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Sinkholes: What are they and should I be Worried?

Sinkholes: What are they and should I be Worried?

Sinkholes: What are they and should I be Worried?

Date: November 22, 2016

That sinking feeling
An Englishman’s home is his castle: somewhere safe, secure, and a place where you can pull up the drawbridge and forget about the troubles of the outside world.  Or at least that’s how it should be. Try telling that to the residents of Magdalen’s Road in Ripon, who had to evacuate their homes recently when a large sinkhole opened up in their back gardens.  Luckily no one was injured but the homes were evacuated as a precaution and also because the sewer system connected to their properties had collapsed.

This isn’t the first time that Ripon has been affected by sinkholes, in 2014 a 100-year-old detached house in a neighbouring street had to be demolished after a 25-foot-wide sinkhole opened up and rendered the property unsafe for habitation. What’s more, it is said that a giant sinkhole which opened up in Ripon in 1834 was the inspiration for the rabbit hole in Lewis Carroll’s Alice in Wonderland.

What is a sinkhole?
Sinkholes are essentially holes in the ground caused by a collapse of the surface layer. They can be naturally forming, or they can be caused by human activity (such as the collapse of an abandoned mine); they can form gradually or literally overnight, and they occur worldwide.  The British Geological Survey have said that Ripon lies in one of the most susceptible areas of the UK for sinkholes because of its gypsum deposits, which can dissolve more quickly than the surrounding limestone.  As the soluble rock dissolves, a space or void develops below the surface, which can result in a dramatic collapse as the surface layer eventually gives way under its own weight.  New sinkholes form more frequently when both the water table is low and heavy rainfall occurs.

Can sinkholes be detected before they collapse?
The good news is that yes, these geological hazards can be detected using methods such as ground penetrating radar (GPR) and electrical resistivity imaging (ERI), which can be used to detect subsurface voids which are associated with ground surface collapse. 

However, sinkhole detection is a specialist field and as such it is not cheap to organise this type of survey, although there are companies in the UK which offer this service. The problem of course is that usually the experts are called in when it is too late – once a property has already started to become unstable or because one sinkhole has already opened up, which naturally raises the question as to whether there are any more in the vicinity.

I’m buying a house in Ripon – should I be worried?
The starting point for any house purchaser is caveat emptor – let the buyer beware, meaning that it is the buyer’s responsibility to carry out sufficient searches and surveys to satisfy him or herself that the property they are buying is structurally sound and free from legal defects in title. Here at Coles Solicitors the starting point for our investigations are the property searches which we carry out on your behalf – for example we would always recommend that you undertake an Environmental Search which reviews flood, contaminated land and ground stability risks to provide comprehensive analysis for any purchaser buying a residential property. 

Sometimes the search results will highlight that a certain property is in an area with a particular risk, for example there may be an increased risk of flooding, or a property may be in an area associated with large scale mining in the past. In these instances, we would recommend that further, more specialist searches are carried out which offer an even greater in-depth analysis of the potential risks caused by (for example) historical coal mining in the area. We also as a matter of course always carry out an assessment of the likely risk of instability to your property caused by historical mining by using the TerraFirma Mining Risk search platform, which can provide a quick response to indicate whether the property you are thinking of buying is in a “Mining Risk Zone” which may warrant further investigation.

For your peace of mind
Sinkholes are certainly a very dramatic example of the type of serious structural problem that can affect a property, and our job as solicitors is to highlight cases where we believe that the property a client wishes to purchase may be at risk – so that the buyer, as any prudent purchaser should, can then instruct a surveyor to fully assess any areas of potential concern. Only once the buyer is in possession of as much information as possible about the property, including where necessary a detailed structural survey report, and have satisfied themselves that the risks of serious structural damage are negligible, would we advise our clients to proceed with their purchase – and to take out buildings insurance as well, of course – so your home really can be safe as a castle.