Manapouri – The Toughest Tunnel

A techno-tale of courage, tragedy, brilliance and the hard, hard work of massive machines and determined people on one of the world’s toughest construction projects.

Produced by NHNZ

New Zealand’s Doubtful Sound is a stunning area of tranquil lakes, plunging fiords and dense rainforests but is also one of the most treacherous and remote places on Earth.

Not only is it one of the wettest places on the planet, with more than 200 inches of rainfall a year, it also lies on the intersection of several active earthquake faults. With extremely hard rock streaked with unstable, crumbling fault lines, this wild place is a tough area to build anything, much less a massive tunnel as part of a hydroelectric power station.

In the 1960s a team of more than a thousand men undertook New Zealand’s biggest ever construction project to build a hydroelectric power station to take advantage of the massive water supply in the region.

The men battled seemingly insurmountable odds in this almost inaccessible, unforgiving area and used the dangerous technique of drilling and blasting ⎯ costing the lives of 16 workers.

After eight years of these dangerous conditions, which tested the resolve and ability of the team, the Manapouri Power Station churned into action. But very quickly it was discovered the plant was not as efficient as originally planned; instead of 700 megawatts, it could only produce 580 megawatts.

Thirty years later, a team of brave men is again attempting to overcome the challenges posed by the extreme remoteness, the masses of hard rock, the endless rain and the five faults to build another tunnel parallel to the existing one.

The idea is for the second tunnel to reduce hydraulic resistance because the same amount of water will be shared between two tunnels instead of just one. Unlike the hazardous method of drilling and blasting used in the 1960s, this ten-kilometre tunnel will be formed using cutting-edge technology designed in the US and shipped in from Europe.

The excavation of the additional tunnel is set to be one of the toughest civil engineering projects in the world, as the massive tunnel boring machine has never before gone head to head with such hard rock as it’s about to face.

But how will the determination of the men and the cutting-edge technology stand up to the challenges posed by the dangerous geology, inhospitable weather, isolation and unforgiving environment? Will this be another story of triumph against overwhelming odds or will the project claim more lives?

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