Once completed at a total cost of about QR920mn, the 10km long outfall will provide a sustainable solution for the disposal of surface and stormwater in the country.
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The main tunnel 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’s connected with rainwater drainage networks in 22 tunnels for vehicular traffic. 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 to a location 10km away from the seashore via the Mesaimeer pumping station and outfall tunnel. The outfall tunnel passes through a depth of 15m below the seabed and has a diameter of about 3.7m. It is considered a “major construction challenge due to the variable geology that increases the exposure to unexpected conditions”.
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The excavation is carried out by using a highly specialised TBM that uses a technique called Earth Pressure Balance and is 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.