An underground survey of the Firs and Byfield mine areas was carried out in 1994, commissioned by the then Bath City Council. It was found that approximately 80% of the mines have less than 6m cover and as little as 2m in some places. Irregular mining and robbing stone from supporting pillars has left the mines unstable.
In March 1999, the then DETR (Department of Environment, Transport and Regions), now known as Communities and Local Government, announced a Land Stabilisation Programme, based on the Derelict Land Act 1982. This programme was designed to “deal with abandoned non-coal mine workings which are likely to collapse and threaten life and property”.
A Bath & North East Somerset Council outline bid for a two-phase stabilisation project was accepted in August 1999 by English Partnerships.
The objective of the Project is to stabilise the mines to protect life and property in line with Homes and Community Agency guidance for the Land Stabilisation Programme (LSP).
There are a number of aims that are also critical to the project such as:
- Safeguarding the Combe Down heritage and environment.
- Avoiding contamination of the water outflows from the Combe Down area.
- Protection of the bat species in accordance to international/EC/UK obligations.
- To mitigate the impact and disruption caused by noise, dust, and traffic movements in the area.
- To ensure, as far as practicable, any work sites associated with the scheme are of low visual impact.
- Design solutions will achieve successful stabilisation for at least the next 100 years.
- Seeking to mitigate any damage to the existing properties in the area due to the consequences of the project works.
Main Contractor: Hydrock
Engineering Design and Supervision: Scott Wilson Mining
Project Management Support: Davis Langdon and Provelio
Archaeology: Oxford Archaeology
Bat Consultants: Batpro
Problems with surface stability of the area were first formally identified in 1986 when the underground mine workings were exposed by a contractor during excavation of a shallow trench. Initial underground investigation revealed the condition of the mines, including ongoing collapse and progressive deterioration of rock pillars and the mine roof. Subsequent detailed investigation involved mapping and classification of the majority of the accessible areas, which indicated that the mine workings posed a hazard to life and property.
In March 1999, the then Department of Environment, Transport and the Regions (DETR) announced a new Land Stabilisation Programme (LSP) which specifically addresses the problem of abandoned mine workings. The LSP (administered by English Partnerships) makes funding available to local authorities to help them stabilise areas which have been left hazardous by abandoned non-coal mine workings.
Following the appointment of a new Mines Manager by Bath & North East Somerset Council, in November 2000, access to the mines was initially prohibited because of their hazardous nature.
Given the significant impact that any mine collapse could have on the safety of life and property in the Combe Down area, an Emergency Works programme was initiated in 2001 by the local authority, Bath & North East Somerset Council. The works focused on the reduction of immediate health and safety risks within selected high hazard areas beneath public highways, including a section of North Road.
Health & Safety roadways were constructed from the Byfield mine entrance and the Firs shaft to enable project personnel designing the scheme to view the condition of the mines.
The construction of these underground roadways enabled engineers to reassess some areas of the mine that were classed as “High Hazard Areas” from the survey undertaken in 1994. As a result of these assessments, on the advice of the engineers, the Council commenced interim stabilisation works in some of these areas in advance of the main stabilisation scheme which commenced 2007.
The Main Scheme commenced April 2007. The Main Scheme works continue the concrete infill and roadway construction, but also focus on bat, archaeological and drainage issues. Investigation of the mine margins continues as part of the Main Scheme to determine the extent of the Firs and Byfield mine complex.
The compound at Firs field increased in size for the Main Scheme and there are now 250 personnel working on site. Following the tender process and approval from central government, Hydrock have been appointed as the main scheme contractors. Also on site are Scott Wilson Mining (Project Consultants) and Davis Langdon and Provelio (Project Management support).
As part of the completion of stabilisation, surface verification is required to establish that the concrete has reached the required levels within the mine. This requires drilling on the surface in various locations in the village, including gardens, drives and roads. Should a void be identified by the drilling works surface topping up will take place. The project is now at the stage where the requirement for this verification drilling is increasing.
Completion of the Main Scheme construction is scheduled for 2010.