When an accidental water pollution incident occurs, the local authority, as Director of Emergency Operations for the municipality, is suddenly propelled into a role as the decision-maker, in a field it knows little of, amidst a crisis situation. ARCOPOL Plus project aim to give this authority keys to decision-making in the event or threat of a spill of pollutant liable to reach the banks or shoreline of his municipality: crude or refined oil, hazardous and noxious substances, drums, containers, or stranded mammals, oiled birds, waste, etc. This guide is divided into two parts: the first is intended for local authorities. A series of Questions and Answers describes the regulatory context of response. It is followed by a series of "What to do?" reflex cards, operational reference sheets on the initial actions to be taken to respond to the most common types of spills. The second part is intended for the various crisis actors: councilors, municipal agents and officers. This section, composed of practical datasheets on each aspect of response - alert, assessment, safety, clean-up, communication, finance, feedback -, constitutes a "toolbox" to enable these actors to successfully carry out their role. It is concluded with a directory, listing the organizations liable to provide them with support. The video serves as a support to explain to stakeholders the main contributions of this guide.