INTEGRATION OF MULTI-SCALE PHYSICAL AND CHEMICAL HETEROGENEITIES USING HIGH-RESOLUTION DIGITAL IMAGES

High-resolution data sets are needed to improve our understanding of the interaction between subsurface advective, dispersive, and exchange processes and the impact of multi-scale heterogeneity. However, development of these data sets has been hampered by disparities in the scale at which these processes occur and typical scalce of characterization. We demonstrate an outcrop analogue concept in which high-resolution digital images are used to integrate physical and chemical heterogeneities across multiple spatial scales. High-resolution visible and infrared images of a dike dig face on the Hanford Site were compiled into a mosaic spanning heterogeneities from the millimeter scale to tens of meters. Measurements with in situ characterization tools (water and air permeameters) were used to develop a coarse-scale hydrofacies map. This map was supplemented with sedimentological (grain size distribution) hydraulic (water retention, permeability) and hydrogeochemical (distribution coefficient, cation exchange capacity) properties derived from sediment samples. These properties were regressed on grain size and sorting parameters to obtain predictive relationships for the measurement scale. Hydrogeological and hydrogeochemical properties showed strong correlations with texture, as represented by a mean grain size and sorting index. The resulting relationships were used to transform the digital images into high-resolution lithofacies, hydrofacies and chemofacies distributions for input into predictive flow and reactive transport models. This approach is applicable to the generation of multi-dimensional, multi-parameter data sets for input into high-resolution numerical models. The impact of multi-scale heterogeneities on subsurface flow in the dike outcrop is demonstrated in a series of simulations with the STOMP simulator. A companion paper by Yabusaki and Ward explores the impact of heterogeneous sorption parameters derived by this method on the transport ⁹⁰Sr. This work was funded through The Hanford Ground Water Protection Project by the U.S. Department of Energy. The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle under Contract DE-AC06-76RL01830.