A translation of Guide de conception et de gestion Des Réseaux d'assainissement unitaires - état de l'art, Paris 1996. The contents include: data on rainstorm run-off pollution; different types of weirs and accessories; computation and measurement of characteristics of weirs; evaluation and improvement of hydraulic output and its treatment; location, checking and choice of weir and its improvement; regulations concerning weir wastes; conclusions and strategy proposed for action and improvement of knowledge; and documents concerning computational methods. The case studies presented are: Impact of wastes of storm weirs; Weirs of Paris; Measurement of quality storm weirs; Measurement of quality of water in sanitary networks; Summary of investigations conducted on weirs of Paris and three districts of première Couronne; Management of works of the Boulogne Loop; Management of interdistrict work of the Parisian agglomeration; The plant at Achères: a new scheme for 2001; and Strategy for overall management of sanitation in Seine Saint Denis.