The Nordmin Group of Companies has put forward the idea of using artificial ground freezing technology at NioCorp’s Elk Creek critical minerals project in Nebraska, US, as part of a plan to accelerate the sinking of the production and ventilation shafts for the underground mine.
Nordmin said use of this technology was “technically feasible” and could assist in controlling the inflow of water encountered during shaft sinking operations, according to NioCorp.
“The technology may also improve productivity during shaft sinking operations, and eliminate the need for substantial dewatering operations prior to the onset of shaft sinking,” NioCorp added.
Elk Creek is currently envisaged as a 2,760 t/d underground mine using long-hole open stoping with backfilling. The mine is expected to cost close to $1 billion to build and produce 7,055 t/y of ferroniobium, 103 t/y of scandium oxide and 11,445 t/y of titanium dioxide over a 32-year life.
This is based on a probable reserve base of 31.7 million tonnes at 0.79% Nb2O5, 71.6 g/t Sc and 2.81% TiO2.
In addition to putting forward the alternative ground freezing technology option, Nordmin also confirmed bedrock water encountered during mining operations could be handled without the 53 km waterline to the Missouri River included in the revised feasibility study from last year.
This could significantly reduce the time required for permitting the mine, NioCorp said.
“Removing the project’s plans for a waterline to the Missouri River eliminates the project’s need for an additional Section 404 permit from the US Army Corps of Engineers,” the company said.
This permit would have triggered the need for an environmental assessment under the National Environmental Policy Act, a process that can take months or more to complete, according to NioCorp.
The waterline removal also eliminates the need for Elk Creek to secure a National Pollutant Discharge Elimination Permit from the Nebraska Department of Environmental Quality.
NioCorp CEO and Executive Chairman Mark Smith said he was particularly pleased that “Nordmin clearly focused its efforts on proposing a mine design that maximises value and minimises environmental impacts”.
While the total upfront capital cost of the waterline and mine dewatering infrastructure, including contingencies, added up to $127.1 million in the latest feasibility study, NioCorp said investors could not simply subtract this amount from the upfront cost.
“A variety of factors beyond underground mining operations may impact the overall economics of the Elk Creek project and these factors may involve higher or lower upfront capex than was previously estimated in the 2017 revised Elk Creek feasibility study,” NioCorp said.
Chief among these is the additional incremental project capital needed for the artificial ground freezing technology not previously included.
NioCorp said its immediate plans involve fully evaluation Nordmin’s designs for the underground mine and initiating detailed engineering for the surface portions of the project as funds become available.
Late last year, the Nebraska government granted conditional approval for a major tax incentives package for Elk Creek.