused to hear arguments related to the dispute between the states.

The EPA in January said it would not pay $1.3 billion in claims related to the spill because it is protected by a federal tort law.

In addition, the agency's inspector general concluded there was no wrongdoing with the Gold King Mine spill, but also conceded there were no specific standards in place for dealing with a collapsed mine portal.

Daniel Burton, a spokesman for the Utah Attorney General's Office, said the state is continuing to negotiate with the EPA to see if a settlement can be reached without the need for litigation.

The mining district that includes where the breach happened was declared a Superfund Site nearly a year ago, which will accelerate cleanup efforts.