A proposal to build a wind farm near Glenties in Co Donegal consisting of 22 turbines has been refused by An Bord Pleanála.
The turbines would each have a hub height of 64 metres and a rotor diameter of 71 metres.
An oral hearing into the case was held in Glenties last October.
There were 15 objections following the decision of Donegal County Council to grant planning permission to Straboy Wind Energy to build the wind farm with 20 conditions attached.
An Bord Pleanála refused permission to go ahead with the proposed development on two grounds.
The first relates to the fact that the proposed development "encompasses watercourses rated at or close to "pristine" condition which have direct hydrological connectivity to the West of Ardara/Maas Road candidate Special Area of Conservation which includes the Owenea River system which hosts Annex II species including the freshwater pearl mussel".
The decision states that the proposed development would have significant adverse impacts on the ecology of the site and of the wider area.
The second reason relates to the excavation of large volumes of peat involved in the proposal.
An Bord Pleanála decided that "the proposed repositories would constitute an unacceptable risk of pollution of nearby watercourses and would seriously injure the amenities of property in the vicinity".