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Elis­a­beth­straße: sewer un­der­go­ing re­fur­bish­ment

Several construction site traffic signs lie in a large pile
© Pixabay/Gerd Altmann

Between 29 March and 2 July 2021, the sewer in Elisabethstraße will undergo refurbishment along a section of 600 metres; the refurbishment will be carried out by Holding Graz Water Management using the low-excavation method. The sewer in Elisabethstraße between Merangasse and the glacis is one of the oldest sewers in Graz – it is around 90 years old and therefore requires a comprehensive refurbishment in order to be able to guarantee the reliable discharge of the waste waters from the surrounding areas in the future too.

Details about the excavation work:

Holding Graz Water Management department has developed several underground procedures over the last few years with which open excavation can be avoided in 90 per cent of cases. “Low excavation” is the key word: The sewers are refurbished through the existing duct openings or by selective excavations with dimensions of around 2 by 2 metres. This results in a substantial reduction not only in dust and noise; in addition, the construction time is also reduced due to the low-excavation method and thus the restrictions for neighbours and traffic minimised.

  • The solution is the low-excavation method of construction. The construction time can be substantially reduced due to the low-excavation method and thus the restrictions for neighbours and traffic minimised.
  • The modern procedures for sewer, pipe and duct refurbishment do not require any or only very little excavation work. We no longer have to dig up the entire street; instead, only selected areas of the street need to be dug up.
  • The low-excavation method of construction using hose liners means that only a few small installation pits are required. If only refurbishment in an open construction method was possible here, the street would probably be substantially impaired over a period of months and the many construction site vehicles, heavy-transport vehicles and construction machines would contaminate the air in Graz throughout the construction period.
  • In the course of the refurbishment project, the lateral pipes which connect to the subsidiary collector in Elisabethstraße will also be refurbished. The work will thus be visible in the side streets.
  • Traffic in Elisabethstraße will be continuously upheld in both directions but with restrictions over the entire period of construction.
  • The water storage in the sewer network plays a major role during the construction period; during the day, up to 150 litres per second and at night up to 100 litres per second need to be diverted using pump technology.
Yellow construction workers' helmets lie next to each other on the ground
© Unsplash/Silvia Brazzoduro

General info on the water management and the low-excavation construction method:

  • The Graz sewer network has a length of 860 kilometres. It is between 20 and 130 years old.
  • The construction of the sewer system began at the end of the 19th century. The network consists of pipe and profile sewers in different materials. The diameters range between 5 centimetres and huge storage sewers measuring 6 by 4 metres.
  • Where possible, open excavation is avoided to prevent traffic jams.
  • With the low-excavation construction method, we can substantially reduce the burden on the population, environment and business during the refurbishment of waste water pipes. The entire street or pavement no longer has to be dug up – instead, we only need to dig up at selective points – we refurbish the pipe underground. Compared to the conventional construction method, the excavation work is reduced by around 80 per cent.
  • The advantages compared to the open construction method are, amongst others, that valuable surfaces are spared and costly excavation and restoration work is reduced to a minimum.
  • The burdens on neighbours and construction workers due to noise, dust and waste gases are lower. In most cases, traffic can flow unhindered as a total blocking of the road is not necessary. No large volumes of earth have to be excavated.