City of Columbia Water Treatment Pl - Executive Summary |
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EXECUTIVE SUMMARY The City of Columbia Water Treatment Plant in McBaine, Missouri (Facility) is located approximately 10 miles south-southwest of Columbia, Missouri, and supplies potable water to Boone County. The Facility stores and uses the following Clean Air Act Section 112r (CAA-112r) regulated substances in the following regulated processes: Substance: Chlorine Process: Water treatment - chlorination The chlorine used at the Facility is stored in 1-ton cylinders and a maximum quantity of approximately 30,000 pounds is present at one time. There is one chlorine process line at the Facility and four cylinders are in use at all times. Although there have been no chlorine releases or accidents at the Facility in the past 5 years, there are public receptors immediately adjacent to the facility. Due to the hazardous nature of chlorine, the City of Columbia Water Treatment Plant has coordinated with the Columbia Fire Department to resp ond to emergencies. The Facility has generated the Risk Management Plan to minimize the risk to plant personnel and surrounding communities. A complete Prevention Program is included that is consistent with the Occupational Safety and Health Administration requirements for Process Safety Manuals. An Emergency Response Plan has also been developed with detailed instructions for handling a chlorine release at the Facility. Water plant employees undergo continuous safety training and the process line is inspected daily. In addition, the Facility has installed an automated discharge detection and response system (including the new Halogenb Valves) that significantly reduces the risk of a chlorine release. The valves are automated and close all four online cylinders immediately following detection of chlorine in the cylinder room, feed room, or in the basement below the cylinder room. As required for the Risk Management Plan, the Facility has evaluated the chlorination process line t o determine possible sources of chlorine releases. In addition, the offsite impact of two possible release scenarios has been evaluated. The first scenario, the Worst Case release scenario, is the release of one entire chlorine cylinder within 10 minutes. The effect of the release is mitigated by the fact that the cylinders are enclosed in a building, and by the earthen berm that surrounds the plant. The second release scenario, the Alternative release scenario, is the rupture of flexible hosing connected to the four active chlorine cylinders. This release scenario was selected because the flexible hosing is the only portion of the process line that is not under vacuum. Therefore, aside from a catastrophic release from the cylinders themselves (represented by the Worst Case scenario), the only reasonable release scenario is the rupture of the process line on the pressure side. The offsite consequence evaluation for this Facility was completed using RMP*Comp. Mitigating factors for both scenarios included the building enclosure and an urban setting (used to represent the 10 foot earthen berm that surrounds the Facility). The building and the berm both act to reduce migration of liquid and vapor phase chlorine. Evaluation of the distance to a toxic endpoint for this facility resulted in a radius of influence of 0.9 miles for the Worst Case release scenario (release of one entire chlorine cylinder) and 0.6 miles for the alternative release scenario (rupture of the flexible connections on the chlorine process line). The area encompassed by the Worst Case radius includes a population of approximately 50 people and one public recreational area. There are no environmental receptors within the potentially affected area. As stated above, the City of Columbia Water Treatment Plant has coordinated with the local fire department to improve their response capabilities in an emergency. An Emergency Response Plan is incorporated into the Risk Management Plan and a ll Facility employees are trained in emergency response. Public notification and evacuation, if necessary, will be conducted by local emergency personnel in a timely and comprehensive manner. In addition to existing prevention and response efforts, the City of Columbia Water Treatment Plant personnel are also making modifications to further insure safe operation. Emergency lighting is being upgraded, the chlorine detectors are being integrated into the SCADA system, and training and maintenance procedures are constantly being improved. |