Note, the failure has already happened, and the EPA is responsible, as predicted:

http://www.usatoday.com/story/news/nation/2015/08/10/navajo-...

Some culpability should also be placed on the original mining operation?

This was an abandoned mining operation from the early 1900's, among thousands of other similar mines across the state.

Yeah. The EPA failed its duty in regulation but it did not create the preconditions of the disaster.

It seems the geologist even underestimated the disaster He was advising residents to check their water at the time so they could compare it later for contamination. Instead of a hidden change in water parameters, we got a river that looks like carrot juice.

The water could have become dangerous before the river changed color?

I just assumed that from the geologist advising people to test their water so they would have a baseline - so they would be able to make claims later. Obviously there's no need for such proof now.