An Bord Pleanála has overturned a decision by North Tipperary County Council to grant a licence to drain water from a disused mine at Silvermines to make way for a large dump.
Waste Management Operations Ireland Ltd (WMI) had planned to locate a landfill, designed to take 450,000 tonnes of waste each year for 25 years, at the disused Magcobar open-cast mine.
The company proposed to pump millions of gallons of water from the mine into a nearby stream as a first step in the process.
But An Bord Pleanála directed the licensing authority, North Tipperary County Council, to refuse the licence it had granted for this in 1999.
"The information provided during the course of the appeal indicates that the ongoing discharge to keep the mine drained was not part of the licence application," the board said in its decision.
Mr Mark Gilligan of WMI said the company was disappointed at the decision. He said the company was examining the board's judgment.
Mr Eamon De Stafort, spokesman for the Silvermines Environmental Action Group, welcomed the move.
"This news marks a great victory for the people of the Silvermines. For us this is like an early Christmas present after a long and hard campaign against the imposition of a superdump on our community."
Locals had appealed the granting of the licence, arguing that raised cadmium levels in water discharged from the mine would have a detrimental effect on fish life in the Kilmastulla River - one of north Tipperary's top Atlantic salmon spawning grounds. They also said the landfill would threaten economic, tourist, heritage and environmental initiatives in the area.