Historic mining practices continue to impact health of North Idaho’s Coeur d’Alene Lake

Governor’s Leading Idaho initiative could help address nearly 80 million metric tons of sediment contaminated with heavy metals at the bottom of the lake

By: - June 15, 2023 4:30 am

Coeur d’Alene Lake is a popular tourist site during the summer, but at the bottom of the lake sits nearly 80 million metric tons of sediment contaminated with heavy metals including lead, arsenic and cadmium. As of June 2023, Idaho Gov. Brad Little has allocated $33 million in funds to focus on improving the lake’s health. (Mia Maldonado / Idaho Capital Sun)

Known for its water sports, fishing and hiking spots, the Coeur d’Alene Lake is a natural lake that lies at the center of concern for many environmentalists in Idaho. 

The Coeur d’Alene Lake, fed primarily by the Coeur d’Alene River and St. Joe River, is the second largest lake in North Idaho. The lake is over 26 miles long with nearly 135 miles of shoreline. 

Over 100 years ago, mining practices in the Silver Valley contaminated the river with lead and other toxic metals. In recent decades, environmental groups and state officials are working to keep the lake from exposing lake habitat and recreational users to harmful chemicals. 

In 2009, the Idaho Department of Environmental Quality adopted the Coeur d’Alene Lake Management Plan to reduce the amount of nutrients from entering the lake and keeping high oxygen levels in the water.

Since then, Idaho Gov. Brad Little has allocated $33 million in funds to focus on improving the lake’s health, according to a press release from the Idaho DEQ Friday. 

As part of the governor’s Leading Idaho initiative, Little allocated $2 million for projects to reduce phosphorus and improve water quality in Coeur d’Alene Lake in 2021. 

The following year, Little allocated an additional $31 million in funding from the American Rescue Plan Act for phosphorus reduction projects to be allocated from 2022 to 2026.

“Coeur d’Alene Lake is the heart of North Idaho, driving the region’s tourism, economy, and outdoor recreation opportunities,”  Little said in a press release in March. “Our continued investment into water quality improvement projects aims to protect this ‘gem’ for current and future generations to enjoy.” 

The Coeur d’Alene Lake Advisory Committee, a group appointed by Little to advise the state on how to distribute the funds, has prioritized projects related to wastewater treatment upgrades and recommendations from a 2022 consensus report developed by the National Academies of Sciences.

Mining history leaves heavy metals at the bottom of Coeur d’Alene Lake

Coeur d’Alene Lake management supervisor for the Idaho DEQ Jamie Brunner told the Idaho Capital Sun that Coeur d’Alene Lake’s issues trace back to early gold and silver mining practices in the Silver Valley. 

“When the metals were discovered in the late 1800s, the mining practices back then were not under regulation, because it was way before we had any environmental regulations,” she said. “The mining practices available at the time weren’t very efficient, so a lot of heavy metals were discharged into the river.”

Brunner said that by the time that the lake is warm enough to swim, most of the contaminated sediment has settled at the bottom of the lake or has moved downstream through the Spokane River.

Currently 80 million metric tons of sediment contaminated with heavy metals sit at the bottom of Coeur d’Alene Lake, and more pour into the lake each year, Brunner said. 

“Every year there’s still contaminants washing downstream when we get high flows in the spring, so we have this constant supply of heavy metals still coming into the lake,” she said.

She said she primarily focuses on lead contamination, since it is the most toxic, but other metals contaminating the lake include arsenic, cadmium and zinc. 

While the presence of zinc is not at a level that is concerning for human health, Brunner said zinc contamination still impacts the food web. 

“It (zinc) is also soluble, so it’s in the water column year-round – as opposed to other metals that are primarily bound to sediment that settles out to the lake bottom after high flows subside,” she said.

Brunner has worked on North Idaho water quality issues for nearly 20 years, and she said her main concern is managing phosphorus growth in the lake. 

According to the Idaho DEQ press release, increased nutrients such as phosphorus that enters into the lake causes low oxygen levels that allow the heavy metals in the lake bottom to resolubilize into overlying water, resulting in increased chemical exposure to the surrounding environment and organisms in it.

Lake’s health vital to regional economy, North Idaho water expert says

While locals and tourists regularly recreate in the lake, Brunner said the lake’s health is vital to Idaho’s community and economy. 

“Coeur d’Alene Lake is a major economic driver of the whole region, and not just the City of Coeur d’Alene, but the whole Coeur d’Alene basin and into Spokane,” she said. “If we don’t have it in a good condition, if it’s not healthy, that would be a huge loss to the function of Coeur d’Alene Lake.”

Brunner said she wants lake users and community members to understand that they have a personal responsibility to keep the lake clean.

“It doesn’t look like there’s a problem in the lake,” she said. “You can go swim in the lake, I go swim in the lake, and it’s good. The hard part is wrapping your mind around the fact that we need to proactively watch all the phosphorus inputs basin wide to keep it the way it is.”

Phosphorus comes from many sources, Brunner said. It is attached to the soil, wastewater treatment facilities, septic tanks and animal and human waste. 

“Even taking your dog for a walk and it poops on the ground, if you don’t pick that up, that is a phosphorus source that is eventually going to run off into some water,” she said. 

The increasing presence of toxic chemicals in the lake could have the potential to impact recreational and fishing activities, Brunner said. 

“My biggest challenge as the lake management supervisor is getting that message out and getting people to realize: Why do we do something today, if there’s not a problem today?” she said. “It’s because we’re managing a problem that could happen tomorrow that we don’t want to happen.” 

Hagadone Marine Group president talks corporate role in lake health

Hagadone Marine Group president Craig Brosenne told the Idaho Capital Sun that his company is extremely environmentally conscious.

Brosenne sits on the Lake Advisory Committee representing the Hagadone Corporation — a Coeur d’Alene-based company with hospitality, golf, real estate, marine and aviation operations. 

The Hagadone Marine Group is a boat dealer and storage and servicing company that operates multiple marinas and cruise opportunities along the Coeur d’Alene Lake. (Mia Maldonado / Idaho Capital Sun)

Brosenne said the company owns 15,251 linear feet of shoreline, and it is one of the largest businesses in Idaho with waterfront property.

In addition to operating along waterfront property, Brosenne said the company’s boat storage facility along the Washington and Idaho stateline is the largest indoor boat storage facility in the U.S., and about 50% of the company’s marina tenants come from Washington.

“That puts it in perspective of how important the lake is to recreation, boating, the golf course, the resort and the marinas,” he said in a phone interview. “We have a big stake in the health of the lake.”

Brosenne said the company had waterfront property that previously functioned as a landfill, but it has spent millions of dollars to remove contaminated soils from the property to the proper containment areas. 

Brosenne said the company has also implemented extensive measures to maintain an environmentally-friendly golf course.

“Our floating green collects all the nutrients and water any fertilizers into a containment and then pumps it back to shore,” he said. “Absolutely zero of it goes into the lake. All along the shoreline of the golf course there’s a liner that does the same thing. People look at how beautiful the golf course is, but back in history, it was an environmental nightmare that our company took years to clean up and mediate the contaminants.”

Brosenne said the company also works to prevent invasive species from entering the lake.

“A lot of people probably see the resort and how big it is and don’t realize that we have extreme care for our community, the people in it and the decisions we make along the way,” he said. “Everybody in our company at the executive level was born and raised here. We’re not an organization coming from out of state trying to make profits and then leave. This is our home.”

Correction: This story has been corrected to reflect that the presence of zinc in the lake is not at a level of human health concern. 


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Mia Maldonado
Mia Maldonado

Mia Maldonado joined the Idaho Capital Sun after working as a breaking news reporter at the Idaho Statesman covering stories related to crime, education, growth and politics. She previously interned at the Idaho Capital Sun through the Voces Internship of Idaho, an equity-driven program for young Latinos to work in Idaho news. Born and raised in Coeur d'Alene, Mia moved to the Treasure Valley for college where she graduated from the College of Idaho with a bachelor's degree in Spanish and international political economy.