Mount Royal Tunnel double arch replacement

Innovating tunnel rehabilitation with the Sequential Demolition Method

CDPQ Infra | Montreal, Quebec, Canada | 2021-2022

The REM is Quebec's largest public transit project in the last 50 years.

Completed demolition in the south tunnel section 102 days ahead of schedule.

2023 Project of the Year (including renovation) Award from the International Tunnelling and Underground Space Association, in the up to 50 million euros category


  • As part of the Réseau express métropolitain (REM) project, extensive replacement and rehabilitation work on the Mount RoyalTunnel (TMR) was critical to constructing a new automated light metro network across the greater Montreal area.
  • Opened in 1918, the double-arched tunnel required major work to meet current safety standards and to adapt the tunnel to the REM's electric light metro system.
  • Fast track observational design in a dense downtown area, just under public infrastructure in a mixed condition of rock and soil.
  • Design of the new replacement tunnel also needed to mitigate concerns regarding ancient explosive residue found in the tunnel from the original construction. The CNESST imposed strict constraints, mandating that excavation, drilling, and other tunnel work be done with remote equipment.


  • Joint venture with CIMA (as CCH) to perform design for the TMR rehabilitation while providing site technical support and full-time site supervision during construction.
  • Employed a unique tunnel replacement (Sequential Demolition Method) to install canopy pipe in an arch pattern above the envelope of the existing double arch and performed demolition and replacement advances in 12 sequences.
  • Contingency plan and clever steel rib design with variable length to adapt to site condition and real-time monitoring to adjust the demolition sequence accordingly.
  • Created innovative solutions to mitigate explosion risk. Developed design modification to comply with remote drilling and remote localized demolition from contractor means and methods.


  • Completed demolition in the south section 102 days ahead of schedule by conducting technical meetings to analyze site-specific conditions and apply lessons learned from previous sequences.
  • Used the Sequential Demolition Method to efficiently replace 92 meters of tunnel section and deliver the project on time, on budget, and below the surface settlement limit.
  • Supported prime contractor (NouvLR) to maintain health and safety standards on site. Navigated complex challenges, including working in a dense urban area and mitigating risks related to explosive residue detected further down the tunnel.
  • Named the TAC 2022 Canadian project of the year and winner of the Hatch Innovation Award.

67 km of new track as part of the REM project.

26 new light metro stations spanning the greater Montreal area.

Mount Royal Tunnel has more than 100 years of continuous operation since opening in 1918.

92 m of tunnel to be replaced.

290 m of tunnel to be rehabilitated.

12 demolition sequences, as part of the innovative "Sequential Demolition Method".

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