Scale-dependent Subsurface Processes: Initial Evaluation

Determination of the distribution and quantity of non-aqueous phase liquids (NAPL) in the subsurface requires accurate evaluation of the effective parameters governing flow in porous media. A great deal of the work done towards the development of effective parameters has focused on analysis techniques for adapting parameters determined from a small-scale to a fieldscale system. These techniques suffer from the inherent limitations of developing conclusions about regional or grid-scale flow based on a limited number of smaller-scale, isolated measurements. A conservative tracer injected into heterogeneous media will, however, be affected by all the heterogeneities encountered in the existing flow-fields between the site of injection and extraction. A tracer test provides a direct measurement of the heterogeneous system. A series of tracer tests were performed to assess the ability of tracers to function as a tool for determining effective fieldscale parameters. Experimental design focused on creating a heterogeneous system with known stochastic parameters which could be modified by NAPL entrapment. The analytical work concentrated on developing techniques to interpret the tracer test results.