The use or abuse of thematic mining information maps

Abstract Thematic and environmental geology mapping has been applied in recent years by the British Geological Survey (BGS) in cities, towns, urban fringes, rural areas and major estuaries. Experience in Scotland indicates that the separate portrayal of particular aspects of the drift and solid geology, former underground mining, and geotechnical properties are of greatest benefit to planners and civil engineers concerned with land use and ground stability. The maps prepared for this purpose may have an additional application in the field of resource assessment. BGS always emphasises that these maps are interpretations of the data available at the date of compilation, that they are only to be used for preliminary studies, and that they are not intended as a substitute for on-site investigation. This paper illustrates some of the pitfalls of a too literal use of thematic mining information maps and indicates ways in which these have evolved to assist the user. Early thematic maps depicted areas of undermining assumed to be (a) within 30 m of surface and (b) at depths greater than 30 m below surface. Known and suspected mining were not differentiated. Modifications were introduced for the Glasgow district, such that only areas of mining shown on mine plans were depicted: no areas of suspected mining were shown. Separate maps were prepared to show areas of total known mining; current mining; known mining within 30 m of rockhead together with locations of shafts and boreholes encountering shallow workings; and mining for minerals other than coal and ironstone. Recent work in Coatbridge and Fife has resulted in further modifications, including the presentation of separate shaft atlases. Attempts have been made to construct seam atlases although these are not available as part of the portfolios. In Fife, known and inferred shallow mining are differentiated, and shown on the same map. Each modification has reflected an attempt to clarify the presentation of known and inferred mining. The maps have, however, been prepared in response to the requirements of different customers, and while it is generally agreed that it is valuable to portray the extent of mining known from mine plans, opinions differ on the desirability and usefulness of showing inferred areas. The latter classification is considered to be beneficial by national and regional planners and also by city engineers. However, there is concern about the release of such maps on open file to the general user who is not fully informed of the background and nature of mining maps. Areas outlined as ‘undermined’ should not automatically be subjected to planning blight, and a recognition is required that engineering problems in urban areas only occur if property was not planned, designed and constructed with reference to the state of undermining.