Black River Wastewater Treatment Plant - Executive Summary |
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City of Dunn Black River Wastewater Treatment Plant Executive Summary The City of Dunn is committed to provide and maintain a safe environment for employees and the surrounding community. The City's chemical accidental release prevention policy involves an approach that integrates management practices, technologies, and operating procedures. All procedures for the U.S. Environmental Protection Agency (EPA) for Risk Management Program 3 are adhered to. The City of Dunn's emergency response policy involves an Emergency Action Plan for each facility and the emergency response services available in the community. The response policy is in compliance with the Risk Management Emergency Response Program requirements. The Black River Wastewater Treatment Facility is located on Susan Tart Road in Dunn, North Carolina. The primary activity is the use of Chlorine to disinfect the city's effluent prior to pumping to the receiving stream. The facility includes a chlorine building, which c ontains two ton containers of chlorine and two vacuum regulators, and a chlorination room, which contains flow rotameters, flow controllers, and additional safety equipment. The facility is manned 24 hours per day. Wastewater Treatment Operators are trained and respond to any alarms, which may occur. The offsite consequence analysis includes two chlorine release scenarios. These are "Worst Case Release" and " Alternative Release." The worst case scenario is defined by EPA, which assumes that the maximum quantity in the single largest vessel is released as a gas in 10 minutes. The alternative scenario is defined as a release which is "more likely to occur." The distance to the endpoint is the distance a toxic chlorine vapor will travel before dissipating to the point that serious injuries from short-term exposures will no longer occur. For both scenarios the City of Dunn used RMP* Comp, which is a software program developed by the National Oceanic and Atmospheric Administration (NOAA) and the EPA, for determining the endpoint distance. The area within a circle with a radius equal to the toxic endpoint distance is defined to estimate the population potentially affected should an accidental release occur. The worst case scenario at the Black River Wastewater Treatment Plant involves the failure of a one Ton (2000 lbs.) container of chlorine. The atmospheric dispersion modeling was performed using EPA assumptions of wind speed: 1.5 meters/second, stability class: F, and air temperature: 77 degrees F. A distance of .9 miles and an estimate of residential population affected of 1800 was obtained. Passive mitigation measures include a release in an enclosed space in direct contact with outside air. The alternative release scenario involves the failure of a flexible connection from the ton chlorine container to the vacuum regulator. The ton container and the flexible connector are the only pressurized areas in the process. The remainder of the process is a vacuum operated system. The atmospheric dispersion modeling was performed using EPA assumptions of wind speed: 3 meters/second, stability class: D, and air temperature: 77 degrees F. The release rate is 15 pounds/minute with a toxic endpoint of .1 miles and an estimated residential population affected of 20 was obtained. Passive mitigation include the release in an enclosed space in direct contact with outside air. The City of Dunn is in compliance with the "OSHA" Process Safety Management and the "EPA" Risk Management rules. The chemical release prevention program includes operator training, state-of-the-art vacuum process equipment, preventive maintenance program, hazard review of the process, and availability of Process Safety Information. Chemical specific prevention steps include detailed Standard Operating Procedures, increased awareness of the hazards and properties of chlorine, and chlorine leak detectors. No accidental releases of chlorine have occurred at this facility in the past five years. The city has an Emergency Action Plan, which complies with OSHA standard 1910.38. Emergency Response is coordinated with Harnett County Emergency Management, local Fire and Rescue Departments, and the Local Emergency Planning Committee (LEPC). |