Overview

Deposit type

• Sedimentary

Summary:

Stratigraphy in the area of the property was subject to extensive folding and faulting during the Late Cretaceous Laramide Orogeny. The major thrust faults that developed are the Ptolemy Thrust, Tent Thrust, Boulton Thrust and Crowsnest Thrust; these thrusts all generally dip to the west. Associated with these major thrust faults are major fold axial surfaces, which also generally dip to the west. The folds range from broad-upright to overturned-concentric, and they have been cut and repeated by thrust faults, tear faults, and late extensional faults. This major faulting and folding affected the coal seam thickness, lateral continuity, geometry and quality.

Although extensive deformation of coal-bearing strata has enhanced the economic potential of the region, it has also complicated mining and exploration. Bedding slip surfaces, joints and cleats, and extension, contraction and wrench faults have been recognised as the fundamental fabric elements within many of the major coal beds of the Kootenay Group (Norris, 1971). Notably, in other areas, shearing of coals has resulted in increased ash yields, locally promoted in situ oxidation and unpredictable roof conditions, making underground mining difficult.

The Tent Mountain property is dominantly comprised of strata from the Jurassic Fernie Group and Late Jurassic to Early Cretaceous Kootenay Group. On the property, the Mist Mountain Formation contains potentially economic coal. No intrusions have been mapped or interpolated to occur within the project area. In the south area of the property, the Ptolemy and Tent thrusts converge leaving only the Fernie Group, Moose Mountain Member and the lower part of the Adanac Member (including seam S2) strata in the Ptolemy Thrust Sheet.

All three members of the Mist Mountain Formation have been identified on the property: the Mutz, Hillcrest and Adanac. The Mutz Member comprises up to 90 m of fluvial siltstone with minor interbedded claystone and coaly partings. Coal seams S5, S6 and S7, as well as a minor coal seam between S5 and S6, occur in the Mutz Member. The Hillcrest Member is ridge-forming and lies conformably below the Mutz Member. It consists is up to 30 m of fluvial channel sandstone deposits with interbedded siltstone and claystone. The Hillcrest Member contains no major coal seams. The Adanac Member is recessive and lies conformably below the Hillcrest Member. It forms the base of the Mist Mountain Formation and consists of shale, siltstone and fine-grained sandstone. Coal seams S2 and S4 occur consistently, while coal seam S3 occurs intermittently in the Adanac Member on the property.

On the property, the complex interplay of thrusting, folding and high relief topography controls the distribution of coal seams and their associated sub-crops, as well as coal seam thickness. Generally, the Tent Mountain coal resources occur in a north-south direction along the strike of the western side of Ptolemy Fault, and in the synclines and anticlines between the Boulton, Tent and Ptolemy faults. Seams may be thickened by either faulting or folding, or they can be thickened by both mechanisms. Such an example is along the south wall of Pit 4, where seam S6 has been thickened along the axis of the Tent Anticline and subsequently thickened further by the Tent Thrust Fault (Wrightson, 1982).

The principal coal seams on the property, in descending topographic order, are seams S7, S6, S5, S4, S3 and S2. Each seam comprises multiple coal, dirty coal and parting horizons. Seams S6, S5, and S4 are currently divided into three plies, and seams S3 and S2 are currently divided into two plies. Though the coal and sediment intervals appear to be complexly interbedded and interfingered, the seam packages have distinct geophysical signatures that can generally be identified along the currently known strike length of the deposit.

Seam S2, the lowest seam in the sequence lies at the base of the Adanac Member. The seam is divided into two plies, S2L which averages 2.20 m thick and S2U with averages 2.83 m thick, exclusive on non coal partings.

Seam S3 consists of an intermittent shaley coal and coal interval that lies in the middle of the Adanac Member, approximately 90 m above S2U. The seam is divided into two plies, S3L and S3U, averaging 1.18 m and 1.15 m thick, respectively. Due to the intermittent nature of the coal seam, previous geological models for the property did not include this marker seam; however, due to the additional data available to Dahrouge, it was incorporated into the current geological model. Historic work mixed intersections of S3 with intersections of S2, resulting in zones where S2 was projected closer to surface than the geology supported.

Seam S4 lies at the top of the Adanac member and is divided into three plies: S4L averaging 1.65 m thick, S4M averaging 2.34 m thick and S4U averaging 2.10 m thick.

Seam S5 is the lowest seam of the Mutz member and is divided into three plies: S5L averaging 4.26 m, S5M averaging 3.33 m and S5U averaging 2.99 m. The S5 seam is persistent and well developed on the property.

Seam S6 is the middle seam of the Mutz member, and is divided into three plies: S6L averaging 2.01 m, S6M averaging 2.58 m and S6U averaging 2.43 m. The S6 seam is a persistent and well-developed seam on the Property. Previous studies modelled S6 as one distinct geological unit; however, the additional data available to Dahrouge allowed the seam to be split into plies.

Seam S7 is the uppermost seam of the Mutz Member found on the property. The Seam is more variable than seams S5 and S6, and averages 1.96 m thick. Available data and coal intersections for seam S7 is limited; therefore, it has not been divided into plies and has been modelled as one geological unit.

Mining Methods

• Truck & Shovel / Loader

Summary:

Tent Mountain will be developed as a conventional open pit, truck-and-shovel operation as a result of the deposit’s topography, and coal seam thickness and geometry.

The ultimate pit limits are divided into a series of pit phase designs, which are designed to exploit high value, low strip ratio areas of the deposit early in the schedule while also incorporating the project’s water management plans and water storage requirements throughout the mine life.

The pit slopes were designed according to the geotechnical design criteria where single or double benching was appropriate, stack heights and geotechnical berms to decouple the pit walls, and footwall slope height requirements.

Pit design parameters:
- Bench Height - 12 m;
- Benches Between Berms - Double and single;
- Two-way Ramp Width - 24 m;
- One-way Ramp Width - 18 m;
- Design Ramp Gradient - 10%;
- Minimum Mining Width - 80 m;
- Maximum Stack Height - 120m;
- Geotechnical Berm Width - 20 m.

Pit phases were determined by location, topography, strip ratio, coal release and backfill strategy. Two zones of the deposit were identified as peripheral to the main syncline coal zone, the Upper East Flank (UEF) and the Boulton pit. The Boulton pit is located north of the historic “Pit 4” and adjacent to the processing plant location. It was identified as a potential water storage location. The UEF is the zone in the upper elevations of the East Flank zone where the coal seams are perched in a higher fault block and result in a zone of low strip ratios for upper benches. This is also the area of the historic Pit 1 and Pit 2.

Lastly, the Seam 2 Trench is a modification to the ultimate pit shell in order to create additional water storage required for the water management plan. The 2 Seam Trench mines the eastern slope of East Flank 3 and it excavates a zone between the East Flank pit shell and the valley to the east where surface water will be stored throughout the mine life.

Coal and waste rock haul access is facilitated through a network of permanent and temporary haul roads and ramps. The main coal haul road is via the eastern haul road, which runs directly south from the processing plant along the eastern crest of the East Flank pit phases. Boulton pit is designed with a ramp in its highwall that facilitates access from the processing plant through Boulton pit to the upper benches of the WSFs. The UEF valley WSF also acts as a fill road and provides haulage routes to the UEF pit. There is also a secondary haul route utilising the safety berms in the western highwall of the East Flank pits and reaches the processing plant via the Boulton pit ramp.

WSFs are designed to ensure physical stability throughout the mine life and into perpetuity. Benching, drainage, geotechnical stability, operational efficiency and closure are all factors considered during the design of waste rock facilities. As there were limited opportunities to place waste rock and overburden externally due to topographical and project footprint constraints, backfilling was utilised wherever possible. WSFs are constructed either by end dumping as backfill or by “bottom-up” methods in ex-pit facilities using 60 m lifts at reclaimed slopes of 2:1.

The UEF valley WSF provides fill road access and a short haul opportunity for waste rock from the UEF pit. The Northwest External WSF (Waste Volume Mined) is the main waste rock destination early in the mine’s life prior to backfill opportunities being available and is constructed “bottom-up”. Once the Boulton pit is exhausted, it is utilised as a saturated backfill, which assists with selenium management. These two waste rock destinations are built up until the early East Flank phases are completed, which will then provide ample backfill and short haul opportunities. The upper benches of the later East Flank phases will have short hauls into the UEF pit backfill.

The Tent Mountain Mine will utilise the water stored in Tent Mountain’s historical “Pit 4”, located in what will eventually be mined out as East Flank Phase 2, as process water in the first five years of operations. Subsequently, a new reservoir will be established to receive and store water from the Pit 4 lake before it is mined. This reservoir is referred to as the Seam 2 Trench and is mined prior to the adjacent East Flank Phases 3 and 4.

The mine schedule assumes a 24-hour, 365-day a year operation with certain operating constraints over winter during periods of heavy snowfall, especially for clearing and soil salvage operations.

Pre production activities associated with the mine plan commence in September 2021 with processing plant operations starting in January 2022. The mine plan was prepared using quarterly pre-production periods followed by monthly periods for years 2022-2023, quarterly for years 2024- 2025, and then annually from 2025-2034 culminating in a 14-year mine life.

The mill targeted an annual production rate of 1.8 Mt ROM coal with a 50% ramp-up in its first month.

The schedule was driven by a balance of the following main factors:
• Mining the lowest strip ratio coal in early mine life;
• Maintaining adequate water supply to the processing plant;
• Opening up sufficient waste backfill capacity as required.

Subsequent to satisfying these main drivers, further scheduling modifications were made to optimise loading and haulage requirements. A maximum of ten benches per annum was assumed for any given mine phase. Raw coal inventories (total in-pit and ROM stockpiles) were kept to a maximum of 60,000 tonnes.

The UEF is targeted early in the mine life as it has the lowest strip ratio coal available, and waste can be short hauled to the adjacent UEF valley WSF facility or otherwise downhill. Boulton pit is excavated next. Waste is stored in external facilities until backfill opportunities are available after Boulton pit is exhausted. Mining continues south through the East Flank Phases 1- 6, and waste is backfilled as opportunities arise.

Comminution

Crushers and Mills

Summary:

The raw coal conveyor will discharge into the dual roll secondary sizer for reduction to a nominal -50 mm top size.

Processing

• Desliming
• CHPP
• Wash plant
• Flotation
• Dense media separation
• Dewatering
• Filter press

Summary:

The Tent Mountain coal handling and processing plant (CHPP) will employ the proven technologies found in modern metallurgical coal plants, including dense media separation, reflux classifiers and flotation.

Raw coal will be fed to the CHPP via a multi-slope desliming screen. Undersize material and water will be collected in the desliming screen underpan and piped into the deslime cyclone feed sump. Oversize will discharge from the end of the desliming screen and will be flushed with correct medium into the dense medium cyclone (DMC) feed sump. Mixed dense medium and coarse coal will be pumped from the DMC feed sump into a DMC cyclone. DMC overflow containing medium and product coal will discharge directly to a screen feed box that will distribute the slurry onto the product side of a partitioned multi-slope drain and rinse screen. Product coal will discharge from the end of the screen into the product centrifuge for dewatering. DMC underflow containing medium and reject coal will discharge directly into a feed box that will distribute the slurry onto the rejects side of the partitioned multi-slope drain and rinse screen. Reject material will directly discharge onto the rejects conveyor from the end of the screen.

The correct medium circuit will be controlled by maintaining over-dense medium in the correct medium sump and injecting clarified water into the suction of the correct medium pump to maintain the target operating density. Desliming screen undersize material will be pumped from the desliming cyclone feed sump into a set of desliming cyclones to separate the fine from the ultrafine raw coal.

Cyclone underflow will be pumped to a reflux classifier and the cyclone overflow will be piped to the flotation feed sump. Reflux classifier product will be further deslimed by a sieve bend and then subsequently dewatered in the fine coal centrifuge. Reflux reject material will report to the fineseffluent sump and will be pumped to reject thickening cyclones for dewatering. Thickened fines reject material will gravitate to a high frequency dewatering screen and will directly discharge onto the rejects conveyor. Reject thickening cyclone overflow and dewatering screen undersize will report to the filtrate sump prior to being pumped to the thickener.

Deslime cyclone overflow and sieve bend underflow will report to the ultrafines feed sump where collector reagent (diesel) will be added. Ultrafine material will be pumped to and processed in two flotation cells operating in a rougher/scavenger two-stage flotation arrangement to maximise the ultrafine coal recovery. Flotation concentrate product from both cells will gravitate and be collected in the screenbowl feed sump and flotation tailings will gravitate to the tailings thickener for thickening prior to dewatering in the belt press filters.

Flotation concentrate will be pumped from the screenbowl feed sump to the screenbowl centrifuge for dewatering. Dewatered ultrafine product coal will be discharged from the screenbowl centrifuge onto the product coal conveyor and both centrifuge centrate and effluent will be collected in the partitioned screenbowl product sump. The screenbowl centrate will be recycled to the screenbowl feed for recovery of product and effluent will then be pumped to the tailings thickener.

Flotation tailings, fines reject thickening cyclone overflow, fines reject screen undersize and belt press filter filtrate will be fed to the tailings thickener. Thickener underflow will be pumped to the belt press filters feed sump at approximately 30% w/w solids. Clarified water will overflow the thickener into a clarified water tank and will be recirculated through the plant for process water requirements. Thickened tailings in the belt press filter feed sump will be pumped up to individual belt press filters by a dedicated feed pump for each filter. Belt press filter cake will discharge directly onto the rejects conveyor for transfer to a radial stacker. Belt press filter effluent will report to the filtrate sump and will be pumped back to the tailings thickener.

Coarse, fine and ultrafine reject material will be combined on the rejects conveyor and will be discharged from the CHPP onto the rejects transfer conveyor, which will direct material into the rejects bin. The reject bin will have a storage capacity of 60 t and will be designed to load articulated (or equivalent) 28-t trucks for co-emplacement back in the pit.

Coarse, fine and ultrafine product material will be combined on the product conveyor and will be transferred from the CHPP and conveyed directly to a product loading bin. The bin will have a capacity of 150 tonnes and an overflow chute for emergency use. A cross-belt sampler and weigh scale will be installed on the product conveyor to allow for product coal sample collection and the instantaneous product rate and cumulative tonnes to be monitored and recorded.

Production

Operational metrics

Personnel

Job Title	Name	Phone	Profile	Ref. Date
Consultant - Mining	Bob McCarthy			Apr 1, 2020
Managing Director and CEO	Peter Doyle	+1-778-888-7604		Aug 16, 2021