Mine Rehabilitation and Closure Part 2 - Where has all the topsoil gone?

Found in: News

In light of the recent release of updated guidance from the Department of Mines and Petroleum (DMP) on the preparation of Mine Closure Plans, Astron’s Rehabilitation Principal Scientist Katina De Sousa, provides some timely advice to clients on the importance of getting the basics of rehabilitation right.

Katina has worked in the mining sector as an Environmental Engineer since 2003 overseeing development of closure and rehabilitation management plans and implementation of rehabilitation.

In the first article of this series, the importance of site characterisation was covered. Following from this, steps two and three of the ten step rehabilitation process proposed by Toy and Daniels (1998) are discussed.

  1. Site characterisation
  2. Rehabilitation planning 
  3. Material management
  4. Topographic reconstruction
  5. Replacement of topsoil and soil reconstruction
  6. Surface manipulation
  7. Addition of soil amendments
  8. Revegetation
  9. Irrigation 
  10. Site monitoring and maintenance.

In the second step of the rehabilitation process, the information gathered through site characterisation is used for planning mine rehabilitation and closure. To ensure the successful closure of a site it is critical that:

  • all relevant people are involved in the planning and implementation of mine closure and progressive rehabilitation and 
  • it is integrated into the way a mine site does business.

Often the site environmental team are made responsible for all aspects of closure and rehabilitation. However, they often have little or no involvement in processes that can have a significant effect on the final outcomes of closure, such as short to medium term mine planning. In the current economic climate it is also important for those planning for mine closure to understand the costs and impacts of the proposed end state of a mine. Collaboration with the mining department in particular may identify alternative, more cost effective ways of achieving the desired outcome. Engagement of the mining department is also likely to result in a higher probability of waste rock being dumped in the correct location in order to manage the potential risk from hostile materials than if the environmental team is working alone.

Anyone that has worked on an old mine site where the topsoil was buried will tell you of the importance of materials management to rehabilitation and closure success. And as discussed in the first part of this series, appropriate management of materials identified as hostile as part of site characterisation is equally important.

Mine sites need to ensure that mining activities involve the identification, harvesting, segregation and management of the resources needed to successfully rehabilitate a disturbance area, principally topsoil, and vegetation material if it is available. Up to date topsoil reconciliations are required to ensure that adequate material is available on site for all rehabilitation required. Regular surveys of stockpiles need to be undertaken to ensure that rehabilitation materials are not slowly disappearing to be used for other purposes. Advances in remote sensing technology mean that survey and calculation of stockpile volumes can be undertaken quickly, accurately and at a low cost without adding significantly to the workload of surveyors on site.

Vegetation material as a resource for rehabilitation is something that has been undervalued in the past. If topsoil and vegetation material are well managed the cost of rehabilitation can be reduced by minimising the requirement for seeding, or removing it altogether if topsoil does not need to be stockpiled for long periods. Use of vegetation mulch also has other additional benefits to being a seed source. Adding wood mulch during rehabilitation can facilitate recovery of flora, soil nutrient cycling and water and nutrient holding as well as providing native plant propagules that would be otherwise commercially unavailable (Brown and Naeth 2014).

Stayed tuned for the next article, Part 3 – It’s Just like Icing a Cake, where the steps for preparing a landform for revegetation are discussed.

 

References

Brown, RL and Naeth, MA 2014, ‘Woody debris amendment enhances reclamation after oils sands mining in Alberta, Canada’, Restoration Ecology, vol.22(1), pp.40-48.

Toy, TJ and Daniels, WL 1998, ‘Reclamation of disturbed lands’, in RA Meyers (ed) Encyclopedia of Environmental Analysis and Remediation, Wiley, New York.

 

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