The massive mine spill that the Environmental Protection Agency caused in August 2015 equaled a week's worth of normal mine leaks in the region of Silverton, Colo., where it occurred, the agency said Friday in its final report on the spill.

The report showed that the spill of 3 million gallons of toxic waste water at the Gold King Mine caused by EPA contractors lasted about nine hours Aug. 5. The spill was "comparable to four to seven days of ongoing acid mine drainage" from the Gold King Mine, or "the average amount of metals carried by the river in one to two days of high spring runoff," the report said.

"However, the concentrations of some metals in the [mine spill's] plume were higher than historical mine drainage," it added. The highest concentrations of metals in the plume included iron and aluminum. "As the yellow plume of metal-laden water traveled downstream after the release, the metal concentrations within the plume decreased as they were diluted by river water and as some of the metals settled to the river bed."

The report's assessment supported previous agency assertions that the spill dissipated rapidly as it traversed and sullied the waterways in three states.

The Navajo Tribe and New Mexico have sought legal action to get EPA to pay for the damage the toxic plume caused. The issue has been a prominent fixture in Republican-led attacks on the agency to hold one its officials accountable for the spill.

In the fall, the EPA's inspector general issued a report that showed the possibility of criminal negligence on the part of at least one EPA official and passed its recommendations to the Justice Department.

The Justice Department said it would not seek criminal prosecution.