SE0200328 Tecnnicai Testing the methodology for site descriptive modelling Application for the Laxem a r area Johan Andersson, JA Streamflow AB Johan Berglund, SwedPower AB Sven Follin, SF Geoiogic AB Eva Hakami, Itasca Geomekanik AB Jan Halvarson, Svensk Kärnbränslehantering AB Jan Hermanson, Golder Associates AB Marcus Laaksoharju, Geopoint Ingvar Rhen, Sweco VBB/VIAK Carl-Henric Wahlgren, Sveriges Geologiska Undersökning August 2002 Svensk Kärnbränslehantering AB Swedish Nuclear Fuel and Waste Management Co Box 5864 SE-102 40 Stockholm Sweden Tel 08-459 84 00 +46 8 459 84 00 Fax 08-661 57 19 +46 8 661 57 19 S/44 Testing the methodology for Application for the Laxemar area Johan Andersson, JA Streamflow AB Johan Berglund, SwedPower AB Sven Follin, SF Geologie AB Eva Hakami, Itasca Geomekanik AB Jan Halvarson, Svensk Kärnbränslehantering AB Jan Hermanson, Golder Associates AB Marcus Laaksoharju, Geopoint Ingvar Rhen, Sweco VBB/VIAK Carl-Henric Wahlgren, Sveriges Geologiska Undersökning August 2002 An important part of the Swedish Nuclear Fuel and Waste Management Company (SKB) preparation for the site investigations starting in 2002 concerns Site Descriptive Modelling. SKB has conducted two parallel subprojects in this area. The first entailed establishing the first version (version 0) of the Site Descriptive Model of the three sites North Tierp, Forsmark and Simpevarp. An essential part of this work is compiling existing data and interpretations of these sites in a regional scale. The other subproject, presented in this report, concerns testing the Methodology for Site Descriptive Model- ling by applying it to the existing data obtained from investigation of the Laxemar area, which is a part of the Simpevarp site. This project is primarily a methodology test. The lessons learned will be implemented in the Site Descriptive Modelling during the coming site investigation. The intent of the project has been to explore whether available methodology for Site Descriptive Modelling based on surface and borehole data is adequate and to identify potential needs for development and improvement in the methodology. SKB wants to demonstrate that a Site Descriptive Model can be established for a real site following structured and discipline integrated procedures in accordance with the intentions earlier presented. The project has also given the opportunity to test the different computer tools associated with building a site descriptive model. The site specific data of Laxemar is comparable to the planned wealth of data after the Initial Site Investigation stage as envisaged by SKB. However, the data have been collected by different methods and the boreholes have partly been a test bed for new measurement techniques. The Site Descriptive Model should be reasonable, but should not be regarded as a 'real' model. There are limitations both in input data and in the scope of the analysis. The work has been conducted by a project group with representatives from the main disciplines, geology, hydrogeology, hydrogeochemistry and rock mechanics. The different experts assessed and evaluated data and explored different modelling options. However, the full project group also met at regular intervals to discuss on a detailed level the current progress and ideas of the different modelling teams. In this way, the project also serves as a test bench for working interdisciplinary in order to reach a consistent understanding of a site. Anders Strom Site Investigation - Analysis PLEASE BE AWARE THAT ALL OF THE MISSING PAGES IN THIS DOCUMENT WERE ORIGINALLY BLANK A special project has been conducted where the currently available data from the Laxemar area, which is part of the Simpevarp site, have been evaluated and interpreted into a Site Descriptive Model covering: geology, hydrogeology, hydrogeochemistry and rock mechanics. Description of the surface ecosystem has been omitted, since it was re-characterised in another, parallel, project. Furthermore, there has been no evaluation of transport properties. The project is primarily a methodology test. The lessons learnt will be implemented in the Site Descriptive Modelling during the coming site investiga- tion. The intent of the project has been to explore whether available methodology for Site Descriptive Modelling based on surface and borehole data is adequate and to identify potential needs for development and improvement in the methodology. The project has developed, with limitations in scope, a Site Descriptive Model in local scale, correspond- ing to the situation after completion of the Initial Site Investigations for the Laxemar area (i.e. 'version 1.2' using the vocabulary of the general execution program for the site investigations /SKB, 2001/). The Site Descriptive Model should be reasonable, but should not be regarded as a 'real' model. There are limitations both in input data and in the scope of the analysis. The modelling process The measured (primary) data constitute a wide range of different measurement results including data from two deep core drilled boreholes. These data both need to be checked for consistency and to be interpreted into a format more amenable for three-dimensional modelling. Examples of such evaluations are estimation of surface geology, lineament interpretation, geological single hole interpretation, hydrogeological single hole interpre- tation and assessment of hydrogeochemical data. Furthermore, while cross-discipline interpretation is encouraged there is also a need for transparency. This means that the evaluations first are made within each discipline and after this compared to check for potential inconsistencies. The processed data are used for three-dimensional modelling. The geological modelling provides the geometrical framework for the modelling in other disciplines and results in descriptions of geometry and properties of deformation zones of sizes down to 'local major zones' (1-10 km) and geometry and properties of rock domains. Two descriptions have been derived; the Base Geological Model and the Alternative Geological Model. Given the limited amount of data, regions of the model domain still have quite uncertain descriptions. The geometry is represented using a 3D CAD software (RVS), which is also used as an active interpretation tool for the geometric modelling. The base for the hydrogeological modelling is the Geological Model with its identified volumetric objects. Essential hydrogeological evaluation tools include: assessment of single hole hydraulic tests, interpretation of interference tests and numerical modelling of groundwater flow tests and other observations. The resulting hydrogeological description comprises hydraulic properties for defined geometrical units and boundary conditions for the present day conditions for the rock volume defined by the Base Geological Model. The major tasks for the hydrogeochemical evaluation include: (i) characterisation of undisturbed groundwater chemistry including the origin, depth/lateral distribution and the turnover time; (ii) focusing on data of importance for the safety evaluation such as pH, Eh, chloride, sulphide, colloids and microbes; (iii) identification of possible dissolved oxygen at repository depth. The hydrogeochemical description concerns distribution of the major water types, the water type mixing proportions and lists the major type of chemical reactions occurring at the site. Even if much of the modelling can be done in parallel with other disciplines, consistency checks with hydrogeology can and have been made. These comparisons enhance the confidence in the model. The rock mechanics description comprises the initial (i.e. prior to excavation) stresses and the distribution of deformation and strength properties of the intact rock, of frac- tures and fracture zones, and of the rock mass. Only limited mechanics data exist from the Laxemar site, still predictions (with low confidence) are made using inferences from the nearby Aspo site combined with assessing the yet available site specific data. Lessons learnt The resulting Laxemar Site Descriptive model can be regarded as a good illustration of the kind of description which will be produced at the end of the Initial Site Investigation stage ('version 1.2'). However, it should also be remembered that the description pro- vided has been produced within the limitations in scope of the project. These limitations concerned the need to test new procedures, limitations in data as compared to the planned site investigations, and to some extent also limitations in resources. Should a version 1.2 model be needed for the area, the modelling work needs to be substantially revised, reflecting the data then being available. The successful completion of the project also demonstrate that site descriptive modelling, as envisaged in the general execution program for the site investigations /SKB, 2001/, is indeed doable, even if it requires significant resources in time and staff. The project has tested a substantial part of the procedures to be applied in the 'real' modelling, and several potential improvements have been identified. When possible, these improvements have already been implemented during the course of the work. The remaining are listed, to be considered for the future site descriptive modelling. Contents 1 Introduction 11 1.1 Background 11 1.2 Scope and Objectives 12 1.2.1 Objectives 13 1.2.2 Limitations in scope 13 1.3 Methodology and organisation of work 14 1.3.1 What shall be estimated? 15 1.3.2 Evaluation of primary data 16 1.3.3 Estimating