No need for sink holes to wreck confidence in Ripon
The hole that opened up under a Ripon house this week left homeowners with a sinking feeling. Should they be worried? Sharon Dale reports.
SENSATIONAL pictures of a house in Ripon being swallowed by the earth and ripped asunder have left homeowners questioning the stability of the ground beneath their foundations.
The 25ft wide sink hole, which opened up on Monday, has prompted frantic Googling and crash courses in geology via Wikipedia.
What’s clear is that sustained monsoon-style rainfall is the most likely catalyst. There is usually an average of two sink holes a year in the UK and there have been six so far in 2014, including a 15ft wide chasm in High Wycombe that consumed a car.
In some areas of Ripon, there is a Permian layer of gypsum deep underground that is apt to dissolve when deluged by seeping groundwater and overloaded underground rivers, known as aquifers.
The issue of gypsum dissolution has been on geologists’ radar for years and the British Geological Survey has reported on the natural phenomenon.
Paul Hildreth, of the Yorkshire Geological Society, says: “As gypsum is soluble, given lots of time, any increase in rainfall is almost certainly going to cause faster solution. However, human activity has a part to play in accelerating this problem.
“The efficiency of urban areas to transport water through Tarmacadam surfaces and drainage systems may direct faster flows and greater volumes to specific areas and make these hot spots more prone to the solution of gypsum. Added to that, the weight of buildings in susceptible areas will contribute to ground failure and subsequent collapse.” He adds: “Gypsum-bearing rocks, such as the ones at Ripon, occur in a narrow belt from Durham to Nottinghamshire but their thickness and purity varies. It has been recorded that as well as being close to the surface, the beds at Ripon are also strongly contorted which could make them more prone to solution than neighbouring areas.”
In 2005, a lecture by Prof. Anthony Cooper of the British Geological Survey, revealed that the gypsum problems in the Ripon area were so severe that “special planning regulations are enforced for development.”
Harrogate Council has long insisted that all planning applications in gypsum affected areas are supported by a ground stability report. That doesn’t apply to older properties, of course, so how concerned should homeowners be about the possibility of subsidence?
Chartered surveyor Jon Charters-Reid, who is keen to put a stop to the panic, says: “Frankly, you have more chance of winning the lottery or being hit by a falling piano than your house falling into a sink hole. They are very rare, so much so that insurers see them as an act of God.”
He adds that although geological maps show gypsum deposits running through Ripon, that doesn’t mean property is at risk.
“Some of the houses have stood for hundreds of years and they’re still standing. What happened this week is a freak occurrence due to freak weather conditions.
“We’ve had some of the heaviest rainfall for 200 years and that has had a knock on effect causing flooding and also causing gypsum to dissolve.”
Jon, who is based in York, suggests that prospective buyers invest in a comprehensive property survey from a local independent surveyor who knows the area well.
The surveys cost from £300. If there are concerns about ground stability then a thorough geological report is a good investment. It should cost around £200. Insurability should also be checked to make sure there is cover available and at what cost.
Taking the DIY approach and fretting over geological maps and scientific data you’ve found on the internet is pointless, says Jon.
“You might see that there is gypsum under or close to a property and panic when there is absolutely no need. It’s the same with flood maps. They assume a worst case scenario. Some villages have been placed in flood plains on the maps when they have never flooded and are not likely to.
“Personally, I am not at all concerned about sink holes.
“I think we should be far more worried about the effects of fracking in this country, where we have a lot of aquifers. There is a lot of uncertainty about what could happen.”
Estate agent Andrew Beadnall, of Beadnall Copley, which has a branch in Ripon, is worried that the media storm could affect Ripon’s soaring popularity. The small city has become increasingly attractive to buyers, who are keen to be close to the grammar school and to live in a pretty, historic area with its own cathedral, a Booth’s supermarket and fantastic links to beautiful countryside and to the A1M.
“Ripon is incredibly popular. At the moment we are selling properties as soon as they come on the market but I am concerned that the sensationalism surrounding the sink hole will affect confidence,” says Andrew. “There is absolutely no need for panic. You really do have more chance of winning millions on the lottery than being affected by a sink hole.”
BY GEORGE: This Georgian townhouse is in a conservation area close to York city centre and has views of the Minster. The period features have been renovated and restored. It was one of a pair of houses that had been carved up into flats, but now is a desirable family home in a sought after area.
DON’T PANIC: The house in Ripon which collapsed into a sink hole. But the chances of your property being similarly affected are very remote.