FILE - In this May 7, 2015, file photo, crews perform dredging work along the upper Hudson River in Waterford, N.Y. Long after the last dredging barge leaves the upper Hudson River, scientists will track the slow fade in contamination levels. General Electric Co. expects to finish this year removing some 2.7 million cubic yards of contaminated river sediment under its landmark Superfund agreement with the federal Environmental Protection Agency. After six years of digging, crews will have removed most of the PCBs on the river bottom discharged decades ago from two GE plants upriver. (AP Photo/Mike Groll, File)
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