I have lived on a river (OK more like a stream) for most of my life that had a RR tie plant on it for 75 years. It became a superfund site and they actually moved about 5 miles of the river a number of years ago to bury the contaminated sediments at a cost of around $40M. When we were kids it wasn't unusual to get creosote burns if you spent any amount of time in the water. Poke a stick in the mud and watch the rainbow oil slick move down stream.
http://www.epa.gov/region5/cleanup/m..._fs_200404.pdf

We did get a new bridge and repaved section of trail out of it.