§ Mr. Richard Shepherd
asked the Secretary of State for the Environment whether he is now able to publish the results of the study into the problem of abandoned limestone mines in the Black Country; and if he will make a statement.
Mr. Patrick Jenkin
The report of the consultants, Ove Amp and Partners, was published today; a copy of its full report has been placed in the Library. In addition, the consultants have written a 24-page summary report. which is also being published today. I am grateful to Ove Amp for its thorough work.
On the 74,000 acres in the Black Country beneath which limestone exists at a depth at which it might reasonably have been worked, only a small proportion of the area studied—less than 2 per cent. —is likely to have been mined for limestone. Within this smaller area, the possibility exists of future surface disturbance in some areas. That risk cannot be identified or assessed with certainty, but the consultants' report provides a much more detailed account of the problem than has been available until now, and also makes proposals for future monitoring of conditions underground and for remedial measures.
The Government, together with the local authorities concerned, will now consider how best to proceed with the various measures recommended by the study. The options chosen for each area will depend on the perceived level of relative risk of ground movement and the likely effects of such movement on land use and surface structures They include:
- i. measures to prevent public access to workings and to fill in subsidence and crown holes as they occur;
- ii. monitoring by sensitive instruments of movements in the ground and of the condition of workings to identify the onset of disturbance being transmitted to the surface and to review the likelihood of such disturbance;
- iii. investigation of the underground voids and the ground above them to provide their existence and extent, to determine their condition so as to enable the likelihood of surface disturbance to be assessed;
- ix. measures to reduce the possibility that future surface disturbance might cause serious damage to structures or services; and
- v. treatment of structures and services so that they can withstand the effects of subsidence or allow evacuation of occupants.
It is essential that the Government and the local authorities involved establish a clear order of priorities for this future work. In order to make rapid and effective progress, I am proposing to establish a panel of experts to advise me on these issues and on the development of a practical programme of work and priorities within it. I am consulting the presidents of the Institution of Civil, Structural and Municipal Engineers and of the Royal Institution of Chartered Surveyors on this proposal and I hope to announce the names of the chairman and members of the expert panel shortly.
The Government have set aside £1 million in this financial year to begin work on the installation of monitoring equipment and remedial measures to preserve surface stability, and they will continue to make provision for such work in future years.
The consultants have suggested a new method of mine filling to stabilise old workings which promises to be cheaper than conventional grouting techniques. This is to inject into the working through boreholes a thick paste of waste rock material, such as colliery spoil, using concrete pumping equipment. Small scale pumping trials have already been successfully carried out by the building research establishment and larger scale trials are to be carried out in the autumn in preparation for injection trials on site in 1984. The results should provide a sound basis for a rational programme of mine filling where this is considered necessary.
During the course of the study, the Institute of Geological Sciences has established instrumentation to monitor and identify the noise emissions from movements in the underground workings. Further work is needed to develop a monitoring system which can be used to give early warning of possible changes in the condition of the workings and my Department will be commissioning such work in the very near future.
The steering group has considered the planning, building regulation, legal and financial problems arising from the existence of these old workings. While some of this work still needs to be completed, two codes of practice covering planning and building regulation matters have been prepared by the steering group. These codes are reproduced in the report of the steering group which is also published today.
My Department is aware of and is in close touch with the similar study commissioned by my right hon. Friend the Secretary of State for Transport involving old limestone workings under the Birmingham to Wolverhampton trunk road (A4123) and possible old workings in the vicinity of M6 in Walsall. The results of the drilling works now under way in these areas will be made available both to my Department and to the local authorities.
The study published today cannot resolve all the problems associated with these old limestone workings, but it has indicated the kind of work that can usefully be done to alleviate those problems and the factors to be borne 236W in mind in deciding priorities. My Department, together with the local authorities concerned, will now tackle that task.