Noront aims to begin production at Eagle’s Nest in 2016 | Courtesy of Noront Resources
The Eagle’s Nest
site, situated in the wetlands of the James Bay Lowlands, first appeared problematic to develop: the lack of exposed bedrock posed obvious
logistical and environmental challenges. Noront’s solution was to develop a subsurface mine plan in which much of the milling facilities would be housed in
a series of underground chambers.
“We have a unique situation,” says Paul Semple, Noront’s COO, “and I think we’ve come up with an innovative solution.” For Eagle’s Nest, the subsurface
mine plan is possible because of the high competency of the subsurface waste rock – a granodiorite – that is much stronger than concrete and can support
large open chambers. The chambers themselves will vary in size, with the largest spanning 16 metres.
The waste rock created by these excavations will be used for roads, concrete and foundations for a base camp.
Producing its own aggregate also allows Noront to control certain logistical and economic risks. “It just made common sense on a lot of fronts,” says CEO
Wes Hanson. “Ultimately, I think it’s going to be a cheaper means of construction.” Making larger underground chambers is much less expensive than
transporting construction materials by plane or winter road; fewer materials are needed, and much of it is already on site.
“The milling equipment is generally anchored to bedrock,” explains Hanson, “so either you’re going to excavate the soft surface material down to bedrock –
between three metres and 20 metres – or drive piles down to bedrock. And that can be a very expensive process. We’ve avoided that whole area of uncertainty
by putting the significant loads underground.” Noront will also save additional operating costs with the underground mill running in a constant temperature
environment. Total mine operating costs over the life of the underground mine will be $1 billion, or $97 per tonne of ore.
A textbook deposit
Eagle’s Nest is set to be one of the world’s lowest cost nickel mines, thanks in large part to the deposit itself, as it is a sulphide, rather than a
laterite, deposit. “The lowest cost producers around the world have been the sulphide miners,” points out Semple. “And I think this is one of the great
undeveloped nickel sulphide deposits anywhere in the world.” Although nickel sulphides account for the majority of nickel mined to date, these reserves are
quickly being depleted. Most new mines around the world are tapping laterites, which, though more abundant, are proving to be challenging to produce nickel
from. “The sulphide technology has been used for a long time,” says Semple. “It has none of the growing pains seen in laterite deposits.”
The shape of the deposit is particularly ideal as well; it is pillar-shaped and nearly vertical, roughly 200 metres long and 60 metres across. “If you were
to give a first-year underground engineering student an assignment to draw a perfect underground mine,” says Hanson, “they’d probably draw something that
looks very much like Eagle’s Nest.” The deposit’s geometry, along with the high competency of the surrounding rock, allow for a straight-forward mine plan
and conventional vertical bulk mining techniques, using blasthole stoping.
“The bigger challenge,” says Hanson, “is arranging the underground chambers so that work in the mine doesn’t impact work in the mill.” The crushing,
grinding and flotation circuits of the milling process must be isolated from the rest of the underground workings.