This shows the relative hardiness of various organisms when it comes to pH levels in water. Remember that the higher the pH, the lower the acidity. Ideal pH is around 6.5. Water draining from the Gold King Mine has a pH of 2.5. Cement Creek can run as low as 3.5 pH, making it virtually uninhabitable to all but extremophiles. Keep in mind that acidity is not the only harmful component of acid mine drainage; heavy metal loading is often worse.
Jonathan P. Thompson 