COEUR d’ALENE — There’s a sleeping giant at the bottom of Lake Coeur d’Alene: heavy metals.

Since the late 1800s, as much as 83 million tons of particulate and dissolved metals from mining-related activities have been deposited into the lake.

Lakebed sediments are highly contaminated with toxic substances such as lead, mercury and zinc.

“We’re not sure when that will wake up and potentially damage our lake and our economy,” said Marie Schmidt, outreach specialist for the Community Water Resource Center at University of Idaho Coeur d’Alene.

Schmidt is part of Our Gem Coeur d’Alene Lake Collaborative, a group dedicated to preserving lake health and protecting water quality by promoting community awareness.

Relatively few North Idaho residents are aware of threats to the lake’s health.

A new survey completed by Our Gem Collaborative found that almost 75% of respondents didn’t know Lake Coeur d’Alene is part of the Environmental Protection Agency’s Superfund program.

Although the lake is included in the federal Bunker Hill Superfund site, it doesn’t receive Superfund money and it’s not part of the EPA’s cleanup plans.

In 2002, state and local leaders feared the stigma of a Superfund site would damage the tourism industry and reduce property values. They also felt strongly that much more research needed to be done before strong measures were taken.

As a result, lake cleanup was essentially turned over to the Coeur d’Alene Tribe and the state of Idaho, rather than the EPA.

Two decades later, survey respondents said negative attention due to the Superfund site is their lowest concern when it comes to threats to the lake.

A similar survey conducted in 2010 indicated that more than half of area residents believed the lake has good or excellent water quality.

Now only about 36% of people believe that, while about 33% believe the lake’s water quality is poor.

Which is correct? Schmidt said the answer isn’t simple.

“Lake dynamics are really complex,” she said.

For the most part, the lake is healthy.

“We look out and see a beautiful, clear, blue lake,” Schmidt said. “We have celebrities who come from all over to play here, so it seems like it’s all right.”

But under the surface, danger lurks in the form of rising phosphorus levels, she said.

Oxygenated water locks heavy metals in the sediment. Too much phosphorus can cause increased growth of algae and large aquatic plants, leading to toxic algae blooms and reducing the lake’s oxygen to a point at which heavy metals are released.

It’s not too late to change course.

“If our community can step up, we can better address (the threats) and keep the lake health and swimmable and fishable for a long time in the future,” Schmidt said.

Public awareness is key.

“The community cares about our lake,” Schmidt said. “We love our lake and we want to help.”

That’s where the survey comes in — to get a sense of what the community already knows about the lake’s health and how to better reach them.

Our Gem Coeur d’Alene Lake Collective will present the survey results to the Coeur d’Alene City Council tonight.