Danube culvert (Linz)

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Entrance building north

The Danube culvert , running between the areas of the municipality of Steyregg and the city of Linz , Upper Austria , forms an approximately 375 meter long connection between the left and right banks of the Danube at a depth of around 25 meters below the water level of the Danube . The culvert with an inner diameter of 2.40 m leads three sewage pipes and a fresh water pipe as well as a 110 kV high voltage line.

construction time

The groundbreaking for the construction of the culvert took place on September 23, 1974. The construction was carried out using the pressing process , which at the time (1974–1978) was considered a pioneering achievement in southern Germany, as there was no relevant experience for a project of these dimensions. Presses with a total pressure of 2200 tons (around 22 MN ) inserted press pipe rings made of reinforced concrete with a wall thickness of 30 cm and an outer diameter of 3.00 m. The puncture took place in August 1975, accurate to the centimeter. The press work (from north to south) lasted 16 weeks and went without incident.

The construction costs at that time amounted to around 50 million schillings (approx. 3.6 million EUR) and were divided in half into structural and mechanical equipment.

Location and technology

Pumps 5 and 6 in the pump house of the Danube culvert

The culvert runs from north to south at Danube river kilometer 2130.5, as the bottom of the main collector Urfahr (HSU) is about 1.6 m lower than that of the main collector middle (HSM). This also results in the need to pump the wastewater. This is done by six pumps with a total output of around 425 kW (570 hp) and a total delivery rate of 1,200 liters of wastewater per second. Two of the six pumps are freely controllable in terms of speed. In rainy weather operation, a maximum of five of the six pumps are used, one serves as a reserve. In the culvert with a diameter of 2.4 m, arranged around a central inspection passage, there are three sewage pressure pipes leading to the regional sewage treatment plant in Asten and one fresh water pipe (each with a nominal diameter of 500 mm).

Danube culvert Linz, to the north

The dry weather intake is around 200-350 liters per second and can be processed by one or two continuously running pumps. In rainy weather, the amount of wastewater is many times over. Quantities that exceed the maximum processing capacity of 1200 liters per second are dammed back gradually in the HSU (profile 3.9 × 3.45 meters, maximum inflow of 8000 liters of wastewater per second) or in the rain overflow basin Pleschingersee processed.

Since deposits occur in the pressure lines during normal operation, they are flushed through regularly. Two of the three pressure lines are closed with valves at intervals of 30 minutes and the wastewater is pumped through the remaining line with the power of three pumps (600 liters per second).

In 2019, a 110 kV line was also laid in the culvert, which will go online in October 2019 and ensure the security of supply for the new district in the port .

Final structures and structure

The semicircular, asphalted rain overflow basin is located 250 m south of the Pleschingersee shore, with embankments 130 m in diameter. The lake and basin are inland and deeper than the flood dam.

550 m south of the lake shore and 40 m away from the left bank of the Danube is the northern entry station to the inlet of the culvert in Plesching, Steyregg vulgo on the Urfahr side. The right-angled building is located in the floodplain and has a slim design on the ground floor, which means it is less in the way of flooding. The upper floor, which protrudes to the south-west to 3 times the width, has an entrance door that can be reached via an external staircase, and near the east corner of the flat roof, 4 outdoor conductors feed the electricity via 3 tension insulators.

Above the part of the pump shaft (mainly 16 m inside diameter) that is not covered by the concrete building, there is a rail crane for craning the pump motors.

In the 2 upper levels there are 3 sewage pumping units, each with a shaft-coupled gear unit and a belt-coupled electric motor with a diameter of about 70 cm. Up to 5 pumps deliver controlled delivery from a concrete reservoir into a thick collecting pipe, which feeds the 3 pipes via gate valves . These pipes are welded spirally from sheet steel and painted green; their knees to the horizontal in the direction of the culvert tunnels are embedded in concrete on the outside, as large forces may also occur intermittently in the area of ​​the flow deflection. There is also a blue painted drinking water pipe of the same nominal size , partly made of bare stainless steel .

Slightly converging, the 4 pipes are threaded into the tunnel, where they fill the bottom two of 3 "compartments" in the steel profile supports on the right and left in the tunnel, the pipes every 4 meters, two cable routes at the top and a central walkway near the ground Carrying gratings. The clearance profile of around 75 × 190 cm is sufficient for walking upright. The tunnel is illuminated and has drainage pumps in both sump pits.

The opposite pipe bends at the “outlet”, on the right bank on the “Linz side”, are also embedded in a concrete embankment. In addition, the upper tubes are extended parallel to the tunnel axis in welded struts that can absorb tension and pressure. A few meters inside the tunnel mouth, the 3 sewage pipes merge into gray fiber-reinforced concrete pipes, but the drinking water pipe, which occupies an upper position, into a pipe made of black polyethylene.

The boarding station on the right bank of the Danube is at Boats Feichtner, Linz, Saxingerstraße 5, not far from Industriezeile, just after the confluence with the commercial port. The riser shaft has a significantly smaller diameter than the pump shaft.

Oddities

An erroneous report from the City of Linz in 1999 incorrectly identified the Danube culvert (here pipes run in the culvert) as the location of the following animal finds instead of another canal (with wastewater with a free water level):

In February 1999 an approximately seven meter long crocodile was discovered while inspecting the diversion canal (not the Danube culvert). After two hours, the Linz professional fire brigade managed to catch the animal. First, it was brought into the empty teaching pool at the Ebelsberg sports complex. A crocodile enclosure was built in the Linz zoo especially for the animal of unknown origin, named by the firefighters Jürgen .

The pipe of the culvert is electrically illuminated. Contrary to the press release, there are also no rodents in the system of the Danube culvert pumping station. An intrusion of a reptile can be ruled out by securely closing the entry points and the regular weekly inspections.

Furthermore

Linz also has another culvert: the "Einziehdüker" installed by the company Bau und Montage GmbH, Perg, has a DN 500 mm and a length of 330 m.

Source

  1. ↑ a b c cf. Natural history chronicle of the city of Linz 1974: PDF (1.2 MB) on ZOBODAT
  2. ↑ cf. Natural history chronicle of the city of Linz 1975: PDF (1.6 MB) on ZOBODAT
  3. ↑ cf. Natural history chronicle of the city of Linz 1978: PDF (1.1 MB) on ZOBODAT
  4. ↑ Spectacular laying of cables under the Danube. In: ooe.orf.at . September 18, 2019, accessed September 18, 2019.
  5. ↑ Picture gallery: Excursion 2012 Danube culvert. ASKÖ water sports club Linz. April 16, 2012, accessed February 9, 2018.
  6. ^ "Animal" fire service in Linz, crocodile hunting in the Danube culvert. ( Memento from March 4, 2016 in the Internet Archive ) Press archive, City of Linz, vol. 46/029, February 15, 1999.
  7. ↑ Danube culverts Linz: Einziehdüker DN 500, length 330 m. ( Memento from March 4, 2016 in the Internet Archive ) Website of the company GLS Bau und Montage GmbH.

Web links

Coordinates: 48 ° 18 ′ 44.4 "  N , 14 ° 19 ′ 54.9"  E