The company has also increased its resource base by 11% to 94.5Mt after an extensive drilling campaign.

Drilling at Buller focused on improving the status and extent of resources, and on confirming coal potential across the Denniston Plateau. This was part of an evaluation program to determine areas best suited for establishing an ecological reserve, Bathurst managing director Hamish Bohannan said.

“There has been a great deal of effort spent not just on expanding our reserve base but on improving our understanding of the technical aspects of the Buller geology and stratigraphy, which has led to a much greater confidence in the resource base of our project,” he said.

“The drilling program for the current year will focus on proving up further reserves for South Buller and expanding our knowledge base of the North Buller permits.”

The work involved collating and analysing data on geology, flora, fauna, historical sites, landscape, water domains and social activities.

The reassessment of resources and reserves was based on a multi-variate approach to resources classification.

“Geo-statistical analysis and practical observation of coal seam thickness and quality variations have shown that the Australian guidelines associated with spacing of observation points is of limited use in the Buller coalfield to classify resources,” the company said.

“This methodology, adopted by Bathurst, allows a detailed classification, with an auditable and reproducible process, in areas where there are higher levels of uncertainty associated with structural deformation, seam geometry and increased levels of historic underground workings.”

Since October 2011, a drilling program of 154 holes was conducted across the North and South Buller permits. In the South Buller area the reserves increase was largely from an additional 9.6Mt in reserves identified across Whareatea West, Coalbrookdale and Cascade.

The reportable reserves identified at Whareatea West have increased from 2.9Mt to 10.3Mt and maiden reserves have been announced for Cascade and Coalbrookdale of 0.6Mt and 1.6Mt respectively. The reserve for Escarpment has increased to 3.8Mt of product coal.