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Workreport 2017-29



Electromagnetic Sampo Monitoring Soundings at Olkiluoto in 2016


Korhonen, K.



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The Geological Survey of Finland (GTK) has carried out electromagnetic soundings annually at fixed stations in Olkiluoto since 2004 as part of a monitoring program. The goal of the monitoring program is to monitor possible changes in the groundwater conditions by detecting changes in the electrical properties of the bedrock in the vicinity of the ONKALO underground research facility which will constitute a part of the final disposal facility. 

A new Sampo monitoring survey was carried out by GTK in October 2016. The survey consists of 32 soundings performed at 15 measurement stations. The nominal coil separations of 200, 400, 500, 600 and 800 metres were used depending on the station.

Layer-model interpretations of soundings at 13 previously selected stations were updated with the new data. In addition, new layer-model interpretations were carried out for one previously unselected station. The results indicate consistent annual changes. Resistivities below the stations to the East of the ONKALO excavation site appear to increase annually. In contrast, resistivities below some stations mostly to the West of the ONKALO excavation site appear to decrease annually.


Electromagnetic soundings, Olkiluoto, monitoring, modelling, saline groundwater


WR 2017-29_web (pdf) (25 MB)


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