Building to last
Salt water and sandy soils are just two of the challenges facing MACE Contractors as it works on the Al Salam Street tunnel project in Abu Dhabi. Nasser Hadba talks to Gay Sutton about efforts to minimise the effect on the public and ensure that the work will last for 100 years.
Oil, like most riches, can be both a benefit and a curse, but for Abu Dhabi, capital of the United Arab Emirates, it has been an opportunity. The city lies on the shores of the Arabian Gulf and today it is a modern, architecturally diverse hub for commerce with a rapidly expanding industrial base. It is also a magnet for tourism and a major retail centre. Cosmopolitan and wealthy, its skyline at night is a brilliantly lit patchwork of shimmering glass tower blocks, and the oil revenue which used to be the cityÔÇÖs main income is now being eclipsed by the thriving business sector. However, Abu Dhabi has expanded far beyond the expectations of those who planned and designed its layout of wide boulevards on a grid system way back in the 1970s.
Traffic congestion, particularly during busy times of the day, has become a blight to residents, and as part of a wider programme of infrastructure improvements across the city, the Abu Dhabi Municipality has undertaken an ambitious two year project to convert one of the cityÔÇÖs arterial routes, the Al Salam Street, into an urban expressway, doubling its capacity so that it will comfortably be able to handle 6,000 cars per hour.
The aim of the project is to ensure that traffic can move uninterrupted along virtually the entire length of Abu Dhabi Island. Previously heavily congested junctions are to be rebuilt. Traffic can only enter or leave Al Salam Street from the right, so traffic crossing the road will do so via a flyover or tunnel. But perhaps the most ambitious part of the plan is the construction of a 3.1 kilometre tunnel accommodating all eight lanes of trafficÔÇöfour in each directionÔÇöwhich will enter the ground at the Al Mina Road intersection at the northern end of the island, to surface again at the Al Falah Street intersection.
One of the companies playing a key role in the tunnel project is MACE Contractors, a construction and maintenance company that specialises in piping / infrastructure services. ÔÇ£The project is not only about construction work on the tunnel,ÔÇØ explains project manager Nasser Hadba. ÔÇ£Before this work can be done, the entire infrastructure in the areaÔÇöthe sewerage, water, electrical and stormwater utilitiesÔÇöhave to be relocated. Our job is to construct temporary bypasses for the sewerage. Then we will demolish the old services, reconstruct the new network, reconnect the services and then remove the bypasses.ÔÇØ
Disruption to the cityÔÇÖs traffic is unavoidable. Detours of about 15 kilometres in total have been put in place, and in some cases temporary roadworks have been carried out to accommodate the extra traffic. But to keep the disruption to a minimum, the tunnel construction project has been fast-tracked. The main contractor, the Samsung/Saif Bin Darwish joint venture, had originally divided the work into four sections with the aim of completing them sequentially. But the four sections are now being undertaken simultaneously, and this has led to a considerable increase in resources on site.┬á
ÔÇ£There are tens of thousands of people working on the site, excavating for the tunnel and working on the sewerage systems, water supply, electrical networks, communications and so on,ÔÇØ explains Hadba. ÔÇ£ItÔÇÖs a very delicate and sensitive business coordinating all these activities on a daily basis to avoid conflict between the contractors.ÔÇØ
While working in such close confinesÔÇöbetween high rise buildingsÔÇöand with so many other utilities being laid down at the same time, accidents can only be avoided by careful planning and extremely accurate working practices. ÔÇ£If, for example, someone was to damage a pressure pipe, within an hour youÔÇÖd have the entire area flooded,ÔÇØ Hadba says. Similarly, if a power or communications cable was to be cut, whole sections of the city could suffer a blackout.┬á
MACE has a long history of engineering excellence in Abu Dhabi. The company is responsible for maintaining the sewerage network throughout the city, and has developed an in-depth knowledge of the area. ÔÇ£This makes it easier for us to forecast possible difficulties and therefore minimise long-term problems.ÔÇØ┬á
The biggest challenge on the tunnel project is that Abu Dhabi is at sea level. Any excavated hole simply fills with water and that water is very salty. The company is therefore employing a mixture of progressive techniques and salt resistant materials in all sewerage and water works on the project. Such work, however, requires considerable investment. ÔÇ£The GovernmentÔÇÖs aim is that the work we are doing in the tunnel should survive for at least 100 years. And they have been very generous to ensure that only the best materials and techniques are used,ÔÇØ Hadba says.
The sandy soil has also necessitated extensive structural studies, and not just on the walls of the trenches being excavated, but also on surrounding structures. ÔÇ£The trenches are deep,ÔÇØ Hadba explains. ÔÇ£Therefore all the buildings along both sides of Al Salam Street have been extensively surveyed, and they will continue to be monitored throughout the project and afterwards for structural integrity.ÔÇØ
The Abu Dhabi Municipality places great importance on safety, both from a human and environmental perspective. ÔÇ£We are looking carefully at issues like dust control, the disposal of construction debris and housekeeping on site,ÔÇØ Hadba says. ÔÇ£All contractors are doing their best to minimise the disturbance to the public and make this an ÔÇÿidealÔÇÖ project. From the safety perspective, only yesterday I was reviewing with my team the first 300 days since we started the project,ÔÇØ he continues. ÔÇ£We have had zero medium or large accidents, only incurring a few very minor accidents like a finger cut. So weÔÇÖre going to throw a big party to celebrate that.ÔÇØ
Abu DhabiÔÇÖs vision is to continue improving the cityÔÇÖs infrastructure. Already there are plans to construct a metro system and tramway. With all the expertise MACE has developed, it will undoubtedly be bidding for work on the projects and hoping to continue playing a key part in the cityÔÇÖs future.
