Abu Dhabi’s super sewer

Last week I did a really interesting interview with the project client, and project manager of Abu Dhabi’s new 40km sewer tunnel. Construction of the tunnel will happen in three contracts and eight bores with the first getting underway in December. It is already a critical project for the emirate for lots of reasons, not least the fact that the current system is overloaded and some of the collection sewers have been surcharging and spilling out sewage. It is also critical because deep tunnelling is not very common in Gulf states so there is a lot that will be learned on this scheme. ADSSC knows this and has set up a training programme with project managers CH2MHill for local engineers to gain transferable major project experience. This bodes well for schemes like Abu Dhabi’s metro. Knowledge gained about the ground conditions will also be important. Gypsum in the existing strata dissolves in water and makes the emirate vulverable to large underground voids “solution features”. Extensive ground investigation has been carried out to avoid such caverns and more will be done as the project progresses.

So far just one contract has been awarded and in this respect progress is slower than originally planned. The onlu award so far is to Italy’s Impregilo who will drive the middle section and a further five contracts are yet to be awarded. Two more for the tunnel, which are awaiting approval from Abu Dhabi’s Executive Council, two for sewers that connect in to the new tunnel, and a final pumping station contract. These three are under consideration of Abu Dhabi Sewerage Services Company’s chief executive. The delays are understood to be because the government is examining its growth forecasts in the light of the global financial crisis. However project parties remain confident that as far as the tunnel contracts go the only issue of award is when they will happen and not if.

The feature will appear in Tunnels and Tunnelling International, July issue (www.tunnelsonline.info). Below is a map of the route:

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