Warsaw begins drilling 2.4 km Mokotowski Bis collector branch under Wisłostrada

Tunnel boring machine specifications and route

Warsaw municipal water utility MPWiK is preparing to launch underground excavation for the second branch of the Mokotowski Bis sewage collector. The work will be carried out by a tunnel boring machine named Jolanta, which weighs 107 tonnes and features a cutting diameter of 3.4 meters. Underground drilling is scheduled to start in early October 2026, advancing under Wisłostrada along Czerniakowska and Solec streets toward Płyta Desantu. The entire underground route covers a total length of 2,378 meters, divided into three consecutive stretches measuring 853 meters, 711 meters, and 814 meters. The operational depth of the machine ranges between 10 and 15 meters beneath street level, running 10 meters deep near the junction of Czerniakowska and Gagarina streets and descending to 15 meters at Płyta Desantu.

Capacity expansion and pumping infrastructure

The new 2.4-kilometer tunnel will add over 17,000 cubic meters of retention capacity dedicated to excess municipal sewage and rainwater. When combined with the first branch, the Mokotowski Bis collector system will increase the overall retention capacity of Warsaw's sewer network by more than 23,000 cubic meters. Near Płyta Desantu, construction crews will also erect a new pumping station. This facility will actively pump the gathered mixture of wastewater and stormwater runoff into the existing Nabrzeżny collector. The infrastructure serves as an underground buffer designed to prevent localized flooding and network overloads during cloudbursts.

Jarosław Robak, director of the project implementation unit at Warsaw Waterworks, detailed the operational objectives of the new retention system.

The Mokotowski Bis collector will relieve the existing sewage system and create an additional retention reserve during heavy rainfall. This solution will allow for more efficient drainage of excess rainwater and better prepare the city for challenges associated with climate change.

Project schedule and construction budget

The tunnel boring machine Jolanta is scheduled to complete all excavation work across the three underground sections in the second half of 2027. Following the completion of boring, secondary concrete works, and technological fitting, the full collector system is slated for commissioning in the first half of 2029. The municipal utility has allocated approximately 218.5 million PLN net for the second branch investment. The project relies on microtunneling methods to construct the large collector without disturbing vehicular transit on the busy Wisłostrada corridor.

Integration with Warsaw retention network

The new tunnel forms the second phase of the Mokotowski Bis project, expanding upon the initial 1.2-kilometer branch built along Gagarina Street. Operating since 2024, that first section already relieves Warsaw's combined sewerage network during periods of torrential rain. The two branches will connect directly at the intersection of Czerniakowska and Gagarina streets to channel surplus flows northward toward the Vistula. The Mokotowski Bis project is part of a larger municipal retention network that includes two previously completed conduits, the Lindego Bis and Wiślany collectors.