|New Zealand’s remote Doubtful Sound, in the south-west of the South Island, is a stunning area of tranquil lakes, plunging fjords and dense rainforests fed by 200 inches of rain a year.
In the 1960s a team of more than a thousand men undertook New Zealand’s biggest ever construction project – building a hydroelectric power station to take advantage of the massive water supply in the region.
The men drilled and blasted a six-mile tunnel and cathedral-sized power hall in extreme conditions – with the cost of the lives of sixteen workers. Almost as difficult was the twelve miles of road building needed to link the top of the tunnel with its outlet at sea level.
Thirty years later it was decided that a second tunnel was needed. This time, the main work was to be done by a state-of-the-art tunnel boring machine. But the geology challenged even this equipment. In most places the rock was so hard that cutters had to be replaced every six feet. To make matters worse, there were five earthquake fault bands where the hazards of crumbling rock and constantly falling water brought the machine to a halt and destroyed morale.
In order to link the tunnels more drill-and-blast work was needed and bulkheads were assembled under water. Tension reached fever pitch as the boring machine approached the hand-built tunnel. Would the two join up?
This absorbing programme from Natural History New Zealand covers both stages of tunnelling, with archive footage from the 1960s and new filming from the 1990s. It shows the skills of tunnel engineering and project management at their highest levels. approx. 50 mins.