An Bord Pleanála has approved a plan to raise the level of a north Donegal lake as part of a €41 million water supply project for the county.
Two dams will be built and flows from the Bunadaowen river will be diverted to lift the lake's level by 4.5m (14.8ft), according to a proposal drawn up by Donegal County Council.
This will allow more water to be abstracted for the Lough Mourne and Letterkenny water supply scheme, which is one of a series of water and sewerage projects earmarked for Donegal in 2006 under a €335 million investment programme.
Lough Mourne is the region's largest lake, lying 9.7km (six miles) from Ballybofey and south of the old mail coach road linking Sligo and Derry.
The 174-acre stretch of water is about 15m (49ft) deep and sits almost 168m (551ft) above sea level.
The lake has one small island. The Mournebeg river rises from it and runs out of its southwest border by the Croaghonagh blanket bog, which is a candidate Special Area of Conservation.
The major engineering plan was the subject of a Bord Pleanála oral hearing, in addition to the submission of an environmental impact statement by the council in which a series of "mitigating" measures to protect the environment were proposed.
The appeals board has found that the plan would not have a significantly adverse effect on the environment, if promised mitigating measures are taken and six conditions are adhered to.
The conditions include conducting a complete archaeological excavation before site development works begin and the monitoring of all ground works by an archaeologist.
It says an archaeological survey should also be carried out before any peat stripping to establish whether there are any surviving field systems beneath the peat.
According to the appeals board, a comprehensive survey of a former railway line bordering the lake should be carried out to "protect the cultural heritage of the area", and a minor access road leading to the proposed southern dam should be strengthened.
A landscaping scheme should be prepared by a landscape architect and laid out as soon as the development is constructed.
The board also sets detailed measures aimed at controlling water pollution, and says a continuing assessment of the development's impact should be undertaken.
According to the board, a fish-pass proposed for the southern dam should be designed in consultation with the Loughs Agency of the Foyle, Carlingford and Irish Lights Commission, to "avoid undue interference with fisheries" in the Mournebeg river.
