New study of Lake Coeur d’Alene shows water quality gradually improving

Spokane Public Radio

The new study says heavy metals, phosphorus levels are steadily decreasing. Doug Nadvornick/Spokane Public Radio

A National Academy of Sciences draft report concludes the quality of the water in Lake Coeur d’Alene has improved over the years.

The report was shared this week at a symposium in Coeur d’Alene.

Dan McCracken from the Idaho Department of Environmental Quality says the study found that the main sources of pollution — heavy metals and phosphorus — are entering the lake at lower levels than in the past.

“Although we are still a long ways away from where we want to be, we’re starting to see some water quality improvements, just in the last five-to-10 years. Metals loading, coming from the upper Coeur d’Alene River, has consistently been improving since we’ve been doing cleanup through the Superfund work,” he said.

That’s 40 years of federally-funded work focused in the Silver Valley. More attention is now being paid to the basin between the valley and the lake.

When it comes to phosphorus, McCracken isn’t sure why the levels are down.

“We would like to think the period, over the last 10 years, focusing on nutrient loading through our lake management plan and raising awareness and talking about the things that we do that contribute phosphorus to the system and upgrading our wastewater treatment systems, but the data aren’t clear,” he said.

McCracken says the National Academy report provides about two dozen recommendations to continue to make improvements.

“One of the really helpful suggestions they had is collecting additional information from some of the bays and tributaries to serve as kind of an early-warning sign of, you’re going to see changes in water quality much more rapidly in some of the shallow areas than you will out in the main body of the lake,” he said.

The final National Academy of Sciences report for Lake Coeur d’Alene is due to be released by the end of the year.

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