Gallatin Wastewater Treatment Plant - Executive Summary |
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The City of Gallatin - Department of Public Utilities uses chlorine at its Wastewater Treatment Plant, this chemical is classified as an extremely hazardous substance by the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA). The same properties that make chlorine effective for disinfecting wastewater prior to discharge into the receivinf stream, also make it necessary to observe certain safety precautions to protect the health and safety of our employees, the members of our community, and the environment. Both the Environmental Protection Agency's - Risk Management Plan and the Occupational Safety and Health Administration's - Process Safety Management regulations were developed to prevent or minimize the impacts of accidental releases of extremely hazardous substances. The City of Gallatin - Department of Public Utilities is committed to complying with these regulations, thereby reducing the risk to our employees and the public. The Gallatin Wastewater Treatment Plant is located at 1501 Lock 4 Road. Sanitary sewge is collected from customers in Gallatin and is piped to lift stations, which then pump the sewage to the wastewater treatment plant. Once the sewage reaches the treatment plant is is treated using the activated sluge process. The activated sludge process is a biological treatment where air is bubbled through the wastewater, suspending microorganisms which breakdown the wastes to carbon dioxide and water. Excess solid matter (sludge) settles out and the resuting treated water is sent to the chlorine contact chamber where chlorine is added to kill any remaining microorganisms. The disinfected water is then discharged into Old Hickory Lake. The chlorine used at the wastewater treatment plant is suppliedin one ton (2,000 pound) cylinder, and there are four to five full cylinders maintained at the treatment plant. There are two chlorine cylinders in use in the chlorine feed room and two or three addit ional cylinders in storage on the loading/storage area. Chlorine is fed to the chlorine contact chamber from the chlorine feed room. Changes at the treatment plant in the coming months will include the addition of a vacuum feed system and process area chlorine detectors, which will greatly reduce the potential for a chlorine release. On-site and off-site consequence analysis have been conducted to determine the potential impacts of a chlorine release at the Gallatin Wastewater Treatment Plant. The off-site consequence analysis considers two chlorine release scenarios, identified as "worst case release scenario" and "alternative release scenario". A "worst case release scenario" is defined as a release that is estimated to create the greatest distance in any direction to an endpoint from an accidental release of a regulated toxic substance from a covered process under worst case conditions. The "worst case release scenario" for the Gallatin Wastewater Treatment Plant involves the failure of a one ton cylinder of chlorine, where the entire contents of the cylinder (2,000 pounds) is released as a gas over ten (10) minutes. The off-site consequence analysis was performed using RMPComp, an EPA computer-modeling program that uses EPA defined release conditions and user data to determine the toxic endpoint. RMPComp calculated the toxic endpoint for the "worst case release scenario" to be 1.3 miles with an estimated affected population of 1,013 persons. An "alternative release scenario" is defined as a release that will reach an endpoint off-site and is more likely to occur than the "worst case release scenario". One "alternative release scenario" was analyzed for the Gallatin Wastewater Treatment Plant. This scenario involved the release of chlorine gas through the 5/16 inch diameter valve body opening on the chlorine cylinder, due to a bad connection or valve failure. This release scenario is outlined in the American Water Works Association Research Foundation 's - Compliance Guidance and Model Risk Management Program for Water Treatment Plants. The release rate, duration and total release data was then entered into RMPComp which calculated a toxic endpoint of 0.1 miles with an estimated affected population of 2 persons. The City of Gallatin - Department of Public Utilities emphasizes the intergration of standard operating procedures, technology and management procedures, at all of its facilities, to control the risks associated with the use of chlorine. The safety features inherent in the design of wastewater treatment plants and the training of our personnel promotes the safe handling of chlorine in the disinfection of wastewater. In fact, we have not had an accidental release of chlorine at the wastewater treatment plant in the past five (5) years. An emergency response plan, which addresses accidental chlorine releases, has been developed for the Gallatin Wastewater Treatment Plant. This plan was prepared using guidance from the Ch lorine Institute, the National Reasponse Team's Integrated Contigecy Plan, the American Water Works Association, and the EPA. The emergency response plan is being coordinated with the Gallatin Fire Department and the Sumner County Emergency Management Agency; and includes procedures for public notification of a release, personal protective equipment, evacuation, first aid, and incident investigation. Also, the City of Gallatin - Department of Public Utilities has formed an in-house Hazardous Incident Response Team to respond to accidental chemical releases and other emergency situations at its facilities. The management and staff of the City of Gallatin- Department of Public Utilities is committed to the safe operation of our facilities and encourages input from our employees and our community. |