Overview

Deposit type

• Breccia pipe / Stockwork
• Vein / narrow vein
• Epithermal

Summary:

The Premier property is mainly underlain by Jurassic-aged Hazelton Group rocks composed of a thick package of homogeneous andesitic tuffs, lapilli tuffs, and flows interpreted to have formed in an Island Arc setting. Dykes and sills of Premier porphyry (a quartz-K-spar-hornblende porphyry of intermediate composition) are the most abundant intrusive rocks in the area, and are spatially associated with some mineralized zones, particularly at Premier.

Gold–silver mineralization is hosted within structural zones expressed by quartz breccias, quartz veins and stockwork often within large areas of quartz-sericite-pyrite alteration. Elevated gold and silver values are closely associated with silicification and sericitic alteration. Gold occurs predominantly as electrum, with native gold present locally. Silver occurs in its native form, and in electrum, argentite, and freibergite.

The most common sulfides are pyrite, sphalerite with minor galena, and chalcopyrite. The mineral assemblage suggests that the style of mineralization at Premier falls into the intermediate sulfidation epithermal category as neither high sulfidation minerals (such as covellite or enargite) nor low-sulfidation minerals (such as arsenopyrite and pyrrhotite) have been observed.

Mineral deposits in the PGP are intermediate-sulfidation epithermal gold-silver deposits with subsidiary base metals. These deposits form at comparatively shallow depths (generally above 1 km depth), often in association with hot-spring activity on surface. Mineralization results from circulation of aqueous solutions driven by remnant heat from intrusive bodies. Where these ascending fluids encounter meteoric waters, and/or as the hydrostatic pressure drops, changes in temperature and chemistry results in precipitation of minerals into fractures, breccias, and open spaces.

Mineralized bodies are structurally controlled veins, stockworks, and breccia bodies, and are broadly tabular with a wide range of orientations. They measure from centimetre scale to many metres in thickness and can often be traced for strike lengths of several hundred metres or even kilometres. Economic minerals comprise native gold and native silver, electrum, silver sulfosalts, and silver sulfides, along with pyrite, sphalerite, and comparatively minor amounts of chalcopyrite and galena. Gold and silver values are quite variable, and average on the order of 5 g/t to 10 g/t Au and 20 g/t to 30 g/t Ag within the historical stopes.

The geology of the Red Mountain area is characterized by Upper Triassic to Lower Jurassic metasedimentary and tuffitic units that have been intruded by a multi-phase intermediate intrusive complex. The intrusive rocks show porphyry style alteration with K-spar alteration and tourmaline as well as lower temperature quartz-sericite-pyrite alteration. Gold mineralization is hosted in a series of pyrite rich breccia bodies and stockwork zones associated with the brecciated contact zone at the edge of the intrusive body. The alteration associated with the high grade-gold mineralization is characterized by sericite and silicification.

Eocene intrusions of the Coast Plutonic Complex occur to the west and south of Red Mountain and are associated with high-grade silver-lead-zinc occurrences; gold-silver-bismuth ± copper-lead-zinc mineralization recently identified in the Lost Valley area is likely of Eocene age. Recent interpretation is that the gold mineralization at Red Mountain is consistent with an intrusive-related hydrothermal system, rather than a porphyry-gold deposit according to previous interpretation.

Mining Methods

• Transverse stoping
• Longitudinal retreat
• Longhole stoping
• Room-and-pillar
• Cut & Fill

Summary:

Mining methods described herein will be applied at both PGP and RMP. In the case of RMP, the orebody is continuous and sufficiently wide to use a transverse longhole stoping method; whereas at PGP, the ore is along more discrete lenses and tend be narrow, requiring a narrow longitudinal retreat approach to longhole mining. These can be single or multiple sub-levels mined in a block.

The project employed mining methods appropriate to the local conditions at each site, where variations in geotechnical character, grade, ore thickness and ore geometry and inclination were all considered in stope optimization. The target was to develop a coordinated plan to supply 2,500 t/d to the Premier mill, optimizing the production of gold ounces at the lowest operational cost.

The Study’s mine plan generally utilizes a combination of three mining methods: longhole (64%), inclined undercut longhole (14%), and room and pillar (12%), with minor amounts of cut and fill (2%) and development ore (8%) to extract the mineral reserves. A particular mining method was chosen based on an economic assessment of each method for a given geometry and geotechnical characteristics depending on its location in the deposit. The stope shapes and mine access development were individually modelled and evaluated to form the final mineable reserve.

Mining dilution occurs at various rates depending on the mining method and ground conditions based on rock quality in geotechnical domains in the block model. Dilution comes in from a number of sources: planned dilution is material taken within the bounds of a stope layout while unplanned material comes from material outside the stope shape such as the hanging wall and footwall, or minor amounts from backfill.

Dilution generally ranges from 10% to 40%. In some cases where two wireframes are very close together, the waste parting between the wireframes was taken providing it was economically justified. Table 1-4 summarizes the annual production from all areas.

A conventional and common mobile mining fleet is shared between the two sites, to reduce spares and capital expense. Development headings and stope accesses used a common approach with key equipment used during preproduction and operations consisting of 2B jumbos, 10-tonne LHDs, 30-tonne mine haul trucks, bolters, shotcreters and production longhole drills.

Mine services such as dewatering, ventilation and electrical reticulation employed a common approach at each site in a similar manner to mobile equipment to standardize pumps, fans and MCC’s reducing the required spares and capital expenditure. Underground water handling at both sites employs a conventional series of sumps and pumps to move the water out to settling ponds on surface. At PGP water from Silver Coin and Big Missouri have a common pond, which is then directed by pipeline to the water treatment plant at the historical 6 level at Premier mine.

The ventilation systems were designed to meet BC regulations based on the requirements of engines sizes and utilization. Fresh air is heated by a propane system when required during winter months. Workforce will consist of technical staff and operations personnel, consisting of miners, mechanics, electricians, and supervision. At peak production the mine department will have 110 people, with about 40 people active at the site at a given time. In some instances, shared technical resources will be based in Stewart supporting both sites.

Personnel will live in the town of Stewart which is an easy drive from both PGP and RMP. Buses will bring staff and operating people to site, in order to limit the number of personal vehicles on the surrounding roads. Some staff and supervision required to move among sites will drive company supplied pickup trucks.

The principle method of backfilling at PGP and RMP will be with CRF comprised of waste development rock or quarried talus from surface. RF will be used to fill ore voids wherever structural fill is not required.

Backfill Methods
The principle method of backfilling at PGP and RMP will be with CRF comprised of waste development rock or quarried talus from surface. RF will be used to fill ore voids wherever structural fill is not required.

As soon as production begins the waste used to backfill the stopes can be managed underground in the re-muck, which will reduce the transport and storage of waste on the surface. All of the development waste produced at both sites will be used as mine backfill, with any excess deposited in historical open stopes. As such, aside from a temporary waste pile at the start of production, no underground waste will remain on surface.

CRF consists of waste development rock mixed with cement slurry, a cement binder content of 5% was assumed for general cost purposes. CRF would be produced on the site with a Mobile Cemented Rock Fill Plant carried out with a cassette-based carrier.

Comminution

Crushers and Mills

Summary:

Crushing
The crushing facility will consist of a single stage of crushing that will process the ROM ore at a nominal processing rate of 208 t/h and it is expected that the crushing plant will be operated over a 12-hour shift to meet the 2,500 t/d production requirement. The major equipment and facilities at the ROM receiving and crushing areas include:
• Re-furbished static ROM bin grizzly;
• Lined ROM surge bin;
• Reciprocating plate feeder;
• Re-furbished double-toggle primary jaw crusher;
• Mobile rock breaker (FEL attachment);
• Covered coarse ore stockpile;
• Two new stockpile-reclaim apron feeders;
• A single re-furbished re-entry vibrating pan feeder.

Grinding
The grinding mills originally installed in the PGP mill building were purchased and removed by other parties in the early part of the 1990s, yet the existing pedestals and pump boxes remain and are in good condition. To suit this arrangement, the new grinding circuit will consist of a new SAG mill (in open circuit) and a new ball mill (SAB) in a closed circuit with new classifying cyclones.

Both mills will share a variable frequency drive (VFD) controller that can be used to start each mill. The VFD will also be used to adjust the SAG Mill speed to meet the optimum power draw and achieve the preferred grinding conditions for each of the different ores.

The SAG and ball milling (SAB) circuit is designed to deliver a product size P80 of 80 µm for PGP ores and between 80 µm and 90 µm for Red Mountain ores which are more competent. The nominal grinding circuit circulating load ratio for the ball milling circuit is 300%. When the Red Mountain ores are introduced in Q4 Year 2, the ore will be further ground in a fine grinding circuit, which consists of a high speed stirred fine grinding mill to reduce the product to a P80 of 25 µm.

For the initial period of processing PGP ores, the major equipment in the grinding circuit will include:
• One 6.7 m ft diameter by 2.4 m effective grinding length (EGL) single pinion SAG Mill driven by a single 2000 kW low speed synchronous motor;
• One 4.4 m diameter by 6.1 m EGL single pinion ball mill driven by a single 2000 kW low-speed synchronous motor;
• One cyclone cluster consisting of three 380 mm diameter cyclones (2 operating, 1 standby).

Following the introduction of the Red Mountain ore in Q4 Year 2, the following additional processing equipment will be installed and commissioned:
• A single-stirred fine-grinding mill in open circuit to reduce the P80 of Red Mountain ore to 25 µm, driven by a 3,000-kW variable speed drive;
• A 27m diameter high rate pre-leach thickener.

Ore addition to the SAG and Ball mills is supplemented with process water to achieve a milling density of approximately 75% and 64% solids weight by weight (w/w) respectively. The SAG mill discharge will flow through a trommel screen and will discharge into the ball mill cyclone feed pump box where it will be diluted with additional process water and pumped by one of the two cyclone feed pumps up to the cyclone distribution manifold. Steel grinding media will be manually added to the SAG and ball mills using a kibble, which will be positioned by the refurbished bridge crane servicing the mill building.

Processing

• Gravity separation
• Carbon re-activation kiln
• Centrifugal concentrator
• Smelting
• Crush & Screen plant
• Concentrate leach
• Agitated tank (VAT) leaching
• Inline Leach Reactor (ILR)
• Carbon in leach (CIL)
• Elution
• Carbon adsorption-desorption-recovery (ADR)
• Solvent Extraction & Electrowinning
• Filter press
• Cyanide (reagent)

Summary:

The Premier mill facility plans for re-starting will feature a combination of upgrades and returning the existing facilities to an operating condition.

A nominal plant treatment rate of 2,500 t/d has been selected as the basis to recover gold and silver at the Premier Gold Project (PGP) Mill site. The plant will operate 365 d/a to produce gold and silver doré with an overall plant availability of 92%.

It is expected that ore will be fed from either one of the PGP or one of the RMP deposits using a method of campaigning as each ore will require subtle adaptations to the processing method and its control. In the initial period after the mine restart, only PGP ore will be fed for approximately the first two years, after which, equal quantities of PGP or RMP ore will be campaigned for the remaining life-of-mine (LOM).

The plant feed will be stored on stockpiles prior to the primary crusher system which will allow for campaigning the ore on a bi-weekly basis. The feed to the plant will be reclaimed from either the PGP or RMP run-of-mine (ROM) stockpiles, and will be introduced to the ROM dump hopper via a haul truck or front-end-loader (FEL) and fed via a reciprocating plate feeder into a jaw crusher for initial size reduction. The primary sized crushed ore will be conveyed and stored in a coarse ore stockpile (COS), the stockpile is sized for approximately one day of capacity. Feed to the mill will be reclaimed by apron feeders, then conveyed to the semi-autogenous grinding (SAG) and ball mills, the latter of which will be operated in a closed circuit with hydrocyclones. While processing the PGP ores, a portion of the ball mill discharge will be pumped to a centrifugal gravity concentrator and the resulting gravity concentrate will discharge into an intensive leach reactor (ILR) for precious metals recovery. The Red Mountain ore types have very low amounts of gravity recoverable gold (GRG) and the gravity recovery circuit will be by-passed during the Red Mountain campaigns. The hydrocyclone overflow with P80 of 80 µm will flow into a carbon-in-leach (CIL) circuit for the PGP ores, or will report to a fine grinding mill for further size reduction (to 25 µm) for Red Mountain ores, which then reports to pre-leach thickening and then the CIL circuit.

Gold and silver leached in the CIL circuit is recovered on carbon and eluted in a pressure Zadra-style elution circuit, then electrowon in the gold room to form a precious metal sludge (gold/silver mixture). For PGP ores, an additional electrowinning cell is used to recover gold from the intensive leach solution. Precious metal sludge is then dried in an oven prior to being mixed with fluxes and smelted in a refining furnace to pour doré bars. Carbon is re-activated in a carbon regeneration kiln before being returned to the CIL circuit.

The updated process plant flowsheet consists of the following unit operations:
• ROM ore management
- PGP ore and RMP ore stockpiles to be used to manage feed into the process plant
• Coarse ore management
- A primary crushing system that sizes the ore and stockpiles the ore onto a coarse ore stockpile system; the primary crusher is in a standalone building complete with dust collection equipment
- A semi covered coarse ore stockpile that places ore directly over the mill feed system reclaim tunnel
- A coarse ore mill feed system that consists of a reclaim tunnel containing two variable rate apron feeders, and a third feed point using a vibrating feeder that can accommodate a front-end loader for returned materials
• Grinding and classification, consisting of a SAG and Ball Mill with hydrocyclones
• Gravity concentration and intensive leaching
• CIL
• Carbon management including carbon regeneration
• Gold room
• Tailings detoxification and deposition.

Gravity Concentration and Intensive Leaching
The centrifugal concentrator is a semi-continuous process and as such, feed is continuously fed for a specified period, then paused to allow the concentrate to be flushed from the concentrator bowl into the new downstream ILR. The combined gravity concentrator tailings and scalping screen oversize streams are pumped via a pumpbox back to the ball mill cyclone feed-pump box. The cycle times are designed to be 45 minutes each and approximately 20 kg to 25 kg of concentrate is expected from each cycle.

As concentrate is accumulated in the ILR feed hopper, excess water from the concentrator flush cycle will be decanted. Once per day, the accumulated concentrate will flow into the ILR where it is dosed with sodium hydroxide and sodium cyanide to leach the gold. Once the leaching process is complete, the pregnant leach solution is separated from the solids, aided by flocculant, and is then subsequently pumped to the gravity electrolyte tank adjacent to the gold room.

Carbon-in-Leach
The passivated slurry overflows the preaeration tank into the first CIL tank where it is further adjusted with lime to meet the target pH of 10-11. Fresh sodium cyanide is also introduced at this point of the process.

Leached gold and silver are adsorbed onto the granular carbon which is present in all seven of the agitated CIL tanks. Fresh and barren carbon is added to the last CIL tank and travels up through the circuit in the opposite direction to the slurry flow (counter-current). Carbon is advanced once per day with carbon transfer pumps which pump loaded carbon to the next tank in the train. Carbon is retained in the tanks after the transfer with inter-stage flat-panel screens located in the overflow launder to allow slurry to pass through, but not carbon.

Acid Wash, Desorption, and Refining (ADR) Circuits
Gold will be recovered from loaded carbon by a modified Zadra style elution circuit. The anticipated batch size is 8 tonnes of carbon per cycle. For PGP ores, a single strip will be conducted once per day using only one elution column per day, whereas for the Red Mountain ores, the strip rate will be 1.5 times per day, utilizing both of the existing elution columns.

The strip cycle will involve making up a strip solution of cyanide and sodium hydroxide in the eluate tank and preheating that via an elution heater system which includes a direct-fired solution heater and primary recovery heat exchangers. Once heated, the solution will be circulated through the carbon bed in the elution column, and back to the eluate tank until it is ready for electrowinning to begin.

Once the pregnant eluate is sufficiently heated and loaded, it will begin transferring to the new electrowinning tank rather than back to the strip solution tank. The electrowinning feed pumps will transfer heated pregnant solution through the electrowinning cells which will then gravity flow back to the eluate tank to be recirculated through the elution and heater circuit.

The barren carbon from the stripping circuit will be transferred to the kiln dewatering screen and the overflow carbon from the screen will be regenerated in the horizontal kiln.

The gold room will contain all the sludge filtering, drying, and smelting equipment. The gravity electrowinning and elution electrowinning tanks will have immersion heaters to keep the solution hot, which will then be pumped in closed circuit with the electrowinning cells. Once the electrowinning cycle is complete, the barren solution can be re-routed to send the barren eluate to the electrowinning barren tank.

Gold sludge recovered from electrowinning will be washed inside the electrowinning cells and then flow via gravity to the sludge filter feed tank, which will batch filter the sludge via a plate and frame filter. Filtered gold sludge will be further dewatered in the drying oven and then finally smelted with flux to produce gold doré.

Water Supply

Summary:

Fresh water will be pumped from the Cascade Creek abstraction point to the fresh water tank. Fresh water in the tank is used to supply the following services:
• Fire water
• Gland seal water
• Potable water
• Reagent mixing
• Make-up water for the process water system.

Fresh water is supplied to the plant by two fresh water pumps in a duty-standby configuration.

Potable Water
Potable water will be sourced from the fresh water tank and treated in a treatment plant. The treated water is stored in the potable water storage tank for use by two potable-water pumps in a duty–standby configuration.

Gland Water
The process plant gland water is supplied from the gland-water tank which has water supplied from the fresh-water system and distributed to the plant by two gland-water pumps in a duty–standby configuration.

Process Water
The process water consists mainly of tailings pond reclaim water. The process water is stored in the process-water storage tank and distributed by the two process water pumps, in a duty–standby configuration.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Consultant - Infrastructure	Frank Grills		Apr 15, 2020
Consultant - Mining & Costs	Frank Palkovits		Apr 15, 2020
Consultant - Recovery Methods & Costs	Aleksandar Petrovic		Apr 15, 2020
Mill Manager	Paul Laframboise		Nov 28, 2024
Operations Manager	Gerry Gagnon		Nov 28, 2024
VP Operations & General Manager	Bryant Schwengler		Nov 28, 2024
VP, Project Development	Matthew Kebe		Nov 28, 2024