SADE goes troglodyte
Caen La Mer intermunicipal authority selected SADE (Rouen Regional Division) to manage a worksite to restructure the rainwater system crossing a giant abandoned underground quarry in Fleury-sur-Orne. A wastewater treatment worksite with multiple challenges.
An environmental issue.
The gutter-shaped stormwater main crossing the quarry overflows regularly, contaminating both the quarry floor and waters from the regionally-important Bathonian reservoir that rise up into the galleries. To resolve these issues, SADE was tasked with handling the gravity ducting (5mm/m) of this 150m segment. Since mid-June, the Giberville agency team has been setting up and slotting together the 64 concrete pipes (Ø 1,200) and 3 chambers required to build this facility that features multiple changes of direction. An 8-week worksite.
A traditional solution… in an unusual setting.
This quarry is a 40ha underground man-made site, lying at a depth of approximately 20m, with a layout that represented a real challenge for our teams. Here, world-renowned Caen limestone was quarried for several centuries and until the end of the 1950s for “chambers and pillars”. Today, this site is a succession of vast chambers, around 4m high, divided by massive limestone pillars. All these obstacles need to be zigzagged between by heavy machines capable of transporting the 3.4t concrete ducts, each lowered down via an access shaft, over a distance of nearly 400m.
A hostile environment!
To work in this setting, you can’t be claustrophobic! The only area of the worksite that is lit and ventilated is far from the access hopper and even further from the “drive” – the slope to access the site – Workers have to walk the route, equipped with a gas detector and a self-rescue mask, in a darkness practically unpierced by the light of a head torch, following a muddy, marked trail to avoid getting lost or risk falling into one of the many reservoirs, some of which are both several metres deep and filled with very cold water!
Incidentally, this site is regularly visited by intrepid underground explorers, who don’t think twice about graffitiing the walls. Will SADE’s facility be their next victim?