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Title: Probability encoding of hydrologic parameters for basalt. Elicitation of expert opinions from a panel of five consulting hydrologists

Technical Report ·
DOI:https://doi.org/10.2172/5563618· OSTI ID:5563618

The Columbia River basalts underlying the Hanford Site in Washington State are being considered as a possible location for a geologic repository for high-level nuclear waste. To investigate the feasibility of a repository at this site, the hydrologic parameters of the site must be evaluated. Among hydrologic parameters of particular interest are the effective porosity of the Cohassett basalt flow top and flow interior and the vertical-to-horizontal hydraulic conductivity, or anisotropy ratio, of the Cohassett basalt flow interior. The Cohassett basalt flow is the prime candidate horizon for repository studies. Site-specific data for these hydrologic parameters are currently inadequate for the purpose of preliminary assessment of candidate repository performance. To obtain credible, auditable, and independently derived estimates of the specified hydrologic parameters, a panel of five nationally recognized hydrologists was assembled. Their expert judgments were quantified during two rounds of Delphi process by means of a probability encoding method developed to estimate the probability distributions of the selected hydrologic variables. The results indicate significant differences of expert opinion for cumulative probabilities of less than 10% and greater than 90%, but relatively close agreement in the middle ranges of values. The principal causes of the diversity of opinion are believed to be the lack of site-specific data and the absence of a single, widely accepted, conceptual or theoretical basis for analyzing these variables.

Research Organization:
Analytic and Computational Research, Inc., Los Angeles, CA (USA); Applied Decision Analysis, Inc., Menlo Park, CA (USA); Rockwell International Corp., Richland, WA (United States). Rockwell Hanford Operations
DOE Contract Number:
AC06-77RL01030
OSTI ID:
5563618
Report Number(s):
RHO-BW-CR-145P; ON: DE85014846
Resource Relation:
Other Information: Portions of this document are illegible in microfiche products. Original copy available until stock is exhausted
Country of Publication:
United States
Language:
English