Roadstone has been ordered to pay £5,000 to the Southern Regional Fisheries Board after the company pleaded guilty to discharging effluent into a stream in Co Kildare.
At a sitting of Naas District Court, the company was prosecuted under Section 4 of the Local Government (Water Pollution) Act 1977.
An officer with the fisheries board told the court that the company was discharging more than five times the permitted amount of "suspended solids" into a tributary of the Pluckerstown stream.
Ms Ciara Lennon said suspended solids could be described as particles of silt and clay which settle on the bed of rivers and streams.
The company was discharging effluent with 165 mg per litre of suspended solids but was only licensed to discharge 30 mg per litre, she said.
The proceedings were initiated by the Southern Regional Fisheries Board following investigations into a breach of the conditions of Roadstone's discharge licence from their effluent treatment works at Pluckerstown, Kilmeague, Naas, Co Kildare, to a tributary of the Pluckerstown Stream on September 22nd, 1999.
Ms Lennon acknowledged that on her most recent inspection of the site on June 21st, 2000, there was a significant improvement in its environmental management.
Roadstone pleaded to the offence and gave an undertaking to pay the costs and expenses incurred by the fisheries board.