Workreport 2007-19



Groundwater Sampling at Olkiluoto, Eurajoki from the Borehole OL-KR6 During a Long-Term Pumping Test in 2006


Hirvonen, H., Hatanpää, E. & Ahokas, H.



Page count:



A long-term pumping test at borehole OL-KR6 at Olkiluoto was initiated in 2001. Since then, flow and in situ EC measurements as well as groundwater sampling from specific sampling sections have been performed yearly. The aim of this study was to obtain information on the potential connections via fractures both to the sea and to deep saline groundwater during long-term pumping of the open borehole. In 2006, four groundwater samples were collected from four different sampling depths (98.5-100.5 m, 125-130 m, 135-137 m and 422-425 m). The groundwater samples were taken in stages using PAVE equipment.

The water types found in the groundwater samples from OL-KR6 were Na-Ca-Cl (for samples from depths of 98.5-100.5 m and 125-130 m) and Na-Cl (for samples from depths of 135-137 m and 422-425 m). The sample from depth 422-425 m was saline (TDS> 10000 mg/l), while other waters were brackish (1000 mg < TDS <10000 mg/l).

This study presents the sampling methods and analysis results of groundwater samples from deep borehole OL-KR6, and draws a comparison between the results of the in situ EC measurements and the EC results measured during groundwater sampling. This report also contains a short comparison of the results obtained from the long-term pumping test conducted between 2001-2006.

In situ EC results and EC results measured in laboratory are in quite good agreement. At sampling depth, 422-425 m, EC increased between 2004-2006. At a depth of 423 m, much variation in situ EC-values indicates that routes of groundwater may change during long-term pumping due to the limited storages of different aquifers or the heterogeneity of the content of groundwater in different locations in the bedrock. The minor systematic difference between in situ and sampling EC at a depth of 136 m was probably due to the different flow fields during flow logging and water sampling.

The dominant gas in the groundwater samples was nitrogen. Carbon dioxide was the second dominant gas, except for the OL-KR6/125-130 m sample, where argon was the second dominant. All sample vessels were argon treated before sampling so contamination by argon was possible.

In 2006, dissolved gas concentrations were higher in OL-KR6 samples than in the two previous years. Higher concentrations were noticed in nitrogen, carbon dioxide and argon (contamination possible) contents at all sampling depths.

One of the conclusions from this and previous studies is that the changes in the three upper sampling points were most remarkable in 2001-2002 just after pumping started. Otherwise, water compositions were invariable.


long-term pumping test, in situ EC-measurement, salinity, groundwater, sampling, analysis, chemical analysis results


Groundwater Sampling at Olkiluoto, Eurajoki from the Borehole OL-KR6 During a Long-Term Pumping Test in 2006 (pdf) (1.4 MB)


Share article:
This website stores cookies on your computer. These cookies are used to improve our website and provide more personalised services to you.


To make this site work properly, we sometimes place small data files called cookies on your device. Most big websites do this too.

1. What are cookies?

A cookie is a small text file that a website saves on your computer or mobile device when you visit the site. It enables the website to remember your actions and preferences (such as login, language, font size and other display preferences) over a period of time, so you don’t have to keep re-entering them whenever you come back to the site or browse from one page to another.

2. How do we use cookies?

A number of our pages use cookies to remember your actions and preferences (such as login, language, font size and other display preferences.)

Also, some videos embedded in our pages use a cookie to anonymously gather statistics on how you got there and what videos you visited.

Enabling these cookies is not strictly necessary for the website to work but it will provide you with a better browsing experience. You can delete or block these cookies, but if you do that some features of this site may not work as intended.

The cookie-related information is not used to identify you personally and the pattern data is fully under our control. These cookies are not used for any purpose other than those described here.

3. How to control cookies

You can control and/or delete cookies as you wish – for details, see You can delete all cookies that are already on your computer and you can set most browsers to prevent them from being placed. If you do this, however, you may have to manually adjust some preferences every time you visit a site and some services and functionalities may not work.