Abu Dhabi Sewerage Services Co. (ADSSC) recently completed construction of its new main sewer tunnel—the primary feature of the city’s Strategic Tunnel Enhancement Programme (STEP). The 41-km sewer tunnel is the major component of one of the largest and longest gravity-driven sewerage networks in the world. Appointed program manager in 2008, CH2M HILL helped oversee the delivery of the tunnel.
STEP, started in 2008, includes not only the 41-km long sewer tunnel, but also 43 km of smaller diameter new link sewers up to 3 meters in diameter, and a large pumping station at Al Wathba Independent Sewerage Treatment Plants. The infrastructure will triple the capacity of Abu Dhabi’s sewerage network, alleviating the pressure on the existing system.
When completed, STEP will meet the long-term wastewater collection and conveyance needs of Abu Dhabi Island and the Mainland. The system will provide for an average wastewater flow of 800,000 cu meters per day, with an ultimate capacity of 1.7 million cu meters per day by 2030.
In addition to increasing capacity; the gravity tunnel and the link sewers feeding into the tunnel will enable ADSSC to eventually decommission 34 existing pumping stations, saving significant operating and maintenance costs over its 80-year life.
“We used a total of eight huge tunnel boring machines to excavate the 41 km of deep tunnel so the recent breakthrough of the last TBM was celebrated as a significant programme milestone and one we have been working towards since 2008,” commented Bob Marshall, CH2M HILL STEP program manager. “With the deep tunnel complete, we can shift our attention to the network of link sewers that connect into the tunnel on both Abu Dhabi Island and the Mainland.”
Excavated using trenchless technology, construction of the deep tunnel sewer posed minimal disruption to the city. The eco-friendly tunnel was designed to dramatically reduce the carbon footprint of Abu Dhabi’s sewerage system. The project is expected to be completed in 2015.
Source: CH2M HILL