FIRST, there was a rumble like thunder, then a roar similar to a train approaching, and finally, the sight and sound of a mountain being carved open, as the nose of a giant tunnelling machine breached the last few metres of rock.
Workers gather after 'Eliza Jane' completes her task
At 11:16am yesterday, to the cheers and applause of hundreds of workers, Eliza Jane finally saw daylight for the first time in 16 months, her giant head spinning as she demolished the solid wall, churning it into rubble.
Through the cloud of dust, the sharp end of the 200 metre-long tunnel- boring machine (TBM), which was given its name by local schoolchildren, emerged on to a bleak plateau, where one of the biggest civil engineering projects in Scotland is taking shape.
It was a significant milestone in the £140 million project to build a major hydro power station at Glendoe, near Fort William, on the shores of Loch Ness, the first development of its kind for 50 years and perhaps the last on this scale in Scotland.
The construction work began in February 2006, 2,000ft above the loch in the Monadhliath mountains.
The scheme, being developed by Scottish and Southern Energy (SSE), involves a dam, 35 metres high and 905 metres long, being built at the head of Glen Tarff and a power station constructed in a cavern 250 metres below ground level, inside Borlum Hill.
It will be fed from a reservoir more than a mile long and capable of holding eight million cubic metres of rainwater, collected from 60 square miles of surrounding hillside.
A 5.3-mile tunnel will collect water and take it to the reservoir, while five miles of tunnels will channel the water from the reservoir to the power station. That is where Eliza Jane, which went to work in September 2006, came in. It has been chewing into the hillside, cutting through about 1.8 metres of rock every hour.
Just before Christmas, there were only 2.3 metres to go and yesterday, the breakthrough was made by the two 14-strong crews employed by the German contractor Hochtief.
Christian Zimmerman, the TBM manager, said: "The moment we pushed through was amazing. It's been 15 months of work in quite a dangerous job and not a nice environment. So to complete a little piece of Scottish history was a great feeling."
Angus Speirs, resident engineer at the tunnel site, said: "This is a major milestone and its exciting for us to see the machine completing its work, but it's by no means the finishing line."
Work will continue to complete the dam, create the reservoir and build the power station. It is hoped it will be operational from the end of next year and, at a capacity of 100 megawatts, there will be enough for a city the size of Glasgow at peak output.
However, for a scheme dubbed the "power of Scotland", the question is, when will we see your likes again?
The arrival of hydropower was a milestone in the development of the Highlands. The North of Scotland Hydro Electric Board was created in 1943 by Tom Johnston, then Secretary of State for Scotland, who saw hydro power as a trigger for economic regeneration. Work was created for 11,000 people, with 56 power stations built, the bulk of them between 1948 and 1963, and the last in Loch Awe.
Today, SSE controls 70 power stations generating 1,000 MW, enough for 2.5 million homes.
But the political and environmental landscape has changed. As one senior SSE official said of new hydro stations: "We have proved we can build them, but it needs the political will. The government has to find a balance between renewable generation and the environmental disbenefits."
Peter Donaldson, renewable generation manager at SSE, said his predecessors had carried out all the good schemes. He said: "What's left is more difficult to develop and therefore more expensive, so can you justify the investment?
"The hills in Scotland are not that high, and once you are away from the west coast, it's not that wet. You have to look for schemes where you can get enough water to make useful amounts of energy."
He said Glendoe could have been developed previously but would have taken longer and cost more. "They did not have a tunnel boring machine so would have had to drill and blast the whole thing, so it wouldn't have been viable," he said.
"At Glendoe we had to come up with a scheme that was relatively environmentally benign. Good schemes in which you can invest so much money and produce a useful amount of energy from are few and far between. There are not really the sites available and if there are, you could run into environmental and cost difficulties."
But Brian Wilson, a former energy minister, believes it can be done and he is calling for a review of Scotland's hydro resources to identify locations that could be developed.
"It's very encouraging that Glendoe has happened with so little opposition, and there are other locations, large and small, which would be used. It's a fantastic resource," he said.
He said environmental opposition has helped to stifle hydro development and added: "
If the same criteria had been applied 40 or 50 years ago, very few of the schemes which grace the Highlands today would exist."
DIGGING OUT THE NUMBERS £140 million
Cost of Glendoe project
£7 million
Cost of the tunnel-boring machine.
600 metres
The height the machine has climbed into the hills.
23 metres
The average distance the machine travels in a day.
10 hours
The length of time tunnellers spend each day working underground.
16km
Total amount of tunnel used in the Glendoe scheme.
250 metres
The distance below ground where the power station will be built.
608 metres
Drop from the reservoir to the hidden power station.
60sq miles
Area of hills from where water will be collected for the scheme using a network of underground pipes.
25 years
Time during which locals will benefit from a fund set up by SSE to support the area.
250
Number which can be accommodated in a workers' village created in the remote hills for resident staff.
905 metres
Length of dam built for the scheme.
50 tonnes
Amount of rock excavated every metre.
400,000 tonnes
Amount of rock to be taken out of the hillside during the operation.
