Ostsee Anbindungs-Leitung Project
Trench Dredging & Backfilling, Microtunnel Marine Works, Concrete Mattress Installation, Reef Reinstatement
In order to meet the German and European demand for natural gas and to avoid potential gas shortages, Gascade Gastransport GmbH is developing an offshore natural gas transmission system near Lubmin in Mecklenburg-Vorpommern, Germany.
The Ostsee Anbindungs-Leitung (OAL) Project concerns the construction of an offshore natural gas transmission system consisting of a 48” diameter pipeline from the onshore facility near Lubmin (Germany) towards the onshore facility near Mukran (Germany), through the Baltic Sea over a distance of approximately 50km, where a Floating Storage and Regasification Unit (FSRU) will be permanently moored in the Port of Mukran.
In August 2023, Rohde Nielsen A/S was awarded the contract, which includes:
- Trench dredging of 50km (2M m3)
- Marine works at two exit pits: one in Lubmin and the other in Mukran. Marine works including:
-
- 2 x dredging of exit pit, exposing a 100t tunnel boring machine.
- 2 x recovery of the tunnel boring machine by use of heavy lift barge.
- 2 x flooding of 750m microtunnel.
- 2 x unmounting and recovery of microtunnel bulkhead.
- 2 x installation of bellmouth and endcap on microtunnel.
- 2 x wirelay of a 1,500m (129mm) pull-in wire for pipepull.
-
- Installation of 700,000m3 intimate fill material around the exposed as built pipeline.
- Trench backfilling of 50km (~ 1,300,000m3).
- Installation of 100 concrete mattresses at 3rd party crossings.
- Reinstatement of subsea reefs (20,000t).
- All associated turbidity monitoring and environmental management.
- Bathymetric surveys to support all operations listed above.
The dredging volume was in the region of 2M m3 consisting of sand, pre- and post-glacial clays and peat. Dredging was carried out in water depths ranging from -2.0m (LAT) to – 22.0m (LAT).
The works commenced on site on the 21st of August 2023 and were completed under a fast-track scheme, to a level allowing Gas-In, on the 15th of February 2024.
- Location: Baltic Sea (GER)
- Scope: 2,000,000m3
- Client: Gascade Gastransport GmbH
- Year: 2023-2024
The fleet that made it possible
- Njord R
- Balder R
- Ask R
- Embla R
- Magni R
- Sif R
- Tjalfe R
- Toste R
- Heimdal R
- Mjølner R
- Gungner R
- Ajax R
- Gere R/ Freke R
- Baugi R/ Bjarke R
- Roar R/ Helge R
- Hugin R/ Munin R
- Skjold R
- Skinfaxe R
- Rimfaxe R
- Sleipner R
- Hopper capacity
- 6,000m3
- Length overall
- 111.3m
- Breadth
- 19.4m
- Draught loaded
- 7.5m
- Draught unloaded
- 5.4m
- Dredging depth
- 62.0m
- Hopper capacity
- 6,000m3
- Length overall
- 111.3m
- Breadth
- 19.4m
- Draught loaded
- 7.5m
- Draught unloaded
- 5.4m
- Dredging depth
- 62.0m
- Hopper capacity
- 2,700m3
- Length overall
- 85.4m
- Breadth
- 17.4m
- Draught loaded
- 5.1m
- Draught unloaded
- 3.1m
- Dredging depth
- 52.0m
- Hopper capacity
- 2,700m3
- Length overall
- 85.4m
- Breadth
- 17.4m
- Draught loaded
- 5.1m
- Draught unloaded
- 3.1m
- Dredging depth
- 52.0m
- Hopper capacity
- 1,550m3
- Length overall
- 75.8m
- Breadth
- 12.8m
- Draught loaded
- 3.8m
- Draught unloaded
- 2.2m
- Dredging depth
- 28.0m
- Hopper capacity
- 2,150m3
- Length overall
- 80.0m
- Breadth
- 13.8m
- Draught loaded
- 4.6m
- Draught unloaded
- 2.9m
- Dredging depth
- 24.0m
- Hopper capacity
- 800m3
- Length overall
- 57.5m
- Breadth
- 14.8m
- Draught loaded
- 4.1m
- Draught unloaded
- 2.3m
- Dredging depth
- <100.0m
- Hopper capacity
- 525m3
- Length overall
- 45.7m
- Breadth
- 10.5m
- Draught loaded
- 3.5m
- Draught unloaded
- 2.7m
- Dredging depth
- <28.0m
- Hopper capacity
- 2,100t
- Length overall
- 84.0m
- Breadth
- 18.7m
- Draught loaded
- 5.8m
- Draught unloaded
- 4.4m
- Dredging/Installation depth
- <60.0m
- Bucket size
- 3.5-16.0m3
- Length overall
- 51.5m
- Breadth
- 17.0m
- Draught loaded
- 2.0m
- Towing draught
- 3.8m
- Dredging/Installation depth
- 22.0m
- Bucket size
- 5.4-11.0m3
- Length overall
- 54.8m
- Breadth
- 15.2m
- Draught loaded
- 2.8m
- Towing draught
- 3.6m
- Dredging/Installation depth
- 20.0m
- Bucket size
- 700lt
- Length overall
- 51.2m
- Breadth
- 11.7m
- Draught
- 3.1m
- Dredging depth
- 4.0/19.5m
- Hopper capacity
- 1,500m3
- Length overall
- 68.4m
- Breadth
- 14.0m
- Draught loaded
- 4.2m
- Draught unloaded
- 2.9m
- Hopper capacity
- 1,225m3
- Length overall
- 49.8m
- Breadth
- 14.0m
- Draught loaded
- 4.3m
- Draught unloaded
- 1.1m
- Hopper capacity
- 950m3
- Length overall
- 60.3m
- Breadth
- 11.0m
- Draught loaded
- 3.5m
- Draught unloaded
- 1.8m
- Hopper capacity
- 700m3
- Length overall
- 59.0m
- Breadth
- 9.5m
- Draught loaded
- 2.9m
- Draught unloaded
- 1.8m
- Length overall
- 11.8m
- Breadth
- 3.9m
- Draught
- 1.3m
- Speed
- 33.0kn
- Length overall
- 27.0m
- Breadth
- 9.1m
- Draught
- 3.2m
- Main engine
- 2×1,230kW
- Speed
- 12.0kn
- Bollard pull
- 38.5t
- Length overall
- 23.3m
- Breadth
- 8.0m
- Draught
- 2.1m
- Main engine
- 2x634kW
- Speed
- 10.5kn
- Bollard pull
- 22t
- Length overall
- 15.3m
- Breadth
- 6.0m
- Draught
- 1.6m
- Main engine
- 2x224kW
- Speed
- 7.0kn
- Bollard pull
- 7.6t
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