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Celtic Interconnector: All trenchless works finished !
17 April 2025
The last trenchless structure for the Celtic Interconnector project has just been completed: a 126-meter-long HDD river crossing that marks the end of 15 months of intense trenchless work in Brittany.
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Celtic Interconnector ; Microtunnel ? DONE !
21 December 2024
Construction of the onshore link from the coast to RTE’s converter station is in full swing. The 84-metre-long AVN 1200 microtunnel section under the River Élorn and the Paris – Brest railway is now complete and the cable ducts installed.
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Can just one core drill really make a difference ? Yes !!!
3 October 2024
Crossing just 40 metres under SNCF rails in Montvicq (Auvergne-Rhône-Alpes) was the missing link in a 20 km project to enable RTE to connect an industrial client in central France to its network.
Following initial feasibility studies, OPTIMUM advised that an additional soil investigation was needed to ensure the geology of the job site was fully appreciated. The results were THE determining factor in selecting the right trenchless technique. Auger boring with a downhole hammer delivered all the power necessary, in the limited space available, to get through the identified granite massif and rock formations under the tracks.
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Microtunnel under France’s busiest transport links
5 September 2024
Completion this week of an important phase of RTE’s Envision project with the successful installation of a 130-metre-long microtunnel near Arras in northern France.
Within the framework of the project owner’s network extension, the DN1200 microtunnel now passes under both the Paris – Lille highspeed railway tracks as well as the 6-lane A1 motorway, two of the country’s busiest transport links.
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Microtunnel at the foot of the Pyrénées
11 July 2024
Proud to have accompanied project owner RTE for the successful completion of a new microtunnel under the River Neste at the foot of the Pyrenees in southern France. The project falls within the framework of RTE’s ongoing network renewal and extension in the region.
Despite the relatively short tunnel length, the 65-metre-long, 12-metre-deep, AVN1800 microtunnel merited close monitoring, given the complex and varied geology of the area. The hard and abrasive nature of the successive alluvium, limestone, marble and granite blocks, made for challenging conditions and called for supervision by trenchless specialists.
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Chevalet : First phase complete
25 April 2024
Proud to announce the successful first phase of RTE’s Chevalet project, which was completed this week in northern France. The 130-metre-long, 1.5 metre wide microtunnel, carried out by EIFFAGE GENIE CIVIL RESEAUX, crosses under the A1 motorway as well as the high-speed Paris - Lille railway link.
The Chevalet project, part of France’s renewable energy development programme, called for in-depth geotechnical analysis and engineering design, which was carried out by OPTIMUM from 2020 to 2022 in collaboration with RTE’s project team. OPTIMUM also accompanied RTE during the contractor selection phase and monitored the construction work, which took place between January and April 2024, ensuring all environmental, technical and regulatory constraints were respected.
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8 HDD crossings to connect new data centre
1 February 2024
Proud to have accompanied RTE for the grid connection of a major new data centre southeast Paris, which was successfully completed this week. Parallel HDPE duct bundles (3 x DN225, 1 x DN110, 2 x DN75) now pass under the busy A6 motorway, access ramp and adjoining roads through 8 HDD crossings (2 x 262ml, 2 x 217ml, 2 x 183ml and 2 x 90ml) to link the data centre to RTE’s substation.
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Celtic Interconnector HDD works begin
31 December 2023
Now we’re starting ! Proud to be alongside RTE this week as the construction of the HDD landfall begins on the coast of Brittany for the 700 MW Celtic interconnector.
This high-quality interconnection will link the south coast of Ireland to northern France, allowing the two countries to export / import electricity to and from each other whenever necessary, strengthening energy security. Supported by the Connecting Europe Facility (CEF) EU funding programme, this will be Ireland's first interconnection with continental Europe.
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Maintaining Abidjan’s electricity with HDD
23 November 2023
Proud to have accompanied HDI - HORIZONTAL DRILLING INTERNATIONAL for the installation of two 634m and 621m long HDD crossings under the Vridi canal in the Ivory Coast; the project is now successfully complete.
Installing the cables using trenchless HDD, rather than via overhead pylons, will ensure Abidjan’s electricity supply is maintained no matter how large the ships passing through the canal to and from the newly expanded port.
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NeuConnect landfall works complete
30 October 2023
Alongside HDI this month for the successful completion of landfall works for the NeuConnect interconnector project. Once connected, this will create the first ever direct power link between Germany and the United Kingdom.
Drilling through essentially silty clay soils, 3 parallel 420-metre-long HDD landfall crossings were completed to house DN400 HDPE ducts where the subsea cables will transition to the onshore underground cables in Kent, England.
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Yeu-Noirmoutier Offshore Windfarm : problem solved
19 October 2023
No trenchless crossing is too small to benefit from the expertise of specialist engineers. Further proof of that just a few days ago as INEO’s 123-metre-long HDD was successfully completed on the French Atlantic coast, a crucial step in the connection of the Yeu - Noirmoutier Offshore Windfarm.
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Marine geothermal energy network extension
26 June 2023
Proud to have helped Engie complete a further network extension of project Thassalia in Marseille last week, to supply both heat and cooling to city buildings through marine geothermal energy.
But just a few months ago, the question of how to cross the tramway on boulevard des Dames in the heart of the city risked derailing the project. OPTIMUM engineers were contacted and, after conducting detailed geotechnical analysis and a 3D modelling of the underground networks, proposed modifying both the crossing path and the trenchless technique. The resulting design proposal, using a large diameter traditional hand boring technique to install the 4 insulated pipes (2 x DN350 and 2 x DN300) in a DN1600 concrete microtunnel, enabled the project to move ahead.
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EOLMED offshore wind turbine project
27 April 2023
Round the clock dedication accompanying HDI on the Mediterranean coast for Friday’s successful installation of an 860-metre-long HDPE pipe for RTE’s EOLMED offshore wind turbine project.
The DN400 HDD landfall will connect 3 floating turbines some 24km off the coast of Port-La-Nouvelle, near Narbonne, to the French electricity network.
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Railway crossing Pont VII to Sainville
27 October 2022
Proud to have accompanied RTE throughout the Pont VII to Sainville trenchless crossing, now successfully installed. Drilling the curved 240m long HDD under an SNCF freight line in a heavily congested overground and underground environment called for the highest levels of vigilance and expertise.
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Supporting project owners at every step
28 July 2022
• Persan : Six 175m - 200m long HDD crossings under rivers and the A16 Paris – Calais motorway
• Noyales : Four 90m – 120m long HDD crossings under rivers and roads in arable / pasture land
• Romainville : Six 85m – 110m long HDD crossings in a heavily built-up urban environment
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OPTIMUM solution for ENEDIS
16 June 2022
Proud to have made it possible this week for ENEDIS to complete the missing link in reinforcing the electricity supply in Deauville, northern France. The project had been blocked for several years until OPTIMUM were called upon to solve the problem less than 12 months ago.
OPTIMUM engineers completely redesigned the trenchless project, filed a new SNCF dossier and handled negotiations to ensure all concerns were addressed and authorisations obtained to safely cross under the Lisieux to Deauville and Deauville to Cabourg railway lines, the River Touques as well as the D27A road.
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HDD landfall Provence Grand Large
2 June 2022
Great to be part of another big renewables project, accompanying EDF Renouvelables during the successful installation of the HDPE duct bundle for the Provence Grand Large offshore wind turbine pilot project. The 743-metre-long HDD landfall will ultimately connect 3 “floating” turbines 17km off the coast of Port-Saint-Louis-du-Rhône, near Marseille, to the French electricity grid.
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Calvados offshore windfarm
6 January 2022
2021 was rounded off in great fashion as OPTIMUM accompanied RTE in the successful completion of the trenchless drilling section of the Calvados offshore windfarm project on the Normandy coast.
No less than 5 dual HDD crossings, from 100m to 430m long, were drilled through Caen limestone to carry the 225 kV cables under 2 roads, a dual carriageway, a canal and the river Orne. This trenchless section is a key step in connecting the offshore wind turbines to the electricity substation.
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HDD under the River Adour
26 October 2021
Another great moment this weekend, accompanying RTE during the successful installation of an HDPE duct bundle for its 63 kV cable in a fully curved 250m-long HDD project in Dax, southwest France.
The HDD crossing passes under the River Adour, a river with a high water flow-rate which gives rise to frequent flooding. The environmentally sensitive nature of the area and the associated need to preserve the riverbanks, aquifers and spa water table, meant that the challenge of finding the best bore path was key to success.
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France’s 3rd offshore wind farm takes shape
5 February 2021
After Saint Nazaire and Saint Brieux, Fécamp will soon be France’s third offshore wind farm. To this end, Rte is currently building a dual electric link ; an 18km maritime connection going underground for a further 43km onland. By 2023, the two 225 kV lines will connect the Fécamp wind farm to the Pont-Sept substation, near Le Havre on France’s north coast.
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Trenchless calculations unique in France
1 December 2020
OPTIMUM’s unique trenchless calculation capacity proved invaluable on a recent HDD project for RTE under the Nantes ring road, near FC Nantes’ Beaujoire stadium.
RTE wanted to reduce the drill path depth of planned HDD crossings under the ring road to limit the project’s impact on nearby municipal sports facilities. Since this would increase the risk not only of drilling fluid break outs on the ring road but also settlement levels, RTE wanted to carefully evaluate the changes before validating the new profile.
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France / UK interconnection
12 May 2020
As part of RTE’s French-UK interconnection project, the dual trenchless crossing in Frénouville is now finished. Both 140 metre-long, 10-metre-deep, HDD crossings, passing under one of Normandy's busiest rail routes, required precision control at every stage.
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Rail crossing in Normandy
5 February 2020
Drilling 20m below the busiest railway in Normandy calls for the highest levels of vigilance and expertise. By accompanying RTE’s trenchless project in Harfleur on a daily basis and assisting drilling operations around the clock, OPTIMUM ensured the railway network was preserved throughout.
• Continuous monitoring of drilling operations by dedicated engineers, present on site 24 hours a day.
• Validation of execution documents
• Enhanced security mechanisms (continuous monitoring of the rail platform and topography)
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