Paul Vernon · Surveyor (retired)
Although it is now virtually extinct as an industry in Britain, there is a long history of coal mining going back to and beyond the middle ages, and whilst you might think that you know where it has taken place, coal is much more widespread than you might think. Aside from areas you may think of, coal mining has historically taken place in such places as Devon, Kent, Somerset, Pembrokeshire, Lincolnshire and Sutherland. MNB Assess is the first platform to provide all relevant coal mining information for England and Wales in an interactive map alongside other constraints to development. Sign up for a free trial. The data is sourced directly from the Coal Authority.
Coal is extracted in one of two ways, by digging an open hole from the surface, or from underground cavities, accessed either by means of tunnels or shafts. When mineral is extracted it leaves a void that, underground at least, is rarely replaced (or backfilled) and if it is, is never replaced with material of the same density, which means that there is a void remaining. The surrounding material is rarely robust enough to bear the weight of the materials above the coal seam and at some time will collapse. This collapse will eventually migrate towards the surface where, depending on what is there, damage may or may not occur. This could manifest itself as something as little as cracked plaster or sticking doors and windows, or as drastic as collapsed buildings. Some buildings can survive (or even thrive) subsidence!
The time and extent that this process can take will vary depending on the thickness of the coal extracted, the nature of the materials above the coal and the depth at which the coal was extracted, and could take days, weeks or even years to manifest itself at the surface.
The tunnels and mineshafts that were used to access the coal seams can also present hazards. In the “old days” these entrances might have simply been abandoned with no care as to the consequences. Any entrances that have been made redundant over the last 50 years or more will have been safely sealed and will present no danger to the public, but there will be mine entries abandoned from before that which will have had no or inadequate means of securing. These might fail without notice and when they do, they often make the news.
Records of early mines are few and far between, and until 1840 there was no legal requirement for plans to be kept of where mine workings were and it was not until 1872 when such maps had to be deposited centrally.
As previously mentioned, coal has also been worked directly from the surface though rarely, if at all before the 20th Century, and so records are pretty good. This is referred to as Opencast Mining. I remember my grandfather telling me that there was nothing as valuable as a hole in the ground and he was right! While often the voids left after coal was extracted were in-filled with the unsaleable mineral that was removed to access the coal, fortunes have been made by filling commercially with other materials the owners of the holes were paid to accept, many becoming municipal waste sites. The regulation and quality of these operations has improved year on year, and early examples of this activity were less than ideal.
The problems arising from opencast sites are that when in-filled, the material may be loosely tipped and so differential settlement of these materials will occur. Depending on the circumstances this may present problems to buildings, but these risks can be eliminated at the design stage. Alternatively the nature of the infill material may present problems, especially if it were an industrial or domestic waste product, which is a separate subject entirely.
The Coal Authority owns, on behalf of the country, the majority of the coal in Britain, and licenses coal mining. It manages the effects of past coal mining, including subsidence damage claims which are not the responsibility of licensed coal mine operators and, relevant to this note, it deals with mine water pollution and other mining legacy issues.
MNB Assess has a really useful interactive map viewer that allows the user to research a particular area. Initially, MNB Assess shows “Coal Mining Reporting Areas”. A Coal Mining Report gives information on: mine entries within 20 metres of a property’s boundaries, gas emissions from coal mines, other coal mining hazards reported in the area and plans for future coal mining in the area. In addition, MNB Assess users can get more detail, including individual known mine entries and, relevant to us, “Development High Risk Areas”, which are the zones in which the coal seams will have been worked.
What can you do when buying a house?
When you’ve found your ideal home, have a look at the websites I’ve mentioned. If your house is located in a Reporting Area then your solicitor should request a Mining Report, and you can be sure that your lender will be aware of this and demand one. In my opinion, the outcome of this report is unlikely to endanger your purchase, but will inform you and your lender.
Would I buy a house in such an area?
Many do, and many cities where large numbers of people live are built on coalfields. I live on one. Most coal extraction finished decades ago and the effects will have shown themselves already. If houses have been built in areas where subsidence is possible, then modern standards will have demanded that buildings will have been constructed with special foundations that will tolerate any movement. If a problem does occur, then the Coal Authority is the first port of call, and with few (if any exceptions) is responsible for making safe and rectifying any problems.