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Drilling through the walls of a microtunnel ? Really ?

19 Jun 2025 | Water

In streets south of Paris, a seemingly ordinary underground construction site. And yet, every day, engineers stopped by to see quite a unique drilling operation …

When renovating the wastewater network in L’Haÿ-les-Roses, one question had project managers scratching their heads: how to connect the existing surface-level wastewater pipes to newly constructed gravity-flow microtunnels 15 meters below ground? After dismissing several potential possibilities, an innovative solution was found: 9 short diagonal boreholes, drilled almost vertically, through the wall of the new microtunnel itself – a first in France !!

OPTIMUM’s trenchless engineers were then commissioned to monitor the drilling operations. Particular attention was paid to water management, since all the works were being carried out below the water table.

Thanks to great teamwork and efficiency, the whole project was completed in just 5 weeks. The houses can now be connected up to the new, improved network. Congratulations to the whole project team.

    • Project owner: Conseil Départemental du Val de Marne
    • Construction contractors: VALENTIN, France Travaux, Eiffage Génie Civil Réseaux
    • Sub-contractors: Zehnder Spezialbau AG (drilling contractors), OPTIMUM (trenchless consultancy)

 

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