The town of Yverdon-les-Bains is taking up an unprecedented technical challenge this spring, the first of its kind in Europe: the laying of a new welded steel sub-lake pipe between the port of Grandson and the mouth of the Bey, over a distance of 1.7 km, in the space of a few weeks! This flagship project, carried out by the Service des énergies de la Cité thermale (SEY), should enable the 30,000 or so people connected to the region's drinking water network to have a more reliable supply thanks to modern infrastructures. Budgeted at more than three million francs, the work in progress will enable a connection to the existing network from summer 2012.
"The current network has a real weak point: for more than a kilometer and a half, the only vector of pumped water is a steel pipe built shortly after 1940, located on the Grandson - Yverdon-les-Bains axis," noted Anne Grandin, head of the Water and Gas Networks section of the Cité thermale's Energy Department, during a demonstration presentation on the lake on Wednesday to the region's elected officials and professional partners of the project. The local elected representatives had understood this risk well and three years ago they supported the credit needed to carry out this important project. Today they were able to witness some of the civil engineering technical prowess required to lay these pipes.
Optimized network
The laying of this pipe is part of a common regional vision, aimed at improving and securing the drinking water supply of a basin of several tens of thousands of inhabitants. "The city of Yverdon-les-Bains is in a way the hub of regional water distribution and many connection projects are currently under study. As such, this new pipeline represents a key stage in the optimisation of our network", emphasised Gloria Capt, Municipal Energy Manager of Yverdon-les-Bains. This new transmission route is part of a coordinated vision of the SEY and ACRG (Association of Municipalities of the Grandson region) networks, which the Société Anonyme de Gestion des Eaux du Nord Vaudois (SAGENORD) is working to optimise.
Off the beaten track
"Such a project represents a significant and unusual technical challenge. The laying method chosen, by sections, is the best suited to the lake conditions", noted Mario Gerodetti, Director of GEOS Consulting Engineers SA, the company responsible for directing and coordinating the works. Barges are used to transport the pipeline sections on the lake and to weld them to their future location. The steel pipeline, with a diameter of around 50 cm, has a high safety potential, particularly against the risk of impact or corrosion: internal lining of cement mortar, external three-layer PE coating (corrosion and electrical insulation) and cathodic protection along the entire route. Once in service, the pipeline will have a flow rate of 16,000 litres per minute, which is higher than the daily consumption in Yverdon.
Environmental constraints respected
The entire route of the new pipeline lies in the OROEM (Ordinance on Waterbird and Migratory Bird Reserves) area of national importance for the wintering and migration of waterbirds. As a result, the construction schedule has been adapted to the environmental constraints associated with this location. In order to reduce as far as possible the nuisance to wintering birds, particularly at the level of the integral reserve located at the mouth of the Bey, the laying of the new sub-lake pipe benefits from a window of only a few weeks. "According to the study carried out by ECOSAN SA, the final impact of the project on the landscape and the lake environment is nil, as the pipe is buried along the entire section," Anne Grandin explains.
Technical data sheet Water network of the city of Yverdon-les-Bains: key figures
30'000 people supplied with drinking water
Nearly 126 km of pipelines in total Total consumption of 2.5 million m3/year
Breakdown of drinking water consumption :
- 1/3 from the sources of the Cossaux, property of the town of Yverdon-les-Bains, located in the commune of Chamblon
- 2/3 supplied by SAGENORD, which is supplied by the Onnens wells.
Underwater driving: key figures
Total length: 1.75 km, of which 1.2 km are on the bottom of Lake Neuchâtel.
Pipe diameter: approx. 50 cm
Installation depth in Lake Neuchâtel: between 2 and 5 m
Maximum flow rate: 16'000 l/min (265l/s)
Driving speed: 1.4m/s
Connections: 2 cells for connection to the existing network at the ends
Budget: more than CHF 3 million
Project planning: GEOS Consulting Engineers SA
Contracting authority: Yverdon-les-Bains Energy Services (SEY)
Realization: GEOS Consulting Engineers SA