Problems Associated with Mining

Types of Mining Surface Mining Deep Mining Open Cast Longwall Retreat Pillar and Stall Drift mining / Adit

Open Cast / Strip Mining Dragline Excavator

Brainstorm a list of problems associated with open cast mining……….

Drift mining / Adit

Pillar and Stall

Long Wall Retreat

Pillar and stall mining 1. Subsidence Pillar and stall mining Cracking & collapse of buildings Cavities open up

Sag Subsidence Pit Subsidence Most common type (gentle depression) Bell shaped hole 2 m deep Spreads over several acres 1m to 30m across Cause: Pillar Collapse Cause: Roof collapse

2. Acid Mine Waste Contaminating Groundwater Mining Surface area Groundwater flow Leaching of mineral deposits Iron pyrite (“fools gold”) Abandoned mines Water Pumping Water Table Prolonged water contact Dissolves Sulphuric Acid Leaching Acidic Mine waste Iron minerals Reddish-brown suspension AFFECTS: Fish Irrigation Industry Livestock Drinking water

3. Release of untreated mine waste into rivers Wheal Jane Tin Mine, Cornwall 1993 – a major spill of mine waste released serious amounts of acid waste into Falmouth Bay.

Map: Showing Deep Mines areas with Acid Mine Waste Risk INTERACTIVE MAP Deep Coalfields 1. 2. 3. 4. 5. 6. 7. Clyde & Ayreshire Durham / Northumberland West Cumbria South Yorkshire Lancashire and North Wales Forest of Dean South Wales

4. Collapse of Mine Waste Mine waste is disposed of near to the mine site due to its weight & amount. 600, 000 tons / yr 1966 1964 Aberfan, South Wales

4. Collapse of Mine Waste On steep slopes, overlooking the village, mine waste tipped since 1914. In 1966, tip No.7 failed killing 147 (116 children) people. Heavy rainfall Tip situated on clay Spring Hydrogeology disturbed by mining

5. Emission of Hazardous Gases Methane is explosive, has a noxious smell and contributes to global warming. Especially coal mining gives off methane as CH4 is produced during the Coalification process when plant material (CHONS) was broken down over millions of years. Mining process – fractures coal – increasing its permeability – releasing GAS! Mining is also a pathway for the colourless, odourless and carcinogenic Radon Gas (produced by radioactive decay deep within earth)!

6. Flooding of Mines Mining below water table requires pumping which causes local disruption of the water table. East Durham coalfield – 36 billion litres of water pumped from mine system each year.

Flooding of Mines Mining below water table requires pumping.

7. Rock Fall / Landslides Quarries / opencast mines have steep open faces Liable to collapse / rockfall Need careful management: Soft rocks e.g. clay – Re-graded to a stable angle and drained! Hard rocks e.g. granite or limestones – Stability analysis to identify weaker areas. Then regrade as well as using cliff stabilization techniques e.g. bolting, mesh curtains and fences to catch boulders