WJ has successfully delivered the complete dewatering works for the western extension of Warsaw Metro Line M2, supporting Main Contractor Gülermak on one of the city’s most ambitious underground infrastructure projects.

Following our previous success completing the dewatering for the S2 motorway tunnel between 2019 and 2021, WJ was appointed to manage groundwater control for seven major underground structures forming part of the M2 extension west of the city centre.

A Complex Dewatering Environment

Due to the potential for high groundwater flows and the challenges of discharging water into Warsaw’s sewer system, the contractor constructed all structures within a fully enclosed “cut‑off box”, featuring diaphragm walls and a jet‑grouted base plug. Although these provided containment, an effective dewatering system remained essential to:

• Maintain base stability
• Resist base uplift
• Control leakage inflows
• Achieve the required groundwater drawdown

While the design permitted flows of less than 50 l/s, the actual pumping requirement to meet target drawdowns exceeded 120 l/s.

Project Scope

WJ delivered groundwater management across a diverse portfolio of underground assets, including:

• Three new metro stations: Karolin, Chrzanów, and Lazurowa
• (up to 270 m long and 25 m wide)
• TBM launch chamber: 270 m × 23 m
• Two ventilation shafts: 40 m × 23 m each
• 275 m of running tunnel

Following completion of the diaphragm walls and base plugs, WJ began installations in September 2023, ultimately deploying:

• 110+ dewatering wells within the structures
• 10 piezometers for continuous groundwater monitoring throughout excavation and construction

Innovation and Rapid Response

The dynamic nature of groundwater conditions required proactive and flexible control. WJ responded quickly to changing flows by:

• Mobilising a low‑headroom drilling rig to install supplementary wells inside restricted spaces
• Using our modular pumping and control systems to rapidly upgrade capacity where needed

These measures ensured uninterrupted excavation progress and prevented programme delays.

Global Metro Dewatering Expertise

With dewatering delivered for more than 20 metro and mass transit projects across 11 cities in 10 countries, WJ has established itself as a trusted global leader in complex urban groundwater control.

      _