Hundreds of homes, three churches, and a primary school are to be saved from collapse into the mines much of Bath was quarried from, Planning Minister Keith Hill has said. 

Above and below ground at Combe Down

The Combe Down Stone Mines near Bath are currently a serious hazard to 1,500 people and their homes. Those homes, and other areas of open space and roads, have been resting on a thin crust of ground - in some places only a few metres thick - above deep underground cavities which were formed when the stone was excavated for the building of Georgian Bath.

The mines at Combe Down are Oolithic Limestone mines, mainly worked in the 18th and 19th century. No records of the workings were made prior to the 1872 Mining Act. Stone was extracted by the 'room and pillar' method, by which chambers were mined, leaving pillars of stone between them to support the roof. Irregular mining practices and robbing stone from supporting pillars has left the mines unstable.

Traffic vibration and climatic conditions have worsened the situation in recent years. Substantial emergency works, costing some £23m already, have been needed over the past three years, to stabilise the ground in the worst affected areas while a longer term solution has been explored.

Traffic weight limits have been placed and roads even closed to traffic altogether to help prevent collapse.

Competing with the human residents are colonies of the Greater Horseshoe Bat, which is one of the largest and rarest bats in the UK. The total UK population is about five thousand and the colony in the mining caverns under Combe Down was in decline.

Construction of heated incubators within the mines has established the mines as a breeding habitat.

The £154.6 million grant, to be paid by English Partnerships – the government’s national regeneration agency – over a period of five years, will stabilise the mines, saving the City of Bath World Heritage Site village from risk, as well as ensuring archaeologically important areas and bat habitats are protected.

The proposed programme – subject to any final approvals required by the local authority – will introduce some 10km of underground "safe routes" to protect the land and properties above, as well as long-term bat routes and roosting and breeding sites for some of the largest and rarest bats in the UK.

The scheme involves infilling with foamed concrete. In some hydrological sensitive areas, 'stowing' - an infill with aggregate limestone - is planned. Archaeologically important areas will be filled with sand.