Lake Clean-Up Work Pays Dividends

Nov 25, 2014

Long running efforts to clean up toxic waste in Idaho's Silver Valley mining district are paying off. A new report from the US Geological Survey concluded that concentrations of three heavy metals - cadmium, lead and zinc - have been cut back significantly since controversial clean-up work by the EPA began in the 1990s.

A trail along Lake Coeur d'Alene, Idaho.
Credit https://www.flickr.com/photos/gregraisman/sets/72157601851711041

A USGS hydrologist, Greg Clark, studied 18 water quality monitors set up from Mullan, in the heart of the mining district, to Post Falls. He found that the three heavy metals have been cut back by 65 percent in the Coeur d'Alene River between 1992 and 2013.

However, Clark also found that in most tributary streams along the river, the volume of cadmium and zinc are still too high to protect fish and other aquatic life.

He also warned that Lake Coeur d'Alene continues to catch large quantities of metal from upstream. Every year, roughly five tons of cadmium, 400 tons of lead and 700 tons of zinc are washed into the lake, primarily from the Coeur d'Alene River.

And much of that mess, Clark said, washes on through the lake into the Spokane River. He said the long clean-up has produced solid measurable progress, but there's still a long way to go.