RSC-Programme - Interim Report. Approach and Basis for - Posiva

11other geophysical methods that study the fracture network beneath the tunnel. Proposedparameters for canister scale classification include hydraulic conductivity, Q', fracturezones, fracture width (aperture + filling) and fracture trace length. Results of thecanister scale HRC should ultimately lead to a decision as to whether or not thedeposition hole can actually be constructed in the planned location. If the decision isaffirmative and the deposition hole is made, the HRC will be confirmed by detailedgeological and hydrological investigations in the deposition hole before approving thehole for deposition.HRC testing was performed on the tunnel scale in two stages. During the first stage,data was collected from the pilot holes (ONK-PH2…ONK-PH5). After the tunnelsection corresponding to each pilot hole was excavated, data obtained from the pilotholes was compared to data collected from the tunnel section (stage 2). Several datasources and methods were used for the HRC testing. Data sources include geologicalmodels, geological core loggings of pilot holes, geological tunnel mapping, andhydrogeological measurements from both the pilot holes and corresponding tunnelsections. Data from probe holes is also suggested to be utilised in the HRC. A shortaccount of these is given below; for a more detailed description, the reader is referred toLampinen (2008) and references therein.Geological modelsThe site models published up to 2003 classified repository scale geological structuresmainly according to their constructability and hydraulic properties, the most importantparameters being fracture frequency, RG-classification (engineering geological mappingdata of the core samples), and fracture hydraulic properties. The Olkiluoto bedrockmodel 2003/1 (Vaittinen et al. 2003) classified modelled structures as fractured zones,crushed zones, or hydraulic features based on the observed properties in the drillholes.The classification followed the RG-classification (RiI-RiV) according to FinnishEngineering Geological Classification. Naming convention distinguished R / RH / H -structures.The methodology of structural modelling changed in 2006. Models now aim atthorough site understanding, where any geological features deviating from the averagehost rock can be detected and classified. The modelling approach utilises bothgeological and geophysical data. The Olkiluoto geological site model 2006 v.0(Paulamäki et al. 2006) is divided into the lithological model, the alteration model, thebrittle deformation model and the ductile deformation model. Of these, the brittledeformation model corresponds most closely to the older bedrock models. R-structuresof the previous structural models were partly re-modelled and re-named as brittle faultzones (BFZ) or brittle joint zones (BJZ).The approach for hydrogeological modelling has also evolved. Since the 2006 sitemodel (Andersson et al. 2007), hydrogeological zones are identified using hydraulicdata, mainly measured transmissivity by the Posiva Flow Log (PFL) and pressureresponses. The hydrogeological model is then compared with the modelled brittledeformation zones (BDZ). These comparisons generally show a good overallconsistency. Although some differences exist as some brittle deformation zones may notbe hydraulically important and, vice versa, there may be hydraulically importantfeatures outside the modelled BDZs.