OceanaGold Corporation’s Waihi mine in the central North Island may get a 10-year life extension boost, with the decision made to tunnel underground below the historic Martha pit.
OceanaGold (TSX & ASX: OGC) announced it will start the resource consenting process to construct and operate the new Martha Underground mine, which could be operational by 2020.
The Martha pit has been closed since April 2015 following a slip, but underground operations at Waihi contributed 119,084 ounces of gold in calendar 2017, or 20.7% of the company's four mines' record production of 574,606 oz last year.
OceanaGold Waihi general manager Bernie O’Leary said the Martha underground operation would deliver a similar production rate to current operations, with a peak of around 420 jobs and an average of 350 full time jobs each year over the 10-year period.
“Mining activity under the open pit could commence in 2020 and extend our current mine life by at least 10 years, meaning we would continue to deliver significant benefits to our community here in Waihi and the broader region,” O’Leary said.
Waihi went underground in 2005 and had since started and closed its Favona and Trio tunnels, with Correnso still operating.
OceanaGold purchased Waihi from Newmont in May 2015 for $132 million and has spent significant sums in exploration drilling around the mine, including the pit area.
This calendar year, Waihi was expected to be working through lower grade underground gold veins for most of the year, with estimated production of around 75,000-85,000 oz having been predicted in February.
“Within the open pit we plan to complete remediation of the North Wall which will give us access to the ore at the bottom of the pit and then use this material to backfill the stopes we plan to mine,” O’Leary said.
Included in the plan, OceanaGold also wants to mine a small ore body below residential Waihi properties over two years, following a year of development. The Correnso underground mine also mined below houses at times.
A mine life extension has been mooted at Macraes in East Otago, with work underway at its Round Hill prospect.
*Simon Hartley is senior business reporter and assistant chief reporter for the Otago Daily Times.