Characterization of Heterogeneities Controlling Transport and Fate of Pollutants in Unconsolidated Sand and Gravel Aquifers

The purpose of this project was to evaluate promising methods for characterization of heterogeneities in hydraulic conductivity and to assess which are best for the prediction of contaminant movement in shallow alluvium. Although work is still ongoing, this research has produced results of considerable practical significance. A major field and theoretical emphasis was on slug tests. A general model for slug tests in partially penetrating wells was developed, the viability of conventional slug-tests methods in homogeneous and heterogeneous formations was assessed, and a general model for slug tests in formations of high hydraulic conductivity was proposed. A major product was a series of practical guidelines for slug tests, which should considerably improve the quality of parameter estimates obtained using this technique. An important theoretical accomplishment of this project was the development of a new approach for the characterization of spatial variations in flow properties based on the principles of tomography. A major field accomplishment was the design and performance of a large-scale induced gradient tracer test. Although data analysis/interpretation is ongoing, this experiment has clearly yielded an extremely detailed data set describing tracer movement in heterogeneous alluvium. Additional field and laboratory work has produced an excellent data set characterizing parameter variations at the core scale. Five articles have been published on this work and additional articles are under preparation.