Effective porosities of basalt: A technical basis for values and probability distributions used in preliminary performance assessments

The Basalt Waste Isolation Project in its role of evaluating the feasibility of siting a high-level nuclear waste repository in the deep basalts of the Columbia Plateau is gathering information on basalt parameters that define waste isolation capability. Effective porosity is an important parameter in fluid transport analysis on repository performance assessment. This report presents and discusses the technical basis for values and probability distributions of effective porosity for the candidate site in basalts of the Hanford Site in Washington State. The appropriateness of different types of probability distributions of values of effective porosity for the major basalt hydrogeologic units (i.e., flow tops and flow interiors) of candidate flows are considered with respect to their applicability in performance assessment models. 36 refs., 23 figs., 9 tabs.