Safety Alert

Bunkers and mineral clearance boreholes


  • Chief Inspector of Mines: D Mitchell
  • Licensed Mine Owners (Working)
  • Licensed Mine Managers (Working)
  • Misc Mine Managers
  • Misc Mine Owners
  • Mining Trade Unions
  • HM Inspectors of Mines SA/01/03/SD

Safety Circular - Reminder


During the 1980's there were a number of fatal and other accidents associated with underground vertical and inclined bunkers and mineral clearance boreholes. The majority of these accidents were due to the sudden and uncontrolled release of slurry, usually during work aimed at releasing blockages. Most accidents involved the mechanical failure of either bunker-bottom hoppers or discharge side plates under the load of released material.

In 1989 HM Inspectorate of Mines looked in detail at the safe operation of such bunkers and boreholes, and made a series of recommendations accepted in full by mine owners, at that time principally British Coal. Inspectors subsequently carried out a series of inspections to identify the extent to which those recommendations were being implemented at mines, and made a second series of inspections to check on progress.

British Coal subsequently published an Operational Instruction (OI/25) on 'Notes for Guidance for the preparation of a Code of Practice for the Operation, Maintenance and Clearing of Blockages of Underground Vertical Bunkers, Inclined Bunkers and Mineral Clearance Boreholes', which incorporated Mines Inspectorate recommendations.


Although there have been no fatal accidents since that time recent inspections have indicated that the knowledge and implementation of control measures needs to be improved. The hazards associated with bunker operations still persist, and mine owners and managers must therefore ensure that they have in place robust but practical measures to control risks to those who work in the vicinity. Acting now will reduce the likelihood of further incidents.

The principles and the detail within OI/25 are still the best available source of recognised good practice guidance for coal and non-coal mines alike.

Managers of mines with either underground vertical or inclined bunkers, or mineral clearance boreholes, or surface bunkers, should therefore review their procedures against the standard set out in OI/25 and take steps to remedy any shortcomings.

Mines owners should ensure that the review is carried out to a satisfactory standard and that the steps taken are appropriate.

The Mines Inspectorate will provide copies of OI/25 on request. It can be freely photocopied thereafter.

S P Wing
HM Principal District Inspector of Mines

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