Project Information

  • Location: Abu Dhabi
  • Client: Abu Dhabi Sewerage Services Company
  • Contractors: Samsung Engineering, Impregilio, Zublin, Oderbrecth
  • Consultant: CH2M Hill
  • Sections: Main Sewer (41 km); Link Sewer (40 km); Pumping Station (100 m underground)
  • Duration: 2012 – 2016


The concept of the proposed Strategic Tunnel Enhancement Programme (STEP) system was to use a series of link sewers to intercept flows from existing gravity sewers upstream. The idea was to transfer the flows by gravity into the deep tunnel sewer, thereby providing relief to the existing main collector system. These flows will again be transferred by gravity via the deep tunnel sewer to centralized wastewater treatment facilities strategically located at Al Wathba, at the southern end of the metropolitan area of Abu Dhabi.


Odour control is a key component of STEP. A centralized odour extraction approach was initially recommended and validated through detailed modelling. However, the client required greater certainty regarding the volumes and movement of air within the tunnel and link sewers. Physical modelling was conducted to quantify air entrainment values at drop structures and further evaluate centralized versus regional odour extraction system approaches. As an outcome, a regional odour extraction system is implemented at tunnel work shaft WS-4 and shaft WS-7, with a two-stage treatment consisting of bio-trickling filters followed by carbon polishing.

Solution offered

Encardio-rite was awarded complete monitoring works of the project. It provided supply & installation of geotechnical/ geodetic instruments, monitoring, surveying, and bi-weekly reporting with evaluation & interpretations. Geotechnical and geodetic instruments were installed in diaphragm walls and soil to provide settlement, deflection and deformation data for the verification of the initial design of permanent structures and temporary works supporting the excavation.