Development of a Conceptual Stratigraphic Model for the Paducah Gaseous Diffusion Plant (PGDP) and Vicinity

Project Summary

Accurate modeling of regional groundwater flow and contaminant transport depends upon accurately characterizing the spatial distribution of hydraulic conductivity (K, the permeability of porous media to water).  Numerical models of the Paducah Gaseous Diffusion Plant (PGDP) area have assumed that K values are relatively uniform within individual flow units, such as the Regional Gravel Aquifer (RGA).  However, the heterogeneity of sediments within the PGDP area makes it likely that the distribution of K values is more complicated than currently modeled.  Site investigations have provided subsurface lithologic logs for hundreds of monitoring wells and borings.

Despite preliminary efforts by various contractors, these logs have not been used to develop detailed correlations of sedimentary units across the study area.  In addition, sedimentary exposures along streams in the vicinity of PGDP have not been systematically described beyond the relatively simple geologic quadrangle (GQ) maps published by the US Geological Survey in 1966-67.  We propose to integrate lithologic logs, outcrop mapping, and shallow, high resolution seismic surveys already conducted by UK Geological Sciences personnel to provide a stratigraphic framework model of the PGDP area.  This detailed, conceptual model would underpin a more realistic groundwater flow model and could be also useful for assessing local amplification of earthquake ground motion by near-surface sediments.

Lithologic and stratigraphic information was compiled digitally from hard-copy historical documents related to the Paducah Gaseous Diffusion Plant (PGDP) and its environs. More than 300 initial boring and monitoring well logs were compiled to develop a preliminary PGDP and vicinity lithostratigraphic model.  Additionally, project investigators and regional subject matter experts conducted extensive field surveys across the two watersheds encompassing the PGDP and TVA Shawnee Steam Plant facilities to identify and correlate the distribution of lithologic materials.  Lithologic log interpretations and field observations were compiled in ArcView, Surfer, and RockWorks 2002 software.  The software modules were used to produce geologic cross-sections and sub-surface maps of the study area. 

Observations and recommendations for future data collection and assessment are presented in "Lithologic and Stratigraphic Compilation of Near-Surface Sediments for the Paducah Gaseous Diffusion Plant" (see below).  A summary presentationof project results and recommendations (see below)  was presented to the Geological Society of America annual meeting in 2005.

Photo reconnaissance Gravel Exposure in Lower Reach of Bayou Creek
Bayou Creek flows to the east in this reach.
Its course is parallel to Ohio River which flows west and is less than 800 feet away.

Illustrated Hydrolithologic Model of PGDP SWMU 4
developed with data from project stratigraphic database (view from south-southwest).