A sinkhole reported on 02/04/18 has appeared in Merthyr Tydfil within a new build site, Cwrt Aneurin Bevan. The sinkhole which is reportedly 20 ft (6m) deep has resulted in local residents losing access to their new homes.
On the 4th January 2018, a 1.2m deep, 0.6m wide ‘’sinkhole’’ opened next to the Whitehaven – Workington railway line, near the coastal village of Harrington in Cumbria. For fears of the hole expanding and damaging the rail line, services were delayed in order to complete emergency repairs and infill the void. Initial observations have led rail engineers to speculate that a collapsed drain or coastal erosion accelerated by Storm Eleanor are the cause of the collapse. However, the correlation with known mine entries and collapses along the railway line have prompted Terrafirma to research further to see if past coal extraction may in fact be the cause.
Exploring the themes behind Sinkholes in the UK
At Terrafirma, understanding the ground is what we do best: Our CEO Tom Backhouse was recently asked to feature in Channel 5’s documentary Sinkholes to provide an expert insight into the roots behind their cause. Inevitably then, when high profile sinkholes such as those at Fontmell Close, in St Albans or in Wednesbury, causing up to six million pounds of damage and evacuating families from their homes, we ask ourselves “can sinkholes be predicted?”.
Over the last few months and years, the experts at Terrafirma have meticulously observed, understood and recorded each sinkhole as they form. Now, armed with this information, Terrafirma is proud to present a new dataset and report feature; ‘SinkholeAlert’, allowing our team to examine the common themes behind these hidden dangers.
Delve behind the scenes of the Channel 5 documentary on Sinkholes.
The word sinkhole has become a term broadly used term to describe any hole in the ground created by erosional processes and the drainage of water. Ground hazards in the UK are often synonymous with the word sinkhole which can span from just a few feet in diameter to gigantic chasms large enough to swallow whole buildings.
They can have devastating consequences as can be seen on the new three-part Sinkhole documentary which began on Monday 20 November on Channel 5 and features extensive commentary from sinkhole expert and Terrafirma CEO and founder, Tom Backhouse.
Terrafirma CEO Discusses Lender Policy on Mine Entries.
Earlier today, Terrafirma's CEO and Founder, Tom Backhouse featured on the new series of the Rip Off Britain: Live Series on BBC One. Tom was invited on to offer advice to a frustrated home-owner who has fallen victim to her property being located close to an historical coal mine shaft, making it impossible to sell.
The property has seen its market value drop by £61,000 and despite being up for sale multiple times, it remained unsold earlier this year at a property auction in the West Midlands.
Land. A word that is defined by its ownership, purpose, value or location and is often viewed, from a local, regional or national economic perspective, for its agricultural or development potential. However, land in the UK is also defined by our geological and extraction history, both of which can pose significant risks to property, investment and people.
The formation of a ‘sinkhole’ beneath a property in Wednesbury, West Midlands has received abundant coverage from the mainstream media during the last week. At Terrafirma, we have been looking into this event to try and understand more about its cause and wider context.
On September 25th, 2017, a large sinkhole appeared on the pavement at a pedestrian crossing in Brow Gate, Baildon, causing traffic disruption indefinitely. According to a pedestrian, the sinkhole opened within a time frame of a few minutes. Gas engineers from Northern Gas Networks are assessing the damage.
The local geological conditions are favourable for subsidence; superficial till (composed of clay) deposits shrink under prolonged dry conditions and 19th Century, unrecorded utilities infrastructure may be the cause of the collapse.
A sinkhole has been reported to have occurred within part of Beechwood Avenue, Cimla in South Wales. This is the second reported sinkhole in the neighbourhood after another ground collapse, later identified to be a mine shaft, opened up in January of 2016. The sinkhole is now being investigated to identify whether it is associated with the extensive shallow coal mining known to have occurred in the area during the 18th and 19th Centuries.
The age of solely relying on data in environmental risk assessment is over, with a visible shift in the way professionals perceive risks such as contaminated land and flood. Where historically data alone was enough to accept due diligence, now both a professional opinion and interpretative data modelling is a standard in assessing and managing these environmental hazards.
However, despite the significant annual financial expenditure (between 4 and 15% of all Buildings Insurance Claims in the past 5 years were attributed to subsidence) and the increasing visibility of the ‘Sinkhole’ phenomena, this shift in due diligence process has not been replicated in assessing the risks the ground pose.
On May 2017, an 8-metre-deep sinkhole appeared on High Street Green, Hemel Hempstead, causing the road to be closed until around November. This is in the same neighbourhood (within 200 metres, or less than a 10-minute walk) from the 6-metre-deep sinkhole that opened up in Oatridge gardens in 2014, resulting in the evacuation of 17 people from their homes .
On 29th June 2017, a 6 metre wide and 3 metre deep sinkhole opened in the middle of a busy Liverpool commuter route to the M62, Edge Lane, closing it for several weeks. United Utilities were called to the scene to assess the damage and discovered the sewer 6 metres down was blocked. The area rests upon superficial till rich with clays which are prone to subsidence which in turn can damage subsurface utilities.
The collapse of a chalk mine in west Reading forced the immediate evacuation of dozens of residents. These residents then suffered for years due to the extensive and drawn out remediation of the affected area, but eventually had their patience rewarded after the works finished and the area declared safe once again.
A large sinkhole opened in the car park of Pinner Wood School, Harrow, forcing its immediate temporary closure. Geotechnical surveys and site investigations have been commissioned to determine the cause of the collapse and assess the stability of the land.
A sinkhole has formed during September 2015 on Bull Street, Lower Gornal Dudley, West Midlands. As a physical example of ground subsidence, the Bull Street Sinkhole (BSS) is hardly remarkable; with a diameter of >2ft and a depth of 6-9ft1, the BSS is a relic of historical mine workings, typical of those that form in the regions of the UK with a pronounced mining legacy.
In this instance, the degradation of historic shallow coal workings (the exploitation of coal seams at depths of <30m) triggered subsidence, though subsidence caused by the exploitation of a further 60 resources (tin, lead, copper, iron, sandstone, chalk and limestone just to name a few) is common across the UK.
On the 14th March 2016, a 90 metre (300ft) deep mine shaft opened destroying the patio and a garage within a bungalow in Scorrier, near Redruth, Cornwall. Fortunately, the £200,000 property was unoccupied. The previously unrecorded 18th Century tin mine shaft opened during a mining investigation of the property during the mortage lending process.
On the 9th November 2016 a naturally occurring sinkhole opened up on Magdalens Road near the River Ure in west Ripon. The collapse, reaching depths of 9m, measured 10m x 20m and extended into the back gardens of three households. The sewage system connecting the residencies collapsed and a safety parameter was set up resulting in the evacuation of 12 homes. On the 11th November BGS undertook investigation works concluding that the site remained at risk of further slippage. Monitoring continued, especially of the surface tension fractures which when recorded, had extended to twice the distance of the collapses 10m surface footprint. The BGS response team, after completing data collection, liaised with Harrogate Borough Council, North Yorkshire Fire and Rescue Service, and utility services in regards to ground stability. Currently, the team then returned to the BGS to analyse the field data. Following this, the Harrogate Borough Council officers met with representatives of North Yorkshire County Council highways department, Yorkshire Water and Northern Powergrid. As of the 14th of November all residents remained displaced, with utility companies working towards making plans for temporary solutions.
On the 2nd May 2016 a sinkhole believed to be 60ft deep and 16ft wide opened up on the doorstep of one of Skillcrown Homes new developments within Brickfield Cottages, Plumstead. The result of which led to the establishment of a 25m hazard zone and evacuation of 50 residents by the combined effort of the emergency services and Hexagon Housing, all of which were provided with assistance at a council run rest centre and overnight accommodation by the housing association. Following this, on the 3rd May evacuated residents were reportedly staying with families or in hotels whilst structural engineers looked to secure the site. The result of which, 30 households were returned to normality, whilst 10 awaited contact by Hexagon Housing. The remediation efforts, whether planned, completed or on-going are unknown.
On 9th April 2016, a 20-foot-deep sinkhole appeared at Norwich’s Plantation Garden, causing subsidence cracks to the neighbouring hotel on Earlham Road. This is a stone’s throw away from the 1988 sinkhole which swallowed a double-decker bus. The Plantation Garden is itself an old chalk quarry, with multiple mining tunnels leading off it. It is the collapse of a mining tunnel that is thought to have caused this sinkhole.