Geoscience Reference
In-Depth Information
physical properties range from excessive stoniness, with an absence of fine soil-form-
ing material, to a predominance of clay minerals at the other extreme, as in the Corby
ironstone workings, where the main problem is lack of free drainage. Some sites suf-
fer from steep and unstable slopes subject to erosion and slumping - the Aberfan dis-
aster is well known; almost all will experience extremes of surface temperature until
a protective vegetation cover has formed. On the chemical side, we can distinguish
nutrient deficiency, which is almost universal, from factors that are actually antagon-
istic to most forms of life, such as the extremes of acidity and alkalinity described.
Practical reclamation schemes must deal with these various problems, and con-
vert the spoil environment into a soil environment within as short a time as possible.
Most sites, however, do not pose problems as extreme as those described above.
Indeed, site restoration is now usually an integral part of the whole process of mineral
working and waste disposal. Modern machinery and technology allows one to 'think
big' and not simply to apply cosmetic solutions. The next section describes some ex-
amples of soil reclamation with a variety of different starting points and end products.
S
OIL RECLAMATION
Reclamation, rehabilitation, restoration and re-creation all have slightly different
shades of meaning depending on the objectives and the efforts required to achieve
them. The key to success in every case lies in the building of a soil ecosystem which
can sustain vegetation, and this can seldom be achieved overnight. First, there may
be the task of creating a desirable land form using large earth-moving machinery. The
removal or reshaping of existing spoil mounds can be a major exercise, but modern
operations integrate soil removal with placement as far as possible to minimize ef-
fort and costs. Next, there is commonly a need to produce good physical conditions
in the top metre or so in order to allow free movement of air and water through the
soil. This may again require special machinery for breaking up compacted ground and
producing good macro-structure. And thirdly, there are often chemical problems and
deficiencies to be overcome, especially when one wishes to restore a site to some pro-
ductive use.
The simplest objective is the 'greening' of waste heaps or quarry faces to sta-
bilize them or to heal unsightly scars on the landscape. This may involve the sowing
of selected grass species or cultivars, the use of fertilizers and/or legumes to raise the
nitrogen level in the soil, or planting with particular trees. We can learn a lot from
understanding natural processes of vegetation establishment, and then trying to accel-
erate them by alleviating the constraints. A great deal of research has been directed at
rehabilitating the legacy of the past. In modern mineral workings, however, it is gen-
erally assumed that the land should be returned to some economic or socially useful
