Soil is a fundamental natural resource that links the different components of our environment. In addition to food production, soil provides many functions, storing vast quantities of carbon, buffering pollution and supporting many forms of life. Safeguarding soil on mineral sites is a key to achieving sustainable development.
Establishment techniques
The priority will be to establish suitable hydrological and soil conditions at the restoration site - generally this will involve a permanently high water table, close to the surface throughout the year, on generally level, peaty soils.
Damage to soil
Soil may be degraded by mixing, inappropriate storage, or damaged by poor handling techniques causing compaction and smearing, particularly when wet. Soil compaction reduces the volume of the soil and the space available for water and air. Compacted soil will restrict plant rooting and the passage of rainwater, leading to poor drainage and sometimes erosion and run-off. The reduced volume of soil that is accessible to plant roots increases problems of drought stress and the availability of nutrients.
Without careful soil handling and storage, restorations may fail, and particularly in the case of arable, may require expensive remedial work. Compaction below about 60 cm depth in the soil profile may be very difficult to remove mechanically and cause problems for many years. The effects of shallower compaction can be lessened by subsoiling (GPG Sheets 18 and19), although this may be expensive and require a pipe under-drainage scheme to be installed where poor drainage remains below subsoiling depth.
Soil handling
Soil handling should only be undertaken when the soil is dry and friable and ground conditions are dry, usually between April and September. Handling soils when wet can lead to smearing and compaction damage to soil structure.
The different soil layers for stripping, storage and restoration need to be identified by an Agricultural Land Classification (ALC) and Soil Resource Surveys at the planning application stage. The agreed method of working and restoration schemes are based on these surveys and all soil handling and storage must be properly supervised to ensure compliance.
Soil handling using backacters and dumptrucks, following Sheets 1-4 of the GPG, is likely to lead to the best restoration, although other methods, such as restoring soils with dozers and dumptrucks (Sheet 15), may also give good results.
Topsoil and subsoil should be stripped from haul routes before they are used. These routes should be fenced or clearly marked to prevent plant and machinery widening them or cutting corners over time.
Soil storage
Careful planning of the working and restoration phasing will ensure that most of the soil can be directly placed into the restoration. This is the most desirable method as it reduces damage to soils and cost, by avoiding double-handling. Soil from the plant site and first phase or two often need to be stored when opening up the site and are used to construct screening bunds.
Different soil types should be stored separately in accordance with the agreed schemes based on the ALC and Soil Resource Surveys. Soil bunds should be seeded with grass where they are to remain for more than 6 months or over winter, and be regularly cut, maintained and clearly marked. Stockpiled soil is subject to heavy loads from the soil above it, as well as additional handling to form the bund. To reduce the impact of storage, topsoil bunds should generally be limited to 3 m in height and subsoil bunds to 5 m.
Further reading
Defra Guidance for successful reclamation of mineral and waste sites (2004)
MAFF Evaluation of mineral sites restored to agriculture (June 2000)
The information set out within this advisory sheet in no way constitutes legal or regulatory advice and is based on circumstances and facts as they existed at the time Nature After Minerals compiled this document. Should there be a change in circumstances or facts, then this may adversely affect any recommendations, opinions or findings contained within this document