Construction of a new storm surge barrier at the Geeste estuary in Bremerhaven, Germany
Initial situation
In the years 1960/1961, the storm surge barrier at the mouth of the Geeste into the Weser was built with the six-lane folding bridge running over it. Shortly after completion, the structure passed its first test by preventing the city of Bremerhaven from being flooded by the storm surge in February 1962. At that time, a water level of 5.35 m above sea level was reached.
The barrier, with its two pairs of mitre gates arranged one behind the other, protects not only Bremerhaven but also the Lower Saxony hinterland from flooding, and was therefore jointly financed by the states of Bremen and Lower Saxony. At the time of construction, some shipyards were located upstream, which is why the bridge over the barrier was implemented as a folding bridge with a passage width of 24 metres. Nowadays, it is rarely opened.
Due to climate change, higher storm surges are expected in the future. Since the barrier cannot be retrofitted due to the bridge running over it, the structure does not offer reliable coastal protection for the future. Therefore, a new barrier and its corresponding inspection cover will be newly constructed.
Task
The new storm surge barrier will be located in the area of the ferry terminal or buoy yard of the WSA (Waterways and Shipping Authority) Bremerhaven. This positioning will protect parts of the "Bussestrasse" and the WSA Bremerhaven. The new construction will also involve extensive dyke relocations. Once all measures are implemented, they will provide protection for the next 100 years.
As part of the General Coastal Protection Plan of 2007, the height for dykes was set at 7 metres and the height for solid structures at 7.75 metres. The facility is designed to withstand a flood up to 6.70 metres. It is also designed so that a subsequent increase of 0.75 metres is possible. The costs for the new barrier amount to approximately €31 million.
Services
The new barrier will be equipped with two sets of mitre gates arranged in the same direction to ensure redundancy and double dyke security. Each mitre gate wing is driven by a hydraulic cylinder. On each side of the barrier, a hydraulic unit (each 74 kW) powers the two mitre gate wings. To ensure the gates can be operated at reduced speed in the event of a motor or pump failure, the hydraulic units are equipped with a redundant motor pump group. The drives are powered via frequency converters. All machine technology, all control cabinets for the drives and the control technology are housed in an underground operational room on each side of the barrier.
The system is controlled via a PLC control system with central control and an individual control for each set of mitre gates. ProfiNET is used as the bus system for networking the control and steering technology. On each side of the barrier, a switchgear is planned for controlling the drives of the hydraulic units, the compressors for the air bubble system and the silt flushing pumps.
In addition to the drive and control technology, we are also tasked with planning the power distribution. Both the main and emergency power supply feed into a low-voltage main distribution, from which the sub-distributions on both sides of the barrier and the UPS system are supplied. The UPS system ensures important system components such as the control and steering technology, the level and video systems continue to receive power for one hour in the event of a power failure. In addition, a feed-in option for a mobile emergency power generator is planned on each side of the barrier. Nevertheless, simultaneous emergency power supply from both sides will not be possible. In addition to the areas mentioned, the power supply for the air bubble systems in the gate chamber niches was also planned.
In normal operation, the storm surge barrier is controlled from the control stand of the Kaiser lock. However, a local control station and a manual control station are provided on each side of the barrier to operate the facility in emergency mode and for maintenance and revision work on site. We designed the required control and operating technology for the remote control as well as for the control points on site. Part of our assignment was also planning the video system and the changeover and loudspeaker system, including connection to the Kaiser lock's systems. In addition, the navigation signals, the lighting of the barrier and the operational building, as well as the earthing system and protective equalisation were planned.
