Drilling work finished on Abu Dhabi’s 41-kilometre main sewer tunnel, a major strategic project, on Tuesday.
The eighth and final segment to be completed was 4.7 km, stretching from the Officers’ Club area to the Abu Dhabi National Exhibitions Centre, Abu Dhabi Sewerage Services Company said.
The second longest gravity-driven tunnel in the world, it now stretches from Al Mushrif to Al Wathba.
Fifteen million working hours went into the project and nearly 1.4 million cubic metres of sand were removed.
The tunnel-boring machine, drilling at a depth of 32 metres, broke through to the surface near Adnec.
Its appearance marked the end to drilling, and was attended by Sheikh Diab bin Mohammed Al Nahyan; Sanbio Kim, Korean minister of state; Mohammed Al Bawardi, chairman of the Abu Dhabi Executive Council’s executive committee; and members of the Executive Council and officials from the Abu Dhabi Government.
The sewer construction is part of the Strategic Tunnel Enhancement Programme (Step) that includes 16.1km of the tunnel, which was divided into three segments with special machinery required for each.
The company said the machines began drilling in July last year and were progressing at an average of 150 metres a week, with an internal diameter of 4.5 metres, and no chance of ground collapse.
The 90 metre-long, 450-tonne machine mined through dolomitic siltstone, clay, mudstone and gypsum without any surface accidents.
Nearly 70 engineers and technicians took part in this one part of the tunnel work.
The construction is one of several phases in the Dh5.7 billion Step project, which will also include 43km of smaller-diameter sewerage links.
There is a main pumping station at the end of the tunnel, which has a capacity of 30 cubic metres a second and an expected capacity of 1.7 million cubic metres of sewage by 2030.
“This breakthrough by the eighth and last [tunnel-boring machine] in the drilling phase adds to the series of successes in the achievement of this huge project,” Abdullah Al Ahbabi, chairman of Abu Dhabi Sewerage Services Company said at the inauguration ceremony yesterday.
Mr Al Ahbabi said work continued in the remaining parts of the projects, including the main pumping station and the sewerage links.
“We are closer than ever today to achieving the project which shall be completed in 2015 and will bring social, environmental and economic benefits to the residents of Abu Dhabi City,” he told Al Ittihad, the Arabic-language sister paper of The National.
“The strategic tunnel enhancement project is part of the company’s strategy 2010-2015, which is based on Abu Dhabi Vision 2030.”
The tunnel project is a milestone in Abu Dhabi Government’s investments in large-scale projects to develop the infrastructure with careful consideration to the environment.