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The Independent
2 days ago
- Climate
- The Independent
New clues over massive Surrey sinkhole after network of tunnels discovered near street
Months after a massive sinkhole sparked a major incident in Surrey, a network of underground Victorian tunnels have been discovered close to the site. Residents of quiet Surrey village of Godstone were told to 'get out as quickly as possible' after a huge crater swallowed a street overnight on February 17. More than 30 homes were evacuated as the sinkhole grew to up 19 metres in length, before a second one opened up days later. Engineers working to repair the hole have now confirmed the discovery of abandoned sand mining tunnels around the site, which may 'provide a clue' into what caused the havoc. Lloyd Allen, infrastructure manager at Surrey County Council, told the BBC: "Currently, we're investigating the Victorian tunnels, plotting them to see the extent of them and where they go. "We'll likely be finished by the early part of December, but there's a lot of reconnecting services and redoing water mains, gas mains and electric cables." He told the broadcaster that the discovery of the eight-metre deep tunnels "puts one of the pieces into place' over why the hole opened up, but added there were 'several scenarios that could have happened that led to this collapse". In February, an expert suggested the incident could be related to the collapse of a nearby abandoned sand mine. Andrew Farrant, the British Geological Survey (BGS) regional geologist for southeast England, said how old maps of the area, published in 1872, appeared to show an entrance to a sand mine very close to the crater. 'It is possible other unrecorded sand mines occurred in this area,' Farrant said. 'It is also possible that a leaking pipe has weakened the rock and led to the failure of a putative mine, assuming it exists and extended under the road. Equally, it is possible that gradual failure of a mine roof caused the water main to fail, triggering further subsidence.' While engineers say they hope the repairs to be finished by December, local businesses told the BBC they have been 'left in the dark' over the repair plans. One businesses owner said his income had been slashed to a third of what it once was due to the sinkhole. "They said they would keep us up to date, but this hasn't happened," Shane Fry, who runs DD Services, a garage on the high street said. "We need to know. It will benefit everyone in the area." Will McLean, the owner of a residential windows and doors company described how the sinkhole had 'reduced footfall to virtually zero'. "Financially it has been massive,' he said."In terms of business, we are down 60% to 70%, which is huge - devastating in fact." Matt Furniss, Cabinet Member Highways, Transport and Economic Growth at Surrey County Council, said, 'This continues to be a highly complex incident involving a number of investigations led by our Highways Officers and other agencies, including specialist teams and utility companies. 'We are continuing to update local residents and businesses as we progress through each stage of the process. We're also looking at how we can minimise the impact on local businesses while the necessary road closures are in place. 'Thorough investigations need to continue to understand the cause of the collapse and subsequently how we fully and effectively repair the area. We hope to have the road re-opened during December this year, but our focus will be on ensuring the road is safe to use so the exact date will be confirmed once we are fully assured of this.'
The Independent
22-02-2025
- Climate
- The Independent
What lies beneath: Could a Victorian map hold the answers to cause of Surrey sinkhole?
A Victorian map could hold the answers to the exact cause of the two sinkholes that opened up to swallow a quiet Surrey village's high street. The crater first appeared in Godstone High Street on Monday with locals woken late at night and told to "get out as quickly as possible" over fears of a gas explosion. A major incident was declared with 30 properties evacuated before a second void split open another part of the road a day later. Almost a week on and experts are scrambling to find the cause of the collapse as locals, who have no idea when they might be able to return to their homes, fear this sinkhole could be just the first sign of trouble for Godstone. One expert has suggested the crater may be related to the collapse of a nearby abandoned sand mine. London's insatiable demand for sand for building during the industrial revolution led to quarries being dug out underneath the Surrey village with the material said to have been used in the 18th century for the flooring of Westminster Hall. British Geological Survey (BGS) regional geologist for South East England, Andrew Farrant explained how maps of the area published in 1872, appear to show an entrance to an old sand mine very close to the 'sinkhole', which could be related to the ground collapse. There are also two old mines nearby with entrances on the east side of the road south of the collapse site. The entrance to the nearest and largest of these is in an old builder's yard and extends around 100m to the east under allotments. 'It is possible other unrecorded sand mines occur in this area,' Andrew Farrant said. 'It is also possible that a leaking pipe has weakened the rock and led to the failure of a putative mine, assuming it exists and extended under the road. 'Equally, it is possible that gradual failure of a mine roof caused the water main to fail, triggering further subsidence.' A dense cave network filled with subterranean passages thought to be about eight miles in length, also lies just 80-200ft below the surface, it has been reported. And the Home Office even looked into protecting Londoners from the horrors of the Blitz in the caves under Godstone, according to a local history website. A Surrey Mirror news cutting from November 1879, dug up by local caver Peter Burgess, also reports that a horse-drawn van trying to connect residents to the water supply was swallowed when a large hole appeared in the same stretch of Godstone High Street. Fortunately both survived after the water flow was shut off just before it reached the horse's head. Back to the present day and Sarah Jones told The Independent she was visiting the site as her daughter was about to exchange contracts and ahead of a big move to Godstone. 'It's a gorgeous village but what a great time to buy', she laughed. 'We saw all the news and had to come see and check it out. Whether we call it [the sale] off altogether is a different story. Would they be able to sell to anyone else now? It's going to be a problem. We're pushing for a reduction.' One grandfather, defying the council's evacuation orders, told The Independent: 'It's all the Londoners' fault really. 'For 400 years they have taken the rock out of here. 'Most of London is built on Godstone stone if you look it up. All their lovely sandstone buildings are from here. That's the truth of the matter. 'We gave them all our nice sand and they just give us s*** back for the dump. That's what they have done.' Shane Fry, who runs garage DD Services next to the sinkhole is fighting to keep his business open as the now-eerily quiet high street has promoted Godstone locals to nickname the village 'Godshole'. Recalling the moment it opened up on Monday night he said: 'I was in the local pub playing with our darts team. We had just left and a couple of lads were walking home and saw the start of it happening. 'They were a bit fascinated more than worried at that point.' As time wears on business owners' anxiety only increases as the usually bustling high street has ground to a halt with fears the road could be shut for up to six months - which could prove devastating. 'The road needs to be closed for everyone's safety but it's going to have a detrimental effect for a long time', Mr Fry said. 'I need to ensure that my customers stay with me. It's hopefully not going to get worse.' He added: 'It's a great village, a great community, a lot of locals have proven that by supporting everyone who needs it. Godstone is a great place to live and work, hopefully we can stay open. But I don't think we're going to get any answers any time soon.' Roger Morel, who has lived in Goldstone for 22 years and woke up to discover his house had no water pressure after the sinkhole appeared, said the problems should have been foreseen. 'There have been problems with the water main forever. They are all Victorian and you have the caves underneath here so it has probably washed all the ground out and it's all sunk down. 'Now we get loads of heavy lorries bulldozing through this high street, some parts are 15th Century and it wasn't designed for these huge vehicles. 'People are just worried about when the next sinkhole is going to come. They've had leaks before coming out of the tarmac. 'I would love to see a 7-tonne weight limit put in to stop the lorries, some must be 30 tonnes they are huge and it's lucky no-one was hurt.' When The Independent visited, Surrey council staff were telling locals it was still too dangerous to move their cars back on their driveways after one was left teetering on the edge of one of the craters. John Thomas, 54, who lives on the edge of a cordon surrounding the vast cavities said there were caves underneath his allotment. He said: 'It's only 50m away so it is as close as you want it to get. One engineer snuck us in to have a look. We hadn't realised there were two holes forming. 'You can see under the road. It's like one massive hole with a road going over the top of it. There is nothing to support it at all.' He added: 'We know there are lots of caves underneath us - so it is a bit worrying. All the kids want to see what is going on but they aren't letting anyone close.' Investigations are continuing to determine the exact cause of the sinkhole and to establish the full extent of the damage. Once the area is stabilised, a repair and reconstruction plan will be developed, Tandridge District Council said. Five families are still being supported with overnight accommodation, with one father even forced to sleep in his car, according to locals. Commenting on the Godstone void, Mainmark UK commercial and infrastructure lead David Hedley warned that the impacts of climate change could lead to more 'devastating' subsidence events and sinkholes. 'As bouts of extreme weather – from washouts to periods of draught – become more prominent with climate change, I would expect these to trigger more ground instability events in years to come,' he told Ground Engineering. 'In the last year alone, sinkholes have appeared in Wimbledon, Merthyr Tydfil and Nottinghamshire, resulting in disruption and costly repairs. Postcodes which lie on soft clay soil are also vulnerable, which covers a lot of the South East.'
New York Times
20-02-2025
- Climate
- New York Times
There's a Big Hole in England
A giant crater in the southeast English county of Surrey has enveloped part of a residential street, causing the county to declare a major incident. Here's what we know. What's going on? There's a hole. A what? A hole. Actually, two holes. The first hole appeared on Godstone High Street on Monday night, and grew on Tuesday to 65 feet by 20 feet and 16 feet deep. The second hole on the other side of the road is 16 feet by 16 feet, and 16 feet deep. Since Tuesday, both holes have stabilized and neither are continuing to expand. What caused this? The cause is unclear, but geologists have some theories. The area is built on weakly cemented sandstones, which formed during the Lower Cretaceous period more than 100 million years ago, that can be eroded by running water, Andrew Farrant, a geologist for the British Geological Survey, said in a statement. While this is not usually an issue, a sudden change in the composition of the ground — caused by heavy rainfall or an influx of water from a burst pipe — can trigger a collapse. In Surrey, a burst water main might have flushed out weak sandstone bedrock beneath the road or caused the collapse of an old, unrecorded sand mine. Or the collapse of a mine roof might have led to the bursting of a water main, said Vanessa Banks, a geologist for the British Geological Survey. More broadly, the push in Britain to build more houses has meant that more water goes into aging infrastructure, putting more pressure on pipes, she said. Periods of intense rainfall, which are likely to become more common because of climate change, can also put more pressure on the seals of aging pipes, she said. Is anyone in danger? No, but people in about 30 properties have had to evacuate, the Surrey County Council said. 'Our house is not secure at all,' one resident who evacuated, Noosh Miri, told the BBC. 'At the moment we don't know the extent of the damage but we do know we won't be going home for some time.' What other havoc has the hole wreaked? Traffic has been diverted from the road, the main road in the village. A car is teetering on the edge of the second, smaller hole, and the owner hasn't been able to move it. Another resident, Josh Neame, told the BBC that he slept in his car on Monday night after the hole first appeared. What are they doing about the hole? They'd like to fill it. The site is currently being tested by structural experts, and more permanent repairs will happen once it is deemed safe, the Surrey Council said. How long will repairs take? Probably months, said Matt Furniss, the Surrey County councilor responsible for highways. Displaced residents may be able to move back sooner than that, but the timeline is unclear, he said. 'We cannot give a definitive date at this point,' he said. Over the last few days, residents have been able to return home for brief visits to collect personal belongings. Are holes like these common? Sinkholes, formed by the dissolution of limestone or other soluble rocks, are common in certain areas, such as near Mammoth Cave National Park in Kentucky, and in parts of Florida. But sinkholes in Britain are usually small and tend to occur in rural locations. Periodically, new holes form in busier areas in Britain. In December, a hole in Wales opened up in the driveway of a past winner of the reality-TV show Love Island, Liam Reardon, according to local media. Heavy rainfall can trigger the collapse of old mine shafts or infrastructure, though these cases are not technically sinkholes because the crater is not formed by the dissolution of soluble rocks, according to the British Geological Survey. Still, people should not be worried, Dr. Banks said. Residences are generally not allowed to be built on areas where abandoned mines are known to have existed. In instances where holes have occurred, houses have been built above medieval mines that had not been recorded.
The Guardian
20-02-2025
- Science
- The Guardian
What are sinkholes, how are they formed and why did one appear in a Surrey street?
Residents of Godstone in Surrey have been evacuated from their homes amid fears that two large sinkholes in their high street could trigger a gas explosion. Here we look at what causes sinkholes, whether they are becoming more common and what can be done to prevent them. Sinkholes are large pits that appear in the ground when the underlying rock either collapses or is washed away, dissolved in water or degraded through other processes. In Britain they are typically 5 to 10 metres deep but can reach down more than 50 metres. Some sinkholes form when soluble rock such as chalk, gypsum or limestone is dissolved by acidic rainfall or groundwater, causing the overlying ground to collapse. Others form when underground caves collapse. Yet more form when loose material under the surface is eroded by flowing water. Heavy rain, surface flooding and drought can all trigger sinkholes by destabilising underground cavities. Mining, burst water mains and construction work, which affects surface drainage and the loads that ground has to bear, can also be a factor. Absolutely. The Mendips, parts of Wales, the Peak District and the northern Pennines which sit on carboniferous limestone, a hard sedimentary rock made of calcium carbonate, are all hotspots. Areas of Dorset, Hampshire and the Chilterns, where clay and sand sit on chalk, are also vulnerable. The riskiest spot in Britain is around Ripon in North Yorkshire, which sits on gypsum, a soft mineral that dissolves much more easily than limestone. Yes. Godstone sits on weakly cemented sands that are prone to erosion and flushing by running water. Andrew Farrant, the British Geological Survey's regional geologist for south-east England, said it was normally not a problem unless there was a sudden change in the hydrogeology. That could happen if someone dug a large hole below the local water table, or if there was heavy rainfall, flooding or a sudden ingress of water from a burst pipe. Godstone sits on a network of tunnels and sand mines that date back to the 17th century. Maps published in 1872 reveal an entrance to an old sand mine very close to the site of the Godstone sinkhole, Farrant said. Two other old mines have entrances south of the sinkhole, on the east side of the road. There could be further sand mines in the area that are not recorded on maps, he added. It is impossible to be sure without more information. 'It's probable that the sinkhole is due to a burst water main flushing out weak unconsolidated sands from beneath the road over a period of time, creating a cavity which then collapsed when it got big enough,' Farrant said. But the sinkhole might have been caused by the collapse of an old, unrecorded sand mine, he added. A leaking pipe could have weakened the rock and led to the collapse of a mine, if one extended under the road, though it's possible that a mine roof collapsed and broke the water main. Dr Arya Assadi Langroudi of the University of East London favours the burst water main theory. 'The high pressure water from the damaged pipe likely 'boiled' the sandy soil beneath the surface, creating cavities that led to the ground collapsing,' he said. A second sinkhole formed on the high street shortly after the first. Hard to know. Many sinkholes are never recorded, not least because the vast majority form in remote parts of Wales, the Peak District and the Pennines. But there are sporadic surges in sinkhole formation, usually linked to prolonged spells of heavy rainfall. The wet winter of 2012 triggered a spate of chalk mine collapses in south-east England. 'I would be very wary of saying that the number of sinkholes appearing across the UK has increased over the last five years or so,' Farrant said. That may change with global heating and more extreme weather. Geologists expect heavier rainfall to exacerbate sinkhole formation, but also collapses of old mine shafts, sewers, drains and culverts. 'Many of our older Victorian culverts and drains simply weren't designed to cope with some of the demands placed on them due to changes in climate and increases in population and urban development,' Farrant said. In vulnerable built-up areas, ensuring sufficient drainage is crucial, said Assadi Langroudi. 'If the ground can be stabilised, investing in proper drainage infrastructure can prevent the dangerous combination of water and loose sand from leading to further collapses,' he said.
Yahoo
19-02-2025
- Climate
- Yahoo
What is a sinkhole and how does it form?
Residents in the Surrey village of Godstone have been evacuated after two sinkholes opened up this week along large parts of the high street. The original hole first appeared late on Monday night, growing to at least 65ft (20m) long by Tuesday lunchtime. Sinkholes are not uncommon in the UK but can sometimes appear suddenly. What might be the causes and should we be more worried about them? A sinkhole is a depression in the surface because the underlying rock has collapsed. They can be saucer-shaped or appear deeper more like shafts. If they occur in built-up areas they can appear more irregular as a road or another structure above can distort the shape. In Godstone, the collapsed ground is under a road which is partially concealing the size of the depression. Sinkholes can appear for many different reasons - it is often due to the geology but human factors can also be a cause. One of the most common reasons for a sinkhole is when rocks like limestone or chalk break down. This happens because carbon dioxide from the air dissolves in rainwater to form carbonic acid - this then percolates through the rock and reacts with it, causing it to dissolve. Sometimes this process can happen gradually, where the depression becomes larger over time. In other instances, the limestone sits below another layer of rock, which means that as it gets dissolved there are no immediate signs at the surface. The overlying rock, sometimes clay or sandstone, will then suddenly collapse into the depression beneath - called a 'collapse sinkhole'. These are most common in South Wales where sandstone rocks lie above caves in the limestone. But human activities can also accelerate the formation of sinkholes or cause the ground to collapse in a similar way. Andrew Farrant, British Geological Survey regional geologist for south-east England, suspects that is what has happened in Godstone and it is not a true sinkhole. He said that one theory is that a burst water main has caused a sudden influx of water into the sandstone bed "flushing" the rock out the way. Pete Burgess, of the Wealden Cave and Mines Society, said a quarry marked "sand pit" can be seen on 19th century maps of land directly under the sinkhole. He added that sand from the pit was dug out and used for building and gardening purposes. Mr Farrant said that sand pit had been filled in but he added that there had been a significant amount of historic mining in the area and it cannot be ruled out that there were some unmapped pits and quarries that have been built on. They are common in the UK because of the abundance of limestone and chalk rock and historic mining activities. Limestone and chalk are formed from the deposit and compression of micro-organisms found in shallow warm seas. Millions of years ago the UK was located further south towards the equator and was much warmer with parts of the country submerged - creating the ideal conditions for these rock types to form. Vanessa Banks, expert in shallow geohazards and risks at the British Geological Survey, told the BBC's Radio 4 PM programme: "Sinkholes occur in spates but many are not recorded as they occur in remote areas." She added that meteorological conditions play a role as extreme downpours can flush water through the rocks or put pressure on infrastructure like water mains. Last December, about 30 homes were evacuated in Merthyr Tydfil after the ground collapsed, and in 2014 sinkholes occurred at five to ten times the normal rate across south-east England after intense storm conditions. 'Collapse sinkholes' which can appear suddenly and without any warnings at the surface, like cracks or subsidence, can be dangerous. In 2010, a sinkhole measuring 20m in diameter and 90m deep, appeared in Guatemala City which resulted in the death of one person. In this case heavy rains and poor drainage are thought to have weakened the underlying rock. And in January a truck driver had to be rescued in the Japanese city of Yashio after the ground collapsed due to a burst pipe. In the case of dissolution sinkholes geologists can indicate which areas are more at risk if the underlying rock is made up of chalk or limestone. For any new development in the UK the local planning authority does review the geology and any potential risks. But Dr Collins, reader in geology and geotechnical engineering at Brunel University, said that in this case where water infrastructure plays a role it is harder to predict potential ground collapses. "The pipe rupture does highlight the challenge that comes with having buried infrastructure as they are often buried at depths in excess of a metre. The depth is to reduce the impact of deep freeze during a very cold winter. "Unfortunately, this makes them hard to monitor and repairs can be difficult, including the replacement of soil in the excavated hole once the repair is complete," he said. British Geological Survey Huge sinkhole swallows up more of Surrey street Rescuers race to pull out truck driver stuck in Japan sinkhole for days Sinkhole road 'closed until further notice'
