A subsea tunnel connecting Gozo and Malta has to be dug some 14 storeys or more below the seabed, according to a Norwegian tunnel expert.
“Norwegian guidelines state that a subsea tunnel should have a minimum 50 metres of rock above it,” said Eivind Grøv, chief scientist and rock engineer from Sintef Building and Infrastructure.
In a phone interview with The Sunday Times, Prof. Grøv said the depth may be more than 50 metres from the bottom of the sea if the sea bed contained sediment.
The depth at which the tunnel would be excavated also determined the location of the tunnel exits, the incline and the length of the onshore approach roads.
Prof. Grøv will be addressing a public meeting in Gozo next week on the proposal to link the two islands with a subsea tunnel. He was invited by the Gozo Business Chamber in junction with the parliamentary secretariat for public dialogue.
Although putting a price tag on the tunnel was premature, Prof. Grøv said similar subsea tunnels in Norway cost around €13,000 per metre.
With a straight line distance between Malta and Gozo of five kilometres, this means the subsea section of the tunnel alone could cost around €65 million to build. Based on a subsea tunnel to be built in the Faroe Islands maintenance costs could be around €130 per metre per year, Prof. Grøv said.
He pointed out that the most important requirement for excavating a subsea tunnel was the presence of hard rock, but thorough geological studies had to be conducted to determine other factors.
“The sedimentary rock that exists in the area can generally be considered to be hard rock but we have to look at the strength of the rock, the cracking systems in place, whether joints exist and whether these can be filled in.”
The geological surveys that have to be done if the project ever gets the green light will also factor in the seismic activity around Malta.
Earthquakes may create issues of safety but Prof. Grøv insisted this concern should not be a major stumbling block.
“If an earthquake occurred and I had the opportunity of making a choice to stay in a surface building or underground, I would rather stay in a tunnel.
“Data from Iceland and Japan, two countries prone to seismic activity, tells us that it is safer to be underground than above it.”
He explained that a subsea tunnel has three major advantages over a bridge or a causeway: it will not be an obstruction to sea traffic; it is an all-weather permanent link and incurs lower maintenance costs.
Speaking from experience of various projects involving subsea tunnels linking remote islands to the mainland, Prof. Grøv said Gozo could see an immediate increase of between 10 and 20 per cent in traffic flow, which could continue to increase gradually in subsequent years.
It is this increase in activity that the Gozo Business Chamber wants to see happening.
Joe Borg, the former Gozo Channel chairman who is behind the Gozo-Malta Permanent Link Committee of the Gozo Business Chamber, said: “During the week Gozo is an old people’s home because our youngsters come to work in Malta.”
He lamented the brain drain of young people, who eventually choose to continue living in Malta because of the inconvenience to cross over on a daily basis.
The lack of a permanent link limited the right of Gozitans and businesses based in Gozo to fully enjoy freedom of movement guaranteed by the EU, he added.
A lot has been said over the years on the best possible solution to link Gozo and Malta but the closest the island ever came to seriously considering a permanent link was in 1972 when government commissioned Japanese engineers to carry out a preliminary survey.
The options studied at the time were a bridge, a causeway and a submerged tunnel. The options were deemed unfeasible but Mr Borg believes the situation today is different.
“In 1972 there were no subsea tunnels being built and since then this technology has developed, giving us an alternative option that is more feasible,” he said. With some four million passenger movements between both islands, Mr Borg insisted the tunnel would be a major artery.
“More passengers cross between Malta and Gozo than passengers who pass through the airport. Every year some 1.1 million cars cross the channel. It is a strategic crossing and it should be treated seriously.”
He played down the argument that a permanent link would change Gozo’s character as a tranquil rural island and insisted that villages like Qrendi and Siġġiewi in Malta had still retained their characteristics despite being accessible.
What started as a private initiative has found government backing with Gozitan Parliamentary Secretary Chris Said endorsing the idea and championing it at Cabinet level.
Government has said that a pre-feasibility study will be conducted to determine whether the project can get to the drawing board but Mr Borg believes the level of political commitment has already changed the prospect from a dream to reality.
The public meeting with Prof. Grøv will take place at the Grand Hotel in Mġarr on Thursday at 7 p.m.