Lake Pend Oreille

Due to unique ecological characteristics, outstanding recreational and aesthetic properties and the high quality of its water, Lake Pend Oreille has been designated a Special Resource Water, meriting the highest level of protection. It also has been deemed a "Health and Recreation Place" by Idaho's Legislature. It is 128 square miles and has 43 miles of shoreline. At 1,158 feet deep, it is among the deepest lakes in the country. It has endured ice ages and floods. It has dealt gracefully with settlement along its shores. Question is, "Can Lake Pend Oreille survive the Rock Creek Mine?"

The Slow Death

The Rock Creek Mine would discharge up to 3 million gallons of polluted wastewater into the Clark Fork River every day. This discharge would contain nutrient pollution (nitrogen and phosphorus) and heavy metals, including arsenic, lead, copper, zinc and mercury. The discharge would flow 20 miles downstream into Idaho, soon entering Lake Pend Oreille. Other mine discharges would include seepage of metals from the bottom of an unlined mine tailings pile that would seep into groundwater feeding the Clark Fork River. And the mine's underground cavity would create a source of perpetual pollution that would escape the mine through fissures and cracks finding its way downstream. In other words, the Rock Creek Mine turns Lake Pend Oreille’s source of pure, clean water into a source of perpetual pollution.

The Toxic Plume

Any number of events could lead to unexpected and uncontrolled releases of polluted wastewater from the mine. Large storm events would allow untreated wastewater to flow into McKay Creek, Rock Creek, and the Clark Fork River. Ten and 100-year storm events (storms of the size that would be expected to occur on average every 10 or 100 years) are not uncommon in the Cabinet Mountains, where an average of 100” of precipitation is received each year. During events of even a 10-year size, the mine is authorized to discharge untreated water from holding ponds into local streams.

Failure of the treatment systems or ruptures in the tailings slurry line would also lead to a release of untreated water or tailings. Tailings line breaks and mishaps have occurred at the Troy Mine resulting in raw tailings entering local creeks.

The unthinkable—a failure of the tailings impoundment—would result in a catastrophic event in which hundreds of thousands of tons of mine tailings could be dumped into the Clark Fork River.