HomeProjects HDDs Burbo Bank Windfarm Extension

HDDs Burbo Bank Windfarm Extension

Liverpool Bay, United Kingdom

Dong Energy is currently engaged in construction work to expand the Burbo Bank wind farm in Liverpool Bay. The VolkerInfra/VBMS joint venture was commissioned to carry out the work for landfall of the export cable from the wind farm extension. Visser & Smit Hanab was subcontracted to perform the two required horizontal directional drillings, using the 250-tonne drilling rig.

 

The first drilling to be carried out was a HDD landfall, which involved drilling from the land to the beach. The drilling crossed under a railway track, a caravan park, a golf course and a sea defence wall and had a length of 638.5 metres. Because the exit point was on the beach, allowances had to be made for the large difference in tides. For the undersea cable, a PE100 SDR 13.6 cable pipe with a diameter of 800 mm was installed. This drilling was performed between mid-May and mid-June 2015.

The second drilling crossed the A525 and the River Clwyd and has a length of approximately 520 metres. Within it was installed a bundle consisting of 3 PE100 pipes with a diameter of 225 mm and 1 PE100 pipe with a diameter of 125 mm. The subsoil for this drilling consisted of very hard clay alternating with a lot of gravel and stones. This therefore represented a big challenge for the Visser & Smit Hanab drilling crew. Because the exit point was difficult to access, a temporary mud return pipe was also drilled alongside the drilling in order to transport the drilling mud to the entry point. The pull-back operation was successfully performed on 5 July in close cooperation with and to the satisfaction of the client.

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