A public inquiry into plans to create England’s largest onshore wind farm is due to open later.
Peel Energy and United Utilities want to add a further 16 turbines at Scout Moor in Greater Manchester, on land between Rochdale and Rossendale.
Planning permission was granted by both Rochdale and Rossendale councils but the government called in the decision.
The hearing is expected to last about a week but a final decision is not expected until next year.
Analysis: Mat Trewern Political Reporter BBC Radio Manchester
There was strong opposition to Scout Moor wind farm being built in the first place with environmental campaigner David Bellamy among the high profile figures who claimed it would damage the countryside and blot on the landscape.
But it was built in 2008 with 26 wind turbines which it is claimed generates renewable electricity for 40,000 homes.
Developers Peel Energy have wanted to expand the site for a number of years – and after scaling down original plans to double the size of it – they settled on an extra 16 wind turbines.
A planning inspector will hear all the arguments for and against then recommend a decision to the Communities Secretary Sajid Javid. He will then make the final decision on the proposals but we are not expecting his decision until next year.
Opponents fear the expansion of the wind farm will impact negatively on the natural beauty of the area.
In the planning application for expansion on Scout Moor and the neighbouring Rooley Moor the document states “if all the proposals… are consented they will result in the largest wind farm in England”.
The hearing is being held at Futures Park in Bacup.