Flateland kraftverk – Rapportering for 4. kvartal 2021 og 1. kvartal 2022 | Flateland kraftverk – Rapportering for 4. kvartal 2021 og 1. kvartal 2022

English summary On behalf of Tinfos AS, NIBIO and Faun Nature Management carry out environmental monitoring of the river Hovlandsåna during the construction of a new powerplant at Flateland in Vegusdal (Birkenes municipality). The environmental monitoring includes continuous monitoring of water quality, quarterly and weekly sampling, as well as biological surveys at a total of three stations in Hovlandsåna. This quarterly report includes results from preliminary studies (water samples, benthic animals and algae carried out on 21.10.2021), results for weekly water samples in the period 30.11.2021 - 30.03.2022 (4th quarter 2021 and 1st quarter 2022) and measurement data from continuous monitoring at two stations in Hovlandselva from 13.10.2021 - 30.11.2021 (4th quarter 2021). The construction work related to the establishment of the Flateland power plant has so far had low impact on the water quality in Hovlandsåna. With the exception of some elevated turbidity values 25.10. - 07.11.2021, no exceedances of the limit values given by the County Governor of Aust- and Vest-Agder (State Administrator in Agder) have been registered. The elevated turbidity values were registered during the establishment of a connection site to provide electrical power to Nygårdsdalen from the power grid running along the river and Fv42. The overall condition in the Hovland River is «good» and the benthic surveys from HOV_REF, HOV_NED1 and HOV_NED2, showed two species of acidification-sensitive mayflies (ephemeroptera) and several other species were found within families with a high ASPT value. This indicates that the impact of acidification in the river is small and that the liming of the watercourse has given good results. A more even water flow as a result of the changed regulation regime in Vikestølvatnet has also contributed to a significant reduction in leaching of sediments from the beach zone. The anadromous stretch of the river reaches up to Trollfoss and is said to have good populations of sea trout. Good populations of stationary trout (upstream of Trollfoss / Flateland) are also recorded. The anadromous section of the river is likely to be somewhat affected by the construction work for the Flateland power plant and increased focus on this part of the river is required Sammendrag På oppdrag fra Tinfos AS gjennomfører NIBIO og Faun naturforvaltning miljøovervåking av Hovlandsåna under bygging av Flateland kraftverk. Miljøovervåkingen omfatter kontinuerlig overvåking av vannkvalitet, kvartalsvis og ukentlig prøvetaking, samt biologiske undersøkelser ved til sammen tre stasjoner i Hovlandsåna. Denne kvartalsrapporten omfatter resultater fra forundersøkelser (vannprøver, bunndyr og begroing utført 21.10.2021), resultater for ukentlige vannprøver i perioden 30.11.2021 – 30.03.2022 (4. kvartal 2021 og 1. kvartal 2022) og måledata fra kontinuerlig overvåking ved to stasjoner i Hovlandselva fra 13.10.2021 – 30.11.2021 (4. kvartal 2021). Anleggsarbeidene i forbindelse med bygging av Flateland kraftverk har til nå gitt svært liten påvirkning på Hovlandsåna. Med unntak av noen forhøyede turbiditetsverdier i forbindelse med etablering av byggestrøm til Nygårdsdalen 25.10. – 07.11.2021 har det ikke blitt registrert noen overskridelser av grenseverdiene gitt av Fylkesmannen i Aust- og Vest-Agder (Statsforvalteren i Agder).

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