Lecture 20 resources 11

Question 1

What are the environmental impacts of mining

Answer 1

1) Air pollution: Air quality effected by mining operations, waste deposit and processing (smelter) operations -> airborne particles.
2) water pollution: metal contamination of surface and groundwater, increased sediment levels in streams, acid mine drainage.
3) Damage to land: open pits, waste rock piles, destabilization of the ground (underground mining) -> physical destruction of the land.
4) Loss of biodiversity: habitat loss for diversity of flora and fauna due to dramatic modification of the pre-mined landscape.
5) long-term III-effects of mining: Remediation efforts are not always successful in restoring the land and biodiversity -> permeant loss.

Question 2

What is the mining process of a gold mine

Answer 2

(1) Location drilling
(2) Blasting
(3) Mining - Removing any overburden
(4) Hauling
(5) Crushing
(6) Leaching
(7) Processing - sodium cyanide has an affinity for gold = gold rich solution.
(8) Pouring

Question 3

what are the effects occur due to mining?

Answer 3

visual effects - huge wide and deep mines.
waste rock is stacked high - visual
bad for copper - now week can mine at smaller ores

Question 4

Why did Aberfan (and other disasters) occur?

Answer 4

Spoil heap stability
- high pore pressures associated with fine grained materials with low permeability and high moisture content.

• in soils with permeability less than 5*10-9 ms there is no dissipation of pore water pressures. if permeability is greater than this there is complete dissipation.

coal discard typically 110-4 to 510 - aberfan occurred due to heavy rain which added to high pore pressures.

Question 5

Why does tip failure occur?

Answer 5

spoil heap and flow
there is high permeability zone underneath the flow
- water increases and increased porosity - produces the glide plane - facilitates movement downhill.
- when there is higher rainfall there is more failures
spoil heaps are both an eyesore and can cause disasters.

Question 6

What are taillings?

Answer 6

• Fine grained slurries
• produced during crushing or ore washing at collieries
• mixed with water (ease of movement)
• water may leach many chemicals from rock and may contain chemicals from extraction
• commonly contain sulphide minerals - oxidise to form acid
• tailings are major environmental hazards.

Question 7

What are Tailing ponds/ storage

Answer 7

• quality that can be stored depends on density
• Tailings increase in density as they settle and compact with time
• eventually tailings allowed to dry and environmental remediation started (basically burry it)
• any seepage from tailing ponds potentially damaging due to toxic nature. Ponds lined and maintained (should be).

Question 8

How are tailling ponds constructed

Answer 8

Up stream
- new embankment raise is constructed partially on embankment, partially on the consolidated tailings beach, dam moves upstream with each raise.

Downstream
- starts with impervious starter dam.
tailings discharged into the dam -> embankment is raised and each new wall is constructed on top of downstream slope of the previous section -> crest moves downstream.

centreline
hybrid of up and downstream, dam is raised vertically from started dam, dam crest remains fixed relative to up/down stream directions.

Question 9

examples of tailings pond failures

Answer 9

los frailes mine spain, 1998
tailings pond for large Cu, Zn, Pb sulphide mine.
15 million m3 tailings in pond in 1998 - mostly pyrite and minor sulphides
- fine frained (80% < 45mm)
- tailings pond built on the rio Agrio.
large amount of acid water was released into the river.

Question 10

Can Tailing ponds be useful

Answer 10

• previously ores were too low grade - now they are mineable.