It was one of the biggest sinkholes that has appeared in Wales. The giant void engulfed part of a road, a pavement and a huge chunk of the driveway belonging to the family of Love Island star Liam Reardon in Merthyr Tydfil during Storm Bert on December 1 forcing the evacuation of 30 homes.
Over several days, it kept growing to be 40ft deep. It made headlines across the world, including Fox News in America which described it as large enough to swallow double decker buses. And it sparked huge confusion and panic with many fearing sinkholes might appear in other areas.
We spoke to a civil engineer who has been helping to lead the effort to make the area safe and who has addressed some of the confusion about what actually happened to reassure residents that holes are not just going to appear under their homes.
Paul Edwards is the managing director at Edwards Diving Services (EDS) based in Pontypridd. It is an multi-disciplined civil and marine engineering services contractor with a wide range of expertise including, but not limited to, diving services, rescue work, various engineering services, geomatics and pollution control.
Paul explained how EDS often works alongside local authorities to prevent sinkholes and fix culverts, while other work includes working alongside police forces to locate missing people and bodies. For the latest Merthyr Tydfil news, sign up to our newsletter here
READ MORE: ‘Water pours through our walls when it rains, there are rats and it smells’
READ MORE: Dramatic footage shows swollen river turn into waterfall outside pub and homes
He said that EDS had become involved early on and assessed the area on the Nant Morlais estate before starting temporary works to secure the cavity. Since then, hundreds of hours of work have been carried out and there is still much more to be done. He said that the problems began when a landslide during the storm sent large rocks down an underground stream, known as a culvert, ripping out the supporting structure and causing the soil above it to be washed away.
He said: “First of all we had to clear the collapsed culvert, It was a big Victorian culvert, 2.5 metres in diameter. It collapsed because [storm Bert caused] a landslip upstream, so an awful lot of boulders came down and ripped up the section where there was construction joining the culvert. It then collapsed and washed out the surrounding soil around it, pushed that downstream and undermined the tarmac which formed the sinkhole.
“We dug it out with a remotely operated vehicle called a Vulcan, which is hydraulically operated from the surface. We then cleared all the debris. It enabled us to put a large 1.8 metre steel reinforced pipe in the hole to join both ends of the culvert.”
The sinkhole after the installation of a steel pipe -Credit:Matthew Horwood/Getty Images
Next Paul said they poured concrete into the sinkhole before putting around 1,290kg of stone on top. He said the temporary works are strong enough to keep the area safe for around a decade, however that a permanent design is currently being drawn up with construction due to begin in January.
He said: “What people can see now is not going to be the finished article. We’ve got to pile drive it, and before you drive the piles you have to fill the hole because they need to be supported by something.
“We are hopefully going to drive the piles in January, then dig it out, remove the temporary section of steel pipe and then rebuild the culvert – which is about 10 metres long.
The temporary work will take any storm now and would last for 10 years. It’s called temporary because we need to get a design for the permanent works, which takes an awful lot of organising through the residents, the council and the designers. Once it is approved we will be sending that out to all the relevant parties. The permanent fix will last about 100 years.”
Paul said neither a date or timeframe for the permanent job has been set at this stage, however, an update will be issued when the plans have been finalised. In the meantime, he said residents can be reassured that the area is safe.
Reassuring the wider public, Paul explained that although his company regularly deals with culverts and sinkholes, it is rare for a collapse of this scale to occur. He said there is no need for people to worry about the possibility of a massive sinkhole appearing near then, however that all sinkholes should be immediately reported.
He explained: “Especially somewhere like Wales, because of our industrial past, we’ve got an awful lot of streams which have been covered over and become a culvert. There are many culverts under industrial estates, but there are culverts in all sorts of places.
“For example we’ve seen culverts collapse before in the middle of someone’s front room. There was also an incident a few years ago in Pontypool where a sinkhole occurred and we were actually inside the culvert when it collapsed. That was quite scary. These things do happen, but they don’t usually happen on quite this scale.”
-Credit:WALES NEWS SERVICE
He explained that local authorities are aware of the culverts in their area, and that they are routinely checked for weakness and other issues by the highways department.
He said: “All culverts, waterways and bridges have an inspection scheme which is carried out by local authorities regularly, so this is not a regular occurrence. Culverts will have a local authority highways team, because usually culverts carry water under a road. They will have a list of culverts of all shapes and sizes.
“If there is any problem with a culvert they usually bring that inspection up every few months and get it repaired. We’ve repaired many of these culverts before they become sinkholes.
“People going about their lives shouldn’t be worried at all about sinkholes. For them to collapse in this way is really rare. We did one earlier this year in Rhymney which was nowhere near the size of the one in Nant Morlais. Because that one is so deep with a fast flowing river, it created a massive sinkhole. It was literally a perfect storm. If you see a sinkhole, report it to the council straight away because you don’t know what is going on underneath the ground.”
READ MORE: Wales weather maps show where worst of storm will hit amid 15 hour Met Office warning
READ MORE: Huge sinkhole appears in woman’s garden after Storm Darragh flooding
Paul said despite the last month being an extremely stressful and disruptive time for those affected by the sinkhole, he is grateful for the patience shown by residents in Nant Morlais.
He said: “Working with the residents has actually been quite touching. Usually you will get people who come up and ask why you won’t do it more quickly. I have seen [recent] social media posts which have picked up so much misinformation. People become keyboard warriors and ‘experts’ because they don’t understand the situation. The residents of Nant Morlais understood exactly what had happened.”
He further thanked the local authority, his colleagues and others involved in the repairs working so hard on such a unique and challenging job. He said: “Welsh Water, British Gas, BT and the local authority are damned if they do and damned if they don’t, but they really have been awesome every step of the way.
“This job has been quite challenging because of the safety side of it and the fact the sinkhole was getting bigger every day we were there. We also had the challenge of potentially losing a house to the sinkhole, but we managed to secure that and prevent it from happening.
“The first week we did around 80-odd hours on site and even worked through Storm Darragh. Everyone realised the situation was really stressful for the residents so everyone pulled together and we have done a good job.”
He added: “We can guarantee the sinkhole is safe and everything will be okay. There will be some disruption in January when we put 16 metre piles in and around the sinkhole, but that will be a permanent fix.”