An Environment Court hearing is underway in Waihi to hear objections to variations to the mining licence for the Martha Mine open pit operations.

The variations will allow Newmont Waihi Gold to undertake the Martha Exploration Project, which involves tunnelling under the open Martha Mine pit.

A side view of the Martha Mine showing Newmont's proposed mining tunnels.

Hauraki District Council, Waikato Regional Council and the Minister of Energy and Resources approved the proposed variations in January, following which objections were lodged with the Environment Court.

The Environment Court hearing began on Monday with an exploration of the mine and is expected to last most of the week with a decision expected by Friday.

The variation to the mining licence follows the process set out in the Mining Act, and is not a Resource Management Act process.

The Mining Act sets out a period of time from public notification in which any person or body can lodge an objection with the Environment Court. These are the objections that are being heard by the Court this week.

The proposal is to see if there is any more gold or silver beneath the existing pit floor. The mining licence in the 260metre deep pit is due to expire in 2017.

The Martha pit showing Newmont Gold's proposed mining tunnels along the side of the mine.

Newmont wants to dig an exploration tunnel under the north-western wall of the open pit and some limited trial stopes under the pit. The exploration tunnels will be used to explore and confirm the nature and extent of this ore.

Trial stopes will determine whether mining beneath the existing Martha pit is viable. The digging will be within the current mining licence boundary.

The pit is the site of the historic underground Martha Mine, which worked between the 1880s and 1952. Those workings descended to a depth of 600metres with 15 levels of tunnels. A substantial amount of gold and silver was mined and a total of around 175kilometres of tunnels were constructed.

The entry portal to the exploration decline is from the ramp on the north-western wall of the pit at an elevation approximately 200metres from the top of the wall. The exploration decline extends to about 280metres below surface and 20metres below the bottom of the pit.

The hearing is at the Chambers building on Haszard Street from 10am.