A large sinkhole that forced more than 30 homes to be evacuated is still growing, a council leader has said.
The void emerged on Nant Morlais in Pant, Merthyr Tydfil, on Sunday morning and council leader Brent Carter said on Monday that “more cracks are coming across the road and into walls and gardens”.
He estimated the hole was “probably 30-40ft (9-12m) deep and five metres (16ft) wide”.
Simon Williams, whose family owns the bungalow where the sinkhole appeared, said it could be months until residents of the cul-de-sac could return home and he felt “desperately sorry for all the residents who’ve had to get out of their homes just before Christmas”.
Mr Carter said two landslides caused the problem, adding: “A couple of residents heard a loud bang.
“Unfortunately, it wasn’t reported, so we couldn’t do anything immediately, but that looks like that’s what caused the collapse, when everything came down from the mountain and washed through the culvert.”
He added that the council would “move heaven and Earth” to make sure it does not happen again.
“The culvert is checked every two years. It’s just the way that Storm Bert has come down and washed everything down with such ferocity, it’s caused structural damage to the arch and that’s what’s brought the collapse,” he said.
He could not give a date when residents would be able to return home and said anyone not able to stay with friends or relatives had been put into hotels by the council.
Mr Williams said he and his wife were devastated by what had happened but were more concerned about their friends who currently live in the house.
He said it was “frightening to think what could have happened when they were reversing their cars off the drive”.
“They could have been injured or worse,” he said.
Mr Williams said they first learned of the sinkhole on Saturday evening, when it was about one foot (0.3m) wide, adding: “To be honest, we wondered if the bungalow would still be standing this morning [Monday], but it’s still standing at the moment.”
Callum Morgan said he and his partner, Niamh – a tenant at the property – had been in an Airbnb property since Sunday night and expected to stay there for a few days.
“Brick by brick she said she could see the driveway going under slowly, and at one point we thought it was going to go up to the house, but at the moment it looks like it’s stopped,” he said.
Resident John Mitchell, 76, whose home sits near the edge of the sinkhole describes his frightening experience of coming home to it being barricaded off.
Adding that, “the hole just gradually got worse and worse as it was opening up.”
“I couldn’t see down to the bottom, but it was a good depth, it was really quite deep.”
What caused the Merthyr sinkhole?
Andrew Farrant, a BGS geologist, said the sinkhole likely resulted from a collapsed culvert and recent heavy rainfall, rather than a natural geological cause and it was “not just a case of filling the hole”.
He explained that repairs would involve stabilizing the void, excavating the site and reinstating the culvert to ensure the stream can flow safely.
Councillor David Hughes praised residents for moving out of their homes “without any fuss or bother” and said an excavator and four lorries loaded with boulders were seen arriving on site on Monday morning, ready for work to begin.
What is a sinkhole?
While any large hole that opens up in the ground tends to be dubbed a sinkhole, this catch-all term is not always an accurate description.
The British Geological Survey (BGS) described a sinkhole as “a natural surface depression caused by dissolution of soluble rocks at depth”.
Sinkholes can be formed by gradual dissolution happening underground, but they can also be caused by heavy rain or surface flooding, construction work, leaking drainage pipes, burst water mains and groundwater abstraction, the BGS said.
