Large-scale drainage works to the north of Tours
5 years after La Riche, Rennes RD and SADE Special Works pooled their expertise once more on behalf of Tours Métropole, for vast drainage works between Tours and Saint-Cyr-sur-Loire.
Broken down into two orders attributed to the Rennes RD and SSW, this 15-month, out-size task involved the extension of the drainage network to the north of the Tours metropolis, with the building of a primary collector to transport wastewater to the main treatment plant (La Grange) in La Riche, the ultimate goal being to close down all the small treatment plants in the locality.
Rennes RD was called on to renew one of the two existing collectors, with 600mm-diameter or 800mm-diameter cast-iron along 3.5km, at an average depth of 4.8m.
To avoid the busy main road (Rouziers) and protect La Petite Gironde river, SADE Special Works used microtunnelling along 255m (1,200mm-diameter AVN) to lay a 3-metre concrete priming pipe which would then house the 800mm-diameter pipe.
Named Emmanuelle after the head of the Tours Métropole Design, Works and Prospects Department, the machine began digging on 16 November to complete its task just before the Christmas holidays.
Alongside the microtunnel boring machine, open-trench works also began to lay cast-iron pipelines lined with polyurethane (pH1 by PAM) and polypropylene-coated concrete manholes (K’LI’EAU by LIBAUD), with a daily progress rate of 10m in urban zones and 20m in rural areas. Rennes RD sought to use French-made materials as far as possible.
As of late December 2022, effluents were transported by the La Riche collector, which had been laid 5 years previously by the same SADE entities.