Models of participatory or consensual planning based on theories of communicative action and rationality are emerging as an important paradigm for interpretation of the process of planning. Within this framework, Forester (1991) has described planning as "anticipatory analysis" - the work of anticipating implementation and managing argumentation. This article uses Forester's framework to analyze the role of planners in managing argument about wellhead protection in Indianapolis, Indiana. The article examines the ways in which planners envisioned alternative futures, structured and managed processes of argumentation, and presented recommendations for risky, technical decisions. It concludes with observations about the usefulness of the model of anticipatory analysis in environmental planning.