كيف نحافض على بيئة المحاجر او المناجم وذلك باتباع مايلى
Long before any submission of formal development plans to an appropriate authority, a number of actions can be undertaken that will ultimately save considerable resources allowing effective development. These include:
The approaches above identify the main methodologies required for mineral developers to approach effective development proposals. Within these methodologies, further technical measures have been identified which will demonstrate minimal dust impact.
- <LI class=bullet>EIA with an early scoping exercise; <LI class=bullet>pre-discussions with relevant formal and informal bodies; <LI class=bullet>community consultation and involvement;
- environmental Management Systems.
Environmental Impact Assessment
EIA should ensure that the likely significant environmental effects of a proposed development are fully understood and taken into account before development is allowed to proceed. Early identification of areas requiring further consideration and action prior to inclusion in any environmental impact statement will reduce the time needed for development approval. EIA methodologies are well known and expertise widely available.
It is extremely important that discussions between mineral operators and the relevant mineral planning authorities about the potential dust impact from proposed workings take place at an early stage in the development process. Discussion details should include as a minimum:
Consultation and Liaison All steps should be undertaken to minimise adverse effects of dust from mineral operations on local host communities. Increased public knowledge and awareness of the environmental, economic and social effects of mineral development means that the local community can exercise considerable influence over decision-making authorities in various ways. A full description of the approaches which can be taken with community consultation and liaison is given in the section on Social and Community.
- <LI class=bullet>the EIA scoping requirements and the need for a dust assessment study and its format; <LI class=bullet>identify potential sensitive local areas, and the applicability of buffer zones between the site activities and sensitive areas;
- the degree of appropriate activity for the land use within local development plans.
Environmental Management Systems
A primary aim of minerals planning is the mitigation and minimisation of the inevitable physical impacts of mineral extraction and processing. The limitation and mitigation of impacts on the environment has been a major issue for mineral development and operating companies for a long time. Many companies are now directing their attention towards their own environmental performance and the potential impacts of their operations. A competently prepared and intelligently used environmental management system (EMS) can assist operational management to meet both current and future environmental requirements and challenges. It is a quality assurance tool which cannot only be used to measure a company's operations against environmental performance indicators. In the best examples it is a positive aid to good operational practice. It should never become an audit driven paper chase not related to real world impacts.
A number of EMS standards exist for implementation and control, including the standard ISO 14001 (1996) of the International Organisation for Standardisation (ISO).
Dust Assessment Study
A dust assessment study should be undertaken for all new and extended mineral workings as part of the impact assessment. The degree of assessment will be influenced by the type and scale of working and proximity of sensitive land uses in surrounding areas. A dust assessment study is best undertaken by a competent person/organisation with acknowledged experience of undertaking this type of work, and may involve the use of computer modelling or other predictions of anticipated deposition rates. It should identify the operations or processes likely to cause dust, taking into account local climate and topography. It should also make recommendations for mitigation measures which will assist the operator and local authority in effectively controlling dust from a site.
Stage 1 Establish existing baseline conditions
Existing ambient conditions should be identified over a period sufficient to identify seasonal variations in the range of existing conditions that naturally exist (ideally by a dust monitoring programme). It should take into account the principal existing dust sources (other than the site) such as air pollution from urban and industrial areas, existing mineral operations, agricultural activities and construction activities, including:
The location of residential areas, schools and other dust-sensitive land uses should be identified in relation to the site, and within-site dust emission sources. The assessment should explain how topography may affect the emission and dispersal of site dust, particularly the influence of areas of woodland, downwind or adjacent to the site boundary and valley or hill formations in altering wind patterns. The assessment should also explain how climate is likely to influence patterns of dispersal by analysing data from the UK Meteorological Office or other recognised agencies on wind conditions, local rainfall or ground moisture conditions.
- <LI class=bullet>identification of the location and nature of existing dust sources and establishment of their relative contributions to dust levels, their patterns of dispersion and rates of deposition. <LI class=bullet>baseline monitoring of meteorological effects (especially prevailing wind direction and rainfall);
- establishment of background dust levels at nearby dust sensitive properties.
Stage 2 Identify site activities that could lead to dust emission without mitigation
Potential dust sources should be identified and their potential to emit dust assessed with respect to the duration of the activity or the potential of dust to become airborne.
Stage 3 Identify site parameters which may increase potential impacts from dust
This brings together information collected in stages 1 and 2 with information on sensitive land uses around the site in order to understand how these uses could be affected by dust. Dust emission, dispersion patterns and impacts are difficult to predict due to the wide range of activities on site that may give rise to dust, and the lack of reliable emission factors for these activities together with the influence of local meteorology and topographic features.
Computer modelling based on reliable meteorological data and the locations of anticipated dust sources can provide crude predictions of likely dispersion patterns, but suffer from the lack of available data for boundary conditions and input parameters. Once site development has commenced, however, various dust monitoring techniques can provide data which allows the development of site specific empirical relationships between site activities and dust levels and patterns of movement around the site.
Ideally, such empirical models will arise from the baseline monitoring and modelling. Whilst the primary purpose of an approved monitoring scheme would be to establish whether or not the site was causing a dust nuisance, inclusion of a simple weather station and directional monitoring capability would allow the development of such a model. The advantage of this approach is that it would provide the operator with a better chance of rapidly identifying the source of any nuisance shown up by monitoring, and a better basis for implementing appropriate remedial controls.
Separate XRD analysis of the background dust and stock minerals produced in the quarrying operation can assist in differentiating between dust sources when the operator is being unjustly criticised for excessive dust generation.
Stage 4 Recommend mitigation measures and site design modifications
Measures to control dust should be specified and described in terms of their potential to reduce dust and consequent impacts.
Dust Action Plan
These include provisions for additional actions to be undertaken for workings close to sensitive premises following adverse weather conditions. They include additional dust suppression measures and temporarily suspended or modified site operations until conditions improve. They also allow for an open system of communications should problems arise.
Sufficient time and thought needs to be devoted to site design, including the phasing of operations, so that careful consideration is given to the relationship of activities within the site to sensitive areas outside it. As far as possible dust management issues should be reflected within the site design and dust generating activities located away from sensitive locations. Ideally, the results of a dust assessment study can be used to inform site design.
Other factors that should be taken into account in the layout of a site to reduce dust impacts are:
The location of dust generating activities can move around a site during different phases of working, and therefore their relationship with dust sensitive land uses around the site will change. It is important that the minimisation of dust through site design is addressed at each phase of the operation.
- <LI class=bullet>placing dust generating activities where maximum protection can be obtained from topography, woodland or other features; <LI class=bullet>locating dust generating activities where prevailing winds will blow dust away from residential properties/sensitive premises/users;
- minimising the need to transport and handle materials by placing adequate storage facilities close to processing areas.
Some activities should ideally be undertaken during favourable weather conditions. Where possible extended periods of dry and windy conditions should be avoided. This should be taken into account in framing conditions specified for activities such as:
Such specifications should also take account of other factors, such as the need to avoid moving top and sub-soils during wet weather to protect soil structure. The potential for different activities to generate dust during the life of a mineral working needs to be carefully considered. There may be circumstances when it would be preferable to allow higher limits during a shorter period than to maintain lower limits over a longer period.
- <LI class=bullet>soil stripping and reinstatement operations (although, as explained below, it can be desirable for other reasons for these to be undertaken during dry conditions);
- overburden handling near to dust sensitive land uses/properties/receptors.
There are a large number of measures which can be taken to prevent dust becoming airborne during site operations. This is the main objective in reducing dust nuisance and of course is most likely to occur during dry periods when there is also a strong wind. This wind not only picks up the dust and moves it around, but also helps the ground to dry out even more quickly, thus exacerbating the problem. Experience has shown that 5 days without rain can cause the ground to dry out sufficiently for dust to become a concern. During a hot windy period, this may be as little as 2 days.
Soil handling and storage The activity should be carried out as quickly as possible and the storage mound surfaces should be sealed and seeded as soon as is practicable (Photo 13). If possible, protect surfaces from strong winds until the disturbed areas are sealed and stable.
Drilling and blasting Dust extraction equipment, such as filters, should always be used on exhaust air emissions from drill rigs. It is important that this material is collected properly and not simply allowed to fall to the ground, where it can then be blown about (Photo 14). If it is possible to remove any dusty material which has collected on the blast area prior to detonation, then do so. Otherwise, in dry conditions it may be helpful to water the blast area first. (Photo 15)
Overburden handling and storage
The first step is to minimise the amount of rehandling which obviously has cost benefits as well.
Exposed material should be protected from the wind by keeping it within voids or protecting them by topographical features. Exposed surfaces should be sprayed regularly to maintain surface moisture unless the mound surface has formed a crust after rainfall or it has been grassed, which is often a very effective way of controlling fugitive dustcs6. If necessary this can be done on steep broken slopes (Photo 16) as well as flatter ground such as haul roads (Photo 17).
Where a dragline is in operation, a high pressure pump can be used to dampen the material as the bucket is being dragged through it (Photo 18). This is mainly to ensure the material is wet when it is cast from the bucket at what may be a considerable height above the surrounding ground.
Dust is most easily picked up in the wind when the material is falling through the air at points of transfer. It is therefore important to reduce the drop heights wherever practicable. Photo 19 shows coal being stockpiled from a conveyor which has a sleeve attached to it to prevent the wind picking up dust as the material falls. In addition it may be necessary to protect the activities from wind by erecting a screen or using a natural barrier such as the high wall of a site.
Fine spray or fog suppression (Photos 20 & 21)cs1 can also be used in loading bays which are exposed to the wind and therefore a likely source of dust.
The solutions to any dust problem will vary depending on the type of equipment used but generally complete enclosure is best with use of air extraction and filter equipment as appropriate. Water sprays can also be used.
A number of measures can be taken here. Material can be dampened, perhaps with a fine spray (Photo 22); it can be covered over in some way to protect it from the wind; or it can be screened to remove dusty fractions prior to external storage.
Transport by conveyor within site
Where conveyors are used, either as the major transfer system or simply as part of the processing, the transfer points should be sheltered from the wind. Indeed, it may be necessary to protect all of the conveyor by partially or completely enclosing it (Photo 23). Once again, drop heights should be minimised and water sprays (Photo 24)cs3 can be beneficial.
Transport by vehicle within and off-site
Use paved roads where practicable and where this is not possible make sure that unsurfaced and paved road are dampened when there is the danger of dust being generated. This can be done using water sprays from fixed pipes (Photo 25), water gunscs2,cs4,cs5 or by using a water bowser (Photo 26). Where surfaced or paved roads are used, they should be swept and washed regularly (Photo 27).
Vehicle speed should be restricted as there is a direct relationship between the speed and the amount of material that is thrown up in the air. The section on traffic states that all lorries leaving site should be properly sheeted (Photo 28) to prevent dust escaping onto the public highways. However, it may also be advantageous to sheet vehicles being used for internal transfer of dusty materials.
Material should be loaded and unloaded in areas protected from the wind and drop heights should be minimised.
المهندس / يحيى بن محمد الشنقيطى