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 10 kilometre 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 yesterday, Sunday 3 February, Ashghal inaugurated the operation commencement of the Tunnel Boring Machine (TBM) that will be used for the tunnel excavation. In presence was H.E. 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.
On this occasion, H.E. Dr. Eng. Saad bin Ahmad Al Muhannadi, President of Ashghal, 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 storm water 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, Manager of Drainage Networks Projects at Ashghal stated 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 project is designed to ensure the preservation of the marine environment, as the water that will be pumped complies with the environmental assessment standards, and it is discharged ten kilometres off-shore to reduce the effect on the marine environment.
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 QR 920 million.
The contractor is obligated to maintain and operate the project for a period of at least three years. The project is being implemented by the JV of Hamad Bin Khalid Contracting Company and PORR Qatar Construction Company. The project management services has been assigned to Mott Macdonald Ltd. who will oversee the design, implementation and operation of the project.
Mesaimeer Surface and Storm Water Drainage Tunnel Project
Mesaimeer Pumping Station and Outfall is the second phase of the Mesaimeer Surface and Storm Water Drainage Tunnel Project that is implemented to achieve the objective of Mesaimeer Tunnel, which aims to discharge the surface and stormwater, thus decreasing the surface water level and reducing pumping costs in construction projects around the country. It will also preserve the foundations of buildings, and reduce land subsidence due to rain.
Mesaimeer Tunnel was completed in late 2016 and it is one of the projects implemented by Ashghal in the field of drainage networks development. In 2017, the project won the Global Best Project award in the wastewater category, during the Engineering News Record (ENR) 5th annual Global Best Projects Awards in New York City, in the presence of a group of the largest international companies executing global construction projects.
The tunnel extends below the F-Ring Road for 10 kilometres with a depth of about 30 metres below the ground surface. This main tunnel is linked to the existing and planned drainage networks in the areas that traverse through, and will collect and discharge surface water from approximately 170 km² of catchment area, as it is connected to rain water drainage networks in 43 vehicle tunnels.