PNG’s topography and seismicity complicate the storing of waste from mine operations. But SRK Consulting’s Ian de Bruyn and Claude Prinsloo believe a new facility planned for Frieda River will be an industry-leading model for tailings management – and renewable power generation.
PNG poses a unique set of challenges when creating tailings storage facilities, according to Ian de Bruyn and Claude Prinsloo, principal geotechnical engineers with extensive experience in PNG at SRK Consulting.
One is the topography because PNG has “relatively young deposits, geologically speaking, that are deeply weathered by the severe tropical environment,” De Bruyn tells Business Advantage PNG. That means potential for landslips.
“You have to be cognisant of creating the design you need whilst limiting the impact on the steep hillsides, because the more you need to excavate into the hillside, the more you create man-made slopes that present greater risk and potentially require onerous management and monitoring,” he says.
Meanwhile, the frequency and magnitude of earthquakes in PNG, as well as the high rainfall, add further layers of complexity, says De Bruyn.
PNG solutions
These characteristics have led almost all PNG’s mine operators to opt for unique tailings storage solutions.
Only 18 of the approximately 2,500 industrial-sized mines operating around the world in 2014 deployed riverine or marine – rather than land-based – tailings disposal, according to a study by American environmental consultant, Craig Vogt.
Of the four mines using riverine disposal, three (Ok Tedi, Porgera and Tolukuma) are in PNG, and the fourth is Grasberg in Indonesia’s Central Papua. Of the 14 mines using deep-sea tailings disposal, three (Lihir, Ramu and Simberi) are in PNG – made possible by the fact that PNG is one of the few places in the world with waters at 1,000 metres depth or greater within 2km of the coast.
Industry-leading model
PanAust’s Frieda River project is planning for land-based tailings storage, but this will be integrated with a more-conventional hydroelectric dam that, Prinsloo says, will be an industry-leading model for mine tailings management and renewable power generation.
SRK produced a 2018 study which devised a design ideal for the project’s unique setting in the northern foothills of PNG’s Highlands.
Its US$3.2 billion design solution features a 190.5 metre-high main embankment, one diversion dam, two cofferdams, two diversion tunnels, a hydropower intake and conveyance system linked to a turbine facility, and a side-hill spillway.
De Bruyn says the design uses the area’s heavy rainfall (averaging around 8 metres per year) and topography to its advantage.
“There is the ideal opportunity – especially with such a high embankment – for it to be a hydroelectric power generation facility,” he says.
“The sheer volume of water that comes into the system is beneficial, because it’s going to keep your dam topped up, keeping the tailings and mine waste rock submerged below water. But you’ve got to manage the storm events coming through. With hydropower, most of the water has a benefit to you because you’re releasing and at the same time generating power for renewable energy.”
Prinsloo adds that the 490 MW in generation capacity helps address the project’s distance from existing grid infrastructure while generating an excess that could potentially be shared with other users.
“It’s a big mine, producing a large volume of tailings and mine waste rock, which needs a lot of power, and this facility solves that problem,” he says.
This article was first published by Business Advantage PNG. It is reproduced here by permission.
