Every evening, a 45-car train rumbles away from the Clark Fork River, loaded not with copper, gold or silver ore, but with the toxic legacy of more than a century of mining: tons of contaminated mud from behind an old dam.

Workers are removing 2.2 million cubic yards of the muck — and dismantling the 101-year-old Milltown Dam — in a breathtakingly scenic part of Montana trout-fishing country.

For decades, metals released into the river by mining and ore-processing in the Butte area collected downstream in the sediment behind the hydroelectric dam, where the toxins are now threatening fish and polluting drinking water in the ground below.

The dam is part of a big swath of southwestern Montana that has been designated the nation’s largest Superfund cleanup site.

[Read](http://www.msnbc.msn.com/id/23696251/ “Read the Article”) (AP via MSNBC)