OceanaGold cleared to return to opencast mine in North Otago after slip
By Pam Graham
July 1 (BusinessDesk) - OceanaGold Corp has clearance from WorkSafe NZ to mine the southwest corner of its opencast gold mine in North Otago while continuing to monitor 45 million tonnes of rock that slipped 200 metres in April.
The “failure” of a wall of the pit about 9am on April 19 came after heavy rain in the region and followed a slip which moved about 50 metres a year earlier.
No one was injured in the April slip but a helicopter was needed to evacuate miners from the underground mine nearby. The opencast mine had been in care and maintenance mode.
BusinessDesk understands the company had invested $1 million in a radar system to monitor the eastern face of the pit but it was the western face that failed.
That face had a monitoring system which sent text messages to an engineer. The engineer received a text about movement of the top half of the slip when it was raining heavily but the system monitoring the bottom of the slip is believed to have failed, BusinessDesk understands.
The alert of the potential disaster was actually raised by a worker, who spotted a crack in the road on his way to the underground mine. The decision was made to pull out workers near the surface of the underground mine while workers further down waited as the crack in the road widened.
WorkSafe NZ put a prohibition order on the opencast mine after the slip. The company has said gold production has continued from the opencast mine but this has been the processing of stockpiled ore. No new ore has been mined from the opencast pit since the slip.
OceanaGold now initially wants to mine the southwest corner of the pit, and the area known as the Goodbye Cut, while it evaluates potential for mining in the new pit landscape, particularly around an area known as the FRIM near one of the portals of the Frasers Underground Mine.
WorkSafe NZ lifted a prohibition on the SW corner of the mine last week but mining of this area will only take six months. It will take a month to put a road in and three months to mine but because there is a lot of overburden to be removed the ore mined is only likely to keep the gold production facility busy for a month.
OceanaGold can potentially mine the FRIM area around a portal to the underground mine but is yet to evaluate fully if it is economic and an approval from WorkSafe NZ will be needed.