Mineral working and land reclamation in the Coalbrookdale coalfield
The study attempts to define the problems arising from mineral land working in relation to after-use and to record the methods of assessment and treatment. The small Coalbrookdale Coalfield contains examples of most problems likely to be found in areas formerly subjected to intensive mineral working. Furthermore it is now an area of wholesale redevelopment for the new town or Telford. Ensuring the safety or these new developments has involved much documentary research and site investigation and this study records both the general aspects and describes some case histories. The problems involved in the study are concerned with the determination of the geology in detail, both stratigraphically and structurally, in relation to topography, mineral exploitation and industrial history. Other aspects of industrial activity which affect the development potential of the land's surface such as waste heaps, abandoned communication systems, disturbed natural drainage and disused massive structures are also considered. A general survey of the extent of dereliction and of the various definitions of 'derelict land' and of its causes is discussed. Underground mining has been carried out extensively for coal, ironstone, clay (both fireclay and brick and tile clays) and limestone and to a lesser extent for fullers earth and sandstone. In addition all these minerals have been heavily worked by surface methods as have the igneous and other 'hard' rocks, marl, sand and gravel, and the useful products of the mine waste heaps, shale (both weathered and burnt) and slag. It has also been found necessary to study the much smaller extractive industries of bitumen, pyrites and salt, since their working has produced cavities and shafts in unexpected positions. The geology of each mineral, the extent, methods and age or workings, and the effect of such workings upon the surface are studied together with the special problems associated with each mineral and their possible restraints on future development. A comprehensive study is made of the development restraints which result from past and present mineral working, the methods or assessment and manner of treatment. Past land reclamation activities, which have been applied patchily and with little or no control, can themselves form a restraint to development. The methods used in the past were not sufficiently developed to ensure that all potential causes of instability were removed. Adequate preliminary site investigation is shown to be of paramount importance when considering development and the methods and extent of investigation required and the type and form of reports to be produced are outlined and discussed. The general restraints resulting from mineral working are described under the following headings: Shafts, wells and gas emission; Shallow mineworkings, adits and subsidence: Opencast mining, quarries and ground settlement; Spoilheaps, lagoons and fires; Drainage, water supply, soughs and other tunnels. Examples or each are given as case histories and site investigation and treatment methods outlined. Special consideration is given to the methods used in dealing with disused mineshafts, or the use of opencast mining as a means of land reclamation and of the problems caused by present day quarrying, underground working and general tipping activities. Natural phenomena such as landslips and geological faults also form restraints to development. The occurrences and types of landslip are examined with a view not only of determining their cause and of defining their limits but of determining means by which they can be anticipated and controlled. Investigations are also described which have been carried out to locate geological faults and to assess the stability implications due to their presence on development sites. Two special studies carried out include;- (1) the use of geophysical methods as aids to site investigation and their application to mineral evaluation, location of faults, shallow workings and mineshafts; and (2) the policy of preservation of features of geological, industrial and mining interest is discussed. The problems associated with preservation, recording, identifying, selecting and ensuring that retention is compatible with both public safety and future planning are outlined. A number of recommendations are given which it is believed would assist if in the future it is decided to carry out a similar land reclamation/new town development scheme elsewhere.