22 June 1984,
A group of ecologists collected the waters poured into the river by the Urumea Chemical Industries plant in Hernani and poured them into the supply of the plant. The company said that the water poured into the river without purification was not harmful. The entrepreneurs formed the human chain and picked up the water that would pour the workshop through a cube and cast it into the inner circuit of the plant.
Source:
Sabino Ormazabal, Grupo Bidea Xede. 500 nonviolent actions, another way to tell the story (Fundación Manu Robles Arangiz)