The valve renewal operation at the Restanca dam, in Arties (Lleida), is the most complicated that the Endesa company has carried out in the Pyrenees in terms of the logistics and bureaucracy required to carry it out.
A week ago the emptying of the lake began and the transfer of heavy parts by helicopter to the area, which is located at more than 2,000 meters above sea level, has already begun.
Albert Lázaro, head of the company's Garona unit, explained that this operation is "the tip of the iceberg" and more will come to adapt it to the 21st century and improve the security of equipment from the middle of the last century.
Lázaro assures that he does not remember any maintenance operation like the one being carried out at the Restanca dam. It is done because the water outlet valves have reached the end of their useful life and in fact, he explains that they were preparing the device for a long time and it could not be carried out until all the perceptual permits had been obtained, since many administrative actors intervene in the area such as the Ebro Hydrographic Confederation (CHE), the Conselh Generau d'Aran, the Aigüestortes and Estany de Sant Maurici National Park, or the Generalitat.
In addition, the difficulty of the area and the weather must be taken into account, which can sometimes delay the tasks. There is no road access to the dam and the material and operators will be transferred by helicopter to more than 2,000 meters.
Last Thursday, about 2,500 kilos were lifted in three different trips to the mouth of the intermediate gallery that connects with the 25-meter well at the bottom of which are the two valves to be changed.
The well is located just below the Restanca refuge, which Endesa ceded to the administration and has been receiving hikers for years who hike and summit the National Park.
New valves arrive disassembled for parts for various reasons. Mainly because the helicopter cannot carry so much weight, but also because the gallery excavated in the mountain is small and the operators must perform filigree to get the pieces to the place where they will be assembled and lowered towards the well.
Albert Lázaro points out that they will carry out more similar operations in other facilities managed by the company in the Pyrenees because the idea is to leave all the valves renewed, with 21st century equipment that "guarantee the maximum possible safety."
The valves communicate the intake of La Restanca with Montcasau, which is on the other side of Montardo, a very crowded and popular 2,833-meter-high peak. There is a gallery that crosses the mountain below to the Arties waterfall, where the hydroelectric power station that produces electricity is located.
The renovation of the Restanca valves has left this lake with an unusual appearance that surprises the hundreds of hikers and tourists who visit it or spend the night every summer. Normally, the water level is always at the top of everything because it is a prominent pond on the most important routes to climb to the tops of the park.
In this sense, Albert Lázaro explains that they have decided to empty the lake now, at the end of summer and before winter, because there are fewer tourists and thus avoid impact. The works will take about six or seven weeks and the dam will be full again in October.
At the same time, the emptying will soon be used to eliminate invasive species from the lake. For this reason, Endesa will hire an external company that will carry out electrofishing of the species to be used, such as trout, and together with the rural agents, they will be transported to the Aiguamoix dam. Invasive species will be removed and treated as waste.
