OF TERNARY DIAGRAMS AND CONTAMINANT HYDROGEOLOGY: ONE PILLAR IN THE VAST LEGACY OF DON SIEGEL

I became a student and protégé of Don Siegel’s in 1992, graduated with a MS in Hydrogeology, and went on to a 25-year career as a professional hydrogeologist, achieving further accomplishments such as earning a PhD in Geological Engineering, getting elected to NGWA’s Scientists and Engineers Section’s Board of Directors, and serving as Technology Editor for the journal Groundwater. Although I take most credit for these successes, I can honestly say I would not have gotten this far were it not for the teachings, friendship, and encouragement of Dr. Siegel.

My MS thesis focused on using ternary diagrams to characterize the fate, transport, and remediation of BTX in groundwater, and was the first scientific work that used ternary diagrams to characterize transport of organic chemicals in groundwater (Lipson and Siegel, 2000). By 1992 ternary diagrams were already a well-established geochemical method for dealing with inorganic solutes in groundwater (i.e., major ions). But it was Don’s idea to apply the method in a contaminant hydrogeology context.

The BTX Ternary Diagram theory was premised on the fact that similarly-structured organic molecules with similar solubility characteristics behave differently in groundwater due to differences in their sorption properties and biotransformation pathways. The theory proved to be correct: the method is straight-forward, cost-effective, and produces insightful results.

Following the success of BTX ternary diagrams, Don and another student-protégé of his extended the method to characterize transport of chlorinated solvents PCE, TCE, and TCA in groundwater (Erbe and Siegel, 2001). The method has proven useful for characterizing sources and transformations of dissolved solvents in groundwater, and for characterizing weathering and compositional changes of chlorinated solvent DNAPLs. As a result, we have used BTX Ternary Diagrams to solve contaminant hydrogeology problems at hundreds of sites. Additionally, we have successfully introduced and defended the ternary diagram method into courts of law, where its strong visual impact has helped judges, juries, and other non-technical audiences to “see” the un-seeable.

This presentation will summarize the BTX Ternary Diagram method, provide real-world case study examples, and discuss the teachings and legacy of Dr. Donald Siegel.