Workreport 2019-45



The Results of Monitoring at Olkiluoto at 2018, Environment


Sojakka, T., Lipping, T.



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This report presents the results of Posiva’s environmental monitoring of Olkiluoto Island for the year 2018. In 2016 the monitoring programme was updated to concern years 2017-2019. The current surface environment monitoring programme is focusing on the traditional environmental impacts of contruction and operation works of the final disposal project. Part of the monitoring is performed by the company running the nuclear power plants on the island, Teollisuuden Voima Oyj. This Working Report presents the main results of Posiva’s environmental monitoring programme on Olkiluoto Island in 2018. Results are presented under four topics: 1. Modelling input data, 2. Interaction between surface environment and groundwater in bedrock, 3. Environmental impact and 4. Baseline of monitoring of radioactive releases.

In 2018, water samples were taken from Korvensuo freshwater reservoir and River Eurajoki to be analysed for isotopes and basic water chemistry parameters. The analyses results did not differ from the results of the previous years. From the sea area no water samples were collected in 2018 for hydrogeochemical characterization. 

Concerning interaction between surface environment and groundwater in bedrock, records were maintained e.g. on changes in infrastructure and other land use. Annual meteorolocigal statistics were derived from weather mast data, and automated measuring weirs produced data on surface runoff. In the monitoring of surface run-off no events deviating from previous years were observed.

Environmental impact analyses of Posiva's activities included e.g. monitoring of noise, effluent waters, nearby water systems and private drilled wells. In 2018 noise measurements were implemented twice. Action limits for the noise levels set by Government decree 993/1992 were not exceeded in these measuring points during 2018. 

During 2018 samples from all surface water measuring points (measuring weirs, ONKALO outlet waters, ditch running by rock heaps) indicated descending trend in SO4 levels but then high values were measured again in autumn. It seems that SO4 levels are generally higher in autumn than in spring. High nitrate levels were measured from ONKALO outlet waters and in ditch running by rock heaps. Reason for high NO3 levels is probably explosives used in underground excavation work. In 2018 new action limits were set for surface waters and these limits were  exceeded 15 times in ONKALO outlet waters during 2018. Action limit for suspended solids in surface waters is result higher than 25 mg/l. Action limits for pH in surface waters is pH<6 and pH>9.

Harmful effects on the nature conservation area of old forests or on the Natura 2000 area in the southern part of the island were not observed in the surface environment. The water quality of the monitored private wells is satisfactory due to their natural properties. Their water levels and water qualities are not affected by the construction of ONKALO®.


Environmental monitoring, ecosystem, baseline condition changes


WR 2019-45_web (pdf) (6.3 MB)


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