A study published in 2004 by the Spanish Council for Scientific Research (CSIC) and the Autonomous University of Barcelona (UAB) showed the presence of about 350,000-500,000 tons of residues from a chlor-alkali factory in the Flix reservoir of the Ebro River. This reservoir does not have the capacity for water storage. It was constructed to act as a weir for deviation of the river water to a hydraulic power plant. Most of the residues were accumulated under the river water while a small portion was emerging above. The accumulated waste was essentially generated between 1972-1990, when the synthesis of dicalcium phosphate from phosphorite produced large amounts of mining residues, which were dumped into the river.