RAG Coal International is understood to be revisiting the possibility of hydraulic mining at the Burton mine to access thick, steeply dipping underground resources of about 140 million tonnes. The method is one of several being evaluated.

Previous owners, Portman Mining, had also examined the hydraulic mining method, which uses high-pressure water to wash the coal out of the seam. The method is being used at the Strongman mine in New Zealand to produce around 1Mt per annum. The challenge will be how to adapt the technology for the larger tonnages Burton produces, currently in the region of 4Mtpa.

The coking coal mine is of major strategic importance to the German company, which bought Portman's 95% stake in September last year for $200 million. It is believed the underground development will double Burton's mine life, currently projected at 10-12 years at an open cut depth of 105m.

The mine, in central Queensland's Bowen Basin, is operated by 5% owner Thiess Contractors. Several Thiess managers have recently spent time in New Zealand assessing the hydraulic method in application at Strongman.

RAG would not comment on the development but anticipates being able to release further information in 3-4 weeks.