Invisible power lines

Running underneath Malta’s roads and built-up areas is a maze of tunnels very few people know about.

The tunnels, numbering nine but with another two in the pipeline, lie 30 metres underground and together cover a total of 31 kilometres.

They were dug up by Enemalta Corporation to eliminate the need of unsightly overhead wires and trenching works in the already busy Maltese roads. Most measure about 3.4 metres high and 3.4 or 5 metres wide.

The tunnels are also ideal for locating and repairing any faults that develop from time to time.

Standing in one of the tunnels being dug underneath San Ġwann and Swieqi, an Enemalta spokesman explained that the tunnels provide a safe environment for the installation of an essential part of Malta’s energy infrastructure.

Enemalta has been excavating tunnels for the past 20 years. Right now it is busy preparing the groundwork, literally, for the electric connection from Sicily to Malta with the excavation of two massive tunnels between Magħtab and Kappara.

€2,000

The cost of digging one metre of tunnel

The excavation of the first tunnel between Kappara and Pembroke started last year and is expected to have been completed by the first three months next year.

Concurrently, work will start on a four-kilometre tunnel between Pembroke and the Magħtab terminal station, which will be the connecting point for the interconnector linking Malta’s high voltage network to Ragusa in Sicily.

Architect Mario Scicluna, head of Enemalta’s civil engineering department, said the tunnel between Kappara and Pembroke was just over three kilometres long. With a width of five metres and a height of three, it lies at a depth of 30 metres.

The excavation is being conducted by an Italian firm, which teamed up with a Maltese company for the project.

At a raw cost of €2,000 per metre, excluding the cost of cables and concrete reinforcements put in place when engineers come across certain patches of rock, the excavation of underground tunnel is expensive.

However, when one considers the long-term savings in terms of trenching whenever a fault occurs, underground tunnels are considered as the most efficient and cost-effective option.

Mr Scicluna said excavation was being carried out by a machine brought to Malta by the Italian contractor which is powered by electricity, to eliminate diesel fumes in the tunnel. The generator which provides the power, and which is placed outside the mouth of the tunnel, consumes €300 to €400 of diesel every day. Excavation takes place between 6 a.m. and 10 p.m.

Cutting through the Maltese limestone (franka) is relatively easy but problems arise when workmen encounter other types of rock, which are usually much more difficult to cut through.

Wherever possible, tunnelling is usually carried out along the shortest route between two points, thereby minimising the length of cables. Cable jointing can also be carried out in a more comfortable environment in jointing bay chambers that are widened areas along the route inside.

The corporation spokesman said the investments in the extension to the Delimara power station and the Malta-Sicily interconnector “highlight the corporation’s commitment to the continuous production, distribution and supply of energy”.

Enemalta’s tunnels