Experts at the Delft University (TU Delft) in the Netherlands, who were asked to review the OPW’s €450m-€1bn cost estimate of a tidal barrier at Little Island, say they believe it could be built for just under €200m.

They described the tidal barrier proposal as “an interesting and attractive option” which warrants further investigation.

The report was commissioned by the Save Cork City (SCC) group, which is leading the opposition to the OPW’s reliance on raised quay walls as part of its Cork flood defence plan.

SCC has repeatedly called for the construction of a tidal barrier at Little Island to protect the city from flooding and released a report it commissioned last year from HR Wallingford which put the cost at between €110m and €180m.

However, the OPW has repeatedly ruled out a tidal barrier on cost and engineering grounds, insisting it could cost anything from €450m to €1bn and while possible from an engineering perspective, it would do nothing to prevent fluvial or river flooding of Cork city centre.

However, SCC said the emergence of this second independent report which questions the OPW’s cost estimates shows that the tidal barrier option must be considered further.

The TU Delft experts said it appears from their review of the OPW’s costs that the body applied a unit rate for tidal sector gates to simpler tidal sluice gates — an approach it said is “not considered appropriate” and which would result in an “unrealistic cost estimate”.

On their first review of the tidal barrier costs, they said a tidal barrier at Little Island could cost around €258m, with the comparable OPW cost of €340m.

A second review would result in a cost below €200m, they said.

The development of a more detailed, and project-specific cost estimate for the Little Island tidal barrier is highly recommended, the experts said.

The Irish Examiner asked the OPW to comment on the TU Delft conclusions and recommendations but a spokesman said the agency could not comment on a report it has not seen in full.

SCC spokesman John Hegarty said the tidal barrier represents the best solution for the city.

“There is still time to address the issue and not destroy Cork with the walls scheme,” he said.