12 movable bridges - 12 challenges!
Restoration of the canal meant rehabilitating many structures. In the Newsletter No 6 sent on 16 January 2008, we focused on the footbridges which are now integrated in the routes for pedestrians and cyclists along the canal and its branches. Challenges on a different scale had to be faced for the movable bridges that are open to vehicles, some of which carry very heavy traffic. This week we focus on these landmark structures along the route, which represent a total investment of €0.7M for the MET, €2.8M for LMCU and €3.8M for the Conseil Général du Nord. The works are presented in the order the structures will be discovered by boaters en route from the Scheldt to the Deûle.
1 to 3 - The lift-bridges in Wallonia
The three lift-bridges on the Canal de l'Espierre in Hainaut province are of similar design, and have all suffered the ravages of time. The works awarded by the MET (Direction des Voies hydrauliques de Tournai) to the contractors De Graeve of Namur included the replacement of the damaged parts, painting, mechanisation by means of hydraulic rams to activate the bridge and replacement of the dolphins*. However, it appeared on inspecting the structures that the bridge-decks themselves were seriously corroded and would have to be replaced. The one on the Centre lift-bridge (meaning the centre of Saint-Léger village) even had to be done urgently, involving an additional cost of €50 000. The works completed early 2007 cost €413 000. For the Mauroy and Petit Preux lift-bridges, the MET did not have sufficient budget under the Blue Links programme. It has thus recently awarded a new contract for replacement of the two remaining bridge decks, for a total cost of €292 000. The works are to begin on 15 March 2008. The three bridges will now be fully operational by August 2008. In the meantime, the Petit Preux lift-bridge will be maintained in the open position and traffic diverted, to allow the dredging barges to pass through.
* These are rows of timber piles which serve as guide-walls, to protect the bridge against vessel impacts.
Overall view of the Centre lift-bridge in August 2007, on completion of the works
The deck of the Centre bridge during its inspection in 2006
The Petit-Preux lift-bridge
4 - Grimonpont lift bridge at Leers
Just in front of the popular canalside auberge at Leers, this bridge crosses the Roubaix Canal between the Grimonpont quarter (in the commune of Wattrelos) and Leers. This steel structure, first built in 1920 then replaced in 1976, links the two communes on the local road RD 91. Although it is movable (with a bascule deck), it has never been operated since the structure was reopened. The expert appraisal of the bridge revealed that a complete rebuild was necessary. The Conseil Général du Nord will therefore proceed with demolition of the bridge in the coming months. New, wider bridge piers and abutments will be erected to accommodate a completely new bridge deck. This means new hydraulic and electrical equipment and associated safety devices (traffic lights on the road and on the canal bank).
The future bridge will work in the same way as previously: a bascule lift-bridge with counterweight on the Leers side. However, it will have more than double the width of the existing bridge, in order to include a pavement 1.50m wide plus a one-way cycle path, also 1.50m wide, on each side. The total width of the future bridge deck comes to 9m compared to 4.20m at present. The superstructures will be of more modern design. With the agreement of the communes concerned, the principle of alternating one-way road traffic is retained.
The works will be carried out by the contracting group Norpac/Ducrocq Ingénierie Process, with engineering and supervision delegated by the Conseil Général to EGIS/Eurodim/PL Carlier Architecte. The works are expected to last 7 months, with an unavoidable period of interruption of vehicle traffic for several months from spring 2008. Traffic diversions will be signposted, and a temporary bridge erected for pedestrians during this period.
The Grimonpont lift-bridge was in too bad a state for it to be repaired. It will be replaced by a new structure.
Architect's drawing of the new lift-bridge
5 - Wattrelos hydraulic lifting bridge
The vertically lifting Wattrelos bridge, Grande Rue in Roubaix, was restored by VNF during the first phase of works, which began in 2000, and was reopened in November 2002.
6 - The bridge de la Vigne in Roubaix
The Vigne lift-bridge was one of the first to be restored under the Blue Links project. The deck was rebuilt and the former abutments were adapted to the project design guidelines. This is a vertically lifting bridge with a single span. It belongs to LMCU, and all the works were delivered and reception trials conducted in late 2006. However, a disorder was observed on the bridge when it was operated to let through the dredging barges. LMCU is currently examining with the contractor responsible for the works the procedures and techniques for repairing the bridge and bringing it back into operation.
7 - Daubenton bridge
This bridge of relatively recent construction was designed to be movable, but the equipment remained to be installed. That is now being done under the Blue Links project. Site installation is complete and work has started on the road works and service connections. The works should continue to the middle of 2008. Owner is LMCU.
8 et 9 - The two Couteaux bridges
The Couteaux roundabout bridges are part of the most complex work-site on the whole canal. Not exactly a “spaghetti junction”, but a complex road interchange above and below the canal. It alone justifies a Newsletter which will be devoted to the subject as the works progress. Owner is LMCU.
Les Couteaux roundabout in Roubaix
10 - The Fontenoy swing-bridge
This foot-bridge on the Union site in Roubaix is one of the three key architectural features of this part of the canal, along with the bridge-keeper’s house, restored under the project, and the lock-keeper’s house, also restored by VNF to accommodate the future canal operating control centre. The bridge deck was rebuilt and the abutments adapted, maintaining the original operating principle of a deck rotating on a central pier. The bridge-keeper’s house now contains the control console for the bridge. The new bridge-deck was placed in mid-January, and the structure should be fully operational in a few weeks. The owner is LMCU.
11 – Halot lift bridge
This bridge is on the Tourcoing branch, close to the limit of navigation, which means it is not in the sequence of structures to be operated for boats on their way through the link from the Deûle to the Scheldt. In this context, straightforward manual operation, as in the past, will be sufficient. This will also make it possible to operate the bridge as an attraction during events such as “Tourcoing Plage” in the summer. Complete verification and repairs to the structure are also covered by the works contract, which should be let during the second semester of 2008. Owner is LMCU.
The Halot lift-bridge on the picturesque Tourcoing branch
12 - Blanc-Seau lift-bridge in Tourcoing
The Blanc-Seau lift-bridge in Tourcoing is a steel structure commissioned in 1989. Local road No 9 (Roubaix-Mouvaux) crosses the canal here, and the structure is extended by a bridge over the Lille-Roubaix-Tourcoing express road which was built in that period. Restoring mobility of this bridge, which remained fixed for more than 15 years, consists in repairing the various mechanical parts – cogs and wheels, bearing plates, operating mechanisms - treating all steel parts against corrosion, installing new electrical and hydraulic equipment necessary for operation, and finally fitting new devices and signage to ensure safety for vehicles, pedestrians and boats.
The Nord Département, owner, awarded the works to contractors Ducrocq Ingénierie Process, based at Montreuil-sur-Mer (62), while works management was delegated to Eurodim. The works should begin in the spring of 2008 and last about 6 months, to a large extent outside the site, for the renovation or fabrication of parts in the contractor’s works. Towards the end of the works, the various operations on the underside of the bridge-deck (sand-blasting, anti-rusting protection and painting) will nevertheless require the bridge to be maintained in the open position for several weeks. An alternative route will be signposted for vehicle traffic, and more details will be given to the local inhabitants in the coming weeks.
The Blanc Seau lift-bridge is raised by a mobile crane to allow the passage of dredging plant.