Databank

Databank

Posiva publishes Working Reports and Posiva Reports. From the year 2006 nearly all the reports have been published on our webpage and they can be found in the databank. In the databank you can also find our Annual Reviews and some other publications as well. You can also find print-quality pictures and useful links in the databank.

Recent publications


Workreport 2017-43

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Name:

Results of Monitoring at Olkiluoto in 2016 – Hydrology and Hydrogeology

Writer:

Vaittinen, T., Hurmerinta, E., Komulainen, J., Nummela, J., Pentti, E., Tammisto, E., Turku, J., Karvonen, T., Sauramo, J.

Language:

English

Page count:

582

Summary:

The impact of the construction of ONKALO is monitored by measuring and observing numerous different parameters related to hydrology, geochemistry, environment, rock mechanics and foreign materials. The Hydrological Monitoring Programme consists of the following parameters: groundwater level, hydraulic head, flow conditions in open drillholes, transverse flow, hydraulic conductivity, precipitation (including snow), sea-water level, surface flow (runoff), infiltration, ground frost, leakages in tunnels, and water balance in the tunnel system and in Korvensuo Reservoir. This Report focuses on hydrogeological parameters. Other parameters, like precipitation, ground frost etc. will be reported in the Monitoring Report of the Environment. From year 2014 on, the parameter groundwater salinity (in situ EC) has been reported in the Monitoring Report of Hydrogeochemistry. In 2015 monitoring measurements with Hydraulic Testing Unit were ended.

The updated monitoring programme was introduced at the beginning of 2012. The updated programme will be used for the period before repository operation. Only minor changes were implemented. Monitoring has been carried out according to plan. This Report presents the results for the year 2016.

The excavation of the access tunnel was completed in 2012 and excavations related to the demonstration area in 2013. In the technical facilities, excavation continued in 2016. Shafts ONK-KU1 and -KU3 were raise bored down to the final level of −455 m during the spring of 2014. The construction project of ONKALO finished and the construction of the final disposal repository started in December 2016.

Total inflow into ONKALO down to chainage 4580 m including shaft ONK-KU2 down to level −437 m and shafts ONK-KU1 and -KU3 down to level −455 m was on average 29–37 l/min in 2016, but the exact range is difficult to determine due to the construction activities carried out in ONKALO. The mapping of water leakages and moisture conditions on the tunnel walls and ceiling has been continued. The general pattern of leakages has remained similar during the construction of ONKALO. The most significant differences are caused by seasonal effects like condensation of warm ventilation air on tunnel walls and ceiling.

The changes observed in groundwater level in the observation tubes in the overburden and in the shallow drillholes in the bedrock are not necessarily caused by the construction of ONKALO. However, weak indications of a local decrease in groundwater level have been observed. The effects on the head deeper in the bedrock have earlier been both short-term and long-term, but in 2016, no short-term effects occurred. Long-term changes, i.e. a decrease in pressure heads near ONKALO have remained at the same level as in 2015. On average, drawdown in heads varies between 10 and 12 m within the HZ20 system and between 0.5 and 1.5 m within the HZ19 system. Due to the intersection of the HZ056 zone and a few local features, long-term drawdowns of over 20 m have occurred and the water level has decreased below the measurable drillhole depth in 11 monitoring sections.

Flow-based monitoring using the PFL (DIFF-tool and TRANS-tool) was carried out in nine drillholes in 2016. The most notable changes were detected in drillhole OL-KR32. Flow changes at fractures at depths of 51.3 m, 81.1 m and 86.9 m indicated hydraulic connection to a sink. Also some other fractures below depth of 80 m seem to be affected by a hydraulic sink. The changes are most likely caused by connections to ONKALO. Slug tests were performed in 10 shallow holes. The interpreted hydraulic conductivity was in agreement with previous results.

Keywords:

Groundwater, groundwater level, hydraulic head, groundwater flow, hydraulic conductivity.

File(s):

WR 2017-43_web (pdf) (90.4 MB)


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