Red7 Marine jack-up barge Haven Seariser 2 is working close to shore while its geotechnical engineering team take samples for Vattenfall’s Norfolk Vanguard and Boreas offshore wind farm developments off east England.
The 500-tonne rig is 29 metres long and is gathering borehole samples, down to a maximum of 30 metres.
The process will build an understanding of seabed sediment layering to decide the installation methodology for the wind farms’ main transmission cables at landfall at Happisburgh.
The barge is expected to be in place for about another two weeks, depending on weather, work progress and operations.
Several 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 started around where the onshore substation will be built near Necton, Vattenfall said.
“Offshore 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,” the company said.
Teams are collecting samples to learn about the properties of soil types at the site and are also completing cone penetration testing, it added.
The samples will be sent for testing in Fugro’s laboratories in Wallingford, UK, and Nootdorp in the Netherlands.
Data collected will be used to shape a ‘ground model’ for the wind farm and final cable design.
Other laboratories carrying out specialised testing include GEO’s laboratory in Denmark.
Vattenfall head of geoscience Andy Galbraith 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.”
The 1.8GW Norfolk Vanguard was granted consent on 1 July.
Onshore construction of Vattenfall’s Norfolk projects is due to start in 2122-23.
Offshore works are due to start in the mid to late 2020s.