If the canaries stopped singing, it meant the air was bad and it was time to make a fast getaway. Wannacut Lake, miners used to run mine wastewater into cedar barrels full of trout. They were concerned about high levels of arsenic and other heavy metals that were present in local rock. If the trout became sickly or died, it was a sure sign that the mine water was poisonous. The old miners were right about the trout.
Fish are exquisitely sensitive to low levels of dissolved poisons and metals in water.
Lethal concentrations for some fish species are as low as 4 ppb. Macroinvertebrates, the water insects on which fish feed, tend to be more resilient to silver, with lethal levels ranging from 30 to 50 ppb. Technical experts use computer programs to model pit water quality on Buckhorn Mountain. They predict that once the open pit filled with water, silver concentrations in the pit pond could be lethal to fish and would exceed state water quality standards. Concentrations of cadmium, arsenic, nickel, and other heavy metals would also be above state-allowed limits.