Pantex Nuclear Plant

An environmental site characterization problem

Dick Gibson analyzed subsurface information from more than 70 wells and borings as part of Argonne National Laboratory's Expedited Site Characterization of the perched aquifer at the Pantex Site. Using lithologic and electrical logs, a model of the complex stratigraphy of the Ogallala Formation was developed. The model was used to predict the positions of horizons underground as well as the water table. Gibson was the wellsite geologist for Argonne's drilling program, in which 4 borings were situated to best characterize the unknown portions of the aquifer section.

The project integrated regional geology, stratigraphy (depositonal environments, facies patterns, and fluvial system geometry), mineralogy and lithology, climatology and fossils (that's Coryphodon, a Tertiary mammal, at upper right), geophysics, hydrology, water chemistry, and politics and policy. The basic conclusion was that a fluvial system within the generally eolian Upper Ogallala Formation follows pre-existing topography (which in turn was related to subsurface collapse because of dissolution of Permian salt) on the confining bed of a perched aquifer system. We were able to predict the geometry of the river system, including its gravels and overbank muds. The wells drilled helped define the southern and eastern edges of the contaminated perched aquifer, which occupies several square miles and is as thick as 30-40 feet. And the study saved several million dollars in what would have been a shotgun-approach to drilling locations.

The work by Argonne's Applied Geosciences and Environmental Management Section (Dr. Jacqueline Burton, head), including Gibson's work, is cited by the Department of Energy as one of the best examples of site characterization in its cleanup program. (Ref: EM Progress, DOE Office of Environmental Management, Vol. 4, No. 5, Fall 1995).

Argonne Frontiers article on this project. That's Dick Gibson in the middle in the image above, which is from this article. The picture shows samples laid out on the ground before the core boxes arrived.

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