Part of the east-coast rail line was closed again yesterday after a mudslide at Killiney.
DART services between Dalkey and Greystones, and train services between Dublin and Rosslare, were suspended at about 9.30 a.m. All services resumed at 5 p.m.
Iarnrod Eireann said recent heavy rain had caused debris to loosen. It fell on to the lines at about 8.20 a.m., and peak-time services had to operate at a reduced speed. Engineers spent the afternoon clearing the line.
Between 3,000 and 4,000 people were affected by the disruption, a spokesman for Iarnrod Eireann said.
Buses were provided to take passengers to Rosslare, and people affected by DART services were advised to take buses from the city centre.
The spokesman added that the area where the debris fell was about 250 yards down the line from the point where 1,000 tonnes of earth fell on to the lines last week.
"It was not nearly as serious as last week," he said. Trains between Dalkey and Greystones were suspended for the entire week last week because of the scale of the problem.
The area from where the earth fell last week was owned privately. Dun Laoghaire/Rathdown County Council said a house was being built at the area where the landslide occurred and planning permission had been given to build two years ago.
The problem last week was probably caused by weather, as there had been problems with loose earth along the coast at Whiterock in previous years, a member of the planning department said.
Fifty personnel were employed by Iarnrod Eireann to work on the site, including subcontractors. There were earth-moving machines, both on the slippage site and on the railway, and lorries were delivering small rocks. The cost of the work was described by Iarnrod Eireann as "significant".
Iarnrod Eireann said it was examining ways to prevent future problems with debris and landslides on rail lines.
A team of consultants from Denmark had been employed to help identify the underlying causes of the problems, the spokesman said.
He said Iarnrod Eireann would also consult Dun Laoghaire-Rathdown County Council on the issue.