Where areas of proposed development lie within a historical mining area, for example coal mining, metalliferous mining or stone quarrying, a mining assessment will often be required by the local authority to support a planning application or to satisfy a planning condition or warranty provider, e.g. NHBC.
Where a proposed development lies within a ‘high risk development zone’ as designated by the Coal Authority, a Coal Mining Risk Assessment would be required to support a planning application for development. Ruddlesden geotechnical produces Coal Mining Risk Assessments in accordance with the guidelines set out by the Coal Authority.
A mining risk assessment would entail a desk study of geological maps and memoirs, historical borehole records and, where available, mine abandonment plans. This data is used to produce a model of the anticipated ground and groundwater conditions beneath the site.
The risk assessment considers whether the proposed development site is likely to be affected by historical mining and hence whether further intrusive investigation, e.g. trial trenches and/ or rotary boreholes, and assessment is required.
Mining risk assessments may also be required for conveyancing purposes.
Coal Mining Assessment, Somerset
A Phase 1 Geotechnical Assessment and Coal Mining Risk Assessment indicated that a proposed residential development site in Nailsea was potentially at risk from mining-related subsidence as a result of shallow mine workings within the coal seam beneath the site.
Ruddlesden geotechnical designed a scope of works to investigate the historical mine workings to assess as to whether the collapse of said workings could foreseeably affect any future residential development of the site.
The geotechnical investigation comprised trial pits and trenches, followed by rotary open-hole boreholes. The trial pits were used to inspect the near surface ground conditions and historical mine entries, whilst the boreholes were used to determine the depth of coal seam(s) and historical workings beneath the site.
The results of the investigation were used to produce a geological cross-section of the site and ground model, which were used to assess the risk of mining-related subsidence.
By virtue of the depth of mine workings, and the working height, it was considered that future development was unlikely to be affected by historical mining.