Cleaning Up
Open pit mining
methods are used to expose and extract the coal seams. This can involve
diverting streams around the site, and removing trees, soil and overburden to
retrieve coal that may be more than 200 metres underground. This significant
alteration of the landscape and ecosystem makes reclamation of an open pit mine
a special challenge.
There are
several factors that limit the ability to reclaim an open pit site to its
previously
undisturbed condition. The climactic conditions in mountainous areas (especially
subalpine and alpine) are generally very limiting to some natural processes.
Soil formation is typically slow, and the resultant thin soils tend to be rocks
and of poor quality. In turn, the cooler temperatures, short growing season,
drying winds and poor soils limit the speed and type of plant growth. Topography
also plays a major role because steeper slopes generally increase the amount of
runoff and soil erosion in exposed areas, further reducing the amount of soil
and moisture available for plant growth. The combined
effect of these factors means that regrowth on reclaimed lands occurs slowly.
Contouring of
the land, grading of overburden and soil, seeding with grass and legume
mixtures, and extensive fertilization are designed to speed plant colonization
and plant development on reclaimed mine sites. When a ground cover is well
established, seedling trees can be planted in locations considered optimum for
tree growth. Streams that were diverted are typically re-routed through their
natural valley, and habitat enhancement methods are used to provide quality fish
habitat. Depleted mine pits may be filled with water and stocked with fish to
provide recreational fishing lakes where none existed previously. These
reclamation techniques have proven successful in helping to restore mined areas,
hastening their colonization by native plants and animals and subsequent use by
people.
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