Cleaning up historic mine waste is paying dividends for water quality in the Coeur d’Alene River Basin, according to a new report published by the U.S. Geological Survey.
The report looked at two decades of water quality monitoring for the Coeur d’Alene River and its tributaries. Since the early 1990s, concentrations of lead, cadmium and zinc have dropped by 65 percent in the South Fork of the Coeur d’Alene River near Pinehurst, Idaho.
Other streams also showed water quality improvements, though most continue to exceed safe limits for heavy metals.
In addition, large amounts of mining waste continue to wash down the Coeur d’Alene River and into Lake Coeur d’Alene, the report said. About 400 tons of lead, 700 tons of zinc and 5 tons of cadmium flow into the lake each year, according to data collected from 2009 through 2013. Most of the metals settle at the bottom of the lake, with some flowing out of the lake and into the Spokane River.
Overall, the report is “good news for the people of the basin,” Rick Albright, the U.S. Environmental Protection Agency’s Superfund cleanup director in Seattle, said in a statement. “We still have a long way to go in our cleanup efforts, but it’s nice to have scientific confirmation that we’ve made solid, measurable progress in reducing metals loads and improving area water quality.”
More than $200 million in federal money has been spent on Superfund cleanup in the basin during the past 20 years. The state of Idaho and mining companies also contributed funding.
Early cleanup efforts focused on protecting human health and reducing childhood lead exposure, said Bill Adams, EPA’s team leader for basin cleanup. Now, several large cleanups of mine tailings and polluted groundwater are underway, which should further benefit water quality.
Those cleanups will reduce zinc concentrations in local waterways, which are particularly toxic to fish and other aquatic creatures, Adams said. But the lead flowing into the lake will continue to be a problem until highly polluted floodplains along the lower Coeur d’Alene River are cleaned up.
More than 130 million tons of silver, lead and zinc ore was mined in Idaho’s Silver Valley during the past century. Before pollution controls, metal-rich tailings were dumped into streams, washing the metals downstream.
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