The work will be carried out with Pöyry as the technical leader of a consortium with Basler & Hofmann AG. Pöyry’s share of the assignment is approximately EUR2M.

The project will start this month, with a duration of 12 months for the tender design and detailed design preparation. Construction supervision will start in spring 2013 and will last for 24 months.

The Hegmatten flood retention reservoir will be one of the most important systems for the protection of the City of Winterthur against catastrophic floods. Because of insufficient capacity of the existing bed of the river Eulach the centre of Winterthur is endangered by the risk of inundations during major flood events, with a big potential for major damage in case of uncontrolled inundations.

The project includes both civil design and environmental related consultancy services. The major project elements are the construction of a 450m long cut and cover flood diversion channel as well as a 1.4km long flood retention dam including the related appurtenant structures, such as a spillway and bottom outlet.

The actual project is based on the concept of flood retention by the creation of an artificial reservoir upstream of the city centre, which in case of major floods enables the release of decreased discharges. After the construction of the Hegmatten Flood Retention Reservoir, the city centre of Winterthur will be protected against inundations up to flood events with a 100-year return period.