The mines in Combe Down are abandoned shallow limestone mines that were worked mainly in the 18th and 19th centuries. They underlie an affluent residential area of some 600 properties. Mining involved the extraction of stone for the development of the City of Bath and surrounding towns. Approximately 80% of the mines, which are up to 9m high and cover a total area of about 18Ha, have less than 6m cover and this is as little as 2m in some places. Irregular mining practices, weathering and robbing stone from supporting pillars have left the mines in danger of collapse and therefore threatening the stability of the properties above.
The mines and surrounding areas are of great historical, archaeological and ecological significance. In particular, the mines are designated as a Site of Special Scientific Interest for the rare Greater Horseshoe bats. The Combe Down area itself is also within the World Heritage Site of the City of Bath.
The project is one of the largest mine stabilisation schemes ever undertaken in the UK. It involves stabilisation mainly by infilling with foamed concrete. For the project to succeed, full consideration had to be given to social, ecological, archaeological and commercial sensitivities, in addition to innovative engineering solutions.