Vezins dam removal

Sélune river, Normandie, France, 2019-2020

Vezins dam 13 january  2020 :  80 % of the 36 m high dam removed © DDTM50 in coop. with ERN

Contexte

As confirmed by the authority of res judicata and separate from the legal justification for  removal, the Selune Valley renaturation project was necessary for both scientific and technical reasons. (See the chronology of the removal).

The Vezins and La Roche-Qui-Boit reservoirs (36 m and 16 m high) create extremely large bodies of water that take away the natural character of close to 25 km of the Sélune River and constitute an unsurmountable hinderance for migratory fish that frequent this coastal river. 700km2 of the Sélune watershed are inaccessible.

The Vezins lake is of poor ecological quality, the environment is eutrophicated. Swimming has been prohibited making the use of the lakes for nautical and aquatic activities impossible. The trophic and ecological imbalance linked to the poor water quality has lead to the development of cyanobacteria.

Given the impacts, the regulatory obligations made previously to bring them up to standard, water quality problems they generate, their low energy productivity and reports which conclude it is technically impossible to rearrange them, removal the dams at the end of the concession period back in 2007 was requested by NGOs and also the represantatives of SAGE. Local opposition has also been strong. The removal project was stopped in 2014 but recommenced in 2017 and is now ongoing. Summer 2019, the Vezins dam is being dismantled until september 2020. An important scientific monitoring program has been supporting this project since 2012.

The Sélune dams removal project

The works and project management

The project is managed by the State (DDTM 50). Most of the complexity and cost of the work is related to sediment management. The volume of sediment stored is estimated at:

• 2 million m3 in the reservoir
• 560,000 m3 in the minor bed of the Sélune, potentially mobilized, during the emptying, by the river seeking to recreate its minor bed
•Also 140 000 m3 in the minor tributary beds (Yvrande, Lair and Isolant)
•A sector with contaminated materials: Yvrande

Sediments management of stored volumes is problematic. Inhabitants still have in mind the disastrous emptying which took place in 1993. To avoid replicating the impacts of the 1993, important management measures are being taken.

Details of the works carried out (sediment management and  removal) – DDTM 50 presentation at the Sélune conference Sept.2019

Videos & Reportage during Vezins removal

Reportage from France 3 – nov. 4. 2019  & Aljazeera – july 2019

 

Characteristics of the Vezins Dam

© Eau et Rivière de Bretagne

– 17km from the see
– Built between 1929 and 1932
– Concession period : 75 years (untill 31/12/2007)
– Power : 12,6 MW
– Production : 20 GWh
– Height : 36 mètres
– Width : 278 mètres
– Volume of the reservoir : 19 millions m3
– Length : 19 km
– Surface : 151 ha

Our activities on Selune dams are supported by .