Thermal leak detection to avoid tailing dam disasters

July 13th, 2018, Published in Articles: PositionIT

Detecting tailing dam problems before they occur can prevent catastrophic events and avoid failure costs. Rocketmine’s thermal leak detection solution offers a way to do this.

There are an estimated 3500 active tailings dams around the world, and as of 2000 there were two to five known “major” failures (about 0,1%) annually and 35 “minor” failures (1%) [1]. Investigations of these failures revealed that seepage played a significant role in the ultimate failure of the dams. At times it was as a direct result of seepage, while at other times seepage was a precursor to seismic and other failures.

On February 1994, there was a major tailings dam failure in Virginia in the Free State, South Africa. The tailings failure killed 17 people, destroyed 80 houses and caused a large amount of environmental destruction. As a result, the 1995 Draft Code of Practice for the Design, Operation, and Closure of Tailings Dams was introduced. This prompted the publication of the Code of Practice for Mine Residue Deposits by the South African Bureau of Standards in 1998 (SABS 0286:1998), later renamed the SANS 10286.

This standard does not address the environmental impact of tailing dam failures but rather outlines objectives, principles and minimum requirements for best practice. The key principles on which the SABS standard is based include continual management, the minimisation of waste and the impacts of waste, precautionary principle, internalisation of costs and assessment of the full life cycle implications. The Guideline for the Compilation of a Mandatory Code of Practice on Mine Residue Deposits issued by the Department of Minerals and Energy in 2000 regulates the monitoring of tailings dams in South Africa. This guideline makes implementation of a code of practice mandatory for each tailings dam, with compulsory adherence to SANS 10286.

Fig. 1. Thermal indicator of seepage.

Fig. 1. Thermal indicator of seepage.

Current tailings dam inspections are carried out on foot. These inspections are labour intensive, involve a moisture meter, trial pits and geotechnical equipment to physically measure saturation levels in the soil. Due to the expense of having an engineering team on site for weeks at a time to cover large perimeters, many mines are not following the requirements. Those that do often only conduct spot checks.

Furthermore, areas with dense vegetation can conceal potential areas of concern and seepage, making them easy to miss during manual inspections. Some mines are now using helicopters to carry out the inspections, which can also be very costly.

Rocketmine, a licensed drone service provider, recently launched its Thermal Leak Detection Solution to alleviate current tailings dam inspection headaches by reducing the turnaround time from three weeks to five days with the use of drone technology and highly-specialised thermal sensors.

This solution indicates temperature differences within the tailings dam wall and toes to identify wet areas where seepage may not be visible to the naked eye. After conducting inspection flights, Rocketmine works with a team of engineers to accurately analyse the thermal imagery and provide certified reports which can be used as evidence when replying to the Department of Water Affairs and Forestry in terms of the National Water Act (Act 36 of 1998), with specific reference to the Regulations on use of Water for Mining Activities. The analysed data allows investigation of the areas of concern, and can further be used to provide a trend analysis going forward.

Using Rocketmine’s Thermal Leak Detection Solution, clients will be able to detect tailing dam problems before they occur, prevent catastrophic events and avoid failure costs.

References

[1] TE Martin and MP Davies, 2000, AGRA Earth and Environmental Limited, Burnaby, B.C. Canada.

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