1. Rehabilitation of a mine site
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Rehabilitation of a mine site

2. Rehabilitation of the Ensham open-cut coal mine near Emerald in Central Queensland.
Image courtesy of Ensham Resources

3. Before mining
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4. After mining
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5. After rehabilitation
The purpose of rehabilitation is to return the site to an agreed land use.
This is a legal requirement of the EPA (Environmental Protection Authority).
Image courtesy of Ensham Resources

6. Open cut coal mining
‘Spoil’ is the overburden removed to reveal the coal seam. Previous spoil is piled behind the pit. In this way, the pit advances, progressively filled with new spoil. Rehabilitation will ultimately occur over the previous spoil behind the mine.
Direction of advance of the pit
Image courtesy of Ensham Resources

7. The Ensham Mine
The pit at the Ensham mine is progressing to the right in the picture. Removal of surface overburden is in progress on the highwall side (right) and is dumped on the spoil pile (left) to fill the pit.
Image courtesy of Ensham Resources

8. Rehabilitation planning
An aerial view of the mine shows the plan for rehabilitation, with the areas to be rehabilitated in green.
Image courtesy of Ensham Resources

9. The rehabilitation requirements are different for every mine.
An Environmental Impact Study (EIS) is conducted to assess the flora and fauna that exists prior to mining.
An Environmental Authority (EA) is then issued with the mining lease to regulate how the mining company is to interact with the environment.
The rehabilitation requirements are different for every mine.
The mine proposes a rehabilitation plan and the government then adds its own conditions prior to approval.
Image courtesy of Ensham Resources

10. This map highlights areas of “Endangered”, “Of concern” and “Not of concern” ecosystems within and surrounding the mine site.
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11. This map depicts broad types of vegetation within and surrounding the mine site.
The EA spells out the rehabilitation requirements that must be achieved in ground coverage and species diversity.
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12. Before mining
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13. After mining
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14. Rehabilitation
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15. Restored land
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16. Stockpiling of topsoil pre-mining
Before mining begins, topsoil is stockpiled on the highwall side. It is kept for a period until the mine has progressed and the slope of the spoil is ready for the topsoil to be replaced. Most mines salvage 200mm of topsoil but at the Ensham mine 300mm is kept.
Image courtesy of Ensham Resources

17. Dumping of spoil
After surface overburden has been removed by trucks, the highwall is detonated to transfer as much burden as possible to the other side of the pit. Draglines pile this overburden into high spoil piles.
Image courtesy of Ensham Resources

18. Steep slopes are unsuitable for rehabilitation
The volume of rock swells by 25 percent after it is detonated. Even after the coal seam is removed, the spoil piles created by draglines create hills with steep slopes formed as the spoil is dumped.
In years past, these slopes were rehabilitated. However, the slope was found to be too steep to be stable. This picture shows how unstable such a hill is with regard to erosion and landslides.
Image courtesy of Ensham Resources

19. Reshaping of the slope
Bulldozers and trucks are used to reshape steep spoil piles into gradual slopes that are suitable for rehabilitation.
Generally, the maximum gradient of slope accepted by the Environmental Authority is one in ten (ten percent), although sometimes one in fifteen is accepted.
Image courtesy of Ensham Resources

20. A site levelled prior to rehabilitation, awaiting another truck and shovel dump of spoil.
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21. Image courtesy of Ensham Resources

22. Once the required gradient is obtained, bulldozers are used to smooth the surface. Working the material in this manner has the added advantage of making it finer on the surface and more conducive to plant growth.
Image courtesy of Ensham Resources

23. Prior to rehabilitation, the surface resembles a big, flat moonscape.
It takes some four or five years from commencement of mining to reach this stage. It’s not possible to rehabilitate right up to the mining point and a further delay results because the ground must be left to settle for twelve months. 1 10
A slope of 1 in 10
Image courtesy of Ensham Resources

24. Swelling of the rock means that it's not possible to return the land to its original contours. A gently sloping hill with a flat top is constructed behind the mine.
Image courtesy of Ensham Resources

25. Laying of topsoil
Topsoil stockpiled prior to commencement of mining is trucked to the rehabilitation site.
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26. Image courtesy of Ensham Resources

27. Image courtesy of Ensham Resources

28. Image courtesy of Ensham Resources

29. Topsoil is dumped, ready to be spread by bulldozers or graders.
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30. Image courtesy of Ensham Resources

31. Spreading of topsoil
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32. Image courtesy of Ensham Resources

33. Topsoil is generally spread to a depth of 200mm
Topsoil is generally spread to a depth of 200mm. At the Ensham mine, 300mm.
Image courtesy of Ensham Resources

34. The importance of topsoil (left) is most apparent adjacent to a site where topsoil is yet to be laid (right).
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35. Laying of manure
Manure is laid over the topsoil to further encourage plant growth..
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36. Manure is spread using a belt-driven bin behind a tractor
Manure is spread using a belt-driven bin behind a tractor. At the Ensham mine, 15 tonnes of manure is spread per hectare.
Image courtesy of Ensham Resources

37. Pegging the contours
Surveyors and environmental engineers peg lines of equal height to mark the contours on the rehabilitation site.
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38. Deep ripping along the contours
A bulldozer follows the pegs to deep rip along the contours to a depth of about one metre. This increases infiltration of water and provides a rough surface to reduce runoff and erosion. Once grass has established itself on this surface, the contours will completely eliminate any rainwater runoff.
Image courtesy of Ensham Resources

39. Image courtesy of Ensham Resources

40. Image courtesy of Ensham Resources

41. Controlling drainage
Drainage is further controlled by means of 20-30m wide horizontal benches between every 100m of sloped rehabilitation land. This reduces the likelihood of rainwater running off in torrents.
Small rock walls called ‘rills’ are constructed around the rehabilitation area to stop runoff from the mine washing away the topsoil or killing the grass.
Image courtesy of Ensham Resources

42. Different grasses and legumes are seeded on rehabilitation sites according to the final land use of the site. At the Ensham mine, grasses that are ideal for cow fodder, such as Buffel grass and Rhodes grass, are used commonly, in addition to six other species according to the soil type. While some mines use both native and introduced species, Ensham has found that the introduced species quickly take over, so native species are no longer seeded.
Image courtesy of Ensham Resources

43. Scattering of seed
Grass is seeded at the rate of 25kg of seed per hectare by a contract farmer. The seed is spread by a fertiliser spreader on the back of a farm tractor.
Summer grasses require a certain soil temperature to strike and grow, so in winter, 20kg per hectare of wheat seed is added to the mix. Wheat provides cover in the winter, ready for grasses to come through in summer.
The aim is to get as much ground cover as quickly as possible so as to reduce erosion.
Image courtesy of Ensham Resources

44. Spreading of fertiliser
Fertiliser is spread at the rate of 100kg per hectare.
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45. Wheat stubble (hay) is spread as mulch to give the land stability and water-holding capacity before the grass is established. 20 six-foot round bales of wheat hay are spread per hectare.
Spreading of mulch
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46. Image courtesy of Ensham Resources

47. Image courtesy of Ensham Resources

48. Early growth
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49. Grass is seeded within a week of the site having been ripped
Grass is seeded within a week of the site having been ripped. Assuming good rainfall there will be cover within a month.
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50. Mature grass, going to seed within six months of planting
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51. Planting of trees
The question of whether to plant trees on a rehabilitation site can be complex.
Some mines are required to return a certain number of acacia and eucalypt stems per square metre. At Ensham, where the land will ultimately be restored as grazing land, trees are not always desired by farmers.
Trees can only be planted on this site after the grass is established. Otherwise, trees can get out-competed by the grass from the outset or trees can hold up the growth of the grass and result in erosion. The most effective way to stabilise the slopes against erosion is with grasses.
Image courtesy of Ensham Resources

52. Seeding trees is not as successful as growing trees from established saplings. Irrigation through dripper lines increases the success rate in the hot climate at the Ensham site, but this is challenging to establish over such vast areas.
Trees may become more common on rehabilitation sites if there is value attached to them in a carbon trading scheme in the future.
Image courtesy of Ensham Resources

53. Benchmark sites Oresomeresources.com
Benchmark sites of undisturbed land called "analogue" sites are used as references for rehabilitation sites.
Oresomeresources.com
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54. Environmental engineer
Jay is a graduate environmental engineer who began working at the Ensham mine in It is part of his role to oversee the rehabilitation process.
“In the long-term we want the site to be self-sustaining and maintenance-free. We assess it every year for erosion rates, damage and water quality.”
Image courtesy of Ensham Resources

55. Restored land
Every mine site has different conditions and requirements for rehabilitation. At the end of the life of the Ensham mine, the site will likely be returned to grazing land.
Some other mines have a rehabilitation requirement defined as "native self sustaining ecosystem," so any native species able to grow on that site are encouraged.
The government provides a financial incentive to rehabilitate because the bond that mining companies are charged for their use of the land applies only to disturbed land. Every hectare of rehabilitation reduces this bond.
At Ensham, between 150 and 200 hectares of land are rehabilitated every year. The company set a Queensland record in 2009 with a total of 280 hectares rehabilitated.
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56. Rehabilitation costs Oresomeresources.com
Rehabilitation is a costly exercise:
$12000 /ha - Bulk earthworks to spread the spoil and establish the slope
$ /ha - Topsoil - hauling in a truck & spreading with a scraper or dozer
$ /ha - Drainage works - drains, bunds, banks, diverting runoff
$ /ha - Manure - purchase, freight and 10t/ha
$ /ha - Fertiliser - purchase, freight and 100kg/ha
$ /ha - Deep ripping - to 1m depth, on the contour, on 2m centres
$ /ha - Seed - purchase, freight and 25kg/ha
$ /ha - Hay - purchase, freight and 20 round bales/ha
$25 000/ha - Total cost
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Image courtesy of Ensham Resources