For the construction of the Calais cross-channel terminal’s public wastewater system.
SEPD, the port operator, has selected the Boulogne-Sur-Mer Agency (Arras Regional Division), in partnership with Veolia, to build the system.
From individual to shared
Currently routed and treated using micro-plants, wastewater from the site’s 15 buildings, i.e. approx. 70m3/h, is set to be collected and discharged into the town’s shared system by next spring. This change of method requires the construction of custom infrastructure.
SADE’s teams built a 1.3km interlocking PVC CR16 ø200 tube gravity system including 55 manholes, a 1.3km, HDPE ø90 backflow system including 20 chambers housing outfalls and vents, and 10 fibre backflow stations (ø1.2m) to be equipped by Veolia. Systems and structures were installed at depths of between 1.3m to 4m in sandy soil and on the edge of the water table.
An environmentally-friendly approach
To reduce the project’s environmental footprint, the sand extracted from the trenches, graded D1, was reused to backfill them. This allowed us to economise 2,500m3 of new material. A similar amount was spared from dumping, and a large number of HGV trips were no longer required. Based on the same logic, road demolition materials were crushed on site, and most of these 1,000T were recycled for road structures.
An operational site
The work was done during the health crisis on a site that remained in operation and was visited by an average of 2,500 lorries every day. To enable smooth and continuous on-site operations and ensure enhanced safety for our teams, the backflow system was built by 10 directional drilling drives, using this technique that is both trenchless and environmentally friendly.
In no time at all!
Built between July and December 2020 by a specially-equipped team of 10, the systems were water-tested (backflow, manholes) or air-tested (gravity) to make sure of their tightness. The quality of the backfilling was checked using both penetrometers and densitometers. The facility will be commissioned in spring 2021 after issuing of the discharge permit. SADE will set up the micro-plants during this secondary phase.