The Public Works Authority (Ashghal) has completed 50% excavation works of the 10-km long outfall tunnel of Mesaimeer Pumping Station and Outfall project.
According to a video by Ashghal on its official social media platforms, the project has achieved remarkable development and will be completed in the last quarter of 2021 at a total cost of about QR920mn.
The outfall tunnel, is described as the longest of its kind in the world and an important step towards providing a sustainable solution for the discharge of surface and stormwater in the country.
The project will accommodate surface and storm water volumes received from the drainage networks located in different areas in Doha. The water is treated according to the highest internationally approved specifications, and then pumped 10km away from the seashore via the Mesaimeer pumping station and outfall tunnel.
The excavation of the outfall tunnel is at a depth of 15m below the seabed and about 3.7m in diameter and considered a “major construction challenge due to the variable geology that increases the exposure to unexpected conditions”.
The main tunnel at Mesaimeer will connect the existing and future drainage networks. The tunnel will “operate to drain surface water from sub-networks located in different areas, spread over an estimated 170sqkm area, and minimise rainwater catchments, especially in tunnels, as it is connected with rainwater drainage networks in 22 tunnels” (for vehicles).
The tunnel project will also decrease the surface water level and reduce pumping costs in construction projects across the country. Besides, it will help preserve the foundations of buildings by reducing waterlogging.
The excavation is carried out using a highly specialised tunnel boring machine (TBM) that uses a technique called Earth Pressure Balance and designed to operate in a range of ground conditions in Qatar, and along the variable geology along the tunnel.
The TBM machine incorporates advanced technologies that ensure the efficiency of the drilling process, providing the maximum safety standards for tunnel workers and operators, as well as monitoring the work execution through all its stages.
The safety features include a “closed mode” feature, used in the case of ground deterioration to prevent water from entering the tunnel and thus protect the workers, in addition to rescue chambers that protect personnel during emergencies, fire detection and suppression, as well as emergency electricity generation systems.