EPA says concentrations of some metals at the Animas river following the spill were found to be higher than historical mine drainage.

EPA said the spill of 3 million gallons of toxic waste water at the Gold King mine caused by its contractors lasted about nine hours and set a record for mine leaks in the region of Silverton, Colorado, where it happened.

It also found the total amount of metals released into the streams, dominated by iron and aluminum, was comparable to four to seven days of ongoing acid drainage from the dormant mine, or the average amount of metals carried by the river in one to two days of high spring runoff.

It further acknowledged that the concentrations of some metals in the Gold King mine plume were higher than historical mine drainage.

“There were no reported fish kills in the affected rivers, and post-release surveys by multiple organizations have found that other aquatic life does not appear to have suffered harmful short-term effects from the GKM plume,” it said in a statement.

EPA added that the concentrations of metals in well-water samples collected after the plume passed did not exceed federal drinking water standards.

The agency has faced a number of legal challenges following the spill. Early last year, the state of New Mexico took a first step to sue EPA and the state of Colorado for their roles in the leakage, which happened as a clean-up crew was working at the mine.

The Navajo Nation filed a suit later in the year seeking more than $160 million in damages and for alleged ongoing injuries the leak caused to one of the tribe’s significant waterways.

An earlier probe conducted by the US Department of the Interior concluded the spill, while avoidable, was “clearly unintentional.”

EPA has made over $29 million available in compensation including $1 million for the Navajo Nation. Last month, it also agreed to pay $4.5 million to state, local and tribal governments for their response the spill, however the agency turned down $20.4 million in other requests for past and future expenses.