|Dealing with dust
Simple remediation work in practice: before and after shot. By adding a rubber shute to the end of this conveyor, dust generation has been drastically reduced.
Annex 1 of the Proposed Extended Minerals Planning Guidance Note 11 : Controlling and Mitigating the Environmental Effects of Minerals Extraction in England (ODPM, 2000) describes good practice in dealing with dust based on research published in 1995. The operator has a number of options for preventing and minimising dust during operation and following closure. Some or all of these may be the subject of planning conditions at specific sites. In general, the most effective way of dealing with dust is to prevent it getting airborne in the open air (GoodQuarry.com, 2005) - once in the open air dust is to all intents and purposes impossible to remove other than by natural settling.
|Prevention of dust generation is critical - once in the open air dust is to all intents and purposes impossible to remove other than by natural settling and the operator will have little or no control over where such settling occurs.
Prevention of dust generation is critical - once in the open air dust is to all intents and purposes impossible to remove other than by natural settling and the operator will have little or no control over where such settling occurs.
It is sensible for an operator to consider undertaking an initial dust assessment study for both new and existing operations before implementing measures to deal with dust. The scope of the study is influenced by the type and scale of the operation and the proximity of dust-sensitive locations and may not be required at all sites. The assessment should establish existing background dust levels, identify potentially sensitive local areas, predict the amount of dust likely to be generated by different on-site activities, define likely dust deposition in areas around the site and recommend measures that will allow the operator to effectively control dust. These measures may include:
- Careful design of the operation to reduce the potential impacts of any dust generated, for example by locating the most significant dust generating activities and areas (such as waste tips) away from local communities.
- The use of buffer zones to isolate dust sources from surrounding communities, often incorporated into local planning policy, with distances of 250-500 m typically adopted, unless there are unusual or exceptional reasons to permit a variation.
- Use of dust extraction equipment when drilling prior to blasting. Where possible, dusty material should be removed from the area before blasting or, if not removed, dampened to reduce the emission of dust.
- Enclosure of the processing plant and any conveyors to prevent the transfer of dust to the open air. Containment may not always possible for mobile or semi-mobile crushing and sizing plant.
- The use of wet rather than dry methods to process aggregates. A water based washing plant can reduce the generation of dust, but may increase consumption of water and give rise to water contamination issues.
Water bowser being used to prevent dust on a haul road.
- Water sprays used in the processing plant and at transfer points, waste disposal areas and on haul roads to control dust transfer to air. However, when the water evaporates, dust may become an issue again. Therefore, damping can be an ongoing process, particularly during long dry periods.
- Soils and overburden can be used to cover waste disposal areas to control wind (and water) erosion of dust. These cover materials can be revegetated to improve resistance to erosion and to integrate waste areas with the surrounding landscape as part of the overall restoration plan for the site.
- Use of physical barriers such as buildings, windbreaks, solid fences, vegetated embankments and trees to reduce wind speed and the potential for erosion.
- Restricting the speed of on-site vehicles to reduce the amount of material thrown up in the air from the road and dust lost from material being transported. Road surfaces should be kept clean and in good repair.
- Vehicles should be sheeted and their wheels cleaned prior to leaving the site to prevent dust escaping onto public highways. It may be necessary to sheet vehicles being used for the on-site transport of dusty material.
- Sheltering transfer points from the wind as dust is easily picked up by the wind when material is falling through the air.
- Halting or reducing significant dust-generating activities during extended periods of dry and windy weather when normal control measures may not be adequate.
- Periodic review of dust control measures as these may change as work on the site progresses.
- Comprehensive dust monitoring to identify any sources of dust that require additional control measures or confirm that the operator's control measures are delivering the required performance.
- Communicating monitoring results to local communities and responding to feedback as part of the process of addressing local concerns.
Dust monitoring station at the edge of a site.
|The range of options for dust prevention is extensive: the careful design of operations, enclosure of dust generating equipment and the use of barriers and buffer zones are all approaches the operator should consider if dust is likely to be an issue.
Sources of further information
- Goodquarry.com. 2005. Air Pollution . Available online click here
- ODPM. 2000. Proposed Extended Minerals Planning Guidance Note 11: Controlling and Mitigating the Environmental Effects of Minerals Extraction in England.
- Gough, K. and Stone, I. 2004. Air quality: Impacts, monitoring and controls. Chapter 3 in Environmental management , The Institute of Quarrying, edited by M S Watkins and M R Smith, ISBN 0-9538003-4-2.
- NECESI/The Environment Practice. 2004. Dust and Air Quality. Chapter 1 (Section B-I) in Environmental Management Guidance Manual for SME Aggregates Companies . March 2004. Available from NECESI, University of Durham, Unit 1R, Mountjoy Research Centre, Stockton Road, Durham DH1 3SW.