Flow measurements at the Olkiluoto site in Eurajoki, Drillholes OL-PP66, OL-PP67, OL-PP68, OL-PP69

The measurements described in this report are a part of the infiltration experiment carried out at Olkiluoto. The emphasis in the infiltration experiment is on hydrogeochemical and on hydrogeological studies. The idea is to monitor the major infiltration flow paths from the ground surface to the depth of 50 to 100 m. The flow measurements were carried out in drillholes OL-PP66, OL-PP67, OL-PP68, OL-PP69 at the Olkiluoto investigation site between March 2009 and November 2010. Two different flowmeters were used at the Olkiluoto site. The Posiva Flow Log, Difference flow method (PFL DIFF) can be used for determination of hydraulic conductivity and hydraulic head in fractures/fractured zones in cored drillholes. The Posiva Flow Log, Transverse flow method (PFL TRANS) is used to determine groundwater flow direction and flow rate in across a drillhole. PFL DIFF was first applied for mapping the hydraulically conductive fractures. PFL DIFF was also used when OL-KR14 was pumped to find out possible connections between the drillholes. PFL TRANS was then used for chosen fractures. The measurements were carried out 'in natural state', when no drillhole was pumped, and when drillhole OL-KR14 was pumped. Both flowmeters have an electrode for single point resistance (SPR). The device has a high depth resolution and the results were used for depth synchronizing between DIFF and TRANS. (orig.)