The Bul River deposit has been described as a Churchill-type vein copper-silver deposit (Lefebure, 1996). The deposit type displays characteristics of relatively low tonnage (typically range from 10Kt to 1Mt) but high grade (typically range from 1% to 4% Cu). Frequently occurring in Proterozoic-age extensional sedimentary basins, Churchill-type deposits are associated with rifting can comprise single vein to complicated vein systems that vary from centimetres to tens of metres in width, and can extend hundreds of metres along strike and down dip. Commonly hosted in clastic meta-sediments, veins and vein systems are often spatially associated with mafic dykes and sills. The veins are generally associated with major faults related to crustal extension that controls the ascent of hydrothermal fluids to favorable sites for metal deposition. Fluids are believed to be derived from those mafic intrusives that are associated with the vein systems. (Snowden 2013).

Mineralization in Churchill-type deposits is predominantly chalcopyrite, pyrite, and chalcocite with subordinate pyrrhotite, galena, bornite, tetrahedrite, argentite, and covellite and is generally younger than the host lithology.

The GBRM deposit is hosted within poorly exposed graded turbidite beds of the middle Aldridge Formation of the Middle Proterozoic Purcell Supergroup. Interbedded quartzites, siltstones, and argillites make up a turbidite sequence whose bedding plane strikes approximately east-west and dips 20° to 30° to the north (Baldys, 2001). The host rocks of the deposit are a northward pinching series of anticlines and synclines (de Souza, 2000).

The GBRM mineralized zones comprise a vertical to sub-vertical network of sulphide-bearing quartz carbonate veins striking approximately east-west hosted in sheared and brecciated Aldridge Formation sediments. Mineralization consists of pyrite, pyrrhotite, and chalcopyrite with minor local galena, sphalerite, arsenopyrite, and cobaltite and traces of tetrahedrite and native gold. Sulphides range from massive, irregular bodies within the vein system to thin discontinuous veins, veinlets, and disseminations in the host rock (Höy et al., 2000). Gangue mineralogy of the veins is variable, with the eastern parts of the deposit consisting of quartz and siderite. The western part of the vein system is dominated by siderite (Baldys, 2001).

A main access ramps and seven levels of development, including vent raises and an escape route, are in place and in operational condition. There are also numerous mill feed access cross-cuts and sill drifts in areas where future mining is planned. The main access ramp is 2555 meters long and there is an additional 14,050 meters of level development.

The base case production plan is based on a mill feed rate of 700tonnes per day (tpd). The mine design can support this production using a longitudinal long-hole open stoping mining method and multiple production headings. Remote scoop-trams will be used for mucking the mill feed from the extraction drifts of each level to a re-muck bay where the mill feed will then be loaded into trucks for haulage up the main access ramp to surface.

Fans will provide ventilation by forcing air down the escape way, through the internal raises to the operating areas, and exhausting via the access ramp to surface. The ventilation raises will double as secondary means of egress.

The mine will operate for a total of six and a half years; an existing stockpile of mill feed will feed the process plant for the first ten months, followed by production from the restart of underground mining operations.

Geotechnical and rock mechanic studies are required for any higher level studies on the property. The potential use of cemented tailings for backfill will also require technical studies.

Cut and fill mining methods should be examined for areas of the mine where LLHOS mining method is not applicable. This could increase the mining recovery.

Underground waste development will be backfilled into old development or stopes as required. The total waste development required is 3,338 metres.

Cemented tailings will be used for backfilling. Year 1 and 2 tailings will be temporarily stored on surface until the mining sequence has opened up enough room for cemented tailings to be stored underground. After construction of the cemented backfill plant, cemented tails will be stored underground and the tailings temporarily stored on surface will be processed and also stored underground. At this time the cemented tailings parameters are assumed with typical values. Detailed testing will be required during future studies.

ROM mill feed is dumped onto a fixed grizzly with 22” openings. Grizzly undersize reports to a 65t coarse mill feed bin. Coarse mill feed is fed to the primary crusher by a 48” wide and 10’ long hydrastroke feeder.

The primary crusher is a 25 x 40D Telsmith jaw crusher operated at a setting of 4 inches. Crushed mill feed, with a work index of 15, passes through a 5’x 10’ Nordberg screen with a 3/8” aperture before reporting to the fine mill feed bin with a capacity of 3100ST. The screen oversize is fed to a 5 1/2 ‘Symons Cone Crusher operated at 5/16” setting. Cone crusher discharge is fed back to the screen.

Dust control in the crusher building is accomplished with American air filter type “R” Roto-Clone exhausting at 17,000cfm.

The current crushing circuit design is able to process mill feed at a significantly higher rate than the mill. This allowed the crushing plant to operate on weekday dayshifts during previous operations. There may be an opportunity to reduce the crusher product feed size reporting to the mill and thereby increase the mill throughput.

Fine mill feed is milled in closed circuit with a 10’x14’ Ball Mill and cyclone. The Ball Mill is driven by a 700HP (522kW) motor connected to the pinion gear with an air clutch control system.

Mill discharge at 78% solids is pumped to cyclones at 6psi. Cyclone overflow containing 40% solids at 65% minus 200 Mesh (75 micron) is fed to the floatation conditioning tank. Cyclone underflow reports back to mill feed.

Dust is collected in the mill building by a Medusa scrubber MR-30 exhausting 300 CFM of air.

Feed to the flotation plant is conditioned for ten minutes in a Denver 8’ x 8’ super agitator at 40% solids.

The flotation circuit included rougher, scavenger, and cleaner flotation. Scavenger concentrate and Cleaner tails are pumped to a 5’x 8’ regrind ball mill.

Rougher and scavenger flotation is carried out in No. 60 Agitair flotation machines at 27% solids. Air is supplied to the flotation machines by a Canadian Forge blower. There are four Rougher and six Scavenger cells. Concentrate from the first two scavenger cells is routed to the rougher concentrate.

The cleaner circuit consisted of ten No. 21 Denver Sub A flotation machines. Launders and piping is arranged for three-stage cleaning.

Cleaner concentrate is pumped to a 30’ thickener at 17% solids. Thickener underflow is pumped to a Door disc filter at 55% solids.

Concentrate from the filter is stored in a 1500t storage bin with moisture levels ranging from 8.8 to 12.6%.

Tailings from the scavenger cells is pumped to tailings management facilities.