Project of the century

Start of mega-canal under the Vienna River

The new sewer will run over nine kilometers underground in the west of Vienna.

(Bild: Wien Kanal)

From now until 2027, a huge tunnel boring machine will be digging unnoticed through half of Vienna - and will thus change the city. The new Wiental Canal is a technical challenge in a class of its own and makes the plans to transform the Vienna River into a recreational area realistic for the first time.

When the construction machinery starts up on the "urban wilderness" near the Margaretengürtel U4 station at the beginning of March 2024, this will be the starting signal for the largest construction project in the history of Vienna's sewer system: the digging of a huge canal under the Wien River, from Aufhof to Margareten. The canal will be nine kilometers long with an internal diameter of three meters. It is due to go into operation in 2028.

The Wien River no longer has to be a flood channel
The canal will free the Wien River from its role as a flood reserve: Until now, the river had to be flooded after heavy rainfall to avoid overloading Vienna's canal network. The new canal also opens up realistic possibilities for redesigning the bed of the Vienna River for the first time. Both Climate City Councillor Jürgen Czernohorszky and the heads of the districts involved - Margareten, Mariahilf, Meidling, Hietzing, Penzing and Rudolfsheim-Fünfhaus - as well as the Vienna Green Party are already pushing for the creation of a new local recreation area.

Climate City Councillor Czernohorszky presented the monster project with Vienna Canal Director Ilmer, all district heads involved and representatives of the red-pink city coalition.

(Bild: Martin Jöchl)

Millimeter work between subway tubes
The population will hardly notice any of the main excavation work: The 135-metre-long tunnel boring machine, operated by 15 men, will be sunk piece by piece in Margareten, first assembled in the tunnel - and then eat its way to Auhof at a depth of 12 to 35 meters to the site of the skater park by summer 2026, 24 hours a day, seven days a week.

(Bild: Krone KREATIV)

The machine will be excavated in Auhof, transported to Margareten and placed back into the 15-metre-deep excavation pit. It will then complete the route eastwards to the end of the canal directly opposite Café Rüdigerhof by 2027. The project has been planned for years, but its implementation remains a technical challenge: at one point, the planned route runs very close between the subway tunnels, with a height clearance of just 1.70 meters to the U2 tube.

A unique construction site experience
As unnoticed as the digging of the new main canal will be, the creation of the new connection points for the canal will be noticeable. Construction work lasting between several weeks and several months is required at 43 points. Vienna Canal Director Andreas Ilmer asked the public on Thursday for patience and understanding over the next few years. Czernohorszky was confident in this regard, because for everyone involved as well as the Viennese, "You only do something like this once in your life."

The entire canal was built to scale for the presentation. In the model, not a finger fits between the canal (blue) and the subway tunnels (green and purple)

(Bild: Martin Jöchl)

Almost a birthday present
With the new Wiental Canal, Vienna's sewer system is also almost giving itself a birthday present: for exactly 100 years, the city's sewer system has also been 100 percent in municipal hands. Until January 1923, it was mainly the clearing and maintenance that was privatized.

Sewer clearer with horse-drawn cart, manure shovel and lantern in the 1920s

(Bild: ÖNB/Wien, OEGZ/H9925)

At the time, the transfer of responsibility to the city had less to do with deficiencies in the work carried out than with the emergency period of the economic crisis: the sewer system had become a refuge for a huge number of people who had become homeless.

Since then, the city has not only got to grips with this problem, but has also expanded the sewer network bit by bit and raised the quality standard. Today, 99.8 percent of all Viennese households are connected to the sewer system and use 500 million liters of wastewater every day.