Myra Falls mine back on-stream — Backfilling, new bolting pattern to improve ground conditions

Satisfied with rehabilitation work on its underground mine, Boliden (BOL-T) has resumed production at the Myra Falls zinc-copper operation on Vancouver Island.

The company had suspended production in December 1998 to give itself time to address ground-control problems (T.N.M., Nov. 23/98). Poor ground conditions had led to dilution of ore and lower head grades. Last October, a miner had narrowly avoided a rock-fall accident.

Boliden had budgeted just under $15 million on the work, which also included 330 metres of underground development. About four-fifths of the workforce remained on the job during the suspension, rebolting 1,330 metres of drifts on a new, tighter pattern. As well, Boliden has placed about 175,000 tonnes of fill, clearing about 90% of backfill work that was behind schedule.

Some rehabilitation work remains to be done, and so Boliden is predicting the mine will be running at 75-85% of capacity in the second quarter. The company hopes to bring production to full capacity (equivalent to 110,000 tonnes of zinc annually) by the third quarter. It expects that better mining control and lower dilution will reduce operating costs.

In Spain, Boliden has just received its permit to reopen the Los Frailes mine, northwest of Seville, which was closed by a tailings spill last April. The cleanup in the surrounding area is essentially complete, and Boliden will be using the exhausted Aznalcollar pit to dispose of future tailings.

Boliden’s Lomas Bayas copper project in northern Chile is operating at about 80% of its rated capacity. The mine is now producing copper cathodes of better quality, with off-specification material down to 5% of production.

The ore carries more chloride and nitrate than had been expected, and the solvent extraction process was being inhibited. Boliden is still working on the nitrate problem but believes it has the other licked.

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