ABU DHABI // Snaking its way over kilometres of terrain, 80 metres beneath the surface of the capital, a multibillion-dirham construction project is well on its way to providing a greener city.
Called the Strategic Tunnel Enhancement Programme (Step) and carrying a price tag of Dh5.7 billion, the project will see more than 40km of underground sewer tunnels built by 2015.
Step, which began construction in late 2009, is one of the longest gravity-driven wastewater tunnels in the world.
The new wastewater system will not replace the existing sewer system, a network that includes nearly 300 pumping stations Emirate-wide, but will help the capital make significant gains in improving infrastructure.
"How many people and where - that's basically what drives our business, and that's what we considered when we were planning infrastructure for the next 25 years," said Shahzad Orakzai, the manager of the programme management department at the Abu Dhabi Sewerage Services Company (ADSSC). "We knew if by 2017 our infrastructure wasn't ready, we'd have problems."
The deep tunnels under construction are just the first component of Step, which will be made up of 91km of sewers that will eventually be able to accommodate an average flow of 1.7 million cubic metres per day.
Because the system will be gravity-driven, 35 pumping stations on the island will be shut down.
"The decommission of the pumping stations will have a huge impact on our carbon footprint," said Omar Husain al Hashimi, the head of the asset management division at ADSSC. "These stations are powered by electricity and when they come offline, we can save energy."
Mr Orakzai said taking the pumping stations offline would cut costs and eliminate the odours that came from the buildings by keeping the gases enclosed within the underground sewer system. The decommissioned land would be converted to public use, probably for parks.
The system, part of a Dh23bn capital investment programme, will deal with the collection, treatment and disposal of wastewater and is expected to last at least 80 years.
Considered "maintenance-free", the Step system works by using link sewers to divert wastewater into the deep tunnel sewer, which will then move to wastewater treatment facilities at Al Wathba. The treated water will be used for landscaping and irrigation in the capital.
"The treated water, which will almost be drinkable, will be used 100 per cent for greening," said Mr al Hashimi.
At a ceremony last week to mark the inauguration of Step, Sheikh Hazza bin Zayed, the National Security Adviser and vice chairman of the Abu Dhabi Executive Council, called the project part of an "aim to attain a well developed and comprehensive infrastructure" for the emirate.
