COEUR D’ALENE — Historic mining activities in the Coeur d’Alene Basin have led to widespread metals contamination from the South Fork Coeur d’Alene River to Lake Coeur d’Alene and on to the Spokane River. Ongoing remediation efforts have been occurring since the 1980s, but the work must continue. One major concern for Coeur d’Alene Lake is the legacy contaminated lakebed sediments deposited from the historic mining activities. As long as the lake’s levels of dissolved oxygen from top to bottom stay high, the metals are expected to remain in place. However, increased nutrients—primarily phosphorus—are entering the lake from its surrounding watershed and result in low oxygen levels that allow the heavy metals in the lake bottom to resolubilize into overlying water, increasing exposure to the surrounding environment and organisms in it.
The goal of the Coeur d’Alene Lake Management Plan (adopted in 2009 by DEQ and the Coeur d’Alene Tribe) is to reduce the amount of nutrients, mainly phosphorus, from entering Coeur d’Alene Lake and keeping high oxygen levels in the water. Some of the phosphorus loading entering the lake from across the basin is from point sources (discharges from wastewater treatment plants). Much of the phosphorus loading reaching the lake is also from “nonpoint sources.” These sources are spread across the landscape and include human and animal waste, phosphorus attached to soil that erodes into waterways, lawn and garden fertilizer, detergents, plant decomposition, and other materials picked up by both rural and urban stormwater runoff.
In 2021, Governor Brad Little allocated $2 million for projects that reduce phosphorus loading into the Coeur d’Alene Lake through the Leading Idaho Initiative. To direct how these funds should be spent, Governor Little appointed the Coeur d’Alene Lake Advisory Committee. Due to the high number of applications submitted for the first $2 million and considering the recommendations in a 2022 consensus report developed by the National Academies of Sciences (NAS) that focused on Coeur d’Alene Lake, Governor Little allocated an additional $31 million for these efforts. The Coeur d’Alene Lake Advisory Committee prioritized projects from three categories, including previous project applications, wastewater treatment upgrades, and NAS recommendations.

A step in the right direction, collectively, these projects will improve the health of Coeur d’Alene Lake by reducing the amount of phosphorus that reaches the lake and by informing our decision-making moving forward. It is important to recognize the value of the lake’s health and the part the Coeur d’Alene Basin community plays in reducing their phosphorus contributions. For more information on the Leading Idaho projects for Coeur d’Alene, visit Caution: EmailHosting.cloud has detected a possible phishing attempt from “r20.rs6.net” claiming to be www.deq.idaho.gov/leading-idaho-and-the-coeur-dalene-lake.