Dr. Eng. Saad bin Ahmad Al Muhannadi (third right), President of Ashghal, with other officials at the excavation site.
Doha: In an important step towards providing a sustainable solution for the discharge of surface and storm water in the country, the Public Works Authority ‘Ashghal’ has announced the commencement of the actual excavation of the 10km-long outfall tunnel, as part of Mesaimeer Pumping Station and Outfall project that started in May last year.
During a site visit to the project on Sunday, Ashghal inaugurated the operation commencement of the Tunnel Boring Machine (TBM) that will be used for the tunnel excavation. In presence were Dr. Eng. Saad bin Ahmad Al Muhannadi, President of the Public Works Authority; Engineer Khalid Al-Khayarin, Manager of Drainage Networks Projects Department; Ashghal officials, and representatives of the supervision consultants and contractors.
Al Muhannadi said: “The commencement of the excavation of the outfall tunnel is an important stage within Mesaimeer Tunnel project, which is one of the most important projects implemented by Ashghal, and that will accommodate surface and storm water volumes received from the drainage networks located in many areas of Doha.
The water is treated according to the highest internationally approved specifications, then its pumped 10 kilometres away from the seashore via Mesaimeer pumping station and outfall tunnel, which is one of the longest outfall tunnels in the world.”
Engineer Khalid Al-Khayarin said that the excavation of the outfall tunnel will be at a depth of 15 metres below the seabed and about 3.7 metres in diametre, which is considered to be a major construction challenge due to the variable geology, increasing the exposure to unexpected conditions. It is also worth mentioning that excavating under water seabed requires a drilling machine and a crew with special capabilities.
The excavation will be done using a highly specialist TBM that uses a technique called “Earth Pressure Balance” (EPB) and is designed to operate in a range of ground conditions in Qatar, and with the variable geology along the tunnel. The TBM machine incorporates advanced technologies that ensure the efficiency of the drilling process, and providing the maximum safety standards for the tunnel workers and operators, as well as monitoring the work execution throughout all its stages.
The safety features include ‘closed mode’ feature, which is 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 at emergencies, in addition to Fire Detection and Suppression, and Emergency Electricity Generation systems.
Mesaimeer Pumping Station and Outfall project: The second part of the project includes a pumping station with 10 pumps and auxiliary facilities. The pumping station will be located at the end of Mesaimeer Tunnel south of Hamad International Airport. The pumping station will operate at a capacity of 19.7 cubic metres per second, and its function is to pump water from Mesaimeer Tunnel, which was completed in 2016, to the new outfall tunnel. The excavation works of the outfall tunnel and the construction of Mesaimeer Pumping Station is scheduled to be completed by Q4, 2021, at a total cost of about QR920m.
