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The City of Cottbus in the German state of Brandenburg is preparing itself for the future: at the beginning of April, work began on a new central sewer right in the heart of the city. This is one of the final stages of the project to renovate the city’s main sewer system which is over 115 years old and transports both rainwater and the wastewater generated by the approx. 80,000 city residents.
“It is a highly complex project – and is right in the heart of the city,” commented Marten Eger, managing director responsible for technology at LWG Lausitzer Wasser GmbH & Co. KG. REMONDIS Aqua’s Cottbus PPP company is financing and managing the work. They have drawn up a complex concept to realise this project, which aims to minimise disruption both for the local residents and for the public transport services.
For the most part, this sophisticated work involves so-called trenchless technology. Similar to tunnel construction work, a boring head tunnels its way through the earth and places the sewer pipes in the ground – with a pressure of up to 300 tonnes. Thanks to this method, only a few shafts need to be dug, namely at the beginning and at the end. At the same time there is no need to dig 7-metre trenches.
The new sewer pipes have been constructed so they can be laid using this special system. They have an outer diameter of 1.72 metres and walls around 7 centimetres thick to be able to withstand the pressure of this process. One of the two starting shafts had to be lined with underwater concrete to prevent groundwater seeping in. The indentations in the steel girders were first cleaned by industrial divers before the work began to ensure that the underwater concrete was flush.
Precision work is called for when laying the sewer – each pipe must be placed in the correct position at the exact right time.
The construction work is due to have been completed by the end of December 2015 – an ambitious schedule as such a heavily built up area that has been used for centuries is bound to throw up a few surprises. Quick and flexible reactions have already been called for to adjust the plan to cope with some unexpected situations. The boring and excavation work has, for example, revealed a number of archaeological findings, including pottery fragments and coins as well as the foundations of an old city gateway.
The section of the main sewer system that is being renovated in Cottbus lies 7 metres below the ground
The newly laid pipes are truly impressive with an outer diameter of 1.72 metres
As the people living in the City of Cottbus are very interested in this construction project, a number of recesses with windows have been built into the 800-metre fence running along the site. They can use these to observe the renovation work and follow the progress being made. LWG has also hung some banners along the fence explaining the different stages of the project. They also held an open day in August and showed those interested around the site and answered any questions the visitors had about the work.
“We have added children’s drawings to the fence to make it more attractive,” explained Marten Eger. The pictures were submitted as part of a competition initiated by LWG and all have to do with the subject of water. More than 120 drawings were handed in to the company.
LWG Lausitzer Wasser GmbH & Co. KG is one of the largest and most well-known water management companies in the German state of Brandenburg. With its workforce of around 170 employees, it supplies drinking water to approx. 130,000 local residents. Moreover, the company is in charge of managing the wastewater generated in Cottbus and eight neighbouring districts. For many years now, REMONDIS Group companies and PPP firms have been providing local authorities with reliable water and wastewater services. The renovation of the sewer in the centre of Cottbus is the biggest project LWG is due to carry out this year.