The company was prosecuted by Inland Fisheries Ireland for allowing aluminium sulphate, described as a highly toxic substance, into the stream near the village of Threemilehouse, a few miles from Monaghan Town, causing discolouration of the water and the death of fish stock.
Judge Sean MacBride was told at Monaghan District Court that an Inland Fisheries officer detected the pollution on April 28. It emerged the seepage resulted from a leak at a water treatment plant in the area.
Judge MacBride, in imposing the penalties, remarked that while Irish Water had come in for a lot of criticism, he believed it was now getting its act together.
Afterwards, the company said of the incident at the Togan Plant: “Unfortunately, as the leak occurred underground, workers were not and could not have been aware of it.” It added that it spent €40,000 to fix the leak.
A spokesperson said the stream should be completely recovered in a few months.