2. Environmental impacts and protective measures
Deep mining impacts the environment in three different areas: in the
deposit itself and the surrounding rock, in the underground spaces created by
and for the mine, and aboveground. Optimal exploitation of the resource with
attendant limitation of environmental effects is dependent on detailed
planning of the sequence of operations and on the mining methods and
technology to be employed.
2.1 Environmental impacts on the deposit and the surrounding rock
2.1.1 Exploitation of resources
The most important environmental consequence of underground mining is
that it involves the exploitation of a nonrenewable resource. The process
of extracting the raw material necessarily also involves mining losses and
impairment of other parts of the deposit. The best way to counter the latter
effects is to carefully plan the extraction operations, stowing measures,
Some raw materials (coal and several sulfidic ores) can under certain
circumstances ignite spontaneously and cause mine fires.
2.1.2 Disruption of rock structure
The opening up of underground workings creates cavities and leads to
stress and motion in the surrounding rocks. The effects of mining
on the rock structure can include:
subsidence due to cave-ins in the cavities. The resultant settling can
propagate to the surface, possibly causing damage to structures and facilities
(subsidence damage; cf. section 2.3.3 for protective measures);
destruction of hanging parts of the deposit (most likely as a result of
inadequate extraction planning).
2.1.3 Disruption of groundwater flow
The opening up of underground workings modifies the formerly stable
water balance of the rock structure by creating new water conduits. Water
drainage, for example, can cause significant recession of the groundwater
level with substantial attendant detriment to vegetation within the affected
area (cf. section 2.3.2).
2.1.4 Alteration of groundwater quality
Mining activities can pollute groundwater in several ways: mine waters
(cf. item 2.2.4), for example, can enter the groundwater system, and various
alkaline and other solutions used in in-situ dressing processes, as well
as leakage losses of refrigerants used in the sinking of shafts, all can
contaminate the groundwater, just as the leaching of dumps produces
percolating water that can alter the character of groundwater. Effective
preventive measures include the sealing off of soils, shafts and
worked-out parts of the deposit, drainage and/or canalization.
2.2 Underground environmental impacts
Man, machine, rock and climate all interact underground, whereas man is
impacted most significantly. Matters concerning the health and safety of
miners are therefore given priority consideration.
2.2.1 Air / climate
The underground climate is influenced by the elevated temperature of deep
rock and by the gases and liquids it contains.
Table 1 - Factors influencing the atmosphere in underground
|Potential hazard / ||caused by ... ||danger of
... ||Preventive measures |
|Reference values || || || |
|Oxygen deficiency (O2)
19 % min.
|displacement by irrespirable
(black) damps and firedamps, respiration, open mining lamps, mine fires ||fatigue, asphyxia ||ventilation |
|Radiation ||radioactive rock
compo-nents, measuring probes ||radiation
affection ||limited exposure time with
dosimetric control |
|Radon ||gas evolution from surrounding rock ||radiation affection ||ventilation, limited exposure time |
5 - 14 % = explosive
|gas evolution from coal ||explosion ||gas extraction,
ventilation, flameproof equipment |
|Coal dust ||mining, handling of
coal ||explosion ||dust precipitation, flameproofing |
|Carbon monoxide (CO) |
> 50 ppm
|exhaust, gas evolution in abandoned hard-coal
mines ||poisoning ||ventilation |
dioxide (CO2) |
> 1 %
|gas eruption in salt, exhaust, gas evolution from thermal
waters ||asphyxia ||ventilation |
sulfide (H2S) |
> 20 ppm
|gas evolution from mine and thermal waters ||poisoning ||ventilation |
|Oxydes of nitrogen (NOx) and blast damp
||blasting ||poisoning ||ventilation,
specification of blasting times |
|Exhaust gases ||engine exhaust
||poisoning ||ventilation |
|Low-temperature carboni-zation gases, smoke ||mine fires ||poisoning ||extinguishment, damming off, precautionary
|Aerosols of oil ||pneumatic equipment ||poisoning ||oil precipitation
|Heat ||elevated rock temperatures, off-heat from engines ||fatigue ||ventilation,
air cooling |
In underground workings, noise is generated by drilling and blasting,
by internal-combustion engines and pneumatic and hydraulic motors, and by
various means of conveyance (conveyor belts, trains, vehicles) and
Machine-generated noise can be reduced by various design measures, and
ear protectors are mandatory beginning at certain sound intensity levels.
Exposure to dust (stone dust in coal mines, for example) must be
limited to minimize the incidence of related diseases, the most dangerous
of which is silicosis resulting from the inhalation of silica particles. Dust
forms when rock is destroyed by mechanical means (drilling, blasting, crushing,
Dust consisting of the following mineral substances poses a hazard
to human health: asbestos, beryllium, fluorspar, nickel ores, quartz,
mercury, cinnabar, titanium dioxide, manganese oxide, uranium compounds and tin
ores. Pulverized asbestos and respirable dust containing nickel ore and/or
beryllium, as well as soot from diesel engines, are carcinogenic. Coal
dust can cause dust explosions.
Countermeasures against dust pollution include its
consolidation during drilling and conveying, either by spraying it with
water or by saturating the face through appropriately arranged boreholes prior
to extraction. Gas masks prevent the inhalation of dust, and
filters on engines bond soot particles.
2.2.4 Mine waters
Mining activities alter the characteristics of mine waters.
Appropriate safety clothing protects miners against aggressive mine waters,
and appropriately resistant materials prevent corrosion of material goods.
Table 2 - Pollution of mine and surface waters
|Type of pollution ||Typical polluting substances ||Preventive Measures |
|Altered pH || ||neutralization |
|Soluble inorganic substances ||heavy
metals, salts, sulfur ||precipitation |
|Insoluble inorganic suspended solids ||mud ||agglomeration and
||oil, grease, lubricants, emulsifying agents
||precipitation in settling tanks |
|Heat || ||cooling, mixing |
2.3 Aboveground environmental impacts
The aboveground environmental consequences derive from communication between
the mine and the surface in the form of ventilation, mine pumping and
conveyance of the product, in combination with establishment of the
requisite aboveground mining infrastructure. Vibrations caused by
blasting and ground movement are also perceptible aboveground.
2.3.1 Air / climate
The harmful effects of air pollution, particularly on nearby vegetation can
be alleviated by filtering the outgoing air from the shafts and tunnel
faces. Dumping and wind-induced erosion of dumps can cause substantial air
pollution, most notably in the form of dust.
Dust evolution can be controlled by appropriate sprinkling in
connection with dumping and by immediate greenbelting, oversowing and
protective dams. In arid regions where land planting is hardly possible,
preventive measures must be taken in the form of restricted use in the
prevailing wind direction.
Coal mining releases large quantities of methane (CH4), one
of the most notorious "greenhouse gases". The best way to
control methane is to "drill and extract" (with subsequent
utilization). Particulate solids in the vitiated air from underground mines can
be extensively eliminated by filtration.
The pH of mine waters, particularly in the presence of sulfidic ores,
can range below 5.5 (acidic). Adherence to the limits prescribed
for sulfates, chlorides and metals is essential.
If the groundwater is being used as drinking water and ore is being
discharged into a body of surface water, the relevant values must be
monitored. It is important to know which anions and cations can occur in
mine water and which of them constitute potential hazards on the basis of
their concentration or toxicity.
It is also important to mention that heaps of material extracted from an
underground mine are liable to contain high concentrations of chlorides and
sulfates and that, in a humid climate, such salts can be leached out by
Whenever minewater is discharged into a body of surface water,
care must be taken to avoid damaging any sensitive ecosystems and to ensure that
no long-term accumulation of pollutants occurs in the sediment and that overall
use of the water in question, e.g., for fishing purposes, is not impaired.
Marine pollution and alteration of the ocean floor or fishing/spawning
grounds can result from the conveyance of polluted water through rivers
leading to the coast.
Finally, underground mining consumes water for such activities as
drilling, gobbing/stowing, hydro-mining, etc.
The measures described in section 2.2.4 (table 2) should be adopted to
prevent pollution of surface and groundwater by mine waters.
For the day surface, the most frequent danger resulting from underground
mining activities is subsidence, or settling. Subsidence-induced tilt,
curvature, thrust, stretch and compression of the day surface can cause
damage to buildings and infrastructural facilities as well as to the
natural environment. Watercourses such as canals and rivers - and rice
paddies, for example - react very sensitively to the slightest change in
Protective measures begin with early regional planning with due
consideration of the potential mining-induced consequences of ground subsidence.
Settling can also be avoided or at least reduced by properly
lining the mine with support material and backfilling the face workings
with rejects and/or the use of certain suitable extraction techniques.
Well-planned and controlled extraction allows slow areal settling that is
unlikely to damage buildings or public utility lines and facilities.
2.3.4 Dumps, land consumption, landscape
Underground mining activities are usually accompanied by the appearance of
large rubbish heaps within the immediate vicinity of the mine, where
rejects and other useless material are dumped. The residual metal
contents of such material should be ascertained, even though the metal
burdens emanating from dressing heaps can be expected to be higher. Frequently,
rubbish dumps are difficult to recultivate, and appropriate measures
therefore should be included in the working plans.
Underground mines require a certain extent of surface area for the requisite
infrastructure (hoists, buildings, workshops, storage areas, power
generating equipment, access road, etc.). The aboveground facilities can impair
the appearance of the landscape, and relevant architectural measures have
limited effects. The establishment of any such industrial complex is bound to
alter the landscape in the vicinity of the mining facilities. To the extent that
resettlement is necessary, the affected parties must receive appropriate
Lowering the groundwater level can have detrimental effects on the
local vegetation, including the drying out of ponds, streams, etc.
Moreover, the local fauna and human population can be adversely affected by a
diminishing supply of drinking water as a result of the altered water
Adequate protection of wetlands against such negative impacts may require the
artificial recharge of groundwater, particularly since receding
groundwater tends to cause settling, with damage to structures as one likely
Finally, vibrations caused by blasting and ground movement are also
2.4 Other consequences of underground mining
Establishing mining operations in remote areas can have the inadvertent
effect of opening the area up to uncontrolled settlement and land use.
Appropriate planning-stage backup measures are therefore called for.
The intensive use of wood for timbering mines can trigger the large-scale
felling of trees and, hence, erosion of the exposed soil. Orderly
silvicultural activities in the area around the mine can help prevent such
problems, especially if fast-growing species of trees are planted. Nonetheless,
long-term effects on the ecosystem remain unavoidable. The use of anchoring
techniques and steel supports in underground mines can extensively reduce
The world over, underground mining provides employment almost exclusively
for men, because cultural and traditional conceptions forbid women to work
underground. If at all, jobs for women are to be found in the areas of mineral
processing, marketing and attendant services. Children should never be allowed
to work in underground mines. Other social problems can arise in
connection with mining if the housing for the miners and their families is
either inadequate or not accompanied by the appropriate infrastructure (water,
markets, schools, etc.) and if the miners are not covered by social