“Not only is it flat, but the major characteristic of the terrain is that it’s also very wet,” said Pearson. “ If you go to the Ring of Fire and look for rocks, I understand there are exactly two outcrops in an area of 20 square kilometres. What you see when you get there is water and peat-saturated wetlands – the third largest wetlands on the planet. This is difficult terrain to even begin to think about how to securely impound tailings.”
Planning for tailings disposal in the Ring of Fire needs to account for the slow dispersal of water that will drain off any surface tailings, as well as the cumulative effects of dispersal in an environment that Pearson describes as a wetlands saturated sponge.
Another concern is that the duration of the ice cover season on Hudson Bay is decreasing by about one day per year, reducing the cooling capability of the refrigerator that has kept Ontario’s Far North cool until now, he said.
By the middle of the century, temperatures in the Hudson Bay Lowlands are projected to be five to seven degrees warmer, and will have as much of an effect on the landscape of the Hudson Bay Lowlands as the warming since the last Ice Age, said Pearson.
“These are very, very large temperature increases – some of the largest projected anywhere on the planet for the middle of the century, and it’s only 40 years away.”
The open pit chromite mine that Cliffs Natural Resources is planning to develop will have a 100-year mine life, “so halfway through the life of the mine, the climate they are working in will change significantly,” said Pearson. “This will certainly affect the security and stability of the tailings disposed of, particularly from the sulphide mines and the waste rock from the chromite mine.”
In addition to higher temperatures, we can also expect more precipitation, he warned.
Another issue to consider is the melting of the permafrost in the Far North.
“The permafrost acts like a layer of cellophane over the top of the ground in which organic peat is slowly decaying,” said Pearson. “It acts as a cap on the potential release of the methane gas produced by that slow decay. The methane gas is a greenhouse gas and as the ice melts, one of the results we can expect and should be concerned about is the release of methane into the atmosphere.”
Tailings management presents enough of a challenge for mining companies operating at much lower latitudes and in much more benign environments, he said. In Elliot Lake, for example, uranium mine operators had to conform to a 10,000-year security requirement for radioactive tailings, while in Sudbury and other locations in Northern Ontario, mining companies have to contend with the risk of acid mine drainage from sulphide ores.
“Tailings are a real challenge,” said Pearson. “They’re sensitive chemically and they’re sensitive physically. They’re fine-grained, they’re easily eroded and they’re easily wind-blown as well. We have 50 years of experience and research with the stabilization of tailings in our own backyard (Sudbury) on very easy terrain – orders of magnitude easier than managing tailings in the Far North.”
Pearson didn’t propose any solutions for tailings disposal in the Hudson Bay Lowlands, but noted that Noront Resources has undertaken to dispose of its tailings underground, and warned that rather than contemplate surface tailings disposal in the Far North, mining companies may have to think about transporting them out of the region.
“If you’re going to build a railroad to bring out the valuable part, maybe you need to face the fact that you can’t leave the tailings there either,” he said.