Solid Energy New Zealand operates the Stockton Opencast Coal Mine, a
unique deposit consisting of high quality hard coking and thermal coals.
Stockton's uniqueness includes high variability of the shipment specifications,
strict quality constraints, minimal stockpiling capacity in the coal transport
chain and the variability of coal quality both vertically within the seam and
laterally across the deposit. The process of resource proving and modelling
results in a high level of understanding of the deposit to allow detailed
planning to be undertaken. The use of computer aided mine planning tools is an
important component of the mine planning at Stockton. Detailed planning is
implemented in the field through selective mining practices and monitoring to
minimise dilution and maximise recovery of the coal resource. The quality
variability in the coal, the just in time' approach of the coal transport chain
and markedly varying quality specifications from shipment to shipment requires a
large coal inventory and the mine to be driven by quality constraints rather
than material movement capacities.