Local authority Communauté d’Agglomération Grand Calais Terres & Mers is at last able to complete the missing link in the renewal of its wastewater network. The project had been on hold for several years until OPTIMUM were contacted to find a solution.
The issue was how to cross the Calais – Dunkerque railway line given the high water table and the unstable sandy geology of the site. A classic gravity-flow tunnel would have needed a temporary lowering of the water table, which is not a viable solution under the railway. OPTIMUM engineers rethought the project, designing a 54-metre-long DN 200 HDD, 5 metres under the railway lines, with a pumping station at the exit point. They also filed a new SNCF dossier and handled negotiations to ensure all concerns were addressed and authorisations obtained.
OPTIMUM then supervised the drilling operations, successfully carried out on Monday night by Coquart. The water board can now complete its upgrading.
