Navarra (EFE).- The Artikutza dam, located in Navarra and owned by the San Sebastián City Council, has been in disuse since 2016 and the reservoir that contained it has been completely empty since 2019, despite which it continues to be part of the landscape, since dismantling it is an environmental and engineering challenge.
The total or partial elimination of this infrastructure, built between 1947 and 1953, is part of the project co-financed with European funds Life Kantauribai, focused on the renaturation of rivers and which, among other actions, includes eliminating 25 weirs or dams and making another seven permeable with the placement of ramps that allow the passage of fish.
With these works, in addition to making it easier for the fish fauna to go up more kilometers of the river, the sediments that are now retained by the dams will be able to travel downstream and, with this, recover the original morphology of the basins, giving stability and improving the habitat. of the animals and plants that live in those areas.
Some 6 million euros will be invested in the demolition and permeabilization of obstacles, of which a large part will correspond to Artikutxa, located in the Urumea Special Conservation Zone (ZEC), which forces us to seek a “sustainable solution”, he highlighted. the person in charge of hydraulic works of the Basque Water Agency (URA), Aitziber Urquijo.
Partial demolition, the best option
Among these options, the San Sebastián City Council has considered three: not intervening and leaving the dam as it was built; open a hole in the structure (partial demolition) or remove it completely (total demolition).
After studying the impacts of the three options on the species and habitats protected in this enclave and with the aim of minimizing them, the council has opted for partial demolition, considering it the most environmentally sound option.
The consistory has already sent its proposal to the Ministry for the Ecological Transition, which must give its approval so that the work can begin, sources from the San Sebastián City Council have explained to EFE.
It remains to be seen how these works would be carried out, which represent a real engineering challenge, since the forecast is to open a 7-meter-wide notch in the left spillway of the dam, from its crest to at least 1 meter below. below ground level.
The demolition of the existing ledge downstream of the damping basin is also planned.
Ten times less debris
It is estimated that with these actions, the demolished concrete would add up to 3,930 cubic meters (m3), which, according to the plan presented by the City Council, would be reused, almost in its entirety, in improving the pavement of the perimeter track of the reservoir.
This amount of rubble is almost ten times less than the total removal of the dam would entail: 39,374 m3 of concrete, of which some 3,600 could be used to improve the pavement of the runways, while the rest would have to be removed from the area with trucks.
This would force 2,832 truck trips to the nearest treatment plant, with their corresponding CO2 emissions, as well as having to reinforce the roads in the area to allow this transit.
Allows passage of wildlife
According to the technicians, partial demolition is the best option because it guarantees fluvial permeability, avoids having to evacuate the material from the demolition, the execution time is much shorter and minimizes the impacts on biodiversity and natural ecosystems.
Thus, it guarantees the regeneration of the hydrological regime and the natural dynamics of sediment and nutrient transport of the Enobieta stream; and the movements, both upward and downward, of aquatic organisms.
In addition, it will create a favorable habitat for the movements of the Iberian desman and will solve the barrier effect that large dams have on the otter and the European mink; At the same time, it will allow the permanence of the population of the Great Mouse Bat and other bats that take refuge in the galleries of the dam.
It also makes it possible to maintain the vegetation that has already colonized the reservoir basin and that plays a valuable role, both for the abiotic and biotic resources present, as well as for landscapes and those related to climate change.