Due to normal sediment deposits, certain areas of the small Tasnan hydropower plant need to be flushed at regular intervals. Since the plant was commissioned in 2014, the flushing concept has been subject to a five-year test phase. The assessment of this shows that flushing has no negative impact on the environment and can continue.
During ongoing operation at the Tasnan power plant, bed-load, sand and fine material settle into deposits across various water catchment areas (gravel remover, sand trap, forebay). This is intentional to prevent the material from ending up in the turbine through the pressure line. To ensure the plant’s bed-load consistency, these areas – depending on the bed-load volume – must be flushed with an additional flow of water. In order to carry out this kind of flushing in an environmentally friendly manner, a flushing concept was developed when the plant was commissioned. This has now been carefully assessed following a five-year test phase. Over these five years, the effects of the flushing operation on the flora and fauna in the underflow of the water and any changes to the waterbed were systematically examined in cooperation with the authorities.
The assessment has concluded that the existing flushing concept – and thus also the prescribed residual water quantity – could be adhered to at all times. The flushing process therefore had no identifiable impact on the waters of the Tasnan and Inn. Axpo believes that the regular transfer of bed-load even has a positive effect on the bodies of water. This flushing concept has therefore proven to be effective and can be continued with minor adjustments.
The Tasnan high-pressure run-of-river power plant in the Engadin is a partner plant of Axpo (93%), the municipality of Scuol (5%), Brüniger + Co. AG in Chur (1%) and Caprez Ingenieure AG in Scuol (1%). The plant has an output of 6.5 megawatts and produces around 19 million kilowatt hours of electricity per year. This equates to the needs of around 4,400 four-person households.
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