What we do

Overview of RijnlandRoute project, Dredging


Due to the lack of east-west connections and the increasing traffic density on the existing routes, the construction of the RijnlandRoute is crucial. The new road connects Katwijk, via the A44, to the A4 at Leiden in the Netherlands.

All the ongoing developments in the region, including house building and business activities, will lead to even more traffic on these busy roads in the future. Therefore, the RijnlandRoute is also necessary to improve liveability in the region.

The RijnlandRoute has three main objectives:

  • a better east-west connection for car traffic (between the A4 and A44 motorways)
  • improvement of liveability in the Holland Rijnland region
  • making spatial-economic developments in this region possible


In 2017, as a member of the COMOL5 joint venture, DEME was awarded the 15-year design, build and maintenance contract for the RijnlandRoute.The COMOL5 joint venture is responsible for the reconstruction of the Leiden West motorway junction and the construction of the 4 km, N434 road, including a 2.2 km bored tunnel.

In 2018, the integrated joint venture team finalised the basic design and the detailed design was completed in 2019. Preparations for the starting shaft for the massive tunnel bore machine, as well as laying the groundwork for the approaches to the bored tunnel, got underway. Eventually, more than 1 million  of soil will have to be excavated during the mega project.

Giant tunnel boring machine

A huge tunnel boring machine has been built for the project, which is 100 m long and 11 m high. This ‘mobile factory’ started work during the summer of 2019. Tunnel boring crews operate the boring machine 24/7. The machine will bore the tunnel at a maximum depth of 32 m below the surface and will simultaneously construct the tunnel itself. Over 15,000 prefab tunnel components are also being built. The boring machine will go into the ground at the start shaft near the A4 motorway (close to the Vlietland recreation area) and will come up in the reception shaft near the Leiden neighbourhood of Stevenshof. There, the road will continue below grade for approximately 1.4 km, after which it will connect to the A44 motorway.

Additionally, we transported and supplied more than 1 million m³ of sand for the project throughout 2018. This represented more than 2,000 ship movements. A total of 1.4 million m³ was eventually delivered, with the final shipments taking place in early 2019. We will also transport the sludge and mud that comes out of the new tunnel to the dumping area situated next to the project, which is known as the Meeslouwer plas. This is a former sand mining area and a nature and leisure area today, so strict rules and regulations have to be taken into consideration.

Overall scope of COMOL5:

  • Design and construct
    • Drilled tunnel of 2,250 m (2x2)
    • Open and closed tunnel sections, including the access slip roads to the drilled tunnel (2x2)
    • 2.8 km A44 widening and 9 km A4 widening motorways and connected roads
    • 20 new engineering structures (aqueduct, flyovers, crossovers etc.)
    • Traffic and tunnel technical installations (TTI)
  • Other work
    • Piping and cables
    • Water management
    • Mitigating and compensating ecological measures
    • Tree compensation
    • Compliance with MEAT commitments
  • Maintenance
    • 15 years of maintenance for the drilled tunnel, tunnel ramps and TTI
    • Existing infrastructure (A4+A44) for the realisation period

Our Scope:

  • Earthworks
    • Road cuttings
    • Watercourse construction
    • Raising at engineering structures
    • Excavating dry cofferdams
  • Measures to compensate soil consolidation
    • Preloading for the benefit of consolidation (including sand delivery)
    • Vertical drainage
  • Disposal of released material
    • Including drill tunnel soil
    • Wet and dry cofferdams
    • Per axis / by ship / hydraulically
  • Remediation
    • Local contamination of expropriated parcels
    • Contaminated drilled up soil (80,000 m3)
  • Soil retaining walls - timber dam walls
  • Soil retaining walls - L-shaped walls (excl. tunnel entrance east)
  • Construction roads and sites: earthworks and sand works
  • Grubbing up/felling + green management

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