General overhaul of the Poppenbüttel weir
Initial situation
The Poppenbüttel lock was built in 1870 as a chamber lock with an upper and lower head and a chamber length of 130 metres. Together with other locks and weirs, also known as impounding locks, it was used to dam the Alster River, enabling navigation from its source to its confluence with the Elbe. In 1961, the lower head of the lock was dismantled and the upper head was converted into a flap weir. Since then, a fish-belly flap gate with a single-sided lifting device and automatic level control has been used to regulate the water level. The weir also retains the Poppenbüttel pond, helping to balance irregular water flow.
Parallel to this main weir, a bypass channel runs along the eastern side, separated from the lock pond by a stoplog weir (secondary weir). This secondary weir is normally closed and only opened to drain water from the pond during maintenance.
Objective
The Poppenbüttel lock weir does not currently ensure ecological continuity. This is to be restored by integrating a fish pass in the form of a rough channel with a basin structure into the bypass channel. At the same time, the main weir is to be refurbished, as both the electrical and mechanical systems require renovation. The decision was made to convert the single-field flap weir into a two-field flap weir, each with a spindle drive. The modernisation will also improve operational safety and flood protection by automating the main weir and upgrading the level control system.
Services
For the refurbishment of the weir, we planned the energy, control and communication systems. All necessary components are housed in an outdoor concrete control cabinet with two internal enclosures, one for the electrical and control technology and the other specifically for the required frequency converters.
Each of the two fish-belly flap gates is operated by a spindle drive, with the motors controlled by separate frequency converters to allow for automatic weir control. A programmable logic controller (PLC) was included to monitor the drive sensors and evaluate the collected data. The control concept developed includes the operating modes: automatic, manual and off. For manual operation, a control panel was integrated into the cabinet.
To determine the facility’s total energy requirements, a power balance calculation was conducted, listing all consumers. The contract also covered the planning of cable routes and the low-voltage main distribution board with all necessary fuses, switches and protective devices. The control cabinet additionally includes a wall-mounted plug for a mobile backup generator to ensure continued operation of the weir control system during power failures. A new earthing system was designed, along with potential equalisation and surge protection, in accordance with the latest standards. In addition, the level measurement system was upgraded and provisions for CCTV monitoring and remote control of the weir were included. An uninterruptible power supply (UPS) was integrated to ensure continued system operation during brief power outages or voltage dips.
Challenges and special features
A particular challenge in this project was working within existing structures. This required a detailed analysis of the current conditions to integrate them into the planning of empty conduit routes, cable ducts and the positioning of electrical components. A high degree of flexibility and precision was necessary, especially since the work was carried out during the ongoing operation of the lock, requiring minimal disruption to water traffic.
Another key focus was close collaboration and coordination with all involved trades. Regular consultations and continuous communication ensured that the interfaces between the trades were clearly defined and potential conflicts were identified and resolved early. This played a crucial role in the successful implementation of the project.
Furthermore, innovative solutions were developed to meet the demands of working in an existing structure while simultaneously ensuring a sustainable and future-proof electrical installation.
