The first Coentunnel
As per the signature date of the contract on 1 June 2008, responsibility for the current Coentunnel was transferred to Coentunnel Company in terms of maintenance of the existing road, the tunnel and all relevant technical traffic and tunnel systems (TTTS). Additionally, the First Coentunnel will be renovated as soon as the Second Coentunnel will become available. Until the end of the contract period, the new construction elements will also be managed by the consortium. In the new situation, the two tunnel pipes of the First Coentunnel, providing three permanent lanes, will be allocated to southbound traffic (Zaandam – Amsterdam).
The second Coentunnel
The Second Coentunnel will be built about ten to fifteen metres east of the current Coentunnel, consisting of a total of five lanes in two asymmetrical tunnel pipes. The east pipe offers a capacity of three permanent northbound lanes (Amsterdam – Zaandam). The west pipe offers space to two changeable lanes that can be switched from southbound to northbound and reverse as required.
Just like the current Coentunnel, the Second Coentunnel is a ‘category 1’ tunnel. This means that there are some limitations relating to carrying hazardous substances. For instance, LPG tanker trucks are not allowed to use the tunnel, but tanker trucks with petrol and diesel are allowed.
Four tunnel elements
Just like its predecessor, the second Coentunnel is a sunken tunnel. The sealed part of the tunnel consists of four elements of about 180 metres long each, which are to be sunk into place. These elements are manufactured in a construction dock near Barendrecht. From this site, they are transported to the sinking location by barge via the Nieuwe Maas, the North Sea and the North Sea Canal, to be positioned accurately – to the centimetre. In order to prevent the work on the second Coentunnel from adversely affecting the first Coentunnel, a robust separation wall of hollow posts will be implanted prior to sinking the second tunnel.
After sinking down the elements, the consortium is still in rough waters. One of the key challenges subsequent to sinking the elements is integrating the road and the tunnel systems. All communication systems, traffic signs, ventilation and extraction systems etc that are part of the tunnel comply with the latest requirements relating to tunnel safety.
Roads and structures
In order to connect the second Coentunnel to the A8 and A10 motorways, various connection roads will be realised. The Coenplein junction is currently undergoing reconstruction and the structures on this section are adjusted to the new situation. Additionally, two new structures are also part of the construction work. Rather than the technique, it is the limited construction time that makes this part of the project complex - and remember that this is one of the busiest traffic areas in the Netherlands! This is why the preparation and logistics of the work must be considered critical factors in successful construction.