Works to install the Borssele Beta export cable in the Netherlands will set TenneT back an additional € 50 million after contractors discovered unstable soil along the cable route.
Namely, the cable installation contract TenneT signed with NKT and VBMS (now Boskalis Subsea) in 2016/2017 will now be worth € 210 million, instead of € 160 million.
The reason for this is that the challenging physical conditions of the Northern slope of the Honte, part of the cable route, have been discovered during cable installation works for the Borssele Alpha platform and have now been marked as unforeseeable.
Although a survey to investigate the soil conditions of the subsea cable route was performed in 2015, TenneT said it had not indicated these specific physical conditions of the Northern slope of the Honte.
“This route survey has been executed by an expert contractor who had extensive experience in performing similar surveys. The data of these surveys did not indicate the physical conditions of the Northern slope of the Honte. When executing the Sea Cable installation these conditions were discovered and made it necessary to apply a different working method.”
TenneT awarded Boskalis Subsea (VBMS) and NKT Cables a contract to supply and install two Borssele Alpha export cables with an option for Borssele Beta in November 2016 .
The option for Borssele Beta was awarded at the end of October 2017, with an additional 7-kilometre interconnector cable to be installed between the Borssele Alpha and Beta offshore substations.
The two companies installed the Borssele Alpha export cables in 2019.