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Conference Proceeding

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A combined tracer and time-lapse radar imaging experiment was conducted in the unconfined coarse fluvial aquifer at the Boise Hydrogeophysical Research Site in August, 2001. Two tracers (bromide and uranine) were injected to form a plume over a 4-m interval that spanned the contact between hydrostratigraphic units with contrasting permeability. The tracer plume traveled 6.9 m to well B6, passing through well A1 instrumented with 20 sampling zones over a 5-m interval that spanned the injection interval. Radar tomographic data were collected periodically on cross-sectional and longitudinal planes, two of which passed through well A1 for quantitative calibration of radar attenuation tomograms in terms of solute concentration. Pre-test three-dimensional modeling was used to provide estimates of bromide concentration distributions under a variety of scenarios to help optimize (a) radar responses in tomographic planes, and (b) pumping rate from B6 to minimize influence on the plume while ensuring plume passage through A1 and complete breakthrough in two weeks. Bromide breakthrough occurred first and with greatest concentration in the higher permeability unit as expected. Time-lapse cross-hole radar data show plume-related differences in expected regions with time-lapse level runs and time-lapse attenuation-difference tomograms. Uranine breakthrough was significantly diminished and delayed relative to bromide; follow-up experiments suggest biological activity associated with cottonwood roots caused the non-conservative uranine behavior.

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This article was originally published by the Environmental and Engineering Geophysical Society (EEGS) in Symposium on the Application of Geophysics to Engineering and Environmental Problems 2003. Copyright restrictions may apply.