Certain key disputes remained unresolved after extensive and for the most part successful efforts by the Columbia River Estuary Study Taskforce (CREST) to develop a management plan for the Columbia River estuary and its shorelands. The remaining disputes, involving conflicts between resource protection and port development, were resolved by the mediation process described in this paper. This process, involving exploration, process design, negotiation, and implementation phases, led to the signing of an agreement by twelve negotiators, the subsequent endorsement of the agreement by the federal, state, and local governmental bodies they represented, and the incorporation of the terms of the agreement into the comprehensive plans of local governments. The agreement describes the particular kinds of port‐related development that might be appropriate at specific sites in the estuary and the conditions under which such development might take place. It also outlines areas where development alteration would not occur. For some of the sites it presents constraints on dredge‐and‐fill activities, turning basin and navigation‐channel depths and widths, corridors for pilesupported causeways and accessways, and mitigation policies.