Progressive closure to achieve sustainable post mining land use
Progressive mine closure describes the activities conducted during the operating life of a mine. It requires the integration of key elements from ICMM's 'Integrated Mine Closure: Good Practice Guide' to identify and realise opportunities for final post closure land use and to reduce environmental, socio-economic and financial liabilities.
Even though Glencore’s Rolleston Open Cut Mine has a significant operational life ahead, it has been designed and operated with closure in mind, highlighting the numerous benefits of progressive closure in reducing closure risks and establishing a sustainable post mine closure land use.
“Pre-mining, this was a grazing landscape and that’s exactly what we’re aiming for post-mining” Ken Dixon, Environment & Community Manager
Rolleston Open Cut coal Mine is located in the southern part of Queensland’s Bowen Basin, approximately 16 km west of the Rolleston township and 140 km southeast of Emerald. Mining at Rolleston commenced in 2010 and is expected to continue until 2045. The mine employs more than 600 people and can produce up to 17 million tonnes of thermal coal per year.
Rolleston mine is surrounded by agricultural land, mainly used for beef cattle grazing and dryland cropping. The Albinia National Park is also located around 2 km from the mine. To mitigate the potential environmental impacts and ensure a positive closure legacy, the mine was designed to minimise the overall disturbed area by reducing the final number of voids (open pits) and undertaking progressive closure of land no longer required for mining purposes. In addition to this, Rolleston has an ecosystem restoration project, which commits to the reinstatement of endangered grassland communities found in the Albinia National Park as part of the mine’s overall rehabilitation strategy.
The closure vision for the site is to return disturbed areas to the pre mining land use of livestock grazing in keeping with the land use of the surrounding area. This was established and agreed with external stakeholders as part of the original mine Environmental Impact Assessment during the permitting of the mine. To do this successfully requires careful management of topsoil resources and successful planting and establishment of native tree and pasture grass species. Ongoing stakeholder engagement conducted during operation of the mine focus on the rehabilitation progress in returning the area to land suitable for grazing upon closure.
The soil has been comprehensively mapped through chemical and physical analysis and a site guideline has been developed to provide information to the mine site team on how to strip, move and use the soil in rehabilitation areas. Direct transfer of stripped topsoil to areas of rehabilitation is undertaken wherever possible. This integration of closure with operational activities results in the lowest cost for the operation and the best rehabilitation outcome as it helps to preserve soil seed banks and soil microbes to maintain soil fertility. It also means the operational mining team are involved in closure activities such as topsoil stripping and spreading. This results in the entire workforce being focused on not just coal production but on successfully returning the mined land to productive pasture. Rolleston’s integrated planning and progressive execution of works continues to deliver some of the lowest cost rehabilitation work within the Bowen Basin, without any compromise on quality.
This approach has allowed Rolleston mine to successfully rehabilitate almost 800 ha of mined land to grazing pasture during operations. Of the 800 ha, 386 ha has received certification from the authorities confirming that the relevant environmental conditions have been met and rehabilitation has been carried out satisfactorily prior to surrender/relinquishment.
Although the mine has only been operating since 2010, the latest certification, received in 2019, means that almost 40% of the total amount of mined land that has been rehabilitated at the site has already been signed off by Government. This commitment to progressive closure not only reduces the amount of financial liability for the mine operator, but also provides an opportunity to demonstrate the effectiveness of closure activities to interested parties such as local communities or landowners / users. This approach to progressive closure helps builds trust between the mine operator and their stakeholders that the closure vision is realistic and that sustainable post mine closure land uses can be achieved.