Sewer restored for the next decades

The sewer pipes of the community of Zell an der Pram were showing serious signs of aging and damage in recent years. “Timely maintenance and repair of the piping system through rehabilitation is an integral part of our public service portfolio”, says Mayor Matthias Bauer. Hence the local government decided to invite tenders for a sewer rehabilitation project. Pipe rehabilitation specialist RTi Rohrtechnik international, based in Altenberg, Upper Austria, turned out the best bidder and was awarded the project. The company performed the pipe rehabilitation project by using trenchless technologies.

“Trenchless technologies are an excellent alternative to conventional (open-dig) methods and provide an environmentally sound solution to restore aging pipes quickly, efficiently and sustainably without digging up the ground”, concludes Ing. Michael Griebaum, Executive Partner of RTi Austria GmbH.

The project was initiated by RTi on July 11^th, 2016, and over a period of three months an egg-shaped sewer section (500/750 mm) with a total length of 2,800 metres and a diameter of 200-500 mm was renewed. The trenchless rehabilitation method which RTi used in this project was a hose lining technique called cured-in-place lining (CIPP). This technology is based on a coated needle fibre hose which is impregnated with epoxy resin. The saturated liner is inverted or pulled into the host pipe with air pressure by using a special machine (inversion process) and the resin is subsequently cured with hot steam. The epoxy resin “glues” the liner to the inner wall of the pipe to form a seamless, tight compound, leaving no annular gap between the host pipe and the liner. The sewer line is now fully restored and functional, and can be reconnected to the sewer system. The project also included a number of preparatory and after-care measures. Prior to the lining process, the joints of the supply tubes protruding into the lumen of the pipe as well as deposits were worked away by using a milling robot. The pertaining shafts and supply lines were manually restored. Following the rehabilitation process, the supply lines were reopened also by using a robot.

The newly installed liner has restored leak tightness and has optimised the hydraulic properties of the pipe, so that both the pipe and the surrounding environment are now permanently protected. The sewer lines can be reconnected and taken into service, and the local government is highly satisfied that the project was completed on schedule.