Rotterdam in development

124 R O T T E R D A M I N D E V E L O P M E N T | 2 0 1 8 The joint mobile office unit for the Combinatie Aanpak Maastunnel (Maastunnel Consortium) and the Municipality of Rotterdam is located on the south bank of the Nieuwe Maas at Doklaan: 40 metres wide and two storeys high, with a sizeable fleet of vehicles in front. Inside, the managers, overseers, work planners, designers, calculators, buyers and other administrative personnel are hard at work. Deep beneath the Nieuwe Maas, around 100 professionals are carrying out the renovation. “This is not only a big assignment in terms of the amount of work, but also because of the precision required. The Maastunnel is a national monument, so its original state has to be maintained as far as possible,” says director Remco Hoeboer from the consortium. The consortium is made up of civil contractor Mobilis, restoration specialist Nico de Bont and technical service provider Croonwolter&dros, all three of which are daughter companies of TBI. “We have found the synergy within the concern and we are taking full advantage of each other’s knowledge and expertise.” What is truly remarkable within the construction industry is that the client is working together with around 20 people in the contractor’s office unit. Around 20 people from the Municipality of Rotterdam work on the open office floor, with a view over the SS Rotterdam, together with the staff from the contractors’ consortium. At first glance, it is hard to tell them apart. “That gives us really short communication lines and prevents misunderstandings.” Hoeboer refers to the work on the Maastunnel as “continually finding a balance between the monumental character and modern functional and safety requirements.” That means that choices sometimes have to be made, in close consultation with the client. REPAIRING ROTTEN CONCRETE The renovation of the 1,373-metre-long tunnel has three main stages: concrete repair, restoration of tiles and lighting fixtures and completely new installation engineering. The concrete repair is the most extensive stage. The main construction consists of a number of linked tunnels, within which two traffic tunnels and a combined cycle- and pedestrian tunnel have been constructed. The lanes in the traffic tunnels rest on concrete walls, which in turn stand on the tunnel’s concrete floor, which is affected by concrete rot. Once the roadway has been demolished, 10 cm will be removed from the concrete floor with the aid of hydrojets, Hoeboer explains. This will expose the reinforcing bars, which will be thoroughly cleaned, allowing a new layer of concrete to be applied. To limit the risk of unintended cracks, this treatment must be carried out on a section-by-section basis. The incorporation of special concrete blocks along the traffic lanes also forms part of the concrete repair work. LOOK AND FEEL The tiles and the yellow lighting largely define the look and feel of the Maastunnel, which must not be altered. All tiles have been inspected individually, with any broken and loose tiles being marked with a sticker and replaced with identical new tiles. The lighting is housed in steel fittings sunk into the walls. These will be removed, thoroughly treated and replaced. The lights are equipped with LED technology. Finally, the mesh of the raised inspection paths (one per tunnel, connected through emergency doors) will be given a makeover. VENTILATION BUILDINGS In addition to another series of smaller structural works, installation engineering is the third major BANNERS READING ‘OUR TUNNEL IS BEING RENOVATED’ HAVE BEEN HUNG ALONG THE TUNNEL WALL. THE MAASTUNNEL IS DEAR TO ROTTERDAM RESIDENTS’ HEARTS. IT IS ‘OURS’, AND HAS BEEN FOR THREE QUARTERS OF A CENTURY. AFTER THOROUGH PREPARATIONS, A TWO-YEAR RENOVATION OF THE TWO TRAFFIC TUNNELS BEGAN IN JULY 2017. THE RENOVATION WILL BRING THE UNDERGROUND MONUMENT UP TO STANDARD, BOTH STRUCTURALLY AND TECHNICALLY, FOR THE LONG TERM. IT WILL ALSO BRING IT INTO LINE WITH NEW, STRICTER REQUIREMENTS FOR TUNNEL SAFETY.