Mine workings range from small-scale, local workings, such as graphite mining in the Lake District or jet mined in Whitby, to large-scale, national resources such as salt extraction in Cheshire. While modern mine workings meet stringent safety standards, many old, disused or abandoned sites are gradually decaying, leaving a long-forgotten legacy that poses potential problems to infrastructure and property. It is therefore essential we have knowledge of the distribution of former mining areas, helping us to plan for future development and ongoing maintenance.
What is a mining hazard?
The voids resulting from past underground mining activity pose a possible hazard. Former underground workings, particularly where shallow, may collapse and cause surface settlement.
Mining hazards in Great Britain can take on various different forms, including surface impacts like ground instability, gradual subsidence, cover collapse and groundwater contamination. As our climate changes, new climate conditions may exacerbate ground conditions further, leading to more incidents of this nature.
Armed with knowledge about potential hazards, preventative steps can be put in place to alleviate the impact of the hazard on people and property. The cost of such prevention may be very low and is often many times lower than the repair bill following ground movement.
Mining hazard examples
- An old mining substructure at Burrow Lead Mine in Derbyshire decayed, leading to a tunnel collapse and propagation to the surface. In turn, this caused roadside subsidence in 2011, which disrupted infrastructure
- Ferniehill in Edinburgh has seen issues where movement in old limestone workings has caused property damage
- Former chalk workings opened up, causing potential risk to life, at Gillingham in Kent (2014) and St Albans, Hertfordshire (2018)
- Ten million gallons of contaminated water flowed out of old mine workings at Wheal Jane tin mine, Cornwall, in 1992. The workings became flooded and the groundwater contaminated with heavy metal pollution; when an underground structure failed, a sudden outrush occurred
New research incorporated into our mining hazard data product
Currently. approximately two per cent of the land area of Great Britain is identified as having high susceptibility to mining hazard. The BGS Mining Hazard (not including coal) data product identifies areas affected by non-coal mining, providing a general assessment of hazard potential, thereby indicating areas at risk of possible subsidence associated with voids resulting from mine workings.
The newly released version of the BGS Mining Hazard data product also introduces a series of derived ‘zones of influence’ (ZOI) for evaporites (e.g. salt; gypsum; anhydrite), oil shales and building stone (e.g. limestone; sandstone; slate).
(Mining of coal is specifically excluded from this dataset. Enquiries on past coal mining should be directed to the Coal Authority.)
What is a zone of influence?
Zones of influence are areas indicating the potential surface extent that may be affected by underground workings. Calculations evaluate a number of criteria, including:
- seam thickness
- depth and dip of seam
- competence of roof and floor
- age of working
By integrating ZOIs into the product, a clearer picture of the surface area of legacy mining on property, people and pursuits can be established.
- Learn more about our mining hazard (not including coal) data
Case study: Long Meg Mine, Cumbria
- Worked for gypsum and anhydrite; approximately five million tonnes were extracted
- Mining was from horizontal adits and drifts driven from the side of the Eden Valley
- The mining method was pillar-and-stall, once underground
Try our open data option for free
BGS offers a generalised 1 km ‘hexgrid’ version of the data in ESRI shapefile format under the Open Government Licence to enable users to get a feel for our mining hazard (not including coal) data.
For further information please contact email@example.com.
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