If CuMo Mining Corp. has its way the headwaters of the Boise River will be transformed by one of the largest open-pit mines on the planet. Since about 2010 CuMo has been working to explore molybdenum, copper and silver deposits at the headwaters of Grimes Creek, a key tributary of the Boise River. 

By 2017 a federal judge had twice remanded exploration proposals to the U.S. Forest Service for further analysis of potential impacts to water quality and a rare endemic plant not found outside the Boise basin. By early 2018 the Forest Service was initiating yet another round of public comment following forest fires in and near the mine site. The bottom line is that the mine is very much still a possibility and would post serious threats to the Boise River.

The people and economy of the Treasure Valley depend on the clean water that comes from the Boise River and its tributaries. 

  • More than 22 percent of Boise's drinking water comes from the Boise River and a third of Idaho's population lives downstream from the proposed mine. 
  • In addition, air and noise pollution from the mine will enter nearby towns and wilderness areas.


In May, 2011, after receiving more than 500 comments from concerned citizens, the U.S. Forest Service released the Final Environmental Assesment for CuMo Exploration Project and issued a Finding of No Significant Impact. 

The decision reached by Forest Supervisor Cecelia Seesholtz permits a Canadian mining company, Mosquito Gold Company, to conduct a five-year mineral exploration project, including the construction of up to 10.2 miles of new temporary roads and four new stream crossings.

In July, 2011, Idaho Rivers United, along with the Idaho Conservation League and Golden Eagle Audubon Society, filed a complaint challenging the Forest Service's approval of the CuMo Exploration Project. Advocates for the West represented our claim that the Forest Service had not evaluated what impact the extensive road construction and round-the-clock drilling activities will have on groundwater and on sensitive species in the project area, including wolverines, northern goshawks, and great grey owls. 

On August 29, 2012, U.S. District Judge Edward J. Lodge found that the U.S. Forest Service’s actions were “arbitrary and capricious” when it approved the CuMo Exploration Project without examining potential effects to groundwater. He remanded the agency’s environmental document for further study and consideration.

The CuMo project is proposed for a forested ridge on the south side of Grimes Creek upstream of Pioneerville and Idaho City, only 38 miles from Boise. While the project is in the Boise River watershed, it's just a stone's throw from Garden Valley and the South Fork of the Payette River. Conceptual drawings of the CuMo molybdenum and copper mine show a massive open pit and complete removal of the ridge.