Renovation of manholes: New process to reduce costs and construction time

During a sewer inspection on Dinxperloer Straße, several sewer manholes were found to be in need of renovation. The manholes made of prefabricated concrete parts are damaged by the influence of wastewater and the resulting hydrogen sulphide. A new, innovative process is now to be used for the renovation.

The trenchless rehabilitation method is intended to significantly reduce costs and construction time compared to conventional methods. "A few years ago, the damage found in the sewer shafts would have been repaired by completely replacing them using the open trench method", explains Claudia Müller from the waste disposal and service company responsible.

This would not only have taken around a week to build each manhole, but would also have been around three times as expensive as trenchless renovation. "In addition, the increased space requirement would have been problematic in the city centre", says Müller.

As part of the search for a more efficient solution, the city of Bocholt became aware of a new rehabilitation method that is now to be used in the first trial on Dinxperloer Strasse. The method is based on the use of a modular system of polymer concrete elements, known as segments, which are installed inside the existing manhole.

The elements are bonded together on site and the remaining gap is filled with backfill mortar. "The material is particularly resistant to sulphuric acid and is therefore ideal for the existing damage", says Müller.

This method reduces the installation time per shaft to around one and a half days. Only the access opening is required for the work, which minimises the impact on the road. Following the first trial on Dinxperloer Strasse, there are now plans to use the method at other locations as well.