Fieldtrip to Pontgibaud

During the 19th century, Pontgibaud opened a mining industry based on the exploitation of silver and lead. As it used to happen at that time, the activity consisted on a rough extraction of valuable minerals, withtout any consideration for environment or health. As a result, many problems linked to lead contamination appeared. Damages due to the mining activity (which stopped around 1895) are still present today and represent a huge source of pollutants.

During their fieldtrip to Pontgibaud, in May 2017, The EnvIM Europe students visited several sites in order to have a direct feeling of the historical mining activity (and its operation) and to understand how the remaining tailings can be managed to mitigate their impacts on the environment and on the inhabitants living nearby.

Former tailings contain a huge quantity of pollutants (lead, arsenic, zinc, magnesium, etc.). Stacked randomly in heaps, they are direct contact with the a nearby river (the Veyssières) and its groundwater, and with people coming around. The airborne dust from those tailings can spread pollutant in a large perimeter. Plus, the runoff water from the heaps go easily into the stream or down to the areas where people and animals live.

Some of the tailings are located close to sport facilities, which can have a major impact considering that it is highly frequented by inhabitants of Pontgibaud. In this same sport area, the football field was even built on a polluted soil. One other polluted site was the blue lake, in which inhabitants used to swim.

How to rehabilitate those contaminated sites?

EnvIM students had to work on possible ways to rehabilitate those polluted sites, in a concrete and pragmatical way. Here are some propositions they made :

  • To raise awareness in order to help social acceptance of the decontamination process. Indeed, the contamination can be hidden as Nature slowly recovered some tailings and pollutants.
  • Empty the blue lake of its highly polluted water, and send it to the ponds to be sedimented and filtrated.
  • Regroup the tailings in one place to limit the surface occupied by the tailings (which cover now an area of 45 ha).
  • Reuse old construction material to contain the tailings inside the heap and provide a fixed structure.
  • Cover the tailings with waste rocks
  • Cover the heap with the topsoil rich with nutrients and vegetation, which will form the last final cover the heap. This part of the cover will be more resistant to runoff water and erosion, and it will avoid visual pollution.
  • To separate the stream from the heap through an embankment made of big rocks
  • Establish a drainage system around the heap to capture the runoff water and send it to the ponds
  • Establish a safety perimeter fence with signs to protect the rehabilitated site from illegal activities that can damage the works and block the access to the site.
  • Monitoring is essential for the success the rehabilitation project, such as monitoring the quality of the water and quantity of arsenic and lead to see if the rehabilitation works are working.