Gozo tunnel proposals ‘cut straight into rock fault’
Geologist raises alarm over tunnel plans which overlook ‘fatal’ underwater rock formation between Malta and Gozo
Never mind how many hundreds of millions of euros the proposed Gozo-Malta tunnel link may end up costing the taxpayer (€500 million, according to one estimate; over €1 billion according to another). Geologists are more concerned with costs of an altogether different kind: the kind that is usually measured in human life and limb.
According to Dr Peter Gatt - a former member of the European Commission's DG Environment, who has recently completed his doctoral research thesis in geology at the University of Durham - the preliminary report submitted by engineering and development consultants Mott MacDonald late last month had been drawn up with scant regard for the geological properties of the Gozo-Malta Channel.
Even at a glance, he argues, the proposed routes were envisaged without taking into consideration the existence of a number of geological characteristics of the area: including a fault running through the rock towards the east of the island, which would (if tunnelled into) entail consequences that Dr Gatt describes as 'fatal'.
"The four tunnel routes proposed by Mott MacDonald will cut into a strike-slip fault complex found along eastern Gozo," he told MaltaToday. "Evidence for this fault is ample along the coast of Gozo, if Mott MacDonald and Transport Malta had bothered to visit the site in the first instance. It is surprising that Transport Malta is unaware of the dangers of planning tunnels through such structures, and probably shows that they know very little about the geology of Gozo Channel."
Geologist Peter Gatt
Dr Gatt, whose area of expertise is precisely the geology of the Maltese islands, explains that the west-east fault is the result of "recent changes in the regional stress field"; and it is therefore possible that this fault is still active.
"Constructing a tunnel through an active fault can produce fatal results," he warns. "Tunnelling though faults increases the possibility of collapse; and if the tunnel is below sea level, that would also entail the risk of flooding."
Nor is the west-east strike-slip fault the only geological feature to have been overlooked in what seems to have been a hasty approach to planning for a possible subterranean Malta-Gozo link. "There are other fault structures between Comino and Malta that need to be considered," Gatt adds, pointing towards the central route that would tunnel through Blue Clay below Comino.
"Any tunnelling here will have to be based on clear understanding of this rock. Even well-known clay formations such as the London Clay can be highly problematic, and can lead to disaster as happened when the Heathrow Express Underground collapsed in 1994..."
Ironically, few are better positioned to appreciate such risks than Mott MacDonald, which was also involved in the same London tunnel project that had led to the expensive 1994 disaster. On that occasion, one of the partially constructed tunnels carrying the Heathrow Express line into the Terminal 1, 2, 3 complex collapsed with almost no advance warning. As a result, an entire office building and a car park disappeared into a huge crater which opened up between Heathrow's two parallel runways. The principal contractor was found guilty of negligence in February 1999, and fined £1.2 million.
"Mott MacDonald was responsible for the works design in that case, and the project was plagued by bad practice and poor understanding of the geotechnical properties of the clay," Gatt explains, adding that failure to consider the local geology is a shortcoming by no means limited to Mott MacDonald... being evidenced in other infrastructural projects, too.
"With hindsight, the history of infrastructure in Malta - especially road-building - is characterised by a total disregard for local geology," he points out. "Transport Malta did not bring a change in mentality in this respect. Not surprisingly, overlooking geological conditions results in unacceptable deformation of road surface, extensional cracking and pothole formation, which have made Maltese roads some of the worst in Europe. The state of local roads is hardly a badge of competence for Transport Malta. If this disregard to geology persists in our tunnelling projects, then the results would be disastrous and even more serious."
Report admits lack of geological study
In July 2011, Transport Malta appointed Mott Macdonald to carry out a preliminary analysis of road tunnel link options between Malta and Gozo.
The five-month study provided a list of technical, engineering, environmental and economic issues relating to potential sub-sea tunnel fixed-link options connecting Malta and Gozo.
The final report, which identified four potential tunnel alignments for further investigation, was presented to the public at a press conference addressed by Transport Minister Austin Gatt and Gozitan ministers Giovanna Debono and Chris Said.
Presenting these findings, Gatt quoted Mott MacDonald to the effect that that an undersea tunnel link between Malta and Gozo would be "doable" and "technically feasible".
And yet the same report also admitted that "a detailed geological and geotechnical investigation is still required to determine more precisely the tunnel alignment, tunnel form, cost and construction methodology".
Despite the lack of detailed geological data (which in turn will have a direct bearing on the choice of technology used to excavate the tunnel in question), the minister publicly declared the project to be not only technical feasible, but also "economically viable".
The consultants estimated a range of costs for each tunnel alignment option: between €156-€492 million for a single-bore, three-lane bi-directional tunnel, up to €1,080 million for a twin-bore two-lane uni-directional tunnel.
The road tunnel link between Malta and Gozo could potentially be co-financed by the European Union under the Cohesion Fund.