The Idaho Conservation League opposes a plan by Midas Gold Corp. to build a 500-foot-tall dam and divert water from the East Fork of the South Fork of the Salmon River if gold mining ever starts east of McCall.
The dam would store tailings from mining behind it, while the East Fork would be diverted into a pipe to allow excavation of the river bed, according to a preliminary plan posted by the company.
"It's a nonstarter," says John Robison, the Idaho Conservation League's public lands director.
The plans for the dam and diversion are preliminary and have not yet been proposed to the Payette National Forest, says Midas Gold Vice President Anne LaBelle.
The Canadian company outlined a possibility of a tailings dam at its Golden Meadows Project in a preliminary economic assessment prepared for investors. Midas has not proposed the plan to the U.S. Forest Service, which controls the mine site near Yellow Pine in Valley County.
"It's a first-pass look into whether we can mine the area economically," LaBelle says. "It is an investment tool."
PLAN COULD CHANGE
Last fall, the Idaho Conservation League successfully appealed the Payette National Forest's approval for Midas Gold to expand its exploration for gold and other metals at the historic Stibnite mining district. Midas has filed a new drilling plan, and the public has until May 17 to comment on it.
The dam would be made with excavated waste rock and a synthetic liner. Some tailings would be mixed with water to create a slurry that would be piped to the reservoir behind the dam.
Robison says a tailings plan is necessary. "If you're going to dig a bunch of holes, you have to have some place to put the rock or dirt," he says.
But he prefers a plan that reduces the risk that heavy metals could be released into surface water.
"We're more comfortable with dry stacking the tailings, the concept of putting it up away from habitat and the river," Robison says.
The plans described in the assessment are just one option, says John Meyer, vice president of development for Midas.
PIPE WOULD CARRY SLURRY OF TAILINGS
Midas would divert the East Fork through a 10-foot-wide tunnel about 4,200 feet long along the east side of the pit. During mining, tailings from the processing plant would be treated and thickened into a slurry. They would be moved through a pipeline to a storage facility southwest of the old tailings in the upper Meadow Creek valley.
The pipe would have containment around it in the event of a spill. The slurry would go into a synthetically lined reservoir.
Excess water in the holding area would be pumped back to the processing plant for re-use. Once processing was stopped, the excess water from the tailings would be evaporated or treated to discharge standards.
The facility would then be capped by rock and soil, then replanted. Meadow Creek would be restored to pre-mining conditions, the proposal says.
"We've been telling Midas that currently, the footprint is too big and the location of the tailings repository is a great bit of concern to us," Robison says. "Rescaling it so it's much smaller means a smaller disturbance and smaller amounts of waste rock and tailings to deal with."
LaBelle says comments from the community and conservation groups will be used for future analysis. Drilling and studies could take up to two years, LaBelle says. If an extraction plan is proposed, an environmental study by the Payette National Forest could take three to five years, she says.
REQUEST FOR WATER CHALLENGED
Separately, the Idaho Conservation League and the Nez Perce Tribe have filed protests to Midas' applications for water rights.
"We are concerned that Midas Gold's water use will reduce critical stream flows and concentrate pollutants in an area that serves as important habitat for Chinook salmon, steelhead and bull trout," Robison says.
LaBelle callsthe protests "good and necessary."
"That's their job, and that's fine," she says. "The protests do not affect our ability to continue exploration work."
The protests claim there is potential for groundwater to contain heavy metals and other contaminants from past mining. The most recent mining from the 1980s used a cyanide heap-leaching process to recover gold from low-grade ore.
The U.S. Environmental Protection Agency has documented antimony, arsenic, mercury, lead and other materials in the Stibnite area, the protests say.