Name and Location
Caribou zinc/lead/silver mine and mill complex, New Brunswick, Canada.

Client
Trevali Mining Corporation.

Project Description
The base case preliminary economic assessment (PEA) on the Caribou project has indicated positive economic results.

The project involves the restart of the Caribou mine project through the reactivation of the 3 000 t/d Caribou mill complex and the associated underground deposit.

Underground operations will take advantage of the existing extensive historical development and infrastructure. A centralised ramp-trucking system will serve as the main access for the mine. The main mining method will be modified Avoca with waste-rock backfill, with the exception of a long-hole retreat mining method for partial sill-pillar recovery near the end of the mine’s life.

The processing circuit will consist of the 3 000 t/d semiautogenous (SAG) grinding and milling circuit, including fine-grinding IsaMills, with standard sulphide flotation recovery circuits to produce three concentrates – zinc, lead/silver and copper/gold. The average life-of-mine (LoM) modelled head grade for mill feed is 6.11% zinc, 2.49% lead, 0.34% copper, 67.9 g/t silver and 0.86 g/t gold.

LoM metallurgical recoveries used in the PEA are 84% for zinc, 65% for lead, 45% for copper, 37.5% for silver and 10.6% for gold. No optimisation of precious metal recoveries has occurred to date, but it is being evaluated.

Net Present Value/Internal rate of Return

Value
Preproduction capital expenditure is estimated at $36.3-million.

Duration
Commissioning of operations is expected in the first half of 2015.

Latest Developments
Trevali has reported that significant progress has been achieved since announcing the start of mill commissioning in late-May.

Underground (UG) mining continues to progress well, resulting in a significant coarse mill-feed stockpile of about 110 000 t of mineralised material readily available for ongoing mill commissioning.

UG dewatering and refurbishment are on schedule to be completed in August and October respectively.

An estimated 10 000 m UG resource conversion and exploration drill programme will start this month.

Mill commissioning has started as per the commissioning strategy.

All mill circuits – crushing, grinding, reagents, flotation, filtering and tailings –are now integrated and functional.

Commissioning initially focused on the zinc circuit, where saleable-quality zinc concentrates had been successfully produced grading 53% to 56% zinc. The commissioning team is concentrating on the lead circuit, where lead has been successfully floated to produce an initial lead concentrate, and ongoing copper circuit installation.
 
Caribou mill commissioning
A multitude of minor troubleshooting challenges have been corrected during the initial June commissioning period. These positive changes have resulted in an about 94% mill availability factor by month end at a 1 500 t/d capacity, or 50% of nameplate design. Based on progress to date, it is expected that mill throughput will continue to ramp-up throughout the summer months, as the plant team increases its familiarity with the mineralised mill feed and reagent characteristics.

The following progress has been made in the various major mill components:
• Instrumentation – various software patches have been installed and all circuits are communicating as designed. The on-stream analyser is functioning and Outotec is completing final training on it this month.
• Crushing – the radial surface crushing circuit is fully operational and feeding into the dual mill feed bins.  From here, feed is conveyed into the SAG mill, which is the first stage of the grinding circuit.  Ongoing optimisation during the remainder of the year will seek to upgrade the conveyor feed system to optimise winter operations.
• Grinding – the newly installed SAG mill, the two ball mills and the three Isa mills have been integrated, charged and are operational. The SAG mill has successfully achieved a primary grind of about 30 µm at current feed rates.  Future optimisation, once sufficient data is collected, will optimise charge rates, grind characteristics and media composition.
• Reagents – the full complement of reagents are all on site and available. The commissioning team initially focused on zinc reagents, with lead reagents gradually being introduced towards the end of June.
• Flotation – zinc and lead flotation, including the rougher and cleaner cells are fully functional. Piping and pumping optimisation and replacement occurred during June, which is expected to result in improved circuit stability.
• Filtration and tailings – the zinc and lead filters are functional. Initial concentrate production is being warehoused on site for shipping once sufficient stockpile is present, currently scheduled for this month. Initial zinc concentrate production has assayed up to 56% zinc and is in line with nameplate design. Ongoing work this month will now focus on lead concentrate optimisation.
• Copper circuit – initial copper-circuit construction is under way and remains on track for commissioning later this year.

Caribou mining
Underground refurbishment, development and mining continue to advance according to plan. There are currently 9 km, of a total of 13.3 km of UG development, refurbished and available for production distributed over eight mining zones

UG is mining at an estimated 1 500 t/d and continues to build a significant surface stockpile of mineralised material for mill commissioning. Production will continue to ramp up, with an additional mining fleet scheduled to arrive.  The surface stockpile is at capacity, with an estimated 110 000 t of stockpile of mineralised material on the coarse mill-feed stockpile.

Dewatering is ongoing and significantly progressing following the Spring melt. About 78 vertical metres of the mine remains to be dewatered, which at current rates will occur in August.  On this basis, it is estimated that the mine will be fully refurbished by October.

UG enhancements are ongoing and continue to focus on drill-and-blast optimisation, road maintenance an haul optimisation.

Trevali has also tendered and awarded a 10 000 m UG drill programme that is scheduled to start in July. The programme is predominantly designed to provide additional detail for mine planning purposes.

Key Contracts and Suppliers
SRK Consulting (Canada), in collaboration with Trevali (underground mine modelling, general and administration costing and project economics), Stantec Consulting (environmental and permitting), Holland & Holland Consulting (metallurgical and processing).

On Budget and on Time?
Not stated.

Contact Details for Project Information
Trevali Mining Corporation, tel +1 604 488 1661, fax +1 604 408 7499 or email info@trevali.com.
SRK Consulting, tel +1 604 681 4196, fax +1 604 687 5532 or email vancouver@srk.com.
Stantec Consulting investor relations, tel +1 780 969 3349 or email investor.relations@stantec.com.