State Plans Project To Stop Cda River Erosion Carefully Placed Rocks Should Help Protect Shoreline

The first large-scale experiment to stop shoreline erosion on the lower Coeur d’Alene River is expected to begin this fall.

The state project will take place in the five-mile stretch of river between the Cataldo boat ramp and Rose Lake. Carefully placed rocks will be used to break the action of waves caused by power boats.

“It’s not a dike,” project coordinator Marti Calabretta said. “It’s designed so we don’t disturb the existing vegetation.”

The goal is to reduce the amount of nutrients and heavy metals being flushed downstream into Lake Coeur d’Alene. The lead and other metals are contained in mine waste that washed downstream from the Silver Valley.

The work will be administered by the Silver Valley Natural Resources Trustees, at the request of the Coeur d’Alene Basin Commission. It will cost $250,000 to $300,000 during the first year, Calabretta said. The money comes from the state of Idaho and Silver Valley mining companies.

The work is scheduled to take three years, which is the length of the required U.S. Army Corps of Engineers permit.

A public meeting will be conducted in October, Calabretta said. The work must be done in November and December, when the release of water from Post Falls Dam drops the level of the river.

The rocks will be 6 to 12 inches in diameter. They will be laid on a bench that is exposed during the winter drawdown, Calabretta said.

The rock won’t be a hidden hazard to boaters, she said. “In the summer, it will be a foot and a half above water level.”

The work probably will be done from barges to reduce further destruction of the bank, she said.

Erosion is a problem along at least half of that 10 miles of shoreline, Calabretta said.

“Our planning team has identified 15,600 feet of bank where severe erosion can occur. These areas will receive the highest priority.”

This sidebar appeared with the story: THE COSTS The erosion-control work on the lower Coeur d’Alene River will cost $250,000 to $300,000 during the first year. The money comes from the state of Idaho and Silver Valley mining companies.