Deep Sewer Tunnel

The Deep Sewer Tunnel is an approximately 40 km long tunnel designed to collect Abu Dhabi's wastewater by gravity and convey it to the Al Wathba treatment plant.

The project involved the construction of two of the three lots of the STEP programme (Strategic Tunnel Enhancement Programme), i.e. 25 km of tunnel with an excavation diameter of approximately 7 metres and 10 access shafts with depths ranging from 40 to 80 metres.

This was a technically and organisationally very complex project, using sophisticated mechanised excavation technology: five earth-pressure TBMs worked simultaneously, excavating and lining the tunnel with precast concrete elements. The tunnels and shafts were then covered with a special membrane that guarantees total protection from the aggressive environment and a minimum lifespan of one hundred years.
The completion of the STEP programme represents a major step forward for Abu Dhabi, which will now be able to treat an average wastewater flow of 800,000 m³ per day.