In April 2011, construction began on a dam at the mouth of the river Tua, a tributary of the Douro River. At the same time, a UNESCO mission visited the site following a complaint by the Ecologist Party “the Greens” against the threat posed by the dam to the World Heritage of Alto Douro Wine Region. This mission was a catalyst that ignited the controversy surrounding the Foz Tua dam that began in 2008 with the Environmental Impact Assessment (EIA) of this project. During this controversy, a coalition involving environmental NGOs and local movements, as well as leftist parties, emerged in opposition to the submergence of the Tua Valley and the Tua Railway. Defending the dam project and its contribution to the increase of renewable energy production were the promoter (Electricity of Portugal - EDP), the government, the then ruling Socialist Party and local mayors. This article examines the controversy surrounding the Foz Tua Dam. It intends to highlight: a) the values mobilized by the various parties in the controversy and the ways to overcome value conflicts; b) the restrictions placed by the public decision mechanisms on the expression of particular values.

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