Flooding in Clonmel, Co Tipperary, has been intensified in recent years by the location of developments in the floodplain of the River Suir, including the town's sewage treatment plant.
The plant, which was commissioned in 1999 at a cost of £13 million (€16.5 million), is located downstream of Clonmel in an area prone to flooding and is protected by embankments.
Other developments previously permitted in the floodplain, between the river and the main road to Waterford, include Dunnes Stores, the town's greyhound track and a number of factories.
Now, a flood relief scheme for the historic town is being considered at an estimated cost of €38 million, including the construction of flood defence walls and the replacement of two medieval bridges.
Clonmel has long been at risk of flooding from the Suir and many of its residents have suffered significant hardship. The centre of the town was inundated in 1995, 1996, 1997 and in November 2000. According to a hydrological study by E.G. Pettit, consulting engineers, flooding starts when the peak flow in the river exceeds 250 cubic metres per second, spreading floodwater over a wide area.
The study, which was commissioned by the Office of Public Works and published in July 1997, established that the peak flow in the January 1996 flood reached a level of 350 cubic metres per second.
The cause of the flooding is attributed to "high water levels downstream of the Gashouse bridge", east of the town centre, on the stretch of floodplain where the sewage treatment plant is located.
"Anything built in the floodplain is bound to have an impact," a senior engineer with Clonmel Borough Council said. "Water levels in the town would still rise in a flood, but probably not as fast as they do."
It is understood that the site for the sewage treatment plant was acquired 30 years ago, when floodplain issues were barely considered at all. Construction started in 1994 and it was finished five years later.
The plant was designed by McCarthy and Partners, now incorporated into W.S. Atkins. It is one of the best run plants in Ireland, according to the Environmental Protection Agency.
One of the engineers involved in designing it insisted that the location of the plant would have a "virtually negligible" impact on flooding in Clonmel, apart from "causing the river to rise sooner upstream".
However, one of the principal recommendations of the 1997 E.G. Pettit study - accepted by Clonmel Borough Council - was the need for "avoidance of new developments within the floodplain" of the Suir.
The latest development plan for Clonmel, adopted earlier this year, says it is now borough council policy "to discourage development within the floodplain" to protect the town against excessive flooding.
Where such development is deemed appropriate, "consideration must be given at the planning stage to avoiding or minimising flood risk" on the site in question and on the impact it might have on other sites.
The plan also states that all planning applications in the area will be referred to the Office of Public Works and "all such applications will be expected to comply with the requirements of the OPW".
A senior OPW official, Mr Jim Blighe, said it was unlikely that a decision would be made before the end of the year on whether to proceed with detailed design work on the flood relief scheme proposed for Clonmel.
"This is not a scheme to which public funding has been irrevocably committed," he stressed. "It is still at a preliminary stage and public consultations are continuing. There is complete scope for changes."
Some 40 submissions have been received following a public display of the scheme last January, ranging from individual concerns about the impact on property to wider conservation issues raised by An Taisce.
