An Bord Gáis is to replace immediately cast-iron gas pipes in a south Dublin housing estate following a gas explosion on Sunday which left a father and his three children seriously injured.
A Bord Gáis manager said yesterday that an initial investigation suggests that subsidence, possibly caused by an underground river, led to the explosion at a house at Glendoher Close in Rathfarnham.
Ms Sandra Carrigan escaped injury in the blast which blew the roof and windows off the house. Her husband, Mr Declan Carrigan, and daughter Sorcha (five) were critical but stable in separate hospitals in Dublin yesterday.
The two other Carrigan children, Laura (eight) and Adam (three) were said to be in a stable condition in Temple Street Children's Hospital.
The Commission for Energy Regulation, the Department of the Marine and An Bord Gáis have launched three separate inquiries into the explosion.
An Bord Gáis had sent an inspector to the area before the explosion on Sunday, following calls from a neighbour, Ms Amanda Kelly.
Yesterday a Bord Gáis distribution manager, Mr Gerry Geoghegan, said it appeared subsidence caused the accident and no other utility provider was involved. He stressed that subsidence in other houses in the estate was unlikely, adding that there had been "few if any reports of gas leakages in the area in the past 15 years".
Meanwhile it has emerged that almost 40,000 households in Dublin and Cork remain connected to the gas distribution network by cast-iron gas pipes of the type which fractured and led to Sunday morning's explosion.
An Bord Gáis said yesterday it would take up to 10 years to replace the estimated 1,060 km of pipework across both cities with newer and more flexible polyethelene material.
In the mid-1980s Bord Gáis Éireann has "inherited" cast-iron networks in Clonmel, Cork, Waterford, Limerick and Dublin, Mr Geoghegan said. With the exception of Dublin and Cork, these networks had all been converted to polyethelene piping.
In Cork, the remaining cast-iron pipes served a maximum of about 1,000 households in Mayfield and older parts of the city.
In Dublin, Mr Geoghegan said up to 30,000 customers were probably still being served by cast-iron piping. These, he said, were most likely in pre-1980s houses in the suburbs, as the older area between the canals had been completely renewed.
The Bord Gáis renewal programme in place since the mid-1980s had concentrated in the city centre initially because the pipes were oldest there, because of the presence of apartment blocks and because of pressure from the city authorities as a result of road works.
In the last 15, years the company had replaced 85 per cent of its network and was currently replacing between five and 10 per cent of the remaining amount, each year.
Mr Geoghegan said the likely cause of the Rathfarnham explosion was a build-up of gas under concrete which could travel into the house through sewers and other ducting.
However he was adamant that the cast-iron pipes were generally not dangerous.
"Something happened to this pipe in Rathfarnham, it didn't break by itself. It was probably subsidence from a local underground river.
"We don't think neighbouring houses are in any danger but as a precautionary measure we will be replacing the cast iron pipes in that entire estate over the next few days."
"In Britain the network is still 40 per cent cast-iron so we are ahead on this internationally," he added.
