CASE STUDY: City of Atlanta CSO Program “Utilization of GIS and SSES Investigations to Develop a Watershed Approach to Sewer Separation Planning & Storm Water Management”

In 1998, the U.S Department of Justice found that Atlanta's CSOs were violating water quality laws; and the city signed a Consent Decree that requires a long-term control plan be implemented to remediate the overflow from its combined sewers. Sewer separation is one of the control measure alternatives being considered by the City. The City entered into the First Amended Consent Decree (Consent Decree) on July 22, 1999. This amendment to the Consent Decree imposed obligations on the City to improve the operation of combined sewer collection and sanitary systems throughout the entire City. This obligation resulted in the sewer separation alternative also be in conformance to the Consent Decree.To thoroughly review the sewer separation alternative, the City of Atlanta decided in the late summer of 1999 that a comprehensive watershed approach to sewer separation planning should be developed. The holistic approach considered future land use and urban development within the combined sewer area basins, and provides for the additional storm water and sanitary sewer conveyance capacity needed to accommodate the City's future growth.To complete the data collection needed to quickly finish the project, the City's Geographic Information Systems (GIS) and Sewer System Evaluation Surveys (SSES) programs had to be accelerated to support the development of required hydraulic models and a GIS Decision Support Framework.When completed, the GIS based tool will provide the City of Atlanta the ability to store and analyze data related to existing and proposed land uses; transportation improvements, storm water detention and other water quality enhancement projects. This tool provides for better management of the existing collection system in each of the six combined sewer watersheds.