"There is a huge potential for small hydro energy schemes across Scotland as part of a wider process of decentralisation of energy production. Locally produced hydro power for local needs will prove to be a valuable resource" - FRIENDS OF THE EARTH, SCOTLAND

BENEATH the ground, 800 metres into the hillside Eliza Jane is hard at work, eating her way though solid rock. Progress is slow but steady - about 1.8 metres every 45 minutes - and she will not see daylight for another 18 months.

Above, diggers rip a deep scar into the soft peat, preparing the foundations for a dam which will eventually stretch one kilometre in length.

This is the sharp end of one of the biggest civil engineering projects currently under way in Scotland. It is half a century since anything like it was undertaken and it is unlikely anything similar will be seen in future.

The project to build a hydro power station at Glendoe, near Fort Augustus on the shores of Loch Ness, is costing £140 million and is still two years away from completion.

The early signs of progress which The Scotsman was given exclusive access to yesterday, are already evident, although the completed scheme will be almost invisible by the time it is generating electricity in 2008.

Construction work began in February last year when Tony Blair detonated a controlled explosion at Glendoe, 1,800ft above the loch in the Monadhliath mountains.

The hydro-electric scheme, which is being developed by Scottish and Southern Energy (SSE) will involve the construction of a 35-metre-high dam at the head of Glen Tarff and a power station in a cavern 250 metres below ground level inside Borlum Hill.

Inside the cavern will be the turbine turned by the force of the water flowing through it, and the generator which converts that force into electricity.

The turbine will be able to generate enough energy to power a city the size of Glasgow, and will be the most efficient hydro plant in the UK.

In all 16 km of tunnels are being built. An 8.6km tunnel will collect water and bring it to the reservoir, while 8 km of tunnels will channel water from the reservoir to the underground power station then out into Loch Ness.

This the work of the huge tunnel boring machine (TBM), costing £7 million and nicknamed Eliza Jane by local schoolchildren.

Since the 200-metre long machine started boring its way into the rock at the end of September it has completed over 800 metres of tunnel. Advancing along on its tracks, the underground monster cuts through an average of 23 metres of rock a day, although yesterday it progressed 55 metres, its biggest advance to date.

As the rock is churned up, a conveyor belt scoops up the rubble and transports it out where it is used to construct access roads.

It is dirty and noisy work with the men sloshing through grey water on the tunnel floor as they push further and further into the hillside, earmuffs shielding them from the noise of the cutting equipment, the machine shaking like a long bus on a bumpy road.

Progress is monitored via a computer control room with CCTV monitors, while a refuge unit provides the 15-strong crew with a safe haven for 24 hours in the event of a fire, gas build-up or other disaster.

Inside the tunnel the walls are surprisingly smooth, the cut rock having been covered with a concrete spray to stabilise it.

Following tradition the tunnels will all be given women's names. A figure of Santa Barbara, the patron saint of tunnelling, will be inserted into the rock and a blessing will take place on 4 December, Santa Barbara Day.

While other green energy schemes have provoked criticism, the Glendoe project - which will create the equivalent power to 50 wind turbines - attracted just seven objections.

A SSE spokeswoman said: "People seem to have an affection for the scheme now. People in Fort Augustus are even organising Christmas hampers for the workers and their families."

The multi-national workforce on site have their own accommodation, canteen and leisure facilities, with enough supplies to ensure the workers can survive a Scottish winter.

INVISIBLE GIANT OF THE MOUNTAINS

MORE than 300 people are working on the site during the construction phase and this could rise to 500 at its peak.

Rainwater from 60 square kilometres will be gathered to produce power.

The average annual rainfall in the hills around Glendoe is about 1500mm - compared to under 700mm in Edinburgh.

Despite being one of the biggest hydro stations, once complete it will be almost invisible.

The turbine house will be underground and the reservoir and dam cannot be seen from any home or public road.

The reservoir will be formed by the building of a 905 metres dam which will be 35 metres high.

Glendoe will be served by 16 km of tunnels - one 8.6km long and 4.5 metres in diameter - will collect water and take it to the reservoir. Another 8km of tunnels, five metres in diameter, will channel water from the reservoir to the power station.

The underground power station will be 38 metres long, 18 metres wide and 32 metres high and be built in a cavern 250 metres underground.

The first 430 metres at the start of the tunnel leading to Loch Ness had to be excavated by drill and blast to allow enough room for the giant boring machine to be assembled in situ.

Fifty tonnes of rock are excavated every metre the boring machine advances. Eventually around 400,000 tonnes of rock will be taken out of the hillside.

Countless opportunities for small-scale projects

A LARGE-SCALE hydro electric project of the scale of Glendoe is unlikely to be repeated in Scotland, but the country has huge capacity for smaller schemes that could help the Executive to meet its targets for renewables.

At present Scotland has 79 hydro projects, providing 1,300MW of conventional capacity, mostly in the Highlands and much of it built in the 1950s. A further ten schemes have consent and another 19 are planned, and it is felt there are still countless opportunities in Scotland for small-scale hydro developments.

It was claimed in a paper published in 1979 that there is additional large-scale hydro potential of 780MW installed capacity.

The government's Renewable Obligations Scheme has put an onus on all electricity suppliers to provide some of their energy from green sources as it strives to achieve its 40 per cent renewable energy target for electricity by 2020.

A British government report found that Scotland has almost 90 per cent of the UK's potential for small hydro power.

Duncan McLaren, the chief executive of Friends of the Earth Scotland said: "There is a huge potential for small hydro energy schemes across Scotland as part of a wider process of decentralisation of energy production. Locally produced hydro power for local needs will prove to be a valuable resource.

"Although there is significant potential left, it will not come in the form of large-scale schemes, which have been found to be quite damaging to wildlife and the ecological interests of waterways. On a global scale, the life of large projects has been shown to be shorter than expected as many old projects are starting to silt up."

Cost, the lack of suitable locations and possible opposition means Glendoe may be the last of the projects of this size.

Neil Sandilands, project officer for Glendoe, said: "It is a combination of things, partly the environmental and landowner opposition to large-scale hydro plants. In engineering terms we could meet the challenges. The number of objections we received for this project was very low for a construction of this scale and doesn't suggest that there is a fundamental objection to schemes of this type.

"The issue tends to be more with government agencies than the public."

Last month, Ross Finnie, the rural development minister, said the surge towards building wind farms may be coming to an end and that the emphasis should now be on other forms of renewable energy, such as tidal, wave and biomass.

Mr Finnie said the executive is keen to ensure a proper mix of renewable energy sources. Currently there is only a single marine energy testing station, in Orkney, with no tidal or wave schemes making energy.

The arrival of hydro power was a major milestone in the development of the Highlands.

The North of Scotland Hydro Electric Board (NSHEB) was created in 1943 by Tom Johnston, then secretary of state for Scotland, who had seen how the Tennessee Valley Authority had used hydro power to trigger economic regeneration.

After the war there was little employment in the area, but the NSHEB created work for 11,000 people. However, one of the great difficulties was finding that number of workers in the area and thousands were brought in from outside.

In all, 56 power stations were built, the bulk between 1948 and 1963. Investment in the industry amounted to some £180 million during the ' 50s and '60s alone.

MONKS WHO LED THE WAY

IN 1890, when Queen Victoria was still using paraffin lamps in Balmoral Castle, some villagers in Fort Augustus had the unlikely luxury of electric light because of a small water turbine installed by the monks at the nearby Benedictine Abbey.

This is believed to be Scotland's first electrical installation and began operating eight years after Edison opened his station at Holborn Viaduct in London in 1882.