Road building and drilling could pollute Boise River headwaters

Exploration of the CuMo project would build 10 miles of roads and drill 259 exploration holes on the ridge pictured in the foreground, which is situated at the headwaters of Grimes Creek in the Boise River basin. Photo by Greg Stahl.

On Monday, Oct. 5, the U.S. Forest Service issued a Decision Notice authorizing the next phase of exploration for the CuMo Project in the Grimes Creek watershed in the headwaters of the Boise River. 

The project involves building up to 10.2 miles of roads, clearing trees for up to 137 drill pads and drilling as many as 259 exploration holes. The purpose is to further delineate an ore body that Canadian mining company CuMo Co. hopes to develop into an open-pit copper, molybdenum and silver mine. 

This is the second time the Forest Service has authorized the exploration. In 2012, a federal judge determined that the Forest Service had not adequately considered potential groundwater impacts and instructed the agency to do additional analysis. 

After reviewing the new analysis, local conservation groups representing citizens who live downstream from the project area remain concerned that the approved project is not as protective of water quality as federal law requires. 

While much of the Grimes Creek watershed was damaged by historic dredge mining, the upper stretches support native fish and wildlife.

Idaho Rivers United Boise River campaign coordinator Liz Paul said the Forest Service is putting the Boise River at risk by allowing mineral exploration.

Historic mines in the area have high arsenic levels and concerned conservation groups are concerned that drilling operations could change groundwater flows or contaminate local springs. The groups argue that the Forest Service has not established the necessary baseline studies to see what effect drilling operations may have on water flowing from springs and seeps. 

“The Forest Service is still not doing its due diligence to protect public water supplies in advance of issuing this decision,” said John Robison, public lands director for the Idaho Conservation League. “We are examining our legal options to protect the Boise River headwaters.”