Department of
Environmental Quality

Coeur d’Alene Lake is a popular recreational destination, an economic catalyst for Northern Idaho and Eastern Washington, and the heart of the local community. The lake is part of the aboriginal homeland of the Coeur d’Alene Tribe, and their Reservation is located around its southern half.

Development along the lake’s shoreline has been dramatic in recent years, and it now features multiple resorts and an ever-increasing number of homes. Counties, cities, and towns in the Coeur d’Alene Lake Basin are growing, and the lake is a significant factor in that growth.

As a result of historical mining activity in the Silver Valley, millions of tons of metals contaminated sediments (e.g., zinc, lead, and cadmium) are present on the lake bottom. Other human activities around the basin, such as logging, farming, and home building, contribute sediments and nutrients (phosphorus and nitrogen) into the lake, often as a result of natural events such as snow, rain, and floods.

Water quality in the lake has generally improved since the mid-1970s as the era of large-scale upstream mining-related activities tapered off, environmental cleanup activities got underway in the Silver Valley, and environmental regulations were implemented throughout the basin. The challenge today is to ensure that land use activity is managed in ways that will protect the lake’s water quality.

2009 Lake Management Plan

In an effort to address the many issues facing Coeur d’Alene Lake, the Coeur d’Alene Tribe (Tribe) and the State of Idaho Department of Environmental Quality (DEQ) collaboratively developed the 2009 Lake Management Plan (2009 LMP) with the goal: to protect and improve lake water quality by limiting basin-wide nutrient inputs that impair lake water quality conditions, which in turn influence the solubility of mining-related metals contamination contained in lake sediments. The United States Environmental Protection Agency (EPA) assisted the Tribe and DEQ in developing the LMP by convening and participating in an Alternative Dispute Resolution (ADR) process.

The 2009 LMP reflects the shared view of the Tribe and DEQ that a collaborative, adaptive, and data-driven approach is the best option at this time to manage water quality in Coeur d’Alene Lake. The 2009 LMP comprehensively identifies the actions and substantial resources that will be required to effectively manage Coeur d’Alene Lake and the large quantities of mining-associated hazardous substances in its waters and lakebed sediments. It is intended to serve as a framework for watershed-based lake management that will achieve the primary 2009 LMP goal and management objectives through a public-private partnership model.

The scope of the 2009 LMP encompasses the entire Coeur d’Alene Lake Basin. The reason for this is practical: loading of the lake with metals, sediments, and nutrients results from activities that occur around the lake, in upland areas, and along tributary streams and rivers. This scope is essential to effectively address the key influences on water quality. The scope is intended to follow natural boundaries, promote integrated solutions, and maximize the use of available resources to benefit water quality.

The 2009 LMP recognizes the importance of setting priorities to accommodate the challenges posed by the scope and cost of implementing this plan. The LMP approach has therefore been separated into two tiers.

Tier I is considered the essential core LMP program that will be the initial focus for funding and implementation. It has the following components:

1. Conduct water quality monitoring and utilize computer modeling to increase scientific understanding of water quality trends
2. Conduct a basin-wide nutrient source inventory to set implementation priorities
3. Use Management Action Tables to coordinate implementation of existing programs with LMP partners
4. Develop and implement an education and outreach program to increase the community’s awareness of lake conditions and promote lake stewardship Tier II of the LMP includes: nutrient reduction projects, special studies, and coordination with TMDL program implementation.

Tier II of the LMP includes nutrient reduction projects, special studies, and coordination with TMDL program implementation.