Pragmatic selection of open cut coal mine rehabilitation goals

Last modified by Vanessa Glenn on 2016/05/10 16:24

Executive summaryMine rehabilitation goals that promise complete restoration of pre-mining conditions are often unattainable because the post-mining geology, landform, hydrology and soil properties are radically different from those of the undisturbed landscape. Selecting the highest standard rehabilitation goals compatible with the actual post-mining landscape will facilitate successful mine closure.
Current situationThe extinguishment of open cut mine leases through attainment of landscape rehabilitation conditions is rare in Australia. Part of the problem is the acceptance by some mine operators of closure goals that are incompatible with the physical and biological potentials of the reconstructed landscapes. If complete restoration of pre-existing landforms, soils and ecosystems is not practicable, a method must be found by which realistic closure goals can be identified.
Objectives
  • To identify practical design and operational criteria for landscape reconstruction.
  • To optimise soil placement for the desired final land use (e.g. pasture or cropping).
  • To identify land surface treatments which optimise the establishment of biodiverse ecosystems containing native plant and animal species.
  • To identify realistic criteria for the assessment of ecosystem condition
Method/Techniques

Negotiation of stakeholder support for overall post-mine land use goals.

Allocation of end land uses according to quantities and qualities of materials available to support these land uses.

Detailed description of lithology and geometry of reconstructed landforms (e.g. slope design appropriate for both material and intended land use).

Selection and application of land surface treatments (e.g. topsoil application or soil amelioration) to optimise intended land use.

Selection of plant species to be established and methods of establishment.

Selection and implementation of appropriate vegetation management regimes (e.g. weed management, pasture or crop management)

Implementation of ecosystem monitoring against agreed habitat, plant and animal criteria.

 

Results/Observations

The dearth of successfully extinguished mine leases (e.g. Alcoa bauxite, WA) means that this is a work in progress. However, there are examples of mine operation plans that are consistent with this model, including that for Ravensworth (coal, NSW).

Outcomes

What was learned?

Topsoil is a very precious resource in the Australia landscape and it cannot be wasted. Many of these topsoils are erodible and should not be spread thinly on moderate to steep slopes, but should be reserved for lower slopes where they can be applied at thicknesses that will support an economically viable post-mine land use.

Native vegetation can often not be established where topsoil containing pasture of weed species has been applied to a reconstructed land surface. It is often most effective to provide soil ameliorants to overburden and to establish native plant species directly.

Rehabilitation targets must be selected with great care and modesty. Too often, aspirational goals have been promised, only to be abandoned when the cost of their attainment became apparent.

 

What were the benefits delivered

More realistic estimates can be made of the true costs of rehabilitation (materials, time, skills), so they can be incorporated in mine planning and operational plans.

More realistic expectations for rehabilitation can be established and tested quantitatively.

A framework can be established to enhance stakeholder involvement (industry, government, community) in the attainment of rehabilitation goals and their preservation after mine closure.

Case Studies

Phosphate Hill (Qld) (Incitec Pivot Ltd), seven-year monitoring of vegetation condition in rehabilitated, self-colonised and undisturbed native vegetation sites led to redefinition of vegetation rehabilitation goals.

Ashton Coal Operations (NSW) experimental testing of overburden treatments for pasture and native vegetation establishment; three-year experimental study that demonstrated that different site preparation techniques should be used in order to re-establish pasture or to establish native vegetation on coal mine overburden.

 

References(s)Gillespie, M., Glenn, V., Doley, D. (2015). Reconciling waste rock rehabilitation goals and practice for a phosphate mine in a semi-arid environment. Ecological Engineering, 85, 1-12.


    
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