Mangualde (Municipality)
4,866,747.48 €
2011 - 2013

Environmental Remediation of the Cunha Baixa Mining Area


The Cunha Baixa mine is located in the civil parish bearing the same name, in the municipality of Mangualde and district of Viseu.

Reconnaissance mining operations began in 1967, followed by an excavation phase lasting from 1970 to 1987. A depth of 150 m was reached with three floors and galleries stretching over 900 m. Almost simultaneously, in 1971, open pit excavations began, at the Open Pit I site, and subsequently at the Open Pit IV site, which lasted until March 1991.

Jointly, through underground mining and open pit mining, production reached a total of 901,432 Kg of U3O8, contained in ore with an average U3O8 content of 0.186%. The lixiviation of poor ores in the pit of Open Pit I began in 1983 and continued until 1993, producing around 76,000 kg of U3O8. In this operation, around 400,000 tons of poor ore were introduced from this mine and others transported from Espinho and Póvoa de Cervães.

The environmental remediation work on the former mining area of Cunha Baixa, which included Valdante, consisted of the following main activities:

  • Preventing the water transfer that existed between open pit I and the underground part of the mine, promoting a decrease in the flow of contaminated influent from open pit I;
  • Eliminating the potential for reactivity, significantly reducing radiometric levels and controlling the geochemical and hydrochemical dispersion associated with existing deposits, whether more enriched spoil heap materials or former treatment sludge;
  • Decreasing the emission and consequent dispersion of radon gas into the atmosphere;
  • Optimizing the structures and processes associated with the control and treatment of acid effluents;
  • Guaranteeing the stability of the slopes of the bulkier spoil heap (E1);
  • Controlling surface runoff around the entire perimeter of the mining area, in order to decrease phenomena of gullies and uncontrolled flows of rainwater into the area of the 4 existing open pits (I, II, III and IV);
  • Improving the general safety conditions for people and animals;
  • Integrating the landscape and ecology of the entire area directly affected by the mining activities, as well as the areas in the immediate vicinity;
  • Treating the contaminated areas with agricultural land and;
  • Promoting the downstream irrigation of areas for agricultural use with proper quality water.

This contract was awarded to Empreigalde – Engenharia e Construção, SA for 4,611,523.66 and had a duration of 540 days.

The investment was co-financed by the Cohesion Fund and allowed the environmental liabilities resulting from mining at this location to be resolved, bringing benefits to local populations through the improvement of current conditions and use of the areas reclaimed for other ends.