This manual for the development of emergency operating plans for municipal wastewater treatment systems was compiled using information provided by over two hundred municipal treatment systems. It covers emergencies caused by natural disasters, civil disorders and strikes, faulty maintenance, negligent operation, and accidents. The effects of such emergencies considered are personnel absence, equipment failure, power loss, blocked access, communication loss, and the protective measures suggested include vulnerability analysis, warning devices, stand-by and/or duplicate procedures, and preventive maintenance. A list of responses to specific emergencies or failure of specific systems is given. A checklist is provided to assist in the preparation of emergency operating and response manuals. (BB)