The little river running through the valley is yellow-red, and doesn't have any aquatic life. According to the signs alongside the road, that's natural for this area (Red Mountain is red because of how iron-rich the rock is, and it affects everything else) and not because of any mine runoff--though they do mention the mines didn't help anything. I wouldn't want to drink it, at least.
All told, in just this area between Ouray and Silverton, there were somewhere around 100 mines, and about 3000 people making a living, mostly going after silver. Adjusted for inflation, billions of dollars worth of silver came out of the ground here. But when the US demonetized silver, it pretty much killed the silver mines. Some of the mines had other metals and lived on, but the boom times were definitely over.
Oh, and noodling around on Wikipedia I saw that Ouray was the area that Ayn Rand modeled Galt's Gulch on. Ya learn something new every day.