A cascade weir has been connected to the main rainwater sewer on the Innovation Campus since the end of October 2025. This complex system makes it possible to optimally control the storage volume of a sewer as required. This was announced by Stadtwerke Offenbach Innovationscampus GmbH & Co. KG. The associated full closure of Mainstrasse was already lifted on November 14 - three days earlier than planned.
The construction site has also been used since the end of September to simultaneously lay water pipes for the water supply association in the city and district of Offenbach (ZWO) and empty conduits for Energienetze Offenbach GmbH (ENO) to expand Offenbach's electricity grid. This meant that three construction measures could be combined so as not to cause any more inconvenience due to staggered full road closures.
Cascade weir was installed up to ten meters deep
In recent weeks, the focus has been on the construction work for the connection of the sewer: This sewer had to be laid at a depth of around six meters below the roadway using the open construction method. The wastewater sewer was connected to the municipal main collector (the largest sewer in a wastewater system) in Mainstraße, which is very deep there due to the gradient situation. Rainwater, on the other hand, continues to be discharged into the Main via the connection to the cascade weir. In order to prevent a possible backflow of the Main water, the cascade weir, which also includes a concrete weir tower with a diameter of four meters, was installed up to ten meters deep in the ground on the Innovation Campus.
In simple terms, the hydraulically operated weir works like a kind of giant backwater flap that is connected to other shafts and pipes. The system gradually slows down the water and is also designed to dam back rainwater if necessary. In dry weather, this also makes it possible to remove deposits in the sewer with regular flushing. In this way, a cascade weir prevents major damage and minimizes potential renovation costs. According to the contractor, the weir is designed to last 100 years.