A well-attended meeting at Frome Rugby Club heard David Gibson, Business Development Manager for Ritchies give a fascinating account of the stabilisation of old mine workings at Coombe Down near Bath. This was part of a £150 million contract for the client Bath and North East Somerset Council.

In places the cover is less than two metres and there have been instances of utilities breaking through. Many of the pillars were also robbed leading to the possibility of roof collapse. The work is designed to ensure the health and safety of people living in the area, safeguarding water supplies to Bath and with due regard to any archaeological preservation.

A further complication was that the mines are one of the top ten sites in the UK for hibernating Greater and Lesser Horseshoe bats, which are a protected species. The long-term work was to create a naturally ventilated space of stable temperature. The contract required a cut and cover tunnel to be constructed between two old mine workings and the sinking of a 10m ventilation shaft.

There were considerable restraints on the work. It could only be done during the summer since rugby pitches had to be dug up and re-instated before the start of the playing season. There had to be minimum disruption to the local population so no blasting was allowed. David explained the difficulties of driving a tunnel through old mine workings, which were inherently unstable and largely unmapped. He described in detail the methods employed.

Despite all the problems the contract was completed on time and to budget. The team had had to overcome severe geotechnical and mining challenges. They achieved this with an excellent safety record and good environmental performance, resulting in a delighted client. The bats are now using the tunnel, blissfully unaware of how much time, effort and money has been spent on their winter quarters!

This talk by a very knowledgeable and enthusiastic speaker was concluded with a lively question and answer session.