Front Range growth boom may tap defunct Colorado mountain gold mines — to get more water for people – The Denver Post

“Utility officials reckon that, by lowering the clean water in that reservoir and preventing it from reaching exposed rock in mine tunnels, which creates a sulfuric acid mix that leaches out cadmium and zinc, Aurora could prevent further degradation of streams and fish life.

https://www.denverpost.com/2018/01/19/colorado-mines-used-for-water/