Pillar & stall working was the usual practice in the Bristol/South Glos
coalfield
Abandonment and other plans show an initial working taking a little over
1/3rd of the available coal and leaving the remaining 2/3rds. Later these
areas of coal were systematically removed starting with those furthest away
and working back towards the shaft (keeping road roadways, drainage and
ventilation routes open). The whole area is coloured in and dated so
presumably was completely removed but I do not know whether some was left.
Pillar robbing is common in Stone mines where originally a sizable pillar of
stone was left and later slices were sawn off it. The extensive (and
expensive!) consolidation works taking place at Combe Down (Bath) are
largely as a result of this -
http://www.bathnes.gov.uk/BathNES/environmentandplanning/majordevelopments/c
ombedownstonemines/
Regards
David
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