Dr. Istok, PE is a groundwater hydrologist who specializes in bioremediation processes for chlorinated solvents, radionuclides, and explosives in contaminated aquifers. He conducts both large-scale laboratory experiments in physical aquifer models and pilot scale field experiments. He has developed the single-well, push-pull test and is the recognized expert in its application. He has performed thousands of push-pull tests to detect and quantify a wide variety of biogeochemical reactions occurring in the subsurface and to pilot test larger scale remedial processes.

He is the author of three widely used books (Push-Pull Tests for Site Characterization, Aquifer Testing: Analysis and Design of Pumping and Slug Tests, and Groundwater Modeling by the Finite Element Method) and he also teaches classes and short courses in groundwater hydrology, groundwater modeling, and groundwater remediation.

Research Interests

Research aimed at developing novel in situ aquifer characterization technologies focuses on the single-well "push-pull" method, which consists of the controlled injection of a prepared test solution into a single well followed by the extraction of the test solution/groundwater mixture from the same well. Within the aquifer, reactive components of the test solution are converted to products by various physical, chemical, and microbiological reactions. By measuring the concentrations of all solutes during the extraction phase, the mass of reactant consumed and product produced and reaction rates can be computed. The test is being applied at a variety of contaminated sites to study and quantify in situ microbial metabolic processes, sorption and ion exchange reactions, NAPL dissolution and mobilization, and heavy metals solubilization and mobilization.