The final trenchless structure of the Celtic Interconnector project has now been completed, marking a major milestone in this pioneering energy initiative.
The last phase involved a 126m horizontal directional drilling (HDD) river crossing in Brittany, France, concluding 15 months of intensive trenchless operations.
This final crossing, executed by Groupe Gendry and closely monitored by OPTIMUM, passed 10m beneath a coastal river, cutting through both sands and granite rock.
Located in a wetland zone with restricted access, the operation presented significant challenges; however, meticulous monitoring of drilling and mud parameters allowed the team to successfully avoid any breakouts. This careful approach was particularly critical given the nearby protected woodlands and residential areas.
Post-drilling inspections have confirmed the structural integrity of the HDD, which is now ready to receive the high-voltage cables: two HDPE ducts of DN 225 and five HDPE ducts of DN 63.
This achievement marks another significant step forward in Europe’s energy transition.
The Celtic Interconnector will be the first high-voltage direct current (HVDC) link between Ireland and mainland Europe, enhancing the safety, stability and quality of electricity supply between the two regions.
From the earliest stages, OPTIMUM has supported Réseau de Transport d’Électricité (RTE), contributing to the selection of the landfall site, the preparatory engineering, and the oversight of all trenchless construction works.
This included three HDD landfalls, totalling 1320m drilled through hard granite, an 84m AVN 1200 microtunnel beneath railway tracks cut through slate schist, and the final 126m HDD crossing beneath the river.
Do you have news for the international trenchless industry? Contact journalist Gerald Lynch at gerald.lynch@primecreative.com.au
