The stage two development is being processed under the Fast-Track Approval Act and a panel has been appointed to process the application.
The first stage of 12 turbines was completed in 2011.
The applicant has sought to add 44 wind turbines across 54 possible locations, down from 88 locations originally.
It is also seeking an increase in the maximum wind turbine blade tip height up to 165m — an increase of 20m.
The new wind farm, known as Puke Kapo Hau, will cost more than $220 million to build and will contribute about 549 GWh of electricity per year, as well as provide diversity and security of supply.
The wind farm was referred to the fast-track process by Mercury Energy last year and accepted for referral in November.
In a minute late last week by panel convener Jane Borthwick, she said the applicant had met territorial authorities and many issues had been resolved.
The Department of Conservation also said there appeared to be no major issues in dispute.
The Otago Regional Council highlighted substantive issues such as offsetting, compensation, monitoring, management certainty and reliance on management plans.
It was prepared for site visits and workshops with the applicant to solve some of these issues.
Ōtākou Rūnaka advised the proposal could have significant cultural impacts.
Ms Borthwick said the decision timeframe was set at 60 working days.
The applicant has asked for 63 working days — similar to that of its Southland wind farm, near Wyndham.
The convener said although the two projects were broadly similar in scale, the Mahinerangi wind farm was less complex.
The shorter timeframe recognised good engagement between the applicant and stakeholders.
The timeframe should be enough to complete engagement between the applicant and Ōtākou Rūnaka, ensure conditions of the consents were clear and certain, and for management plan provisions to be carefully considered.
The three-person panel is made up of Bianca Sullivan (chairwoman), Maria Bartlett and Andrew Whaley.
Ms Sullivan is a planner with more than 25 years experience and a certified RMA decision-maker.
Ms Bartlett, who was nominated by the territorial authorities, has more than 20 years experience in resource management strategy, policy and planning and is also a certified RMA decision-maker.
Mr Whaley is a civil engineer with more than 30 years of experience covering project governance, management and design as well as being a site engineer.
Mercury Energy strategic consents manager Ryan Piddington said there had been extensive consultation between Mercury Energy, local authorities and administering agencies.
"Everyone commented favourably on the process.
"The timeframe for a decision has been set for 60 days.
"We think this recognises the positive relationships and ongoing engagement between us and the people who attended the conference."
The panel’s commencement date was set for next Monday, despite it being appointed yesterday.
The panel will invite comments starting March 2 and closing March 30.
The applicant’s response was due on April 8.
The decision on the application was due on June 26.
