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35. Reconnaissance, prospection and exploration of geological resources
2. Environmental impacts and protective measures
2.1 Access to work area
2.1.1 Access roads
2.1.2 Lanes
2.2 Topographical and geological mapping
2.3 Camps and support facilities
2.4 Geophysics
2.4.1 Airborne techniques
2.4.2 Prospection seismics
2.4.3 Nonseismic geophysical investigations
2.4.4 Well-shooting
2.5 Hydrogeological investigations
2.5.1 Long-time pumping tests
2.5.2 Injection tests
2.5.3 Tracer tests
2.6 Exploratory work
2.6.1 Trial pits
2.6.2 Shafts/tunnels
2.6.3 Drilling
2.6.4 Solid waste/dumps
2.7 Sampling
2.7.1 Surface sampling
2.7.2 Marine sampling
2.8 Laboratory testing
2.8.1 Laboratory analysis
2.8.2 Dressing tests
3. Notes on the analysis and evaluation of environmental impacts
4. Interaction with other sectors
5. Summary assessment of environmental relevance
This brief describes the environmental consequences and potential means of pollution control in connection with the reconnaissance, prospection and exploration of geological resources.
Geological resources in the present context comprise mainly raw minerals and groundwater, with attention to soil being restricted to the reconnaissance aspect. Reconnaissance, prospection and exploration are the terms used for steps taken in preparation for the commercial extraction, i.e., utilization, of geological resources. The environmental consequences of extracting, dressing, refining and distributing such resources are not dealt with in this brief. The entire petroleum/natural-gas exploration complex has also been excluded. Those areas and related sectors are investigated in separate briefs.
The purpose of reconnaissance, including stock taking and mapping of resources, is to obtain regional overviews and to identify and demarcate mineral prospects and/or pedological location factors.
Prospection aims to locate prospects and exploitation areas by way of geological, geophysical and geochemical methods of field investigation.
Exploration - the detailed study of prospective areas - uses the same methods as those employed for prospection, but also involves direct disturbance of the environment.
While there are various basic types of reconnaissance, prospection and exploration projects, their respective environmental impacts depend primarily on the individual activities involved.
Both direct and indirect geoscientific methods are employed in the reconnaissance, prospection and exploration of geological resources. As a rule, the indirect methods yield less accurate results but offer the capacity for covering large areas at low specific expense. More precise, and substantially more expensive, direct methods applied preferentially to prospective zones and already identified anomalies or deposits enable the refinement of data bases. The raw minerals sector, for example, employs the following methods of investigation (listed in the order of increasing exactitude):
– interpretation of satellite photographs
– interpretation of aerial photographs
– interpretation of thematic geoscientific maps
– interpretation of geophysical test data
– interpretation of borings with the help of geochemistry and well logging; analysis of core samples
– investigation of explored deposits via shafts and tunnels
– interpretation of dressing tests
Groundwater prospection investigates the demand for water, its quantitative management, quality and protection, and the ecological consequences of its extraction (for details, cf. section 4). The protection-worthiness and sensitivity of the existing ecosystems, the volumetric and pollution-load capacities of the receiving waters, the effects of relevant road-building measures, and the social, sociocultural and ecological impacts of the anticipated settlement effects must be duly considered and assessed (for details, cf. section 4).
The "soils" subsector involves the evaluation and assessment of soils on the basis of soil surveys and the appraisal of soil utilization potentials. Moreover, measures designed to protect the soil from erosion, salinization and the effects of fertilizers and plant phytopharmaceutical products demand appropriate illumination.
2. Environmental impacts and protective measures
The environmental consequences of the subject sectoral measures are extensively limited, and the relevant protective measures are for the most part uncomplicated and inexpensive. Unavoidable damage of tolerable extent demands settlement by material compensation.
Reconnaissance, prospection and exploration activities can impose various hazards on the environment. The environmental consequences tend to increase as the activities progress from reconnaissance to prospection to exploration. In the first two cases, the impacts are usually modest and temporary. Exploratory measures are more elaborate and expensive, and the cost factor therefore helps retard their excessive implementation.
The main purpose of protective measures is to minimize the environmental consequences and to prevent environmental damage with respect to both time and space. The avoidance of permanent damage is especially important. Since geological resources are immobile, field investigations are usually limited to a particular site. Proper consideration of seasonal weather conditions can help avoid damage to the environment, e.g., by performing such work outside of the growing/breeding season.
Damage to the environment can be extensively avoided, or at least limited, by:
– careful execution of exploratory work - e.g., by avoiding the use of heavy (and accordingly expensive) equipment - inclusive of soil- and water-protection measures, stabilization measures, recultivation, etc.,
– choosing environmentally benign (micro-)sites for (prospecting) lanes in order to minimize the environmental burden, e.g., through dissection; the same applies to the choice of locations for camps and support facilities,
– taking measures to prevent environmental mishaps, e.g., by installing traps for oil and chemicals.
Environmental consequences can also be limited by recovering and recycling materials and substances. Recycling is preferable to (controlled) disposal. The ultimate goal is to restore the site as closely as possible to the state it was in prior to commencement of the work, or at least to preclude lasting detriment to the environment.
2.1 Access to work area
2.1.1 Access roads
It is frequently necessary to fell trees and move earth to make way for access roads. The damage resulting from such activities can by far exceed that caused by reconnaissance, prospection and exploration. Moreover, establishing access to a previously inaccessible area can lead to such social consequences as public unrest and land speculation. Controlling access to such roads can help prevent the subsequent uncontrolled generation of settlements.
2.1.2 Lanes
Geophysical investigations may require the cutting of narrow lanes as footpaths. This can cause temporary damage to the vegetation and expose the soil and subsoil to erosion.
In the tropics and subtropics, much more so than in semi-arid regions, the vegetation is normally able to close off such lanes within a year or two, so that no permanent damage remains. Protective measures are rarely necessary. The inadvertent provision of general access to the area in question must be avoided.
In areas characterized by a very fragile balance of nature (marginal locations, slopes) it may be necessary to impose certain restrictions and to carefully accommodate the local situation, e.g., by disturbing as small an area as possible and reducing the felling of trees to a minimum. If farmland is involved, the competent authorities and those affected must be consulted with regard to compensation.
2.2 Topographical and geological mapping
Unless mapping activities are intensive and require extensive field checking, little impairment of flora and fauna need be anticipated.
2.3 Camps and support facilities
In many cases, permanent camps comprising lodgings, workshops, field laboratories, storeyards, etc. can be required. The attendant land use, sealing of soil and general detriment to and disturbance of local flora and fauna are disadvantageous. Controlled disposal of liquid and solid wastes must be ensured.
2.4 Geophysics
2.4.1 Airborne techniques
The noise caused by flyovers, most notably in connection with helicopter-assisted methods of surveying, is disturbing to local animal populations.
2.4.2 Prospection seismics
The environmental consequences of prospection-seismic activities (blasting) on lanes can be extensively minimized by carefully plugging the blasting charges in the boreholes. Such activities cause no permanent damage to the environment.
2.4.3 Nonseismic geophysical investigations
All nonseismic geophysical investigative methods involve the use of portable measuring instruments at or slightly above ground level (£ 1.5 m). The hauling and handling of the requisite equipment and the movements of personnel within the areas of interest can be expected to cause modest impairment of the local environment.
The electricity required for a camp and, possibly, for one or the other electric-powered piece of equipment may necessitate the use of a diesel- or gasoline-fueled generator. Environmental damage can result from improper or careless handling and storage of fuels and lubricants.
2.4.4 Well-shooting
Well-shooting is the term applied to measurements conducted in an existing borehole according to radiometric, electric, magnetic, acoustic, mechanical and thermal techniques to gain information on the immediate surroundings of the hole itself. Consequently, any effects on the environment are limited to the immediate vicinity of the measuring point - one exception to the rule being radiometric measurements performed with the aid of active radiation sources that require certain precautionary measures in connection with calibration and introduction of the probe - the loss of which must be avoided - into the borehole. Radioactive cores must be duly marked, and appropriate protective measures up to and including the services of a radiological safety officer must be taken in case of high-level radiation.
2.5 Hydrogeological investigations
2.5.1 Long-time pumping tests
The sustainable yield and/or groundwater permeability of wells and boreholes is determined by long-time pumping tests. Lowering of the groundwater level in the vicinity of the tested well can cause temporary detriment to other wells situated nearby.
2.5.2 Injection tests
Long-time injection tests serve in determining the sustainable injectivity of drainage wells. Such tests can temporarily alter the groundwater regimen. Care must be taken to ensure that the injected water is environmentally compatible.
2.5.3 Tracer tests
In karst areas, tracer tests are conducted to locate and determine watercourses and groundwater retention times. The methods employed rely on fluorescent dyes (1), radioactive substances (2), salts (3) and pollen (4). Tracers (1) and (4) have no
environmental consequences, although fluorescent dyes could be perceived as a visual infringement. The initial activity and concentration levels of tracers (2) and (3) must be kept low enough to avoid detrimental effects on the environment.
2.6 Exploratory work
Exploratory work serves to enable sampling activities. Depending on the depth of the planned sampling point and on the geological situation, different opening operations are appropriate:
2.6.1 Trial pits
The main environmental consequences of establishing a project result from removal of the local vegetation and soil. It is sometimes necessary to penetrate more deeply into the exposed rock, although such measures normally involve depths of a few meters at most. Cutting into a steep slope causes erosion. Upon completion of the exploratory work, the prospect must be refilled with the excavated material and separately stored topsoil to prevent aggravated erosion and accidents. Additional case-specific measures may be necessary to preclude erosion.
2.6.2 Shafts/tunnels
If boreholes and trial pits are insufficient for the envisioned scope of exploratory work, horizontal or slightly inclined tunnels and/or vertical shafts can be dug to enable underground reconnaissance, including sampling. Due consideration must be given to the fact that tunnels require appropriate entrances and that they tend to collect groundwater, possibly resulting in the dewatering/drainage of overlying rock. Special protective measures may be required in connection with the location and exploration of uranium deposits. In the absence of appropriate national directives, the radiation protection ordinance of the Federal Republic of Germany should be applied accordingly.
Major exploratory operations quickly equate to regular mining operations, the environmental consequences and relevant protective measures of which are dealt with in detail in the respective sections of this handbook.
Tunnel faces and shaft mouths must be closed off for safety reasons whenever the work is interrupted and following its completion.
Any shaft or tunnel that interrupts the flow of groundwater can simultaneously jeopardize its quality. Consequently, when the work is finished, all such holes should be completely refilled. As long as the work is ongoing, shafts must be secured to prevent unauthorized access and accidents. If regular measures are not possible, a sturdy cover must be installed.
Dug wells providing potable water in rural areas of dry-climate regions are especially important. If the exposed groundwater is not effectively protected against pollution, such wells can have negative qualitative effects on the environment. The same applies in essence to groundwater trial pits, while groundwater stemming from an adit is, as a rule, hygienically unobjectionable.
2.6.3 Drilling
Drilling serves as a means of subterranean geological
exploration. It allows geological surveys, geophysical
measurements and sampling. Pumping tests are conducted for
hydrogeological purposes (cf. 2.5.1). Drilling can cause a
substantial noise nuisance, with attendant disturbance of
the local populace and animal life. Thus, all requisite active
and passive means of noise control must be adopted, and the
applicable work safety directives in particular must be followed.
Depending on the climatic zone, some extent of land may have
to be cleared around the drilling site.
Wells and boreholes are potential hazards for groundwater. In the absence of protective measures, detrimental effects can result from cutting through confined groundwater (artesian, for example), from interconnecting different groundwater stories (possibly of divergent quality), and/or from piercing the bases of multiaquifer formations.
Bleeding artesian wells are a waste of groundwater reserves and can do damage to the borehole environs, e.g., by causing the soil to salt up. The hydraulic interconnection of different groundwater stories can detract from both the quantity and the quality of the entire resource. Intermediate groundwater stories can drain out to such an extent that wells run dry and the work of fetching potable water - mainly by women - for household purposes increases in relation to the distance to the next intact well.
Appropriate technical measures, however, can be taken for drilling operations (pressure regulating valves, special flushings, packers, clay seals) to prevent such damage. In areas with a relevant hazard potential, the geological and technical aspects of drilling must be carefully planned in all detail, with all the appropriate equipment provided and properly serviced. (For details, please refer to the environmental brief Petroleum and Natural Gas.)
In semi-arid regions, drill bits often encounter aquifers filled with fossil, nonrenewable groundwater. Thus, in any such case the demand forecasts and proven reserves must be carefully balanced in order to avoid both an unprofitable investment and consequential damage to the ecology.
Drilling operations can also have negative environmental consequences as a result of drill cuttings, chemicals, process water and improper fuel storage procedures. The incidental drill cuttings and flushings must be collected and properly clarified at the end of the drilling operations, so that only cleansed wastewater is returned to the environment. The drilling site must be cleaned up and restored as closely as possible to its original condition.
2.6.4 Solid waste/dumps
Solid waste can derive from laboratory work as well as from exploration and production operations. All scraps, e.g., worn drill rods, must be collected and either properly disposed of or recycled. The same applies to sludgy residues from flushing operations.
Trial pits, tunnels and shafts yield excavated material that requires temporary or permanent storage. The size of the requisite storage area depends both on how much material is excavated and on the local topography. Wind, precipitation and percolation can erode, leach, scour and elutriate excavation dumps and cause water pollution in the process. In particularly severe cases, the dump may slump or slide. The storage of any material with a high hazard potential, e.g., due to radioactivity, requires appropriate measures for:
– preventing washout and dust deflation,
– collecting wastewater/effluent (packing and possible percolation drainage) with subsequent clarification, and
– monitoring its discharge.
Environmental detriment attributable to erosion can be extensively avoided - and the dump's stability enhanced - by turfing, greenbelting or otherwise covering it.
2.7 Sampling
2.7.1 Surface sampling
Sampling for analytical purposes often requires either the removal of near-surface strata or the extraction of material from special-purpose exposures. In some rare cases, sampling can impose a burden on the environment in the form of noise given off by jackhammers. As a rule, though, such problems are short-lived and
not particularly serious. By comparison, the work involved in establishing exposures is more likely to have negative environmental impacts, as described in section 2.6.
2.7.2 Marine sampling
Marine sampling operations can have environmental consequences for ecosystems in shelf waters as well as in the deep sea: alteration of the seafloor morphology, disruption of pediment, destruction of marine life, turbidity.
The following techniques and technology must therefore be employed for minimizing such effects:
– exploration of the seafloor via TV probes in order to confine and delimit the sampling area,
– selective sampling with TV-guided grabs,
– no large-scale clearance or scavenging of the seafloor,
– separating the sludge and fine slush from the liquid phase (undissociated suspensions can jeopardize marine fauna, especially if they get into the photic zone.),
– avoiding the local release (into the seawater) of acidic processing residues.
In some cases, in-situ analytical instruments use radioisotopes as a source of excitation, with a possible attendant (normally harmless) increase in radioactivity.
2.8 Laboratory testing
2.8.1 Laboratory analysis
Activities in connection with chemical and physical laboratory testing and analysis can yield substantial amounts of solid, liquid and gaseous wastes, some of which may contain toxic reagents. Exhaust air and exhaust gases may require filtration or scrubbing, while liquid wastes and effluents can be neutralized, precipitated, clarified, separated, etc. Organic solvents must be collected and the escape of noxious fumes and vapors to the atmosphere prevented. Additionally, appropriate
measures must be adopted to ensure either the orderly disposal (incineration, dumping, ultimate storage) or recycling of liquid and solid waste products. The environmental brief Analysis, Diagnosis and Testing contains pertinent information in detail.
2.8.2 Dressing tests
Deposit exploration projects sometimes necessarily include dressing tests. The incidental wastewater must be collected in settling tanks and appropriately treated to the extent that it contains substances capable of polluting the recipient body or groundwater; cf. environmental brief Minerals Handling and Processing.
3. Notes on the analysis and evaluation of environmental impacts
Distinction must be drawn between the environmental consequences dealt with in section 2 and those which may result from follow-up measures. Any study, expert opinion or commentary prepared in connection with such projects should include references to the potential environmental impacts of subsequent project implementation. Even at the initial reconnaissance and exploration stage, such consequential effects should be appraised. If necessary, pertinent studies must be conducted in parallel with the prospecting activities. Such preliminary studies should focus on the data requirements of the subsequent environmental impact assessment. Section 4 and other environmental briefs offer further-reaching information on the scope, evaluation and possible countermeasures.
4. Interaction with other sectors
The following other environmental briefs are also of relevance:
– Spatial and Regional Planning
– Water Framework Planning
– Urban Water Supply
– Rural Water Supply
– Road Building and Maintenance, Building of Rural Roads
– Rural Hydraulic Engineering
– Large-scale Hydraulic Engineering
– Surface Mining
– Underground Mining
– Petroleum and Natural Gas - Exploration, Production, Handling, Storage
– Minerals - Handling and Processing
– Cement and Lime, Gypsum
– Glass.
The groundwater domain is a focal point of interest in that connection. Regional planning, in particular for rural development, is heavily dependent on access to properly protected groundwater, and timely evaluation of the potential environmental consequences of project measures is therefore of major significance. Diverse cross-links also exist between the groundwater domain and the mineral resources and mining sector, since potential environmental impacts often become apparent at the feasibility-study stage.
5. Summary assessment of environmental relevance
The project goals encompass preparations for the environmentally appropriate satisfaction of basic needs (e.g., access to potable water), the protective use of resources (such as water), appropriate use of soils, self-sufficiency in the environmentally sound exploitation of mineral and fuel resources and, as a result, improved employment perspectives in conjunction with the extraction and exportation of resources. Two of the most important project objectives are the transfer of know-how and the enhancement of environmental awareness.
As long as the project is carefully planned and executed with due regard for the described consequences and protective measures, activities in connection with the reconnaissance, prospection and exploration of geological resources can be expected to have only limited impacts on the environment.
Appropriate and available means of controlling or remedying environmental damage can be implemented with relatively modest inputs.
The subject studies and investigations also serve to supply the environmentally relevant data and information needed to achieve sustainable utilization of soil and groundwater and the protective extraction of nonrenewable mineral resources.
In connection with the implementation of protective measures, the interested and concerned parties must be made aware of environmental concerns. The analysis and evaluation of potential environmental impacts must be considered an integral part of the project appraisal phase.
Pertinent directives serve to ensure that:
– intervention in the environment is limited to the smallest possible, essential scope;
– unavoidable encroachments are accommodated to the natural situation;
– resultant damage is remedied or, if that is not possible, at least controlled;
– permanent damage is avoided to the greatest possible extent.
The necessary measures and corresponding responsibilities must be defined and established during the project planning phase.
Controls aimed at ensuring the success of the protective measures should be conducted during and at the end of the project.
Attention must be drawn to potential environmental consequences resulting from the continuation or expansion of a project.
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