The spill began August 5 when EPA workers were trying to drain water from the mine but accidentally sent the toxic water flowing into a tributary of the Animas River.
The EPA originally said about one million gallons (3.8 million liters) of polluted water -- containing dissolved heavy metals -- spilled into the river.
But yesterday, the agency revised that figure to three million gallons.
The normally clear waters turned a mustardy-orange color and discolored waters stretched for more than 100 miles, all the way into the neighboring state of New Mexico.