Belinau underground mine experiences unplanned dilution
Tuesday, July 26 2016 - 01:33 AM WIB
ASX-listed Sumatra Copper & Gold plc announced Tuesday that following the introduction of long hole stoping at the Belinau underground mine at its Tembang gold and silver project in southern Sumatra during the second quarter of 2016 to accelerate ore production, significant unplanned dilution has been experienced above Level 4 in an area of poor ground conditions.
The company said in a statement that this has resulted in undercutting of the cemented rock fill on Levels 2 and 3 breaching to the surface and a localized collapse into a stope on Level 4.
?The area was being monitored and the safety of our underground crew was not compromised at any time by the incident and no lost time injuries were recorded,? the statement said.
The remaining void above Level 4 will be backfilled with competent rock and is not expected to impact on any long term infrastructure as the decline, escape ways and return air rises are all located in the hanging wall, away from the orebody, Sumatra Copper explained.
The company said an interim ore extraction method by ore drives between Levels 4 and 5 will be implemented to attain a competent sill pillar through this zone above Level 5. This will provide long term access to the extremities of the orebody on Level 5 and allow the decline to advance so that a more appropriate stoping method to suit the geotechnical conditions in this area can resume. The Level 5 ore drive is expected to be established by early August, with ore development continuing as planned along the Level 4 West drive.
The modification to the stoping method will result in a slightly lower ore tonnage at a higher grade. Increased ore production from the open pits is anticipated due to favorable weather conditions during the current dry season making up for any tonnage shortfall from underground. Further details as to the effect on the company?s production guidance, if any, will be provided as soon as the underground mine plan is updated to reflect these modifications.
Sumatra?s Managing Director, David Fowler, commented: ?Over the past month we have appointed Rob Gregory as our Chief Operating Officer and have also added two mining engineers with significant underground experience to enhance our planning, design and implementation capability at Tembang. The benefits from this strengthened team will be seen during the September quarter.?
Editing by Reiner Simanjuntak