Originally, the company planned to close the mine after it lost a major commercial supply contract in 2007.
Rapidly declining reserves at the mine have reduced the volume of coal that can be bagged for the household market before closure to 5000 tonnes which, based on previous years, will not meet demand beyond the 2009 winter.
Solid Energy, which spent recent years re-working old underground mines at Ohai, had thought the last pit would provide enough coal to supply the household market through the 2010 winter. But chief executive officer Barry Bragg says this outlook has been affected by the diminishing reserves.
“Estimating coal reserves in pits that have been previously worked by underground mining is difficult and on this occasion we have 20% less coal than predicted.
“The last remaining pit currently contains 45,000 tonnes of coal but most of that is needed to honour commercial supply contracts, leaving us with only 5,000 tonnes of household coal that we hope will last most of this winter.”
Bragg said that while most of the 13 Ohai staff will be made redundant by the closure, the company is looking to see if it can offer alternative employment at other Solid Energy sites, such as New Vale.
Following Ohai mine’s closure, many of the buildings and plant will be dismantled and either redistributed to other Solid Energy sites, with most going to New Vale, or offered for tender.
Rehabilitation and environmental monitoring will continue at the site for several years.
There will be five pits to rehabilitate, which will be reshaped and partially filled with available overburden before being seeded with pasture for grazing.
After this is done, three remaining hollows will be formed into lakes of 29 hectares, 12ha and 7ha, with wetland vegetation sown along the banks.
Bragg said that the rehabilitation had been designed to allow for the resumption of mining if a substantial long-term supply contract could provide the economies of scale needed to open a new pit.
To facilitate rehabilitation, Solid Energy hopes to remove about 40,000 tonnes of coal fines from the site, which may be railed to Lyttelton for export if no local buyers can be found. About 20,000 tonnes of fines had been exported this year.
