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Crosswell Radar Tomography Investigation Of The Eastern Snake River Plain Basalt Flows At The IneelNormal access

Authors: Jared D. Abraham and David L. Wright
Event name: 15th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: Borehole geophysics
Publication date: 10 February 2002
Organisations: EEGS
Language: English
Info: Extended abstract, PDF ( 1.46Mb )

Summary:
A radar tomography investigation was conducted to delineate the hydro-stratigraphy of
the unsaturated zone in the area of the Radioactive Waste Management Complex (RWMC),
Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The RWMC lies on
the eastern Snake River Plain Basalt flows. These flows are typically less than 10 m thick and
are controlled by the underlying topography. The basalt flows are commonly interbedded and
overlain with alluvial, lacustrine, and eolian sediments. These interbedded sedimentary units,
with the complex basalt flow structures, create an area where the hydrology is controlled by the
complex assemblage of interbeds and basalt fractures. To better understand the potential
contaminant transport processes in the interbedded basalts and sediments, crosswell radar was
employed to delineate the complex basalt flow and volcaniclastic environment. The US
Geological Survey's (USGS) borehole tomography radar system was employed in a well pair at
the RWMC in a wet year, 1999, and in a relative dry year, 2001. Tomograms were constructed
from the crosswell data and compared. Results indicate that the radar system can detect the
electromagnetic structure of the basalt flows at the study site. The radar data indicate that the
structure of the basalt can vary significantly in a lateral distance of 4 m. Comparisons between
the wet year and the dry year tomograms indicate that the radar data show changes in water
saturation.

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