The Lake and Its People

Lake Coeur d’Alene takes its name from the Coeur d’Alene people, whose traditional territory once stretched across 4.5 million acres of what is now northern Idaho, eastern Washington, and western Montana. The Tribe lived along the Coeur d’Alene, St. Joe, Clark Fork, and Spokane Rivers, as well as on the shores of Lake Coeur d’Alene, Lake Pend Oreille, and Hayden Lake.

Today, the Coeur d’Alene Tribe is a sovereign nation, governing a reservation that includes a significant portion of Lake Coeur d’Alene and its submerged lands. The Tribe continues to play a leading role in protecting the lake and its cultural and ecological significance.

Why Spokane Should Care

The Spokane River and Lake Coeur d’Alene are directly connected. Water from the lake forms the headwaters of the Spokane River, meaning everything that happens upstream—development, runoff, or pollution—affects the health of the river downstream. Many people from the Spokane area recreate on the lake or on the rivers that feed it.

Protecting Lake Coeur d’Alene is essential for protecting the Spokane River. Local and regional partners, including the Coeur d’Alene Tribe, Idaho Department of Environmental Quality, and Kootenai Environmental Alliance, are working together under the 2009 Coeur d’Alene Lake Management Plan to manage this shared resource.

Threats to the Lake

Overdevelopment and Nutrient Pollution

Lakeside development has dramatically altered natural shorelines and increased phosphorus pollution flowing into Lake Coeur d’Alene. Phosphorus, a naturally occurring mineral, enters the lake when vegetation and topsoil are stripped away during construction. In the water, it fuels excessive growth of aquatic plants and algae.

When those plants decompose, they consume oxygen, suffocating fish and other aquatic life. This process, known as eutrophication, accelerates as native vegetation is replaced with lawns and artificial beaches. Today, only about 25% of the lake’s natural shoreline vegetation remains intact, contributing to warming waters, increased erosion, and degraded water quality.

The Invisible Problem Beneath the Surface

Beneath the beauty of Lake Coeur d’Alene lies a more serious, unseen threat: roughly 75 million tons of contaminated sediment containing lead, cadmium, arsenic, and zinc. These toxic metals originated from more than a century of mining in Idaho’s Silver Valley—one of the most productive metal-mining regions in the world.

The Mining Legacy of the Silver Valley

Between 1886 and 1982, the Silver Valley produced more silver than any other place on Earth, along with millions of tons of lead and zinc. Early mining practices were primitive and wasteful. Mills recovered only 50–85% of the lead from ores; the rest was dumped into the South Fork of the Coeur d’Alene River as tailings and “slimes.”

By the early 1900s, heavy-metal contamination had reached far downstream, poisoning farmlands and river habitats. In 1931, lead levels in Coeur d’Alene’s drinking water were found to be more than 20 times higher than federal standards. By 1932, the South Fork of the river was virtually lifeless.

Decades of pollution transformed the lower valley into a toxic landscape. Efforts to contain tailings—such as the Central Impoundment Area (CIA) built by the Bunker Hill Mine—were inadequate, and waste continued to flow downstream.

Lead and other metals have lasting impacts on human health, especially for children. During the 1970s, children in Kellogg recorded some of the highest blood-lead levels in the country. Lead exposure damages the nervous system, reduces intellectual development, and affects nearly every organ in the body.

The Bunker Hill smelter, once one of the largest in the world, became infamous for toxic emissions. In 1973, a fire destroyed part of the smelter’s air pollution controls, causing lead levels in surrounding neighborhoods to quadruple. Hundreds of children suffered acute lead poisoning before the smelter finally closed in 1982, eliminating 2,000 jobs but ending decades of unchecked contamination.

In 1983, the Bunker Hill site was designated as a federal Superfund site, one of the largest in the nation. Cleanup efforts have included removing contaminated soil, restoring vegetation, and building engineered repositories to safely store toxic waste. Over $200 million has been invested in remediation, though a vast amount of contaminated sediment remains in the watershed.

The Coeur d’Alene Tribe, EPA, and Idaho DEQ continue to monitor and manage contamination as part of the Bunker Hill and Coeur d’Alene Basin cleanup. The goal is to keep the lake’s oxygen levels high enough to prevent the buried metals from dissolving back into the water column—a delicate balance that depends on controlling phosphorus and nutrient inputs.

Despite progress, contamination from the Silver Valley continues to affect the Coeur d’Alene and Spokane Rivers, especially during high flows and sediment movement events. And now, the Bunker Hill site is reopening.

Lake Coeur d’Alene is a place of incredible beauty and deep cultural importance. Protecting it requires collaboration across the watershed—from the Silver Valley to Spokane. Maintaining low nutrient levels, limiting shoreline development, and continuing to address the legacy of mining pollution are all essential to safeguarding the health of the lake—and, by extension, the Spokane River itself.

Further Reading