City of Minot Water Treatment Plant - Executive Summary |
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Risk Management Plan Executive Summary Water Treatment Plant City of Minot, North Dakota General The Clean Air Act (CAA) requires facilities that handle hazardous substances bear the primary responsibility for ensuring their safe use. The CAA section 112(r)(1) general duty clause outlines the basic statutory principle that facilities are responsible for designing and maintaining a safe plant, identifying their hazards and minimizing the consequences of accidental chemical releases. Facilities that exceed threshold quantities established by the Environmental Protection Agency (EPA) are required to prepare risk management plans that include hazard assessment, an accident prevention program and emergency response program. The City of Minot water treatment plant (WTP) is required to develop a Risk Management Plan because the facility exceeds the chlorine quantity threshold as established by the EPA. Chlorine is used as a disinfectant in the treatment process. A maximum of eight on e ton cylinders are stored at the WTP at any one time. Chlorine Storage and Handling Four chlorine cylinders are stored in a room specifically designed for the storage of these tanks. The remaining four cylinders are stored outside. The room is equipped with chlorine gas detection equipment and an active ventilation system. If chlorine gas is detected within the storage room an alarm will alert WTP personnel and the ventilation system will start removing the gas from the storage room. Access to the chlorine room is through an outside entrance that is kept locked. The chlorine cylinders are equipped with a valve that requires a vacuum to be applied to it in order to open. This eliminates discharges from the cylinder if a line or fitting fails. Self contained breathing apparatuses are also available to WTP personnel if needed in case of an emergency. Five Year Accident History There have been no chlorine related accidents at the WTP in the last five years. Release Scenarios Two release scenarios have been developed to estimate the toxic endpoints if a release occurs (worst case and alternative). Distance to toxic endpoints were calculated by the RMP*CompTM software program developed by the EPA and NOAA (National Oceanic and Atmospheric Administration). Following are the parameters and results for each of the two scenarios. A) Worst Case Scenario * Chemical - Chlorine Liquefied Under Pressure * Quantity Released - 2,000 Pounds * Release Duration - 10 Minutes * Release Rate - 200 pounds per minute * Mitigation Measures - Release in enclosed space, in direct contact with outside air. * Toxic Endpoint - 0.0087 mg/L * Wind Speed - 1.5 meters/second * Stability Class - F * Air Temperature - 77 degrees F * Estimated Distance to Toxic Endpoint - 0.9 Miles * Estimated Population Affected - 9,200 B) Alternative Scenario * Chemical - Chlorine Liquefied Under Pressure * Quantity Released - 2,000 Pounds * Release Duration - 3.2 Minutes * Release Rate - 620 po unds per minute * Mitigation Measures - Release in enclosed space, in direct contact with outside air. * Toxic Endpoint - 0.0087 mg/L * Wind Speed - 3 meters/second * Stability Class - D * Air Temperature - 77 degrees F * Estimated Distance to Toxic Endpoint - 0.3 Miles * Estimated Population Affected - 3,700 Safety Training WTP personnel are trained on the proper safety procedures if an accidental chlorine release occurs every six months. The training consists of notification requirements, use of SCBA's, health affects, proper use of leak repair kit, and proper procedures to take if a release occurs. Emergency Response WTP personnel are trained to handle all minor chlorine releases. The local fire department would be contacted if a large release occurred. The fire department would make the decision if an evacuation operation would be required. Planned Change to Improve Safety The City of Minot is planning on installing a chlorine scrubber on the discharge side of the chlorine storage room ventilation system. This scrubber will be installed on the next major improvement project at the WTP (scheduled for 2005). |