On the basis of the Abu Dhabi Master Plan 2030, a drainage network is being constructed for the urban area and the industrial districts. The Strategic Tunnel Enhancement Program (STEP) encompasses a 40-kilometer-long main sewer, together with supply tunnels (link sewer) and pump stations. The tunnel starts in the city and runs out into the desert (from Abu Dhabi island to the mainland and then onto Al Mafraq). Around 550 million liters of sewage are produced daily in Abu Dhabi, most of which is treated and used for irrigation. With the STEP project, Abu Dhabi is laying the foundation stone for future urban development to ensure that it will be able to meet the needs of the anticipated population growth.
Five Herrenknecht EPB Shields (6,310 mm and 6,950 mm diameter) are being used for the construction of approx. 25 kilometers of the main sewer (Lots T-02 and T-03). The TBMs are the first of this size in Abu Dhabi. The first three Earth Pressure Balance Shields started tunnelling in April, July and August 2011. As early as December 18, 2012, the last of the five machines arrived in the target shaft after best weekly performances of up to 214 meters.
An additional EPB Shield (diameter 3,745 mm) and 8 AVN Machines (diameters 975 – 3,395 mm) are in charge of tunnelling a total of approx. 43 kilometers of the supply tunnels (Lots LS-01 and LS-02). From January 2013 tunnelling went at full speed. The cutting wheels are exactly adapted to the geology. With the machines‘ extensions kits they can be adapted to the changing tunnel diameters on some sections. With the last breakthrough in summer 2016, all drives are completed successfully.
The Herrenknecht Group scope of supply comprised together with the EPB Shields and AVN machines a segment production plant planned and delivered by Formwork as well as rolling stock by MSD.
The excavation of the supply tunnels receives the best possible support by the Herrenknecht subsidiary founded in Abu Dhabi in November 2012. Herrenknecht Tunnelling Systems LLC supplies spare and wear parts and refurbishes machines if required. The customer service additionally offers extensive technical support during advance directly on the jobsite.