Environmental specialists working on the Bandon River flood relief project in the West Cork town have said they raised concerns with the company who subcontracted them about the porous nature of a haul road the night before it suddenly drained, leading to stricken fish become trapped.
The case involves a May 2017 incident in which Inland Fisheries Ireland (IFI) claim as many as 400 fish died when water flooded out of an area created by the haul road during works on what is currently one of the biggest drainage projects in Europe.
The number of fish killed is disputed with the court previously hearing that around 200 fish, or 100 fish or as few as five, may have died.
Byrne Looby Partners Water Services Ltd - contracted on the flood relief project by the Office of Public Works - as well as Wills Bros Ltd of Foxford in Co Mayo, and Rivus Ltd of Clonmel in Co Tipperary all deny a charge under the Fisheries (Consolidation) Act 1959 as amended, of injuring or disturbing the spawn or fry of salmon, trout or eels.
Judge Mary Dorgan heard that within the 3.5km stretch of the river in question there was an estimated one million fish and Alan Sullivan, an ecologist and director with Rivus Ltd who were subcontracted to Wills Bros, said that the number killed was "probably 0.0001%" of the total.
He added that it was "impossible" for such a large scale project not to have an impact on the environment.
However, Mr Sullivan admitted that what happened on May 10 that year was “a mess” and that environmental considerations tended to generally come “bottom of the list in the majority of infrastructure schemes”.
The Rivus concerns were that the haul road could have been on the other side of the river, that it was not tight to the bank, and relating to the large quantity of aggregate material needed to construct it.
A limited dredging trial took place in 2016 but Mr Sullivan said: “The concept of it drying out quite literally in seconds was alien to us.”
Mr Sullivan claimed it was a struggle to get their concerns across to Wills Bros on the night of May 9. The following morning it was discussed at a two-hour meeting starting at 10.30am. By 2.30pm Rivus got a call to say the water level had collapsed.
When alerted, he went to the site and with others immediately started to net fish to move them out of the dewatered areas, a process that ran until around 8pm.
He told the court that while he only photographed fish he knew were dead, five lampreys and one minnow, he estimated as many as 200 fish may have died as some of those netted were "moribund" or struggling in what he described as 'a fire brigade job'.
"We were deeply annoyed at this arising and potential for killing the thing we were supposed to be looking after," he said.
Mr Sullivan said lessons were learned and dredging mechanisms changed, claiming that on the day Rivus were understaffed given the scale of the project.
Today, in court, the IFI withdrew another charge of injuring or disturbing spawning beds, banks or shallows.
Legal submissions will now be made by April 30 before a verdict is delivered at Bandon District Court.