CPK completes Retkinia launching chamber ahead of Poland’s longest high-speed rail tunnel construction

Credit: Centralny Port Komunikacyjny (CPK)

Work is progressing on CPK’s high-speed rail investments, particularly on Line 85, which will run through Łódź. A major milestone has been reached with the completion of the Retkinia launching chamber, the starting point for the tunnel boring machine (TBM) that will excavate Poland’s longest and widest single-bore railway tunnel.

The chamber, over 180 metres long and 23 metres deep, features diaphragm walls reaching 43.5 metres. It includes two underground levels: the first for technical systems and the second for the track bed. Excavation is set to begin by Q4 2026, with the Warsaw–Łódź section scheduled to open in 2032.

“The development of sustainable and efficient transport requires modern solutions. That’s exactly what we’ve applied in building the Retkinia chamber – a key component of the HSR tunnel in Łódź,” said Piotr Rachwalski, CPK Board Member for Railway Investments.

At the Fabryczna site, construction is underway on the receiving chamber, which will serve as the TBM’s endpoint. Budimex has built 150 cm thick diaphragm walls around a chamber measuring 22 by 30 metres and excavated to a depth of 26 metres. Jet grouting is being used to separate the high-speed tunnel from an adjacent PKP PLK tunnel, with additional concrete and steel structures now being installed.

Reinforcement works at the Łódź Cultural Centre are also nearing completion. Approximately 1,400 micropiles and jet grouting columns have been installed to stabilise the soil under the historic building. Steel bracing is being added to the northern wing, and dismantled areas are being rebuilt.

The tunnel will span 4.6 km and have a diameter of 14 metres, designed for trains running in both directions at speeds of up to 160 km/h. Tunnel depth will range from 23 to 34 metres. It will include five underground evacuation chambers, technical walkways, and comprehensive fire safety systems.

To protect buildings along the route, CPK has commissioned structural assessments from Albraco. These surveys focus on safety and load-bearing capacity in urban areas.

The full 480 km Y-line, linking Warsaw, the future CPK airport, Łódź, Wrocław, and Poznań, is expected to be completed by 2035.