Ashghal celebrated on Sunday the completion of the tunnelling works in the western branch of the main trunk sewer of its ambitious Doha South Sewage (DSS) infrastructure project.
The project site witnessed the breakthrough of the tunnel boring machine into the wall of the tunnel shaft, in the presence of Ashghal assistant president and senior engineer Abdulla Hamad al-Attiyah and Drainage Networks Projects Department manager and senior engineer Khalid Saif al-Khayareen along with a number of officials and engineers from the project’s consulting and contracting companies.
This major milestone represents the completion of one of the three main branches forming the main trunk sewer of Doha South Sewage Infrastructure project, which will transfer the sewage flows through pumping stations to the existing Doha South Treatment Works.
Senior Ashghal officials and project consultants at the completion of the western main tank sewer
Workers at one of the deep points of Doha South Sewage treatment works.
On the occasion, Abdulla Hamad al-Attiyah said the tunnel extends 5km underground reaching several areas including Al Sadd, Al Maamoura, and Salwa Road, up to the Doha South Sewage Treatment Works. Al-Attiyah said the achievement shows Ashghal is still making progress in all its roads, expressways, buildings projects as well as the infrastructure and drainage projects that are being carried out deep underground.
The senior Ashghal official added the completion of works proved Qatar is able to move ahead and deliver projects with the stipulated standards and quality and on schedule or even before.
Khalid Saif Al-Khayareen said the western branch is one of the three parts of the main trunk sewer which will serve Al Sadd, Al Maamoura, Umm Ghuwailina, and Al Matar areas.
Al-Khayareen said the main tunnel will withdraw the drainage water in a smoother way via gravitational factors to get it to the treatment plants, which will contribute to eliminate around 20 old pumping stations.
The western branch of the main trunk sewer, which was completed, stretches from Al Thumama Area to Salwa Road through Abu Hamour Area, with a length of about 5km, representing about 30% of the total length of the main tunnel. The tunnelling works, which started in the beginning of January 2017, took a period of 12 months at an average rate of 13.7m per day.
The tunnelling works were implemented using a tunnel-boring machine (TBM) which was named “Al Zubara”, and it is one of the project’s two TBMs which were designed specifically for the geological features encountered in Doha. Excavation works were implemented using the earth pressure balance (EPB) tunnelling technique, which is ideal for Doha's soft ground and rock conditions, at a depth ranging between 30 and 40m, without impacting the traffic flow or the buildings surrounding the tunnel.
The main trunk sewer of Doha South Sewage infrastructure project comprises three branches, eastern, western, and northern with a total length of 16km.
The eastern branch extends for about 7.5km from Al Thumama to Old Airport area, passing through the E-Ring Road and its tunnelling works are expected to be completed in third quarter of this year. The northern branch extends for about 4km from Al Thumama to Rawdat al-Khail area, through Al Najma area and it is expected to be completed in the last quarter of this year.
The main trunk sewer is being constructed using pre-cast segments, where it takes six segments to build one concrete ring of the tunnel, which includes 13,537 concrete rings with an internal diameter of three metres.
The project also includes the construction of seven lateral interceptor sewers with a total length of about 24km, which will convey flows from areas in the centre of Doha to the main tunnel.
This is in addition to the construction of 11 shafts at a depth ranging from 20 to 40m, which will be used to excavate the main tunnel. To minimise the impact and space of construction works within the city of Doha, four of these shafts will be excavated using a vertical shaft machine.
The shafts also lead to inspection rooms that will be constructed as part of the project through which inspection and periodic maintenance to ensure proper operations of the tunnel's facilities.
The Doha South Sewage Infrastructure Project is designed to serve areas in the south of Doha and the expected population growth. The project can be linked to future infrastructure projects, and when completed, it will enable the decommissioning of more than twenty old pumping stations currently located in the residential and commercial areas in the south of Doha.
One of the important benefits of the project is the gravity based main trunk sewer that will link a number of areas in the south of Doha to the sewage network. As a result, it will reduce the environmental impacts through the full control of odours in sewage treatment works and conveying system, and reduce other environmental problems arising from sewage overflow due to excess hydraulic pressure on the existing drainage network, where sewage flows exceed its capacity.
Ashghal started implementing the Doha South Sewage Infrastructure Project in August 2015, and 70% of the works are completed so far. The project is planned to be completed in the first quarter of 2019.
It is worth mentioning that the Doha South Sewage Infrastructure Project is the first project in the region to implement the ‘CEEQUAL’ an international evidence-based sustainability assessment, rating and awards scheme for civil engineering, infrastructure, landscaping and works in public spaces.
The joint Vvnture Bouygues Travaux Publics and UCC is the project contractor and CH2M is the project management consultant.
Employees of contracting firms and Ashghal officials at the completion of the tunnelling of the western main tank sewer
*Tunnelling works in the western branch of the main trunk sewer completed
TBM at the `breakthrough' of the western main tank sewer
