Step 5. Rehabilitation
Restoring the environment to it’s natural state.
Mine site rehabilitation is important to environmental sustainability. Rehabilitation involves returning the land to it’s natural state post mining through strict, well researched strategies of revegetation and the regeneration of natural ecosystems. Work to restore disturbed areas is carried out progressively as soon as practicable.
Griffin Coal’s environmental commitment includes the progressive rehabilitation of its mining operations. The objective of mine rehabilitation is to create a structurally stable landform capable of future productive use.
Rehabilitation also occurs to return land to a scale and morphology similar to that which exists elsewhere in the Collie Basin.
Rehabilitation involves a comprehensive process of classifying overburden material, land recontouring, seeding and regeneration.
1. Overburden Material Classification
Overburden material is classified according to its potential to cause geochemical impacts (acid rock drainage) on the environment. Dumping of waste material is undertaken so the best materials end up near the surface of waste landforms and the other material is encapsulated in the middle.
2. Land Recontouring
When the landforms are no longer needed for mining or dumping purposes the slopes are recontoured to around 10 degrees to control surface runoff and to ensure a stable slope. Topsoil is then spread to a depth of 150 millimetres before the area is contour ripped, fertilised and seeded with local natives.
Rehabilitation areas are seeded at the break of the winter rainy season, and initially are susceptible to erosion damage until germination and root development has occurred. Historically dumps were rehabilitated to pasture species. This approach was chosen to stabilise the dump outslope quickly to prevent erosion. More recently efforts have been directed to the re-establishment of native flora.
Native species do not germinate and develop until the following spring, therefore the potential for massive erosion is present during the winter. A strategy has been developed whereby native bush species comprising grasses, groundcovers, shrubs and trees, are sown together with a “nurse” crop of cereal rye.
The cereal rye germinates quickly and stabilises the surface through the winter and the natives emerge the following spring. The seed mix includes Jarrah, Wandoo, Flooded Gum, numerous Acacias and understorey species.
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