The project consists of the excavation with a double shield TBM of two hydraulic tunnels with a diameter of 3.70 m and a total length of approximately 12 km. The two tunnels located in Southern Riyadh are part of a main sewer collector of 33.4 km which collects the entire of urban wastewater from the city of Riyadh and conveys it to the new purifier built in Al-Haer.