Control of Biologically Active Degradation Zones By Vertical Heterogeneity: Applications In Fractured Media EM SCIENCE PROGRAM YEAR END SUMMARY

The objective of this research is to determine the relationship between of biologically active contaminant degradation zones in a fractured, subsurface medium and vertical geological heterogeneities. The research is being performed on samples collected from the Test Area North (TAN) site at the Idaho National Engineering and Environmental Laboratory (INEEL) where a dissolved trichloroethylene (TCE) plume is migrating in the basalts and interbed sediments of the Eastern Snake River Plain (ESRP) aquifer. Research results are leading to an enhanced understanding of the constraints that the geochemical and hydrological environment place on the activities and distribution of TCE-degrading organisms in this fractured subsurface medium. Enhanced understanding allows better decisions to be made regarding the use of remedial technologies such as natural attenuation and in situ bioremediation at geologically complex waste sites. Through this research, investigations conducted by the Subsurface Science Program (SSP) at TAN are being extended in order to develop a mechanistic understanding of the coupled geomicrobial and hydrogeochemical processes that are necessary to predict the field-scale intrinsic degradation rates of TCE. The research objective is being accomplished by characterizing paired cores and water samples from boreholes located in differing geochemical and flow environments within the plume. Analysis of these samples will allow the determination of the spatial correlation