Contaminant hydrogeology ― dollars and sense

Abstract The unprecedented growth in contaminant-related aspects of hydrogeology has left an amazing legacy of science and technology. The stimulus for this growth in the United States was a group of regulations designed to clean up existing problems involving hazardous wastes and eliminate future problems. At the same time, there has been a continuing effort in developing subsurface repositories for the disposal of high-level nuclear waste. There have been impressive technological achievements in direct and indirect methods for plume definition, new techniques for site remediation, and measurement of hydraulic parameters for low-permeability rock at great depths. Achievements on the theoretical side of the science are no less impressive. Great strides have been made in understanding some old transport processes (e.g., dispersion) and describing new ones (e.g., diffusion into the matrix), verifying these theoretical ideas in field tests, and dealing with an old nemesis — fractured rocks. Sprinkled in this mix are some disappointments, the great difficulty that seems to exist in translating theory into practice, the apparent difficulty in technology transfer. and the aimlessness of too much of our theoretical work. Trends for the future that seem to be emerging include a return to field and experimental work, a more systematic look at problems, an increased reliance on computer technology, and the demise of “blue-sky research”.