Conclusions from working group 1: partially-saturated porous and fractured media test cases Las Cruces trench and Apache leap tuff studies

This paper describes the results of two test case studies carried out in the framework of the INTRAVAL project devoted to the performance assessments of radioactive waste repositories. The studies were conducted using data from the Las Cruces Trench (LCT, New Mexico, USA) and Apache Leap Tuff Site (ALTS, Arizona, USA) experiments to evaluate models for water flow and contaminant transport in unsaturated, heterogeneous soils and fractured tuff. Experimental data and detailed field characterization studies from the LCT experiments provided informations for developing and calibrating the models. Point comparison of water content and solute concentration, and predicted mean behavior for water flow and tritium transport indicated that no model, whether uniform or heterogeneous, proved superior. The ALTS experiments were designed to evaluate characterization methods and associated conceptual models for coupled matrix-fracture continua over a range of scales. Laboratory and field tests were conducted for estimating pneumatic, thermal, hydraulic and transport property values for different models. Comparisons between models and field-scale experiments are discussed. The study stresses on the importance for experimentalists and modelers of working together to solve complex flow and transport problems. (J.S.). 32 refs., 6 figs., 4 tabs