Why Coal Reports Matter

Coal mining may have ended, but its legacy has not. Millions of properties across the UK sit above historic workings, mine entries, geological features or areas shaped by past extraction. These legacy risks remain live and capable of causing real-world issues, from subsidence to gas migration, long after active mining has ceased.

Here, we explain why coal searches continue to be an essential part of conveyancing due diligence, and why understanding the behaviours of historic mining is critical to protecting clients, lenders and property professionals today:

Underground Mining. Mining coal below ground causes subsidence. In deep mining, the lowering of the surface tends to occur over a relatively short period and may show as tension or compression strains that cause damage to buildings or sometimes simply a uniform lowering of the ground with no damage at all.

Shallow workings behave differently: they do not consolidate in the same way, meaning the effects can continue for much longer and present a continued, present-day risk. When shallow workings do settle, this is most likely to appear at the surface as a crown hole or sinkhole. In most cases, the 1991 Coal Mining Subsidence Act provides a degree of protection to landowners.

Opencast Mining (quarrying). With planning policy often favouring development on brownfield land, many new homes are now built on former opencast sites. Coal mining subsidence legislation generally does not cover damage arising from these sites, and new developments may also present environmental considerations.

Mine Entries (Shafts and Adits). Historic mine entry records evolve over time and earlier reports cannot always be relied upon. After the Lofthouse disaster and the subsequent Mines (Precautions Against Inrushes) Regulations 1979, extensive research was undertaken to identify and map shafts and adits. This work continues today, with new entries added or revised as evidence emerges.

Coal Mining Geology. Historic mining can alter the geology near the surface, causing rocks to fracture and form fissures. These voids may remain hidden beneath superficial deposits, which can fail unexpectedly and fall into the underlying cavity.

Subsidence claims. Subsidence claims provide a valuable indication of past ground movement and can help identify whether remediation has already taken place. They are an important part of understanding localised mining impacts.

Mine gas. Mine gas issues are uncommon but, when they occur, they can be serious. Two types of gas are typically associated with historic coal workings:

Blackdamp (carbon dioxide and nitrogen):
Produced by coal, this gas is heavier than air and can displace oxygen. While not poisonous, it is dangerous in enclosed or underground spaces. Under certain atmospheric conditions, blackdamp can migrate towards the surface. Known adits have now been secured to reduce access, though some remain vulnerable to unauthorised removal of surface grills.

Methane:
Methane is lighter than air and can migrate easily to the surface through conduits such as shafts, adits, fissures or cracks in the rock. Where methane risks are identified, the Coal Authority undertakes remediation, often through controlled venting. In some locations, methane is commercially extracted.

Known gas issues are reported in coal mining reports, however it is not possible to predict gas migration. Properties located near mine entries, particularly those without recorded treatment, are generally considered more susceptible.