When it comes to water quality in Lake Coeur d’Alene, local residents are pretty savvy.
They think the lake is cleaner now than it was 40 years ago. That’s generally true. Upstream mining companies no longer dump tailings into the Coeur d’Alene River, and tighter pollution controls have reduced erosion from logging and construction activity.
But the public’s knowledge of heavy metals remains hazy, a recent survey indicates. Few people realize that historic mine waste is still washing into Lake Coeur d’Alene.
“The Coeur d’Alene River acts like a conveyor belt,” said Rebecca Stevens, the Coeur d’Alene Tribe’s lake management coordinator. “It’s still moving (metals) down through the system.”
She cited flooding on Jan. 18 as an example. An estimated 352,000 pounds of lead flowed into the lake over a 24-hour period.
To gauge the public’s understanding of lake conditions, the tribe and Idaho Department of Environmental Quality hired Robinson Research of Spokane to poll local residents. Nearly 500 people participated in surveys.
Some of the key findings:
• Most people listed Eurasian milfoil, an invasive aquatic weed, as the top perceived threat facing Lake Coeur d’Alene. Metals were much lower on people’s radar.
• Many said they were concerned about the impact of lakeshore development on water quality.
• Forty-nine percent said mandatory regulations were needed to protect water quality. Forty percent supported voluntary regulations.
Perhaps it’s not a surprise that heavy metals aren’t more of a concern, said Janet Torline, president of the Kootenai Environmental Alliance’s board of directors, who was at Thursday’s KEA lunch meeting where the survey results were unveiled.
“You look at the lake, it’s beautiful and clear,” Torline said. The metals are “insidious and invisible,” she said.
Stevens said the survey results will be used for public outreach programs to help protect Lake Coeur d’Alene’s water quality.
In 2008, the tribe and state unveiled a plan for managing 83 million metric tons of polluted sediment at the lake’s bottom. It’s laced with lead, cadmium, arsenic and zinc. The plan relies on keeping high levels of dissolved oxygen in the water, since the oxygen acts as a cap on the metals.
Algae blooms in the lake could disrupt that balance. The tribe and DEQ are in the midst of a three-year monitoring program to identify where algae-fertilizing phosphorous is flowing into the lake and how it can be reduced, said Becki Witherow, a lake scientist for DEQ.
Phosphorus and other nutrients come from many sources, Stevens said. Waterfront construction can be a culprit, if developers don’t control runoff and leave buffers of native plants along the shoreline. Septic systems and lawn fertilizers also contribute to the lake’s nutrient load. Urban residents need to be responsible, too, she said. “Our storm drains flow into the lake,” Stevens said. “If we know that, we might not use a phosphorus-rich soap when we wash our cars.”