Updated

The cost of cleaning up a major toxic waste spill in the West caused by an Environmental Protection Agency contractor could soar as high as $27.7 billion.

That's the conclusion of study released Tuesday morning by the right-leaning American Action Forum. The group is one of the first to attempt to estimate the clean-up cost of what will likely be remembered as one of the biggest environmental disasters of 2015.

The toxic spill began Aug. 5 when an EPA contractor accidentally ruptured a wall holding back millions of gallons of wastewater containing a variety of toxic substances such as mercury and lead at a closed gold mine in Colorado.

The resulting spill created a yellow plume of toxic sludge that flowed through Colorado, New Mexico and Utah via the Animas and San Juan rivers.

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