While the Strategic Tunnel Enhancement Programme (STEP) may not have grabbed as many headlines as some of Abu Dhabi’s larger infrastructure projects, the new wastewater network is crucial to the long-term health and welfare of the city.
At the centre of the STEP project is a 41-km tunnel that will start on Abu Dhabi Island and pass beneath Maqta Creek to the mainland, descending from an initial depth of 24 metres to 80 metres. Along with a grid of 43 km of smaller feeder tunnels that will bring wastewater to the main tunnel, there will also be a large pumping station located next to the Al Wathba independent sewage treatment plants. When completed, the $1.6bn network will carry 800,000 cu metres of wastewater per day, with flow expected to increase to 1.7m cu metres per day by 2030.
The STEP project is the result of the Plan Abu Dhabi 2030: Urban Structure Framework Plan, unveiled in 2007, which called for a fully integrated infrastructure system that would be able to cope with the future demands of the emirate and its people for decades to come.
On May 14, Alan Thomson, the managing director of the Abu Dhabi Sewerage Services Company (ADSSC), the state utility, announced that well over one-third of the development work on the tunnelling had been completed, with about 15 km of the tunnel finished. As such, the project was on schedule to be completed by early 2015, allowing for 35 older pumping stations to be shut down and a far more environmentally sound wastewater process to operate.
Almost all of the work is being carried out underground, with machines boring the tunnels directly rather than the cut and cover method – which involves digging deep trenches, laying pipelines and refilling the excavated site – often used in the past. The much less intrusive process now being used means there will be no damage to above-ground structures and minimal disruption to life in the city.
The STEP project is a multinational affair: Italian firm Impregilo is constructing two of the three sections of tunnel; South Korean company Samsung C&T is responsible for the third section; Japan-based Kawasaki and the German company Herrenknecht is providing the tunnelling machines; and US international project management and engineering firm CH2M Hill is acting as the programme manager on behalf of ADSSC.
In early 2012, the ADSSC announced it was awarding a Dh1.3bn ($354.22m) contract for the STEP pumping station to Construtora Norberto Odebrecht, a Brazil-based engineering and construction conglomerate.
Despite delays in awarding some of the contracts, in part due to the government re-evaluating many of its major infrastructure expenditures in the wake of the global financial crisis, the contracts are now all started and completion in early 2015 is still the target.
Other Gulf states are now also looking to use the STEP model as an example when upgrading their own sewerage systems, with both Qatar and Saudi Arabia considering similar schemes. Though perhaps not as glamorous as other infrastructure projects in the emirate, the development of STEP is providing a number of opportunities for international construction firms.
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