1. Task #8: Hydraulic interaction rock/bentonite Objectives: Scientific understanding of the exchange of water across the bentonite-rock interface. Better predictions of the wetting of the bentonite buffer. Better characterisation methods of the canister boreholes.

2. Modelling task The task would be to model the evolution in space and time of: the rock: the water pressure and water flow in the rock matrix and fractures the bentonite: the water pressure, total pressure (swelling pressure), density and water content the interface: Exchange of water over the interface between the bentonite and a sparsely fractured rock. The interface as a mutual boundary.

3. Bentonite Rock Interaction Experiment (BRIE) Åsa Fransson, Chalmers University of Technology, Sweden The experiment includes two major parts: Part I Includes the selection and characterization of a test site and central borehole(s). Part II Handles the deposition and extraction of the bentonite buffer.

4. Experiment layout (prel.)

5. Objectives Part I Select a site: Choice of an experiment area based on Äspö hydrogeological conditions and a few exploratory boreholes. Characterise the site. Including cored boreholes, borehole logging and hydraulic tests. Characterise a central borehole(s) for deposition of bentonite buffer. Drilling and testing of the central borehole(s) (and surrounding boreholes). Structural model of the experiment area.

6. Ongoing and planned work (Aug. – Oct.) An introductory literature review to present an overview of SKB methods for deposition hole excavation and bentonite deposition. Identification of important investigation stages, parameters and processes. Meeting at Äspö to discuss possible sites for the experiment. Initial description of one (or a few) of the sites based on available data.

7. Wish list test site *Low inflow* Time 3 – 5 years

8. Suggested investigation stages (prel.) a)3. Selection of site b)4. Site characterization c)6. Drilling of central borehole (and characterization) d)Draw-down and stabilization e)9. Deposition of bentonite buffer f)12. Pressure recovery and saturation g)12. Recovered and saturated (overcoring) Numbers related to activities for Task #8. a) & b) c) d) e) f) g) Part I Par t II

9. 0.8 2 – (3) m 1.1 0.4 0.6 1.0 3. Site selection (prel.) ActivityObjective * Cored drilling of 5 – 10 exploratory boreholes (3-5 m)Identify depth of fractures and inflows during drilling. Drill 1 st borehole Identify contacts between boreholes. Installation of packer (single) and logging of pressure. Drilling of 2 nd borehole (synchronise time) Installation of packer and logging of pressure etc. * Posiva Flow Log or similarIdentify depth of conductive fractures, flow and T. * BIPS (Borehole Image Processing System)Identify depth and orientation of fractures * Geological mapping of all cores (Boremap).Identify depth of fractures, open, sealed, filling etc  Select site(s) for central borehole(s) / change site / continue investigations * Full-length Pressure Build-up tests, logging of pressure.Identify fractures, contacts between boreholes, T & S.  Select site(s) for central borehole(s) / change site

10. 4. Site characterisation a) ActivityObjective * Cored drilling of 5 – 10 new boreholes(3-5 m)Identify depth of fractures and inflows during drilling. Drill 1 st borehole (synchronise time) Identify contacts between boreholes. Installation of packer (single) and logging of pressure. Drilling of 2 nd borehole Installation of packer and logging of pressure etc. * Posiva Flow Log (PFL) or similarIdentify depth of conductive fractures, flow and T. * BIPS (Borehole Image Processing System)Identify depth and orientation of fractures * Geological mapping of all cores (Boremap).Identify depth of fractures, open, sealed, filling etc * Geological mapping of tunnelIdentify location, strike dip of fract., inflow, dripping etc * Measurement of coordinates for all boreholesIdentify x, y,z 0.8 2 – (3) m 1.1 0.4 0.6 1.0

11. 4. Site characterisation b) ActivityObjective  Selection of sections for additional hydraulic tests (based on PFL or similar) * Full-length (change packer) and section Pressure Identify fractures, contacts between boreholes, T & S. Build-up Tests, logging of pressure all boreholes.Saturated conditions Towards central borehole, improved characterisation * Section Constant pressure tests, logging of pressure.Identify fractures, contacts between boreholes, Q(p): De-gassing, deformation, turbulence * Measurement of inflow central borehole (76 mm), Identify total and point inflows, locations pressure logging all other boreholes. 5. Prediction (A) of the inflow to the central borehole. Data available Sept (July) 2010 (meeting). 0.8 2 – (3) m 1.1 0.4 0.6 1.0

12. 6. Characterisation of central borehole(s) a) ActivityObjective * Measurement of inflow central borehole (76 mm), Identify total and point inflows, locations, pressure pressure logging all other boreholes (synchronise time) * Drilling of (two) central borehole(s). Identify depth of fractures and inflows during drilling. * Measurement of inflow central boreh., pressure loggingIdentify total and point inflows, locations, pressure * Full-length and section Pressure Build-up Tests, Identify fractures, contacts between boreholes, T & S. logging of pressure all boreholes (central boreh. open.Unsaturated conditions * Section Constant pressure tests, logging of pressure.Identify fractures, contacts between boreholes, Q(p): De-gassing, deformation, turbulence * BIPS or similar (300 mm borehole)Identify depth and orientation of fractures, inflows 0.8 2 – (3) m 1.1 0.4 0.6 1.0

13. 6. Characterisation of central borehole(s) b) ActivityObjective * Measurement of inflow central boreh., pressure loggingIdentify total and point inflows, locations, pressure prior to installation of bentonite. Special packer (300 mm).Unsaturated to saturated conditions Data available Dec 2010 (workshop). 7. Comparison of prediction (A) to data of central borehole 8. Prediction (B) of the wetting of the bentonite in central borehole. Part II * Measurement of inflow central boreh., pressure loggingIdentify total and point inflows, locations, pressure (*Section PressureBuild-up Tests, Identify fractures, contacts between boreholes, T & S. logging of pressure all boreholes.Initial (unsaturated) conditions. ) 9. Installation of monitoring equipment and bentonite in central borehole. Monitoring. 0.8 2 – (3) m 1.1 0.4 0.6 1.0

14. Modelling task / Monitoring The task would be to model the evolution in space and time of: the rock: the water pressure and water flow in the rock matrix and fractures. Monitoring following installation of bentonite: Pressure the bentonite: the water pressure, total pressure (swelling pressure), density and water content. Monitoring following installation of bentonite: Pressure, Moisture the interface: Exchange of water over the interface between the bentonite and a sparsely fractured rock. The interface as a mutual boundary. Initial (unsaturated) conditions: Measured water pressure and flow (just) before installation of bentonite. Data from 6. Characterisation of central borehole(s): Transmissivity, T, Storage coefficient, S, Hydr. cond., K, all boreholes. Measured pressure and flow (central borehole) prior to installation of bentonite (Q(p): natural recovery and different pressures). Special packer (300 mm). Saturated conditions: Data from 3. & 4. Site selection & Site characterisation: T, S and K all boreholes.

15. DFN / Hydro-DFN (deterministic) DFN: Compilation of fracture mapping. Location (x,y,z) and orientation (strike/dip) of fractures (sealed, open) along boreholes and tunnel. Hydro-DFN: Compilation of fracture mapping and hydraulic tests. Location (x,y,z) and orientation (strike/dip) of (flowing, dripping) fractures along boreholes and tunnel. 3D compilation to identify (verify) hydraulic connections between fractures.