RE: Grasberg disruptions13 Oct 2025 13:21
This was posted by Element1 on a different board, is a really strong case made that Grasberg will never reopen, I agree with after following up on this.
Worth a repost to add to the discussion.
E1- This is absolutely huge, if true. Seriously. This mine produces so much copper and gold... and word from the 'well connected' is that it’s completely screwed and will probably never reopen.
What I’m really saying is that there is a not insignificant technical risk (and now political ones too) that the Grasberg mine may never restart. Not in years. I mean ever.
Two clues:
First, location. Grasberg sits in one of the wettest climates on the planet. The mine site and its access road get around 12 metres of rainfall each year, with rain on about 330 days annually. Papua often records monthly peaks above 2 metres. And remember — this mine is in the mountains. It’s absurd.
Now compare that with El Teniente in Chile, another block cave. There, the “normal” is about half a metre per year. Same mining method, completely different hydrological setting. And Chile is not tropical humid — infiltration and groundwater pressure risks are fundamentally lower.
Second, the mining method. Block caving is rare — in over a century of mining, only ~20–25 block caves have ever been mined, and fewer than 10 are active today. You undercut a giant orebody, let the rock collapse under its own weight, and draw the broken rock. It’s an engineered collapse of part of a mountain — every single day.
But when water infiltrates, that broken rock can turn into a dense slurry — wet muck — that suddenly rushes into tunnels. One of the most feared failure modes underground. That is precisely what happened here. Google the accident. It’s nightmare material.
And the sheep-like analysts? Everyone parrots “force majeure” and “back by 2027.” Why are they missing wet muck risk? Why is everyone so lazy?
At El Teniente, engineers led by Prof. Raúl Castro (University of Chile), Omar Salas, and the Codelco team built a predictive wet muck model. They used logistic regression — math plus mining — to estimate the probability of wet muck at each drawpoint. It worked: over 80% accuracy, operational heat maps, lives saved.
Obviously, you cannot just copy-paste their model into Grasberg without local geology and mine data. Surface rain ≠ tunnel inflow. The translation depends on faults, fractures, drainage, barriers, and time lags. The model has to blend rainfall, inflows, drawpoint conditions, and neighbour effects to capture where the real risk lies.
But here’s the rub: Grasberg’s Block Cave is one of the largest ever attempted — and it sits in a hyper-wet tropical mountain climate. Rain-to-inflow coupling here is the great unknown. Put 1+1 together… oops.
That’s the point: only 20-25 block caves have ever been mined over the past 100 years, and none in conditions remotely like Grasberg’s. Wet muck is a ris
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