Designs for all new quarries should start with the after use in mind and develop the working plan accordingly. In general terms this has been the case for several years in most locations, especially for sand and gravel quarries. However in some quarries, particularly hard-rock quarries, the restoration plan has been applied retrospectively and this can cause problems with any work that has begun on a site and may result in extra costs. Existing quarries that apply for extensions should be encouraged to develop restoration plans for the whole site.
Advanced tree planting
At some locations trees may have been planted up to 10 years before a planning application has been submitted. This allows the trees to become established, thus providing an effective visual screen before extraction begins.
Environmental management plan
The ecological study during the preliminary investigations should have identified any particular areas of the site that are important for their flora and fauna and the quarry design should take these factors into account. It may be that certain areas should not be worked at all, in order to protect wildlife. In some cases areas of wildlife importance (e.g. a species rich grassland) can be relocated to an appropriate part of the site away from the working areas, or alternative areas can be created to replace those temporarily lost to extraction.
The environmental management plan should also include details of how the day-to-day operations on site will be carried out to minimise adverse environmental impacts. For example there should be steps to reduce the visual impact, manage water, suppress dust and noise, reduce the risk of pollution, control wastes, etc. There should also be details of on-site monitoring, regular audits of environmental performance and positive steps to be taken to improve the site for wildlife.
A useful booklet on biodiversity in the minerals industry has been published by the Minerals and Nature Conservation Forum (which comprises English Nature, the Quarry Products Association and the Silica and Moulding Sands Association) and this can be downloaded from their website. Also available from their website is a similar booklet on geodiversity in the minerals industry.
(http://www.qpa.org/natureconservation/pdf/biod.pdf) - biodiversity
(http://www.qpa.org/natureconservation/pdf/geod.pdf) - geodiversity
Soil movement plan
The process of stripping soil from above the mineral needs to be done carefully because the quality of the restoration will be adversely affected if the stripped soils are seriously damaged, and this may have long-term effects on the future use of the site.
Advance tree planting.
It is therefore essential for the operator to determine the depths and quality of the different soil layers across the site, and to work out where this soil will be placed, when it will be moved and how this work will be done. Guidance can be obtained from the 'Code of Good Agricultural Practice for the Protection of Soil' (The Soil Code) which is available from DEFRA (http://www.defra.gov.uk/farm/environment/
cogap/pdf/summary.pdf). Although the majority of this publication is addressed to farmers and landowners, section 6 refers specifically to soils disturbed by quarrying. The main points in this section are:
The code also includes advice on aftercare of the restored areas in order to ensure a good recovery of the soil structure.
- Different soil layers should be stripped and stored separately (i.e. topsoil separate from subsoil, or different quality layers of subsoil separate from each other).
- Soils should only be moved when they are dry and friable.
- Soil should only be stored where essential. Direct placement onto restored areas is preferable wherever this is possible.
- Soils stored in mounds for longer than six months should be grass seeded to prevent erosion.
- Reinstatement of soils should only be done in dry conditions, in the correct sequence (i.e. subsoil before topsoil) and with care to avoid unnecessary compaction.
In sand and gravel quarries generally the first soil strip is used to form amenity banks, which help to visually screen the site. Thereafter it should be possible to directly place stripped soils onto worked out areas as part of phased restoration. The amenity banks are then used to provide the soils for the final restoration phase.
However, in hard rock quarries the soils are often thinner and usually cover a smaller surface area relative to the quantity of material to be extracted (because the quarry tends to be deeper). This makes phased restoration more difficult and most soils will be stored in amenity banks.
This plan outlines what mineral will be extracted from which part of the site and in what order. It will fit in closely with the soil movement plan and ideally should be worked out for the entire life of the quarry. For a sand and gravel quarry, usually one phase represents one year of working because this will fit in neatly with soil stripping seasons. Included in this plan will be the geotechnical considerations to ensure safe extraction faces, such as the depth of the mineral, the slope required for face stability and the level of the water table.
With a hard rock quarry the phasing plan needs to have a three-dimensional element. The geotechnical considerations become much more important. The stability of the rock will affect the depth of extraction faces, and combined with the surface area this will determine how many benches are possible and hence how deep the quarry can go. Factors to consider include the geology (including faults, bedding planes, etc), the water table and whether there is any interburden (clay layers in between the rock bands).
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