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Tulsequah Chief mine determined ‘substantially started’ – BC Ministry of Environment

15th January 2015

By: Henry Lazenby

Creamer Media Deputy Editor: North America

  

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TORONTO (miningweekly.com) – The British Columbia Environment Minister Mary Polak has determined that Chieftain Metals Corp’s Tulsequah Chief polymetallic project was 'substantially started', ending a First Nation challenge to the validity of the original Ministerial determination in 2012.

The Ministry of Environment stated on Wednesday that, therefore, the environmental assessment certificate would remain in effect for the life of the project and Chieftain could continue building the mine.

The decision was needed owing to a legal requirement stipulating that approved projects must be substantially started within a time limit set out in the certificate or the certificate would expire.

Polak said ‘substantially started’ decisions were considered on a case-by-case basis. The Minister focused on the physical activities that had taken place at the project site and considered whether a significant investment of time, effort and resources had been made to develop one or more elements of the project, whether the activities represented a significant or important step in developing the project and whether the company would have undertaken the activities regardless of the project.

As part of the decision-making process, the Minister considered information submitted by the Taku River Tlingit First Nation, which had fiercely opposed the project, since the mine was located in their traditional territory.

There were 125 commitments that were part of the project approval certificate. The commitments were legally binding requirements that Chieftain Metals needed to meet in order to be in compliance with the certificate. The Environmental Assessment Office would coordinate compliance management efforts with other government agencies to ensure that the office was satisfied that certificate conditions were met.

TULSEQUAH CHIEF

The C$198-million Tulesquah Chief project is based on a 1 100 t/d underground mining operation with an 11-year mine life. Focused mainly on zinc output, it has reserves of 4.4-million tonnes, of which 684 000 t (15%) are proven.

The 2014 feasibility update on the Tulsequah Chief project, updating Chieftain’s 2012 feasibility study, incorporated improvements to the Tulsequah Chief polymetallic deposit and the nearby Big Bull deposit, in north-western British Columbia, collectively referred to as the Tulsequah Shazah camp.

The updated study included optimising production configuration, operations, logistics and mill size, dramatically improving the financeability of the project.

The feasibility update yielded a pretax net present value at 8% (NPV 8%) of C$212-million with an internal rate of return (IRR) of 25.2% and an after-tax NPV at 8% of C$146-million with an IRR of 21.9%.

A new underground mine, adjacent to and beneath old workings that were previously operated by Cominco, is planned to be developed through the existing 5 200 and 5 400 level adits and will be used as the primary access to the mine for all personnel, mine services, equipment and supplies.

In the 2014 feasibility update, the new mine was proposed to operate as a ramp-entry truck haulage operation using a spiral ramp that would be developed to a vertical depth of 570 m, with mining levels located at 30 m vertical intervals.

Transverse and longitudinal sublevel stoping would be the primary mining methods with a minor amount of mechanised cut-and-fill stoping. Paste backfill and unconsolidated loose waste rock were planned to be used for the replacement of mined voids for both methods. Additional cement would be added to the paste backfill for strength where future mining would be adjacent to exposed backfill.

The update contemplated the design of a process plant for the Tulsequah Chief project to process massive sulphide mineralisation at a nominal rate of 1 100 t/d. The process facility was planned to consist of a primary crushing plant, a mill feed storage bin and conveyor corridors located underground, grinding, flotation, filtration, an effluent treatment plant – part of which was constructed in 2011 – and a backfill plant.

The process plant operation was scheduled to operate two shifts a day and 365 days a year, with an overall availability of 90%. The process plant was designed to produce copper, lead and zinc concentrates and gold/silver doré.

Concentrate produced during operations were planned to be barged in containerised bags, along the Taku river to a transfer barge at the mouth of the river and then to the Port of Seattle to be shipped to Asia. Operating supplies were planned to be barged to site in containers and stored at Paddy’s Flats, 12 km south of the mine.

All surface buildings were planned to be laid out and located in close proximity to the mine, including the mineral process building, an administration building – which included first aid, a fire truck and an ambulance – a diesel-generated power plant, a maintenance/warehouse facility for surface equipment and an existing effluent treatment plant. Bulk diesel was proposed to be stored in two five-million-litre tanks, located within a lined spill containment area at Paddy’s Flats. A 160-person camp and kitchen/dining facility had been designed to complement the existing 50-person camp located at the Shazah airstrip. The mine dry was planned to be located near the camp.

A 1.7-million-tonne-capacity tailings facility was planned to be built about 5 km north of the mine, in the valley of Shazah Creek.

Depyritised tailings with limestone added was proposed to be transported in the form of a dense slurry by pipe. The final dam height would be 9 m and was designed to have an emergency spillway for unexpected flood events, a toe berm to ensure stability and a liner to prevent seepage. Seismic stability was ensured with a shallow, overall designed dam slope of 5 horizontal to 1 vertical. The dam was scheduled to be constructed in two phases, involving the construction of a small starter dam in preproduction and a second phase, ultimate dam in year two of operations. Surplus water would be treated and discharged to prevent the accumulation of surplus water in the impoundment.

Potentially acid-generating (PAG) waste rock and pyrite concentrate were planned to be temporarily stored in separate lined impoundments 1 km south of the mine. PAG waste rock and pyrite concentrate would be used as backfill during the mine life. These materials would be stored subaqueous to reduce the potential for acid generation.

Edited by Tracy Hancock
Creamer Media Contributing Editor

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