Exclusive first-look at Saadiyat Cultural District’s tunnel project from Louvre Abu Dhabi

A look into the latest addition to Saadiyat Island, a secure and private tunnel almost as long as the Sheikh Khalifa Bridge that will allow the delivery of priceless artefacts to the Cultural District's new museums.

Construction on the 1.2km-long service tunnel that will connect all the museums in the Saadiyat Cultural District. Works are preparing for cement casting near the exit tunnel to the Louvre Abu Dhabi. Antonie Robertson / The National
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For the sake of clarity and for the reader, journalists are often encouraged to make comparisons when it comes to explaining complex facts and figures.
If an object measures 300 metres, for example, it's as tall as the Eiffel Tower. If it weighs six tonnes, then it's as heavy as an African elephant.
Things become rather more complex, however, when you're trying to visualise 200,000 cubic metres. That's the amount of rock and sand that's been excavated to create the "almost tunnel" that now snakes, canyon-like, past Louvre Abu Dhabi.
The latest addition to Saadiyat Island will eventually act as the connective tissue between the institutions that will define the heart of the Saadiyat Island Cultural District: Louvre Abu Dhabi, Guggenheim Abu Dhabi and the Zayed National Museum.
Twelve metres wide, six metres deep and 1.2 kilometres long, the tunnel will only be 200 metres shorter than the nearby Sheikh Khalifa Bridge, which links Saadiyat Island to the city, and half as long as Abu Dhabi's record-breaking Sheikh Zayed ­Tunnel.
Jassim Al Hammadi, the director of buildings and infrastructure at the Tourism Development & Investment Company (TDIC), Saadiyat Island's master developer, explains the tunnel's purpose. "Unseen to the museums' future visitors, the tunnel is going to be the entry way for all that is going to be on display at the three museums."
It will also allow deliveries to each of the new museums to take place in a secure and private environment – a key consideration when external temperatures can top 40°C and when priceless pieces by the likes of Picasso, Manet and Gauguin are the ­likely consignment.
The design and location of the new museums is another factor that has made the tunnel a necessity. All three have been designed to be viewed in the round, a decision that leaves little room for back-of-house operations to take place at ground level. It's a situation that's exacerbated by the fact that both Louvre Abu Dhabi and the Guggenheim occupy island sites and are surrounded by water.
"The tunnel is one of the most important parts of the Cultural District jigsaw," explains Lee Kandalaft, the engineer charged with overseeing the tunnel's delivery. Kandalaft is the project's deputy director of infrastructure delivery. "It will be private, so there won't be any public traffic travelling through it, and it will have two lanes, one for traffic and the other for use in case of breakdowns. There will never be a traffic jam in the tunnel."
The tunnel will also provide separate entrances and exits for each of the museums, meaning that traffic will always flow through it in one direction, like blood through a vein.
Kandalaft is responsible for making sure that Saadiyat receives all of the critical infrastructure that it needs – the roads, bridges, water, sewage, district cooling and electricity – to enable the museums to be built on time, to budget and for the whole island to function once construction has finally finished. Louvre Abu Dhabi is scheduled for completion in December 2015.
"I am the client's representative," the engineer explains, "but I work as a team with the design consultant, the project management consultant and the contractor.
"I have a role to make sure the contractor is getting everything he needs to allow him to get the job finished on time. To complete a job of this magnitude, you have to work as a team."
Luckily, Kandalaft has more than 35 years of experience to draw on when it comes to infrastructure, tunnels and islands. Before joining TDIC, the 56-year-old worked for Aldar on Yas Island, where he was responsible for delivering the infrastructure and another tunnel in time for the inaugural Abu Dhabi Grand Prix, which took place in 2009.
"On Yas, the tunnel was underwater," Kandalaft explains. "Here, it's a little bit easier. The tunnel is close to the water, so we have to shore it up and dewater it, but the real challenge is the coordination and the logistics."
On Saadiyat, this process of coordination has kept Kandalaft and his colleagues occupied for almost three years.
Not only have Louvre Abu Dhabi and the Saadiyat tunnel been designed and constructed by different consultants, they have to coordinate with a level of precision that ensures each remains watertight. That's no mean feat on an island where basements frequently descend below the groundwater line, a line that rises to a depth of just one-and-a-half metres below ground level in certain parts of the island. Considering the art and artefacts that will be stored in the museum's subterranean precincts, it's a challenge that's freighted with risk.
On a tour of the construction site, Nebojsa Zivkovic, a construction manager with the tunnel's project management consultant Turner International Middle East, explains the intricacies of the coordination ­procedure.
"The Louvre has its own shoring, waterproofing and dewatering system, but it occupies the lowest point on the site, so we have to finish before they do, otherwise there could be flooding."
By the time that it's complete, the tunnel will have consumed 11,000 tonnes of steel and 70,000 cubic metres of concrete – however, in comparison with the fiendish complexity of the museum, its construction process is a beguiling model of simplicity.
Wider, deeper and longer than the tunnel itself, a huge trench descends like an enormous piece of land art from the northern tip of the Cultural District to a point that is now visible from the Sheikh Khalifa Bridge.
To prevent the walls of this trench from collapsing, the tunnel's contractors had first to install a system of shoring and sheet piling that's held in place by enormous posts drilled directly into Saadiyat's bedrock.
They then had to dig wells at regular intervals along both walls of the trench that would enable dewatering to begin before the excavation of the trench could take place. Pumped from each well to a system of settlement tanks, the groundwater is cleaned and checked before it's then pumped out to sea.
"It's a dewatering process that can finish only once the tunnel is complete," Zivkovic explains. "We don't want water here at any stage of the works, and we don't want water in the tunnel, so we need to complete some larger sections of the tunnel completely, and only once it is safe will we be able to turn some of the wells off."
Leaks, however, are not the only potential problem posed by Saadiyat's groundwater. Despite the tunnel's enormous size, there's also a possibility that groundwater might cause the whole structure to float – to counteract this, 600 concrete-and-steel tension piles have been drilled into the bedrock to hold the whole structure in place.
"Typically, piles will work under pressure, transferring the weight of a structure down through the sand and into the rock layer," Zivkovic explains. "But the tension piles are squeezed into the rock. They keep everything down."
Once the tunnel is finished, the land around it will be backfilled and then the whole structure will disappear from view, buried under more than a metre of fill. A major road and a light-rail transit system will then be built on top, but before this can happen, the tunnel must be completed – a jigsaw of 41 separate parts. The first seven of these are U-shaped and will leave the first 200 metres of tunnel open to the sky. The remaining 37 are box-shaped and will eventually be joined together to form the tunnel before it's buried.
Of these box sections, the ones closest to the underground entrance to Louvre Abu Dhabi have to be finished first, to allow deliveries to the museum to begin next April.
At that stage, the entire length of the tunnel will still not have been completed, so for the only time in its life, traffic will travel in both directions in the tunnel. It's an exception that's been determined by the deadline for Louvre Abu Dhabi's opening.
Of the giant concrete sections closest to the museum's entrance, the construction of Unit 25 is the furthest advanced and the techniques used for this element act as a microcosm for the tunnel as a whole.
With the steel reinforcement for its concrete in place, Unit 25's one-metre-thick slab has already been poured and its walls are standing, ready to support the weight of the tunnel's mighty roof. During the construction process, this will be supported on a thicket of scaffolding that will gradually be lowered and removed once the concrete roof has set. The procedure may sound simple, and in comparison to the complexity of Louvre Abu Dhabi's canopy it is, but to get this far, even, has taken five months.
To complete the tunnel on time, day and night shifts will be required once Ramadan has ended.
"We are working to complete the tunnel before the contractors move in for the Zayed National Museum and the Guggenheim," Kandalaft explains. "You can just imagine how busy the site will be then. The Cultural District is going to be one of the busiest construction areas in the whole of Abu Dhabi."
nleech@thenational.ae