The village of Combe Down, near Bath has been associated with stone mining since Roman times. It was in the 18th century however, with the pioneering technological advances introduced by Ralph Allen, that most of the mining activity took place. After his death, stone quarrying at Combe Down continued, but by the early 1900s the majority of the mining activity had ceased.
The Combe Down Stone Mines Stabilisation Project was necessary to counteract the years of extensive mining and subsequent damage that by the 1900s had left Combe Down village in a dangerous position.
The mines stabilisation area lies directly below the centre of the village and mainly consists of two large mines: Byfield and Firs. In addition two smaller mines, Horsecombe Vale and Entry Hill, are also included within the stabilisation project as well as parts of Grey Gables and Mount Pleasant mines.
The mines complex covers approximately 22 hectares, of which only 64% had been surveyed due to some parts of the mine complex being inaccessible. In places the mine was very close to the surface and the extraction rate within the mines was around 85%. This contrasts with an extraction rate of 70% which can often be stable in deep mines; however the shallowness of the Combe Down mines made even an extraction rate of 70% potentially unstable. Stable mines typically require 30% or more rock to be retained to provide roof support. In addition, the mines had also deteriorated over the years with some pillars being crushed and loads transferred to adjacent pillars.