The Department of Conservation is among groups opposing the extension.
Oceana wants to open a new pit called Coronation North, in what could prompt a two- to three-year mine life extension at Macraes, in East Otago.
Oceana has applied to construct the 63ha Coronation North, extend the existing Coronation pit to 83ha and build a waste rock stack of up to 280 million tonnes, covering 230ha.
Oceana also wants a dam, at Coal Creek, to hold up to 685 million litres and, once mining is complete, to create a ``pit lake''.
Because of boundary overlaps, Oceana needs resource consent from the Otago Regional Council, Waitaki District Council and Dunedin City Council. The process is being collated and overseen by the ORC, to avoid three resource consent hearings.
Across all submissions to the three councils, there were three parties opposing the application, four neutral and two in favour. A hearing is scheduled for October 31.
On behalf of Doc, Central Otago operations manager Michael Tubbs said, while opposing Oceana's application, the department was still in discussions with Oceana and its concerns could be addressed by imposition of ``appropriate conditions''.
He hopes a ``pre-hearing'' meeting between Doc and Oceana Gold, on Tuesday next week, could resolve concerns.
Doc is concerned about effects on the area's native fish and aquatic life, such as the Taieri flathead galaxias, long-and short-fin eels and koura, the water take and discharge consents.
Concerns about effects on vegetation, lizards, invertebrates and the New Zealand falcon were also raised.
No assessment had been done on breeding falcon, and grey scrub could be considered for planting as it was the bird's foraging habitat.
Doc recommended a ``three-pronged approach'': protection of an equivalent or greater area of habitat, enhancement of species or eco-systems, and the salvage or transfer of important threatened species.
Macraes Community Incorporated also opposes the application and wants to make a submission at the hearing.
As well as concerns about noise and weed control, Macraes Community highlighted some of the roads were in poor condition and were used by a local school bus. It wants the roads upgraded.
Other submitters, either in support or neutral, and the third opposer, also raised concerns mainly regarding roading, noise and dust.
Te Runanga o Moeraki, Kati Huirapa Runaka ki Puketeraki and Te Runanga o Otakou is ``neutral'' in the combined submission and does not wish to be heard.
However, should consent be granted, they ask for conditions to be imposed, which include mitigation for water quality in lower catchments than the mine, protection of in-stream habitats and an emergency plan be in place in the event of ``failure'' of the waste rock stacks or the freshwater dam.
Heritage New Zealand Pouhere Taonga, which is still in discussions with Oceana, does not want consents issued unless five sites in the area remain unaffected, and requests work stops if new historical sites are found. HNZ wants to make a submission at the hearing.
A submission by neighbouring farmers David and Jocelyn Kinney was ``neutral'' and they did not want to heard.
However, they highlighted the farm, which had been in the family since the 1920s, was ``heavily reliant'' on natural spring and aquifer waters and wanted conditions to be considered by the ORC, whereby Oceana would ``rectify these effects''; if there was any disruption to the natural water flow.
