One of the leading causes of failure for mine rehabilitation is erosion – and it can be very difficult and expensive to repair. So how can you minimise the risk of erosion and avoid large repair costs in the future?
Remote sensing could be the answer as it can be used to identify at risk areas across all stages of the landform construction process, from operations to post-closure. Data from remote sensing surveys can be analysed to identify high risk areas for erosion and sections of a landform in non-compliance with approved designs. This information can be used to guide management decisions to reduce the cost of long-term maintenance and repairs.
In this article the benefits of undertaking remote sensing during the operations to primary rehabilitation earthworks stages of landform construction are summarised.
Identifying areas of potential high risk at this early stage gives you the opportunity to implement management actions at the minimum cost, potentially at no additional cost to ongoing operations. It also means you don’t have to wait for 10 years or more until you find out your rehabilitation is not going to receive sign off from the government. Aspects to measure at this stage that prevent a potential risk of erosion could include:
- Batter height
- Berm width
Undertaking a survey of your landform prior to undertaking rehabilitation earthworks can save you money in the long term. It also minimises the risk of wasting precious rehabilitation resources such as topsoil and vegetation mulch. A remote sensing survey conducted at this stage can identify areas:
- Out of compliance with the approved design
- At high risk of rehabilitation failure due to ponding or concentration of surface water.
Addressing high risk areas at this stage saves you the cost of rectifying future erosion and landform instability as well as the effort involved in conducting remedial rehabilitation works.
After Completion of Primary Earthworks
After completion of primary earthworks on a landform (pushing down batters, installing drains and crest bunds, shaping the top surface) a remote sensing survey can identify areas where:
- Water ponding is likely to occur
- Batter angles are too steep
- Berms are not wide enough
- Crest bunds are not high or wide enough
- Berms and ripping are not on the contour
- Drains are not located correctly.
All of these areas present a high risk of erosion in the future if they are not rectified. To enable effective mine rehabilitation, these problems are best identified and assessed prior to applying topsoil to the landform.
The images below show how remote sensing can be utilised to identify areas where the batter angle does not conform to the approved design.
Similarly, the images below identify areas where the berm width is too narrow. These areas are at risk of overtopping and excessive erosion.
Stay tuned for the next article in this series which goes through the benefits of remote sensing in the secondary earthworks to post rehabilitation stages of landform construction, or view Part 1 of this article here.