Historically underground extraction of various commodities has been carried out across much of the UK, for example:

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Coal - mined for hundreds of years using techniques such as bell-pits, pillar-and-stall, and long-wall mining in areas including the Midlands, South Wales and Bristol, North Wales, Lancashire, Yorkshire, North-East England, Cumbria and the Midland Valley of Scotland.

 

Chalk and Flint - mined for thousands of years in areas of England underlain by chalk strata at shallow depth, most notably in East Anglia (especially around Norwich), Greater London, Essex, Surrey, the North Downs, the South Downs, the Chilterns and the Marlborough Downs. Methods of extraction included simple shafts (neolithic), bell-pits, a variety of 'dene holes', and pillar-and-stall.

 

Metal ores - mined in places for thousands of years in places lie Cornwall, Devon, the Mendips, North and Central Wales, the Peak District and Pennines, the Lake District, and southern and central Scotland. Metals mined for include tin, copper, lead, zinc, manganese, barium, and gold. Mines were accessed by shafts or adits and typically when an ore-bearing vein was encountered the mine workings simply followed it.

 

Evaporites including halite (rock salt), gypsum, potash and alum - typically extracted by mechanical methods such as pillar-and-stall and longwall mining, although halite (and to a lesser extent potash) has also been extracted using solution (brine) mining. Halite extraction has caused significant areas of subsidence in parts of Cheshire, Worcestershire, Staffordshire and parts of Northern Ireland. Gypsum mining has caused areas of surface subsidence in parts of the Midlands.

 

Limestone - although more commonly extracted by quarrying, limestone has also been mined using underground methods in areas such as Dudley and Walsall in the West Midlands, and the Peak District.

 

Ironstone - underground mining of various ironstone horizons has taken place in parts of Cleveland, Lincolnshire, and Northamptonshire as well as in some coal mining areas where ironstone bands are also present.

 

Opencast Mining / Quarrying - surface extraction of building stone and aggregate (e.g. limestone, sandstone and sand and gravel) has taken place over much of the UK. Ironstone has been quarried in areas such as Northamptonshire, Lincolnshire, Cleveland and Oxfordshire, as well as in some opencast coal mines in other parts of the country. Once abandoned many of these locations were filled with to significant depths with landfill, spoil or other non-engineered materials.

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Issues associated with old mine workings include:

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• Subsidence associated with collapse of mine shaft, adits and underground workings.

• Emission of gases such as methane, carbon dioxide and hydrogen sulphide.

• Settlement of fill materials in backfilled quarries/opencast pits.

• Contamination associated with remnant metals and hydrocarbons in spoil, as well as acidic groundwater draining from old workings.

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Examples of mining and mineral-related services offered by G&J are:

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• Provision of Coal Mining Risk Assessments (CMRA) and similar assessments for other mining activities. For a typical CMRA G&J will acquire site specific  information from the Coal Authority and use this, together with, for example, geological maps, borehole records, and historical maps to assess the risk posed to the site by shallow mine workings and/or mine entries.

• Investigation and treatment of shallow mine workings and mine entries. On most sites this is likely to include drilling a number of boreholes to confirm the depths of underlying coal seams and historical workings, the number of boreholes required typically being steered by the size of the site and the layout of any proposed development scheme. An investigation to search for a reported mine shaft may involve drilling a closely spaced grid of boreholes; alternatively, if any Made Ground present is only thin, the mine entry could be located by excavating a series of trenches down to natural strata or simply carrying out a site strip to the same depth in the suspect area.

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Costs:

The cost of a typical Coal Mining Risk Assessment is in the region of £650* plus VAT.
On some very straightforward sites with a potential risk from shallow mine workings a simple rotary borehole investigation may cost in the region of £5000* plus VAT.

*Costs may be higher for larger, more complex sites.