MAKING OLD MINE ENTRIES SAFE
Following its limited 2005/06 programme of works to ensure the safety of sixteen old mine entries the Department of Trade & Industry (DTI) is seeking to implement a further programme to carry out similar work for all the identified former mineworkings around the Island.
The Isle of Man has a long history of mining - surface and underground mining for a variety of metalliferous ores (including lead, copper, zinc and iron) was carried out from the Bronze Age up to the early decades of the 20th century. An extensive survey carried out for the DTI – which has responsibility for all abandoned underground mineworkings – indicated that there are some 350 untreated mine entries where physical works are required to prevent accidental or unauthorised entry. This will require a far more ambitious programme of works than that carried in 2005/06 and the Department is looking towards a five year scheme in which the first year will be devoted to planning, liaison with landowners and occupiers and preparation and the following four years given to site works.
Steps will be taken to ensure that the work is carried out safely and with the minimum possible environmental disturbance. To this end preliminary discussions have already been held with the Department of Local Government and Environment, the Wildlife and Conservation Office of the Department of Agriculture, Fisheries and Forestry and Manx National Heritage. Close liaison with these groups would continue on a site-by-site basis throughout the life of the programme.
As with the previous, limited, programme, the preferred method of treatment for mine shafts will be to construct a cap or plug over the shaft that will be founded, where possible, on bedrock. Construction of such a structure requires excavation of the soil around the shaft and the casting, in-situ, of a reinforced concrete cap or plug, which is then covered with soil and the surface reinstated to its original condition. In some cases it may not be possible to found the cap on bedrock, for example, where the soils or superficial deposits are very deep. In such cases an alternative design of concrete cap or plug would be used.
In most cases, the abandoned mine shafts which are to be treated are obstructed with unconsolidated fill materials and there are no open voids near the surface which can be used by important wildlife such as bats or nesting birds. In such cases the cap will be constructed as a solid slab or plug and covered with soil. If there are voids present which may be used by bats or nesting birds, an opening in the cap can be constructed, with a suitable steel grille to allow wildlife to enter. Where such caps are completely covered over, their locations would be carefully mapped and recorded for future reference.
In some cases it is not practicable to construct a shaft cap. In such instances shafts will be made safe by the erection of a secure fence, accompanied by signage warning of the danger.
Adits are level or inclined mine entry tunnels and many are in an open condition. Adits may be made safe by a number of methods, including filling with concrete, but they are frequently refuges for wildlife and can be important for industrial archaeology. It is therefore proposed that each adit will be made safe by the construction of an engineered steel grille securely fixed to the surrounding rock or tunnel lining. The design of the steel grilles will allow wildlife, including birds and bats, to enter freely. Where appropriate a secure gate will be incorporated into the grille to provide for future access for purposes of monitoring or study.
Further information: Neil Corlett, Development Manager, Minerals & Properties – e-mail neil.corlett@dti.gov.im , tel. 682399
