3. Notes on the analysis and evaluation of environmental impacts
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3.1 Air / climate
The gas contents of air in underground mines is regulated in Germany by pertinent laws such as the mining ordinances (Bergbauverordnung) BVOSt and BVOE of the North Rhine-Westphalian mining inspectorate (Landesoberbergamt LOBA) and its pertinent and specific directives.
For methane (CH4), the following limits apply to free airflow:
more than 0.3 % : tram shutdown
more than 0.5 % : recorded monitoring
more than 1.0 % : electrical equipment shutdown
more than 2.0 % : monitoring equipment shutdown
Gas extraction equipment is subject to measures in accordance with the relevant gas extraction directives.
Carbon monoxide (CO) in concentrations of 50 ppm and higher calls for special rescue, recovery and security measures according to a life-saving plan (Hauptstelle für das Grubenrettungswesen der Bergbau-Forschung GmbH, 1982).
Mines must be evacuated if the carbon dioxide (CO2) level reaches 1.0 % or higher.
Nitrous gas levels of 300 ppm NOx, including 30 ppm NO2, allow a maximum exposure time of 5 minutes. A level of 100 ppm NOx (including not more than 10 ppm NO2) extends the maximum exposure time to 15 minutes per shift.
The oxygen content must amount to at least 19 %.
The hydrogen sulfide (H2S) concentration must not exceed 20 ppm.
All gas measurements must be performed using calibrated commercial-type instruments.
The airflow velocity should amount to at least 0.1 m/s in large spaces and at least 1.0 m/s in fast-line sections. The air velocity in levels used for travel (tram levels) should not exceed 6.0 m/s.
Minimum air volumes amount to 6 m3/min per person, plus 3 - 6 m3/min per diesel horsepower for CO levels ranging from 0.06 % to 0.12 %.
Airflow velocities are measured with anemometers, and the airflow volumes are calculated by multiplying the velocity by the cross-sectional area.
The regulations governing gas contents, air volumes and airflow velocities differ from country to country (hard-coal mines in India, mines in Chile, the People's Republic of China, etc.).
Underground noise limits can be drawn up along the lines of rules issued by the North Rhine-Westphalian Mines Inspectorate (LOBA) in Dortmund.
The sound intensity level of noise generated by drills should not exceed 106 dB (A) at a distance of 1 m (LOBA Rundverfügung).
Transgression of a certain reference intensity calls for the use of ear protectors. The 1988 EC directive on noise in mining came into force in Germany in 1992. Noise measuring specifications have been developed by the Westphalian miners' union fund Westfälische Berggewerkschaftskasse in Bochum, and the appropriate measuring instruments are commercially available.
In the Federal Republic of Germany, the German Research Foundation (DFG - Deutsche Forschungsgemeinschaft) publishes yearly dust emission limits/standards in the form of occupational exposure limits (MAK-Werte), technical exposure limits (TRK) and biological tolerance values for working materials (BAT). To the extent that the limit values in question are directly relevant to human health, the above or comparable guidelines, e.g., from the World Bank or other international organizations, should be adhered to.
The most important occupational exposure limit, or MAK-value, is that pertaining to fine silica dust, which amounts to 0.15 mg/m3. The corresponding value for siliceous fine dust is 4 mg/m3. In hard-coal mining, the limits for fine silica and siliceous dust presently (as of this writing) amount to 0.60 mg/m3 and 12 mg/m3, respectively, and were scheduled for reduction in 1992. Fine dust is referred to as siliceous if it contains more than 1 % quartz.
The maximum personal dust exposure, measured in mg/m3 x number of shifts worked in five years, shall not exceed 2500. All underground work is classified according to different dust-exposure categories.
Workers suffering from incipient pneumonoconiosis (or anthracosis) may not be exposed to more than 1500 (mg/m3 x number of shifts worked) in the span of five years. In North Rhine-Westphalia, the German land with the largest number of mines, the mining ordinance for hard-coal mines Bergbauverordnung für Steinkohlebergwerke, section 44 - 48, version dating from February 19, 1979) governs the measurements and interpretation.
Table 3 - Miscellaneous dust limits (MAK-values) with mining relevance
|Asbestos, crocidolite||0.5 x 106*||0.025*|
|All other types of asbestos-laden fine dust||1 x 106*
|Nickel-ore dust (sulfid.)||carcinogenic|
|Determined by means of
atomic absorption analysis and X-ray fluorescence
analysis. Application to projects in developing countries
in accommodation of local measuring techniques and
analytical methods (cf. references) is recommended.
* technical exposure limit (TRK)
The discharge of industrial process water and mining effluent is strictly regulated in Europe. The EC Council Directive 80/778 relating to the quality of water intended for human consumption, dated July 16, 1975, supplemented July 15, 1980, lists three water categories requiring less extensive (category A1) or more extensive (categories A2 and A3) treatment. The guideline values (G) and imperative values (I) for the third category are listed in the following table along with the threshold values (TV) and limit values (LV) stipulated by the North-Rhine Westphalian State Agency for Water and Waste (Landesamt für Wasser und Abfall Nordrhein-Westfalen) in the draft ordinance on potable water Trinkwasserverordnung (TVO) dated July 26, 1994, selected on the basis of relevance to deep-mine waters.
Table 4 - Potable water obtainment guidelines
Oversown dumps are rarely used for agricultural purposes. In the event that such a use is envisioned, the applicable heavy-metal tolerance values for soils are to be found in the guidelines and directives issued by the Darmstadt-based Verband Deutscher Landwirtschaftlicher Untersuchungs- und Forschungsanstalten (German association of agricultural research and analysis stations) and by the Biologische Bundesanstalt für Land- und Forstwirtschaft (Federal Biological Research Centre for Agriculture and Forestry) in Berlin. It is generally necessary to determine the constituents of the dump and any leaching behavior that could impose limits on the available soil utilization options.
4. Interaction with other sectors
With regard to environmental consequences, underground mining is closely linked to a number of other sectors, including in particular:
prospection and exploration of deposits in preparation for the actual underground extraction activities;
processing of the raw materials to obtain marketable products, with such processing normally taking place in centralized plants situated directly at or near the mine;
conversion into electricity in thermal power stations, many of which are located in the near vicinity of brown-coal mining operations;
building construction and civil engineering as sectors pertinent to establishment of the requisite mining infrastructure and means of transportation to the market. (Mines tend to be found in isolated locations, accordingly intensive construction activities are required.);
waste disposal, e.g., for thickener sludge, hydraulic oil, spent oil and the like, and problems concerning ultimate disposal;
water management, since natural water is quantitatively and qualitatively altered by the discharge of mine water into surface waters or groundwater as well as by the extraction of water for use as process water;
forestry as a bulk provider of timbering wood;
and, finally, regional development, which consistently derives strong impetus from mining activities.
5. Summary assessment of environmental relevance
In sum, underground mining can be referred to as an activity with substantial impact on the environment. The consequences can be very detrimental to the environment, especially through the extraction of resources, alteration of the rock structure and groundwater regimen, pollution of the air, the effects of noise and dust, pollution of surface water and alteration and disruption of the landscape. Compared to surface mining, underground mining has modest surface area requirements, both for the winning of raw materials and for other industries. With the exception of leftover rubbish dumps, the area in question is only needed for as long as the deep mine remains in operation.
Among the most significant environmental effects of underground mining is its impact on the miners themselves, whose health and safety are quickly and seriously jeopardized, if the protective rules, regulations and measures are not systematically adhered to.
Finally, underground mining has social consequences, especially in connection with speculative forms of mining, e.g., for precious metals or gems.
Many environmental consequences can be moderated but not prevented. Extensive data is needed as a basis for assessing the environmental impacts and designing protective measures; the uncertainty levels are accordingly high. Even the preparatory activities (reconnaissance, prospection and exploration) necessitate good coordination between the relevant environmental impact assessments and their data requirements.
The stipulation, enforcement, monitoring and control of limit values and underground mining operations has, to a certain extent, evolved to exemplary levels. Direct application of limit-value enforcement and monitoring to other countries is only conditionally possible, since the basic prerequisites usually differ. Nevertheless, every attempt should be made to apply and meet standards designed to preclude detrimental effects on man and the environment. Probably the biggest problem from an environmental standpoint are the uncounted "informal" small-scale mining activities employing uncontrolled, inadequate, unsafe methods that also tend to be hazardous to the environment.
Proper and orderly mining operations require stringent supervision (routine measurements, data collection and monitored adherence to essential limit values). That, in turn, calls for competent executing agencies.
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