The Yukon highways department says it's confident using waste rock from a mine in construction projects is safe.
Earlier this week, New Democrat MLA Jim Tredger questioned the use of waste rock from the Minto Mine for bridge and road repair at Tatchun Creek.
“Tatchun Creek is a salmon bearing creek and the waste rock is from a copper mine. Research has shown that salmon do not return to waters where there are copper traces as little as 10 parts per billion,” he said.
Tredger asked Mines minister, Scott Kent, if there had been a permitting process to ensure the rock won't pollute the creek.
At the time, Kent hadn’t heard of the matter.
Now the highways department confirms that waste rock is being used to prevent erosion at Tatchun Creek.
Spokesperson Kendra Black says testing has been done by both the government and the contractor, and the rock is safe.
But Lewis Rifkind with the Yukon Conservation Society says copper and other metals could be leaching into the salmon-bearing creek.
“We're very uncomfortable with the idea of using waste rock from a mine site,” Rifkind says. “If there is a problem and it can sometimes take a few years for these problems to develop as the rock is exposed to air and water, over time metals and chemicals and minerals can leach out of the rock and cause all sorts of environmental problems.”
He also questions how the department can be sure the rock is safe.
“You get a whole mix-match of where the rock is coming from, so you could get what is termed hot spots of contaminated rock within a waste rock pile, and how often do you have to test and how is the sampling regime done on the waste rock to ensure you aren't picking up any contaminated hot spots?”
Rifkind says it makes sense to leave waste rock at the mine site where it's contained and monitored.
The highways department says there is no reason to be concerned.
They say the rock poses no danger to the environment.