See this article for a history of the mining and this event.http://www.hcn.org/articles/when-our-river-turned-orange-animas-river-spill
The article is left leaning, but has a lot of good history.
One issue to keep clear is that there are two Cement Creeks in Colorado that are well known. One is this one that is one of the three tributaries to the Animas River above Durango. The other is a tributary to the East River which with the Taylor form the Gunnison — that one is below Crested Butte.
The Cement Creek at Silverton is the polluted area going into the Animas.
another good article
http://www.denverpost.com/environment/ci_28608746/epas-colorado-mine-disaster-plume-flows-west-toward