How overcoming environmental challenges shaped the design of a new reservoir in North West Ireland

Lough Mourne is a natural upland lake situated in the Blue Stack mountain range to the north-east of Donegal Town in County Donegal, Ireland. The lake has been a water supply source since the 1960s and was identified in the 1980s as having significant development potential. However, as it is situated within and adjacent to a number of sites of high environmental value, any development was believed to have significant planning obstacles. A proposed major development in the mid 1990s, involving the raising in top water level of 6.5m, was abandoned at pre-planning stage as it was considered that the environmental impacts could not be appropriately addressed.

In 2001 Donegal County Council appointed Nicholas O’Dwyer Ltd and Ferguson McIlveen LLP (now URS) to reopen investigations into the Lough’s development potential by preparing a detailed feasibility report on a range of options and an associated Environmental Impact Statement (EIS). Following various appropriate studies, the EIS was published in 2005 and the scheme was granted full Planning Approval in 2006 following a public inquiry. The scheme has progressed to full contract document stage and is awaiting funding approval from Irish Water to progress to Tender.

This paper will outline how the range of environmental challenges associated with the scheme were dealt with during the feasibility, outline and detailed design stages of the project and how they have shaped the design of the impoundment, its dams and ancillary features.