CONSTRUCTING a tidal barrier would not solve Cork city's flooding issues, according to the OPW, which has warned that heightened quay walls would still be needed to protect against river flooding.
The state body has put the total cost of a tidal barrier at Little Island in the region of €1 billion, with an alternative proposal at Great Island estimated at more than €1.8 billion.
Part of this cost includes the construction of new city walls, which the OPW says would still be needed to protect the city from fluvial flooding.
The figures were outlined in a presentation to members of Cork City Council this week and can be viewed on the Lower Lee Flood Relief Scheme website, www.lowerleefrs.ie
The tidal barrier was the preferred solution of many interest groups in and around Cork city, including the Save Cork City banner organisation of architects and engineers, who favoured it over the new quay walls proposed by the OPW under existing plans.
Save Cork City has argued that the tidal barrier would cost just €140 million, a figure disputed by the OPW.
In a behind-closed-doors meeting with city councillors, engineers detailed a range of issues with the tidal barrier proposals.
The Little Island barrier, which would be placed at Lough Mahon, would increase peak velocity flows in the river by a factor of three, resulting in potentially unsafe conditions, according to engineers.
They said these increased flows would have a significant impact on nearby environmentally sensitive areas and would require a 500m stretch of the N25 to be raised and new embankments to be constructed along the Cork-Midleton railway line.
The cost of the Little Island barrier construction was put at €656m, rising to €1 billion when maintenance and additional fluvial defences are factored in.
An alternative plan for a double barrier on the west and east of Great Island would not have the same environmental impact, according to engineers, though its cost would be €1.2 billion, rising to €1.8 billion when additional costs are included.
Neither option was deemed financially viable, with the current scheme due to cost €140 million.
In addition, engineers were explicit in stating that the tidal barriers would not solve the flood issues and that walls would still be needed to protect the city from fluvial flooding.