Abu Dhabi completes ‘green’ main sewer

Abu Dhabi: Abu Dhabi has completed the construction of a 41-kilometre main sewer tunnel, one of the largest and longest gravity-driven sewerage networks in the world.

The eco-friendly sewer main is the major part of the city’s ambitious Strategic Tunnel Enhancement Programme (STEP), costing Dh5.7 billion, which will almost triple the capacity of its sewerage network.

The STEP features three key components: 41 kilometres of deep sewer pipes, 43 kilometres of smaller diameter link sewers, and a pumping station adjacent to the Al Wathba Independent Sewerage Treatment Plants, where the major sewer main ends.

An initiative in compliance with Abu Dhabi’s Vision 2030, the project will cater to future needs arising with an increasing population.

“It is meant for the increased population by 2030; however if the population growth is slow, this system may be enough until 2040 or even beyond,” the officials of Abu Dhabi Sewerage Services Company (ADSSC) said here yesterday at a ceremony.

The company organised the ceremony to celebrate the sewer main breakthrough of the eighth Tunnel Boring Machine (TBM) of the tunnel project. The final breakthrough completed the excavation of all sections of the sewer main tunnel.

Shaikh Diab Bin Mohammad Bin Zayed Al Nahyan, Mohammad Ahmad Al Bawardi, Secretary General of the Abu Dhabi Executive Council, joined ADSSC Chairman Abdullah Musleh Al Ahbabi, to witness the final TBM tunnel breakthrough.

The TBMs mined the tunnel through mixed ground conditions of dolomitic siltstone, clay stone, mudstone, and gypsum without causing any adverse surface settlements.

Over 1,500 skilled tunnel workers were employed on all of the eight TBM drives.

As the backbone of the project, the major tunnel has been completed, the focus has been shifted to the construction of 43-km long sewerage links that will join the tunnel from its adjoining areas, a senior official told Gulf News.

About 26 per cent of the construction of sewer links is over and the rest will be completed by 2015, Alan Thomson, managing director of ADSSC, said.

The pumping station at Al Wathba, one of the biggest in the world, will replace 34 existing pumping stations across the city, he said.

The eco-friendly tunnel will drastically reduce the carbon footprint of Abu Dhabi’s sewerage system and save Dh4.2 billion to be spent on energy and maintenance costs in the next 25 years.

The tunnel — starting at 27 metres underground and reaching a depth of 100 metres — will not require regular maintenance in its entire lifespan of 80 years.

The project began in 2009.

The existing system deals with 600,000 m3 (cubic metre) sewage a day, but the new tunnel can carry 1.7 million m3 sewage, which is the expected demand by 2030.

The sewage will be carried by gravity alone.

Abu Dhabi Sewerage Services Company (ADSSC) is the service provider for sewerage services and, owns and operates the sewerage network and treatment plants throughout the Emirate of Abu Dhabi. To meet growing sewerage infrastructure demands, ADSSC has developed a comprehensive plan to accommodate the projected sewage flows in future.

As part of ADSSC’s five-year strategic plan initiatives, the project is being carried out without disturbing the traffic, main roads and other infrastructure works.