Eastern barrier
The Ostesperrwerk is a barrage that protects the Oste , a left tributary of the Lower Elbe , from storm surges .
After the storm surge of 1962 , in which 19 km of the Ostedeich were damaged and water from over 36 so-called ground fractures flooded approx. 10,000 hectares of land, a barrage was planned for the Oste and construction began two years later. The catchment area of the Oste covers an area of approx. 68,200 ha. The drainage is supported by 41 pumping stations along the Oste. Due to the eastern barrier, the dike line of the Elbe is shortened by 135 km during a storm surge . The eastern dykes are still required in normal tidal conditions and are used and maintained as a second line of dykes.
Since a storm surge in the Oste due to the destruction or flooding of the eastern barrier was not taken into account in the planning, the eastern dikes are neglected today, although they are about 60 cm higher than the barrage itself, which is 7.8 m above sea level . There are two other points in the dike defense line from Cuxhaven to Hamburg with lower dike heights: the Otterndorf lock is approx. 80 cm deeper than the new dykes at Otterndorf, and the dike in Altenbrucher Bogen has probably sagged by approx. 50 cm due to the last deepening of the Elbe .
description
The structure consists of five openings, each 22 meters wide. In the two right and left openings, almost semicircular shell-shaped segments with a weight of 70 t were installed. These shells are driven by electric motors and are in the rest position with the opening facing downwards in order to show the least possible visual obstruction for shipping (see pictures). The connection between the drives and the counter bearing was realized with cardan shafts. To be on the safe side, all locks are double.
The navigable middle part of the barrier was realized with a pair of mortise gates each weighing 75 t and a bascule bridge consisting of two prestressed concrete parts . This construction was necessary for a dike defense and connection path between Balje and Neuhaus . The two wings manage without counterweights, as a powerful hydraulic system with a large punch each was installed. The track is 5 meters wide and designed for a maximum weight of 2.8 t.
Heaters with a total output of 50 kW in the concrete walls and the mortise gates as well as an air bubble system with two compressors are to prevent the barrier from icing up and silting up. Two emergency diesel generators of 137 kVA each and three UPS (uninterruptible power supply) for around 20 minutes of emergency power, four air bags behind the caulking gates and two mobile hydraulic pumps enable the barrier to be closed quickly even without an external power supply.
Planning
Even before the storm surge of 1962 there were various plans for a barrage on the Oste. Preparatory work for a barrage near Hechthausen took place around 1930 . In the years 1935/1936 there was a "preliminary work office", and in the 1950s the Stade Shipping Office carried out plans for a barrage at the mouth of the East. In 1961 and increasingly in 1963, various model tests were carried out at the Franzius Institute in Hanover .
The water and soil association Oste acted as the builder, 30% of the barrage was paid for from the Lower Saxony coastal protection plan , and the federal government contributed 70% to the structure. The planning approval authority was the Stade district government, the building authority was the Stade Waterways and Shipping Authority; it is operated by the Stade Waterways and Shipping Authority, and since 1978 the WSA Cuxhaven .
Technical specifications:
- Width: 136.5 m
- Length: 42.2 m
- Width of the five openings: 22 m
The construction
In October 1964, construction work began east of the natural Ostelauf in the Balje district, districts Hörne and Neuhaus , near the confluence with the Elbe, by digging a large open excavation pit, which was kept dry by lowering the groundwater using 101 wells with associated pumps. This huge pit was protected from possible storm surges by newly constructed dikes , a large transshipment point for gravel and other building materials was built on the old arm of the Oste, in today's Baltic Sea - still recognizable on the sheet pile wall . In the spring of 1966 all preparatory work was completed and the concrete work could begin. Part of the sole with the corresponding concrete pillar was poured in one work step. A total of 20,000 m³ of concrete was processed. The entire concrete body is framed with a steel sheet pile wall as well as wing sheet pile walls by means of a steel tension pile anchorage.
timeline
October 1964
A 1.8 km long access road and a sheet pile wall loading point for all building materials will be built.
Fall 1965
Beginning of the groundwater lowering to 15 meters below sea level (NN), 101 wells for the lowering to −14 m NN and 16 wells to −22 m NN are drilled. These deep wells also serve as relief wells. At the same time, dikes were built to secure the excavation pit that is now being built.
Spring 1966
Start of concrete work. The concrete floors are 1.6 m thick, the pillars 30 or 40 m long, 4 or 5.5 m wide and have a height of 12.6 m, which means a height of 7.8 m above sea level (the newer Today dikes are approx. 60 cm higher). The sole parts and pillars were always poured together to achieve a better connection. The largest part of the sole is almost 4000 m². 20,000 m³ of B 225 with four separate grain sizes up to 70 mm were installed. This Portland cement from the nearby Hemmoor cement works with the designation 275 “Aquafirm” was built with sand from sand pits in the neighboring Cadenberge and with gravel from Denmark. There was always a cement supply of approx. 400 t with retarder. Two "Ibag compulsory mixers" with a capacity of 1.5 m³ each, automatic loading and a continuous output of 60 m³ concrete per hour as well as a gantry crane 52 m long and 26 m high with a 10 t bucket supplied the construction site with concrete.
October 1966
Beginning of the excavations for the new course of the river, this cut is approx. 2.6 km long, has a width of 155 m and its bottom is at −5 m in relation to NN. During the earthworks, over 3 million m³ of earth was spent, one third each was used for the connecting dykes, driveways, summer dykes and the old arm shoring, for the elevation of the island with the Natureum between the old and new east, and the last third as a ground reserve for the new Kehdinger dyke, today's height 8.2 m, is planned. In the process, earth flushes were achieved with cutter excavators through an intermediate pumping station up to a distance of 10 km. In the vicinity of the barrage, the new embankments with revetments made of rubble stones of class 3 as well as gravel and pile walls with a length of 6 m were driven in.
Fall 1967
The hydraulic steelwork has been completed, all closures are double for safety reasons, the upper edge is calculated at 7 m above sea level, plus the concrete slab, this results in a height of 7.8 m above sea level.
Summer 1968
All earthworks and the damming of the old arm are finished. Three cutter excavators with a total hourly flushing capacity of 3,000 m³ dam the old river in two places, with the pressure dam on the Elbe side being implemented as the main dike.
15th October 1968
The barrage is ready for use - one year ahead of schedule, although further work was required: So the Neuhauser had Ostebogen be secured, the drainage had within the dike changed and new sluices are dug. The tail unit at the shipping opening as well as two ship piers, water levels, three residential buildings, a workshop building and a slipway for the emergency closures had to be built, as well as the dike defense roads and numerous clay covers , seeds and plantings on the island.
1994
The entire electrics and hydraulics are replaced in order to bring the plant up to the state of the art; every important unit is redundant. If necessary, a lot can be moved by its own weight.
building-costs
The costs for the construction of the barrage including the work listed here should cost about 57 million DM according to the planning. Contrary to the currently usual excess of the estimated construction costs, only 54 million DM were required.
Use of the barrage
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The operating regulations stipulate that the barrage must close the gates if water level forecasts and observations indicate a water level of over one meter above the MThw . In addition, the Rockstedt gauge is monitored and is included in the selection of the closing time. The year with the most frequent closings (120) was the year 2002. The year with the lowest closings (7) was 1996 (as of 2009). Since 2006 it has been observed that the barrage is closed later. B. in the port of Neuhaus boat yards and old jetties partially flooded. There the water is around 30–50 cm higher than in previous years. Reasons for this are not officially given, assumptions about the changed condition of the barrage are always a topic of conversation.
Web links
Individual evidence
- ↑ The No. 3 is a lighter and was built under construction number 253 in 1925 by Henry Koch at the shipyard for a German owner. It had a load capacity of 185 t, 26.50 m in the CWL and a width of 9.50 m.
Coordinates: 53 ° 49 ′ 6 ″ N , 9 ° 2 ′ 32 ″ E