Rolf Ostmeier, Redeker GmbH, Franz Römer, Steinzeug-Keramo GmbH

In February 2013, Redeker GmbH, an engineering consultancy company, started work on the detailed plans for the second construction phase of a major infiltration-water transport system for the city of Detmold. The plans for the city center foresaw not only the construction of a new combined wastewater sewer system capable of transporting rainwater, but also for wastewater. Due to its obsolete dimensions, the existing sewer system was totally incapable of coping with current-day hydraulic burdens; what’s more, the concrete pipes had suffered badly from corrosion.

Definitive decisions

In its major project, the city of Detmold had also decided to install new rainwater and infiltration-water sewers in a residential street in the city center. Despite the confined conditions – parts of the construction site were just six to eight meters wide – it was decided to construct the system using the open trench method, since the high number of house connections and also the parallel installation of the rainwater sewer precluded the possibility of using a trenchless method. The already existing concrete wastewater system remained in operation throughout the construction work. The municipal office responsible for the project opted for a sewer system constructed with vitrified-clay pipes, convinced that this was “economically the best alternative.”

The whole range: pipes from DN 150 to DN 1200

Starting in October 2013 and finishing in August 2014, Kögel Bau GmbH & Co. KG installed the combined wastewater system parallel to the rainwater sewer in the following sections:

  • 25 m with DN 300 to 900 vitrified-clay pipes
  • 240 m with DN 1000 vitrified-clay pipes 
  • 75 m with DN 1200 vitrified-clay pipes, and
  • 430 m of household connections with DN 150 vitrified-clay pipes

The sewer lies at a depth of 3.00 m to 5.50 m in silty subsoil, with some sections in soils of the LAGA Z2 classification; groundwater is not present in these soils. The house sewers were connected with the new main sewer using flexible couplings type 2B DN 150. The pipes were embedded by the DIN EN 1610, Type 1 method and the pressure tests were carried out section for section with compressed air; the entire system was finally inspected by a video camera mounted on a remote-control sled. 

The costs for the rainwater and combined wastewater sewer amounted to approx. 1.6 million euros. The decision in favor of vitrified-clay pipe systems as the most economical alternative for the combined wastewater sewer also plays a major role in the calculation of the wastewater charges used to finance the project. Not every local authority can offer its citizens such a positive benefit.


Client:Stadt Detmold | Planning: Ingenieurbüro für Bauwesen und Umwelttechnik Redeker GmbH, Detmold | Construction: Kögel Bau GmbH & Co. KG, Bad Oeynhausen | Construction-materials supplier: H. Fretthold GmbH & Co. KG, Bünde