Intervention Areas


Alto Tejo (Peñalén, Guadalajara)

In Spain, in a protected area, in the region of Alto Tajo (Peñalén, Guadalajara), integrated in a protected Area of the Natura 2000 Network, the “Parque Natural del Alto Tajo” (ES4000092 Alto Tajo) there will be intervened four places. These include an abandoned mine (Mina de Santa Engracia) and associated heaps, formed during the exploration time.
These exploitations of kaolin are open pits, which present complicated scenarios: steep slopes (>40 %) and very high exploitation fronts, up to 100 m high.
The most important natural values of the protected area of Alto Tajo, are precisely the quality of the water of the hydrographic network, the species and communities that there occur, and the fluvial and hydro morphologic landscapes.
The erosion on the abandoned slopes of the Santa Engracia mine is very high.
Although it was the target of restoration measures in the 1990s, they were insufficient to halt the erosion that currently stands above 300 t/ha/year (being the normal values in this type of natural environment of 5-10 t/ha/year). The Suspended Sediment Concentration values (CSS) of 390 g/L, downstream the mine, are also much superior to the baseline values of 24 g/L.

The large amount of sediments released and dragged to the river network, modifies the hydromorphology of the system and negatively affects the natural habitats of the Natura 2000 network that occur there: Habitat 3140 – Hard oligo-mesotrophic waters with benthic vegetation of Chara spp.; Habitat 3110 – H3110 – Oligotrophic waters containing very few minerals of sandy plains (Littorelletalia uniflorae); Habitat 92A0 – Salix alba and Populus alba galleries.
Also upstream of the river, negative impacts occur. This situation is recognized by the Management Plan of the “Tajo Superior” as a terrible threat:
“Mining operations can cause environmental impacts of great magnitude and are practically irreversible, if they are not carried out in an orderly manner (…) and with effective restoration measures”.
Thus, a set of the BAT techniques will be applied (fluvial geomorphology solutions and revegetation of degraded areas with native species) with the aim to restoring the landscape, reducing the erosion, decreasing the SSC and restoring the natural habitats.

In total, an approximate area of 30 ha will be intervened:

“Frente del cementerio”: an area of 1.5 ha will be remodeled. Approximately 11,024 m3 of land (from the external deposits on the front of the road to Poveda, located at 1 km) will be used to fill the current platform.

“Frente Pista a Poveda”: the remodeling surface will be of 6.7 ha and approximately 315 700 m3 of material will be mobilized, either directly on site or moved up to a distance of 160 m. It will also be necessary to pump the water accumulated in the depression.

“Escombreras exteriores de Santa Engracia”: 5.6 ha will be remodeled. Approximately 92 174 m3 will be excavated, of which about 20 000 m3 to fill the depression in front of the cemetery. The rest will be used to fill the cavity of the road to Poveda and to remodel stable surfaces between the heaps..

“Escombrera Hoya Grande”: the remodeled area will be 11.3 ha, for which 8 483 m3 of material will be mobilized.

Sado and Mira (Lousal, Grândola – Ribeira de Corona)

Lousal is located in the River Sado River Hydrographic Basin (Grândola, Portugal), close to “Ribeira de Corona”. This old pyrite mine (pyrite is an iron disulfide, FeS2, exploited to obtain sulfur used in the manufacture of fertilizers), was abandoned in 1988 and is currently inactive. The exploration system was in-depth, and the ore was extracted only through galleries dug in the ground.
Currently, there is a tailing deposit in this location, resulting from the mining activity. Due to its metallic content, occurs the oxidation of sulfides, and when in contact with rainwater, the leaching of heavy metals, such as Copper (Cu), Lead (Pb), Zinc (Zn) and Arsenic (As). Consequently, Acid Mine Drainage (DAM) is produced. The water drained from this area has an intense red color, caused by the high concentration of dissolved metals and salts, and an extremely low pH (an average of pH 2.5). The groundwater is also contaminated, due to minerals explored in depth.

The occurrence of superficial and superficial AMD, together with intense erosive processes, inhibits the development of the native vegetation, affecting the downstream waterways through physical and chemical pollution, and, resulting in high environmental risks.
Despite previous efforts to mitigate the problem, using different techniques (for example, DAM containment and correction tanks, bioremediation, etc.), the problem persists.
In Lousal, a pilot experimentation field is going to be implemented in an area of 1.5 ha, so that the potential of the methodologies used in the project can be demonstrated and adapted.