Hydraulic Modeling for Emergency Water Supply and Disaster Planning

The City of Atlanta’s water distribution network was evaluated for meeting the minimum production of 65% of the average daily demand (ADD) in emergency shutdown condition at one of the water treatment plants. The study also investigated new locations of intergovernmental emergency water connections between the City of Atlanta (COA) system and neighboring water systems. The results of hydraulic modeling indicated that COA has an internal redundancy in place which meets the 65% ADD requirements. The interconnection capacity coming from other jurisdictions will definitely enhance reliability to COA system. The study proposed certain criteria and methods for emergency situation analysis which can be used by other utilities undertaking similar studies. BACKGROUND The City of Atlanta (COA) water system serves a population of approximately 1.0 million. Three water treatments plants (WTPs) serve the system with the following total permitted capacity: Hemphill WTP (136.5 million gallons per day [mgd]), Chattahoochee WTP (64.9 mgd) and Atlanta-Fulton County (AFC) WTP (90 mgd with 45 mgd Atlanta water system’s share). The service area consists of three pressure zones: the 1020 zone, served by the Chattahoochee WTP; the 1175 zone, served primarily by Hemphill WTP; and the 1225 zone, served primarily by the AFC WTP. The water system includes approximately 2,600 miles of water mains ranging from 2 to 72 inches in diameter. The distribution system consists of both ground and elevated tanks, with a total storage volume of approximately 37.0 million gallons (MG). The topic of emergency water supply and disaster planning has been discussed by the Metropolitan North Georgia Water Planning District (MNGWPD) for several years. It emphasized the need for water jurisdictions to evaluate their system for emergency situations. The MNGWPD has issued certain guidelines for the system evaluation. The City of Atlanta as part of MNGWPD realized the importance of planning for sufficient emergency water supply during desperate times, such as major pipeline failure, water treatment plant failure, or other emergency situations. COA initiated its own internal system verification, for its reliability and redundancy. In May 2010, Georgia enacted the Water System Interconnection, Redundancy and Reliability Act. As directed by the act, the Georgia Environmental Finance Authority (GEFA) undertook a thorough and detailed engineering study to develop a District-wide emergency plan that examines the ability of qualified water systems to accept or share water with adjacent providers during emergencies. This act has most of the