The sewer network under the City of Brussels is nearly 350 km long! Thousands of m3 of waste water flow through these 350 km of underground drains and tunnels every day.
The Sewer Museum invites you on an unusual trip into a very hidden side of Brussels but which is absolutely vital for the running of the city.
And unlike other museums, this one is active, with the River Senne playing the leading role. A museum that tells the story of when, why and how the sewers were built, describes the jobs that people do in this underground world and explains the city's water cycle.
Since the 17th century Brussels has had a proper sewerage network, essentially intended to divert water from the streets. However, this network remained largely incomplete and some City regulations invited inhabitants to dispose of waste in the Senne, which meandered through the centre. With the industrial development of the Canal, the Senne effectively lost its primary economic function over time and ended up for this use alone. At the beginning of the 19th century, pollution levels were at their highest. The river carried waste and rotting carcasses; it used to overflow in heavy rain and dry up in summer, releasing foul odours. It was not unusual, explained Camille Lemonnier in 1888, to see the bloated stomach of a dog floating by, interspersed with young animals and household waste, drifting in the swill and filthy water. Just imagine it …
Decontamination, quite a project
Undertaken under Jules Anspach’s term as mayor (1863-1879), the clean-up operations of the Senne were the largest civil engineering project to take place in Brussels in the 19th century. The authorities sought to reduce the pollution in the river and prevent the periodic floods. The city authorities were also motivated by the complete redevelopment of the down town part of the city; unsanitary little streets and alleyways were to be replaced with wide Hausmannesque boulevards bringing in light and air. On the request of the burgomaster, the clean-up operations, around 40 in total, were on the drawing board from 1861. Remediation of the river, opening up of great boulevards and the creation of squares, railway links or the layout of a new port were among the many variations proposed by engineers at the time. Two options stood out, however. The first consisted of diverting the Senne to skirt around Brussels to the West. The second was to vault it where it crossed the centre. The solution chosen in 1865, following much deliberation over expert reports, was to vault it.
Second vaulting plan
No sooner was the first vaulting project inaugurated in 1871, than the efficiency of the enormous construction was found to have limited value in the lower part of the city... The districts located upstream and downstream of the vaulted section were still affected by river floods. Since the end of the 19th century, plans have been drafted to carry the flood water overflow towards the canal. Several special projects have since been constructed for this purpose. However, it was not until the inter-war period that the project to divert the Senne by means of peripheral by-passes began, and a second subterranean tunnel going from the Gare du Midi station to the Pont Van Praet bridge passed through the Porte d’Anderlecht. From 1931 to 1955, over 20 years were necessary for the Société intercommunale pour le Détournement et le Voûtement de la Senne [Inter-municipal Company for the Diversion and Vaulting of the Senne] to complete the diversion of the river over six kilometres towards and along the canal. The vaulting tunnel required modifications to the toll pavilions at the Porte d’Anderlecht, through which a branch of the river Senne once flowed. Once the drains for the second vaulting were complete, the pavilions were reconstructed in the same fashion, but further apart in order to ease traffic flow along the Chaussée de Mons.
A little information on the Toll Pavilions
The toponymy and the pavilions constitute in themselves a good chunk of Brussels’ history. Until the end of the 18th century, seven “portes” or gates intersected the Brussels city wall. The Porte d’Anderlecht opened the city up to travellers coming from Hainaut along the Chaussée de Mons. It was transformed into a prison around the mid-18th century before being demolished in 1784. At the beginning of the 19th century, the dilapidated ramparts faced the same fate and their demolition, ordered by Napoleon, gave way to the Boulevards de la Petite Ceinture. These were flanked by a moat and fence which limited access to the city only through the toll pavilions, intended to collect taxes on all goods entering the capital. In 1831, the City architect, Auguste Payen, drew up the plans for the two current buildings, which were completed in 1836. Adorned with two allegorical pediments – the City of Brussels and Commerce – these pavilions remained operational until the toll was abolished in 1860.
Returning to our previous subject – the sewers
The sewer network of the city of Brussels has gradually expanded. From 45 km in 1847, the date of the first plan, it exceeded 110 km in 1878. Today, there are over 350 km! The sewers collect both rainwater or run-off and waste water from dwellings and human activity. Finally, there is also clear water inflow coming from drainage or infiltrations into the water table.
On the Brussels-City territory, approximately 200,000 m3 of waste water is carried away each day by the sewer system in dry weather. Average water consumption stands at nearly 130 litres per day per person. Collective requirements (offices, hospitals, the fire service, street cleaning, etc.) and industry increase this volume to 180 litres.
The waste water disposal system was designed from the outset to employ the gravity principal, ensuring natural flow to the outlet at the lowest point: the Senne. Several installations (pumping stations, siphons, pumps, etc.) facilitate this progression. The sewerage network is in effect only one player among the numerous arrangements interspersed in the Brussels underground. Cables and pipe-work, road tunnels, the metro system or canal tunnels are just some of the urban amenities which compete with the sewer system. Specific structures or installations make it possible to offset, or even get round certain obstacles inherent to the variations in depth of the city and the complexity of its underground universe.
The first vaulting of the Senne was focused on separating the waters of the Senne from those of the sewers, henceforth connected to mains drainage, that is to say large sewers, which ran the length of the double gate. These rejoin at the intersection of Rue Masui and the Chaussée d’Anvers and from that point on, form a single drain known as an “outlet”, 5,500 m long. This terminates at a treatment station located in Haeren, that was provided for in the First Vaulting Project but never constructed.
The waste water continues to discharge into the Senne but upstream of Brussels-City. Today, the sewers are connected to the Brussels North purification station, inaugurated in 2008.
The increase in the aggressive chemical nature of effluents, vibrations caused by continuously increasing amounts of vehicular traffic, water infiltrations, continuous works in the city, plant roots and even tunnels dug by rats are just some of the factors causing damage to the Brussels sewer system. The results are varied: poor run-off conditions, water-tightness issues and alterations to the structure. Close surveillance and fast intervention make it possible to maintain the condition of the network in which some sections are over 200 years old.