Data Show Northern Idaho Superfund Cleanup is Improving Water Quality

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COEUR D’ALENE, Idaho —A new report published by the U.S. Geological Survey shows that U.S. Environmental Protection Agency-led efforts to clean up historical mining contamination in the Coeur d’Alene and Spokane River basins are improving water quality. Concentrations of three trace metals of concern—cadmium, lead and zinc—have been significantly reduced since cleanup activities began in the 1990s. 

From the late 19^th century through 1987, more than 130 million tons of lead, zinc and silver sulfide ores were mined from the Coeur d’Alene mining district. Ore processing often included dumping large amounts of metal-rich tailings into and along area streams that then transported those metals downstream.

In 2004, the USGS, in cooperation with the EPA, established a water-quality monitoring network totaling 18 sites from Mullan to Post Falls, Idaho. USGS hydrologist Greg Clark analyzed water-quality data collected from October 2009 through September 2013. Clark also examined data dating back to the early 1990s to look for any long-term trends. Results of those analyses include:

• Concentrations of cadmium, lead and zinc have decreased significantly in streams throughout the Coeur d’Alene and Spokane River basins since the early 1990s. In the South Fork Coeur d’Alene River near Pinehurst, the concentrations of each of the three metals decreased by about 65 percent between 1992 and 2013. In most streams, however, concentrations of cadmium and zinc continue to exceed water-quality criteria established to protect aquatic organisms from toxic exposure to these metals.
• The rate of decrease in metal concentrations in streams has slowed since 2003. Continued decreases will require a reduction in the contributions of metals to the South Fork Coeur d’Alene River from Canyon and Ninemile Creeks and from groundwater underlying the Central Impoundment Area near Kellogg, Idaho. The EPA is implementing remedial actions in these locations.
• Coeur d’Alene Lake continues to receive large amounts of metals from upstream sources. From 2009 through 2013, the lake received an annual average of nearly 5 tons of cadmium, 400 tons of lead and 700 tons of zinc, about 99 percent of which were delivered from the Coeur d’Alene River. Of these totals, about 1.5 tons of cadmium, 380 tons of lead and 350 tons of zinc settled in the lake; the remainder flowed out of the lake to the Spokane River.

“This is good news for the people of the basin,” said Rick Albright, EPA Superfund cleanup director in Seattle. “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 metal loads and improving area water quality. The USGS report underscores that we’re on our way to celebrating the basin’s recovery and ensuring that it remains a beautiful, healthy place to live, work and play.”

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