Germany – Architectural, construction, engineering and inspection services – ASG Abwasserentsorgung Salzgitter GmbH - Neubau/Sanierung zweier Ablaufleitungen DN700

The Abwasserentsorgung Salzgitter GmbH (ASG) operates the Salzgitter Nord sewage treatment plant in the northern part of the city. The wastewater treated at the Nord sewage treatment plant is pumped through two parallel pressure pipelines in the area of the former sewage treatment plant site at Feldstraße 2 into the receiving water Krähenriede. The pressure pipelines, which run largely in parallel, were laid between 1992 and 1993. The material used was HOBAS fibre cement with epoxy coating. The total length of each pipeline is approximately 3,320 m. The pipes were installed in 5 m long segments with spigot sockets and feature various bends and couplings. Some of the spigot connections were provided with concrete abutments. The nominal diameter of the pipes is DN 700 with an outside diameter of 718 mm. The system was designed for the pressure stage PN6. Several damage incidents have occurred on the pipelines in the last two years. On 08.10.2024, the damage did not occur at a typical weak point, such as sockets or couplings, but in the middle of the pipe. For this reason, a feasibility study was commissioned to examine the possibilities for the rehabilitation of the wastewater pressure pipelines between the KA Nord and the receiving water Krähenriede. As part of the feasibility study, it was to be examined whether rehabilitation of the existing pipelines is technically feasible, hydraulically acceptable and economically viable, or whether a complete renewal is necessary. As a result of the feasibility study, based on the cost comparison calculation carried out as well as the technical, hydraulic and operational framework conditions, the renewal of the pressure pipelines in open construction method is recommended as the preferred option. The first pipeline should possibly be laid in an alternative route. For the second line, it is to be examined whether the line is to be newly built or rehabilitated. A route survey is to be prepared. Cleaning possibilities should be included in the planning of the line. The total costs (2 sections) for the renewal of the pressure pipeline are estimated at around 12.6 million EUR (gross). Work should begin immediately after the contract is awarded and the measure should be implemented as quickly as possible.