FILE - In this Aug. 12, 2015 file photo, water flows through a series of retention ponds built to contain and filter out heavy metals and chemicals from the Gold King mine chemical accident, in the spillway about 1/4 mile downstream from the mine, outside Silverton, Colo. A U.S. House probe of the mine waste accident in Colorado that fouled rivers in three states with arsenic, lead and other toxic substances has found further evidence that EPA workers knew a spill from the gold mine was possible, according to documents released Thursday, Feb. 11, 2016 by a U.S. House committee. (AP Photo/Brennan Linsley, file)