ABSTRACT
Ashghal (Public Works Authority) has developed the Musaimeer Pump Station and Outfall project (MPSO) project to receive ground water, from dewatering activities (2 m³/s) and stormwater (up to 19.7 m³/s) from a 270 km² catchment area of southern Doha. This area contains extensive current and future planned urbanization, the industrial heart of Doha along with four FIFA 2022 world cup stadiums and provides protection for 30% of Doha’s population. The project was constructed over the period 2018 to 2022. A key element of the project is the 10.2 km long outfall tunnel. This tunnel commences onshore and continues under the Arabian Gulf connecting via a riser shaft to a 270 x 70 m diffuser structure, located on the seabed. The excavation utilized a 4.4 m diameter Earth pressure balance (EPB) Tunnel Boring Machine (TBM) which commenced from a 40 m deep shaft and has an inclination of 0.05% upward to the riser shaft. This project was designated as strategic importance for the state of Qatar and as such was required to be completed on schedule. The client stipulated that safety during construction should be of the highest priority. However, this project contained significant additional safety concerns, including single access for the whole construction duration, complex geology, fractured strata to the seabed and finally, the construction period incorporated the entire COVID-19 pandemic period 2020/21. Due to the project strategic importance the construction activities could not stop, and the managing and mitigation measures taken to continue operating during the COVID-19 period were extensive and had far reaching impacts upon the day-to-day tunnelling operation, these issues were overcome by the project team and the tunnel was completed on time. This technical paper elaborates upon the safety issues and measures planned and implemented to successfully complete this project.
