Odd sight for beachgoers at Happisburgh as jack-up vessel takes samples offshore

The Haven Seariser 2, owned by Ipswich-based Red7 Marine, off Happisburgh, where geotechnical engineers are collecting soil samples for seabed data to decide the route of the cable from the offshore turbines on Vattenfall’s Norfolk Vanguard and Norfolk Boreas wind farms. Picture: Vattenfall (Image: Archant)

The Haven Seariser 2 has been stationed close to shore while its geotechnical engineering team take samples ahead of the construction of two huge offshore wind farms planned by Swedish energy giant Vattenfall – Norfolk Vanguard and Boreas

The 29-metre long barge is fitted with long support legs jacked down onto the seafloor. It is gathering borehole samples down to a maximum of 30 metres.

Andy Galbraith, Vattenfall’s head of geoscience, said: “The information gathered during these site investigation surveys will be used to fine tune the design of the export cable and associated installation techniques.

“Horizontal directional drilling will be considered for installing the cable underneath the beach and the area of the shore which is submerged at high tide and exposed at low tide. These surveys will help determine the best technique to use.

“A jack-up vessel provides a very stable sampling environment compared to other offshore drilling rigs and this is important to preserve the quality of the samples.

“It also helps that the current weather conditions are favourable for the campaign.”

Day and night shift crews working on the vessel – which is owned by Red7 Marine of Ipswich – are transported by boat to and from Lowestoft harbour each day, a journey of 25 miles.

The process will build an understanding of seabed sediment layering to decide the installation methodology for the wind farms’ main transmission cables at their landfall at Happisburgh.

Larger vessels are working further offshore carrying out similar sampling in a four-month campaign by geo-data experts Fugro.

Onshore site investigations have also begun around where the onshore substation could be built near Necton.

Data will feed into planning the most efficient turbine locations within the array, appropriate foundation design, as well as the final cable route from the turbines to connect into the National Grid at the onshore project substation.

Norfolk Vanguard was granted permission earlier this year, and a decision on Boreas is expected by April 12, 2021.The vessel will be in place for about two weeks.