The filling in of the mining excavation of As Pontes in La Coruña and the restoration of the natural environment of the old coal mine is one of Endesa`s priority projects for the reclamation of industrial areas. The aim is to provide an economic, social and environmental solution for the closure of the As Pontes mine through the creation of a large lake in the hole left by the mine and the restoration of the waste dump.
Endesa mined the As Pontes open cast lignite mine from 1976 until 2007 to supply fuel to a thermal power plant it owned situated at the foot of the mine. As a consequence of this activity an exterior waste dump of 1,200 hectares and 720 million cubic metres was created, an interior one of 80 hectares and of some 93 million cubic metres and a residual hole. The exterior dump is 160 metres high, whilst the interior one has disappeared from view as it forms part of the bottom of the lake.
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In order to recover this land, Endesa developed a Restoration Plan which will allow the earth to grow correctly as well as a self-sustaining range of vegetation offering a suitable habitat for local fauna.
The main objectives of this Restoration Plan are:
- To create a stable vegetative cover that will control erosion and the quality of run-off water and is conducive to the formation of fertile soil.
- To recover the countryside affected by the mining.
- To return it to its former state , and make it even better if possible.
- To reintroduce fauna.
To transform the exterior waste dump. The materials that make up the exterior waste dump are the sterile clay silts from the lignite mine, shale, and the ashes produced by the As Pontes Thermal Production Unit. Given the poor quality of the material, for stability purposes, the dump was designed with gentle inclines separated by horizontal platforms to give it a smoothly rounded topography that would blend in with its surroundings.
At the foot of each partial slope there is a ditch for water collection. Parallel to that, there is a path that gives access to all levels. Like the mine, the dump site had to be protected from water flows and before it came into use, a network of channels was dug around its periphery, with a total length of around 20 kilometres.
The restoration of the exterior waste dump began in 1985 and was completed in 2007. In order to do this, physicochemical analyses were carried out on about 6,000 earth and water samples, more than 3 million cubic metres of topsoil or selected spoil was used and 67km of roads and 56km of ditches were built. It also required 40,000 m3 of organic fertiliser, 500,000kg of chemical fertilisers, 120,000kg of seeds and the planting of 600,000 trees.
The end of the restoration work does not mean that the various habitats created are stable, rather that they continue to evolve rapidly. In this sense, the waste dump is an ecosystem that is constantly changing, where herbaceous plants, shrubs, trees and water coexist.
This diverse habitat has been exploited by fauna, which has progressively and rapidly colonised the ground, to such an extent that now 172 vertebrate species live there on a full-time or temporary basis, some very important for their rarity or uniqueness within Iberian fauna.
The filling of the lake. The mine excavation has been filled with runoff water and water from the river Eume. The lake has a volume of 547million cubic metres, a maximum depth of 205 metres and a perimeter of 17.8 kilometres. Once full the lake will stop taking water from the river Eume and overflow water will feed into the course of the old river Carracedo. The lake will then be fed by the small rivers being diverted to the Eume: the Illade, Meidelo, Chao and Maciñeira, restoring the water system to its original state.
The creation of the lake does not only suppose the filling of the hole and its reintegration to the water system, but also means the restoration of its banks and its protection against erosion. Two projects are being carried out to protect the banks of the lake from wave erosion: the construction of a beach in the area closest to the town of As Pontes and the placement of a layer of landfill around the lake’s perimeter which is most at risk.
Two islands have also been built in the centre of the lake to facilitate the implantation of flora and fauna. One of them, which will be in the western part of the lake will have a surface area of 55,000 square metres and will house a bird reserve. The island opposite where the interior waste dump emerges, has a surface area of 13,000 square metres and is home to an important representation of Galician tree species.