Monitoring measurements by the difference flow method during the year 2009, Drillholes OL-KR22, -KR30, -KR31, -KR35, -KR36 and -KR40

The Posiva Flow Log, Difference Flow Method (PFL DIFF) uses a flowmeter that incorporates a flow guide and can be used for relatively quick determinations of hydraulic conductivity and fresh water head in fractures/fractured zones in cored drillholes. This report presents the principles of the method and the results of measurements carried out in drillholes OL-KR22, -KR30, -KR31, -KR35, -KR36 and -KR40 at the Olkiluoto investigation site during the year 2009. These measurements are a part of the Olkiluoto monitoring programme (OMO). The section length of the flow guide in the flow logging measurements was 2 m and 0.5 m. Flow into the drillhole or from the drillhole to the bedrock was measured within the section lengths and carried out in both pumped and natural (i.e. un-pumped) conditions. Calculations of the transmissivity (T) and the fresh water head (hfw) of the zones are shown in the results. The device used includes a sensor for single point resistance (SPR). SPR was measured in connection with flow measurements. The electrical conductivity (EC) of fracture-specific water was measured in chosen fractures in most of the drillholes. Fractures were selected on the basis of the measured flow from fracture to drillhole. In addition, some previously selected fractures were measured. The EC of the drillhole water was also measured. (orig.)