Chris GimberKBR
Chris Gimber is a Principal Environmental Engineer with KBR, providing specialist expertise in the areas of mine water management, hydrogeochemistry, catchment management and soils. He has provided expert advice within the international arena on these topics. He has almost 20 years consulting experience in the environmental sector, with experience in a number of geographies including Australia, Thailand, Indonesia, PNG, India, Brazil and New Zealand.
Brad O'ReillyWest Moreton Operations
New Hope Group 
Brad O’Reilly is an Environmental Engineer with New Hope Group, responsible for environmental management and rehabilitation at a number of operational and legacy mine sites which make up the New Hope Group’s West Moreton Operations in South-East Queensland. Brad has over 12 years of experience working in environmental roles in the planning and development, construction and operation of projects within the mining, oil and gas, and civil construction sectors.
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Abstract
Backfill or not?? Water management considerations during rehabilitation.
A key consideration for many open cut mining operations is how to manage mine voids at closure. One of the main decisions to be made during decommissioning and rehabilitation is whether or not to backfill mine voids.
Often the economics of backfilling result in this method of site management being deemed unfavourable and it is quickly ruled out, although there is increasing pressure on the mining community as part of its social and environmental responsibilities to properly consider and schedule mining to enable backfilling to occur. This paper discusses the practical water management considerations that arise during the process of backfilling mine voids, and draws on experience from a number of operations that have undertaken backfilling.
Most operating open cut mines have the ability to store large volumes of stormwater runoff in mine voids, and subsequently undertake release from these voids in a controlled manner when water quality is acceptable for discharge. As mine voids are progressively backfilled the capacity to store water diminishes and operators must transition into a new stormwater release regime that involves minimal or no storage and in-line stormwater treatment. Careful planning and management strategies are required to schedule bulk earthworks required for backfilling with landform rehabilitation for source control. Changes to licencing and sediment controls will also be necessary.
In this paper a case study is presented from a mine that backfilled its mine void to minimise its environmental liabilities and ensure it met corporate responsibilities. The catchment draining to the mine void prior to rehabilitation was considerable, so when backfilling occurred a very large sediment basin would have been required if the traditional sediment settling approach was used. Instead, a much smaller basin was installed with an in-line flocculation dosing system (High Efficient Sediment basin), enabling a storage volume of roughly 25% of that required for a traditional sediment basin. The flocculation system will be removed when the catchment is fully revegetated and the sediment loads have stabilised.
Water management difficulties that arise during backfilling are manageable provided they are anticipated and planned for.
Backfill or not?? Water management considerations during rehabilitation.
A key consideration for many open cut mining operations is how to manage mine voids at closure. One of the main decisions to be made during decommissioning and rehabilitation is whether or not to backfill mine voids.
Often the economics of backfilling result in this method of site management being deemed unfavourable and it is quickly ruled out, although there is increasing pressure on the mining community as part of its social and environmental responsibilities to properly consider and schedule mining to enable backfilling to occur. This paper discusses the practical water management considerations that arise during the process of backfilling mine voids, and draws on experience from a number of operations that have undertaken backfilling.
Most operating open cut mines have the ability to store large volumes of stormwater runoff in mine voids, and subsequently undertake release from these voids in a controlled manner when water quality is acceptable for discharge. As mine voids are progressively backfilled the capacity to store water diminishes and operators must transition into a new stormwater release regime that involves minimal or no storage and in-line stormwater treatment. Careful planning and management strategies are required to schedule bulk earthworks required for backfilling with landform rehabilitation for source control. Changes to licencing and sediment controls will also be necessary.
In this paper a case study is presented from a mine that backfilled its mine void to minimise its environmental liabilities and ensure it met corporate responsibilities. The catchment draining to the mine void prior to rehabilitation was considerable, so when backfilling occurred a very large sediment basin would have been required if the traditional sediment settling approach was used. Instead, a much smaller basin was installed with an in-line flocculation dosing system (High Efficient Sediment basin), enabling a storage volume of roughly 25% of that required for a traditional sediment basin. The flocculation system will be removed when the catchment is fully revegetated and the sediment loads have stabilised.
Water management difficulties that arise during backfilling are manageable provided they are anticipated and planned for.
Presentation
Backfill or not?? Water management considerations during rehabilitation.
Presented on 31st March 2017 at the 7th Annual Best Practice Ecological Rehabilitation of Mined Lands Conference (2017)
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