It's part of the long sad legacy of the building of the Cherohala Skyway aka Scarway aka Screamway, now used as a loud motorcycle racetrack cutting thru the last unbroken mountains of the Cherokee NF wilderness. Anyway, the dynamite and bulldozers polluted creeks with iron pyrite, a leaching acid. See---
http://books.google.com/books?id=7WZ...pyrite&f=false