Highland Copper Company has announced positive results of a feasibility study for its 100%-owned Copperwood project located in Gogebic County, in the Western Upper Peninsula of Michigan, US.
The Feasibility Study was conducted by, and under the supervision of, G Mining Services Inc (GMSI) in collaboration with SGS Canada Inc (Lakefield), Lycopodium Minerals Canada Ltd, Golder Associates and Foth Infrastructure and Environment. The study provides a comprehensive overview of the Copperwood Project and defines an economically feasible, technically and environmentally sound project.
Highlights:
– Initial capital expenditures of $245 million, net of pre-production revenue of $30 million
– Life-of-mine (“LOM”) cash costs of $1.53/lb, including royalties and $1.29/lb in the first five years of production
– Proven and Probable Reserves of 25.4 Mt @ 1.43% Cu and 3.83 g/t Ag, containing 801.8 Mlbs of copper and 3.1 Moz of silver
– Additional Mineral Resources of 49.9 My @ 1.15 % Cu and 3.42 g/t Ag in the Inferred category, containing 1.3 Blbs of copper and 5.5 Moz of silver using a 1% Cu cut-off
– Average annual LOM payable copper production of 61.7 M lbs and 100,570 oz of silver
– Initial copper production expected in early 2021
Highland and its consultants have identified a number of opportunities to increase the value of the Copperwood Project. These include upgrading inferred mineral resources, increasing mine productivity utilising innovative continuous mining technologies, conducting further geotechnical studies to optimise ore recovery and minimise mining dilution, reviewing tailings disposal alternatives, and conducting additional testing to maximise metallurgical recoveries.
It is proposed to mine the deposit with a conventional highly mechanised, drill and blast room-and- pillar mining method. The method consists of the extraction of a series of entries and cross-cuts in the ore, leaving pillars in place to support the back. The entries, cross cuts and pillars have been sized using geotechnical analysis of the local host rocks, and experience from other mines sharing similar ground conditions.
The mine will be accessed via covered box-cut to establish a portal at the mine entrance from the surface, located at the central-west part of the deposit. The mine consists of two mining sectors: West and East. The western part, being higher grade with a thicker mineralised zone, will be mined in priority.
The mine is split into panels, which consist of at least 12 rooms that provide multiple headings where all activities of the mining cycle can be done in parallel to achieve high productivities, as opposed to activities in series as is the case in a single heading. The mining cycle consists of drilling, explosives loading and blasting, mucking, scaling and bolting.
Mining operations are planned with two 10-hour shifts per day, 360 days per year to achieve a production target of 2.4 Mt per year, or 6,600 t per day. To achieve this production, a total of 7 to 9 panels must be in production at any given time.
The mining operation begins with drilling of the working face, which is accomplished with two- boom hydraulic-electric jumbo drills. Each round is drilled 4.25 m (14 ft) in length with an effective break of 4.00 m. The rooms are 6.1 m wide with a height that varies according to the ore column thickness. The height dimension dictates the productivity, which varies from panel to panel.
Mucking will be done with 10 t LHD units that will load muck at the mine face and transport it to the conveyor loading point established for the production panel. The LHD performance will be a function of dip of the stope and distance. The conveyor loading points will be regularly moved as production advances in the panel to be less than 250 m from the headings.
Scaling of the rooms is planned with a smaller low-profile LHD unit equipped with a scaling arm that rubs the roof to remove any loose rocks.
Bolting will be done by a mechanised bolter to install roof support and wall bolts. In the stopes, 1.8 m rebar bolts are required on a 1.2 m by 1.2 m pattern with wire mesh. In addition, 1.8 m friction bolts are planned in the pillars (i.e. walls) on a 1.5 m by 1.5 m pattern with wire mesh. At room intersection rebar bolt length is increased to 2.4 m.
Highland continues to study the use of tailings as back-fill in the open stopes. If this approach is selected, it would provide cost savings for tailing disposal and closure costs.
Ventilation for the mine will be provided by a 400 m3/s fresh air raise and two exhaust raises at the eastern and western end of the mine. The dewatering system will consist of six pumping stations capable of evacuating 2,220 l/min of underground water inflow and mine water.