City of Boca Raton Utility Services - Executive Summary |
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Executive Summary Risk Management Plan, Glades Road Water and WastewaterTreatment Plant Introduction At the turn of this century water borne diseases were leading causes of death in the United States. Epidemics of typhoid, cholera, dysentery and other water-borne diseases occurred. After the introduction of chlorine into public water supplies, deaths from typhoid in the U.S. dropped dramatically from 25,000 in 1900 to less than 20 in 1960. Water-borne disease is still a leading cause of infant mortality in many countries throughout Asia, Africa, and Latin America where infant mortality rates are 10 to 20 times greater than in the U.S. In the U.S., however, water-borne disease has been virtually eliminated due to an effective public health strategy of using chlorine for drinking water disinfection. Chlorine disinfection is arguably one of the greatest achievements for public health worldwide in the last hundred years and is credited with increasing the life expectancy of Americans by more than 50 percent. The use of chlorine is not risk free, however. Historically it is clear that utilities have recognized the risks and have been successful in developing procedures to handle chlorine safely and to protect the off-site public and the environment from potential accidental releases. The United States Environmental Protection Agency promulgated Hazardous Chemical Risk Management Program regulations to further ensure that facility owners understand the risks and take proactive efforts to reduce risk through comprehensive training programs, procedures, and risk mitigation measures. Additionally, EPA wanted the public to be informed regarding these issues. The City of Boca Raton Utility Services Department (CBRUSD) has always understood these risks and has maintained a well-trained staff and a safely operated and maintained facility. The CBRUSD has taken a comprehensive approach to be in full compliance with the RMP regulation by June 21, 1999. Facility Background T he City of Boca Raton owns and operates the Glades Road Water Treatment Plant (GRWTP) and Wastewater Treatment Plant (GRWWTP). The facility's mission is to protect public health by providing our community with safe drinking water, free of harmful pathogens and produce a disinfected effluent for discharge . Approximately 3500 pounds per day of chlorine gas is used to disinfect the drinking water and make it safe for human consumption. A maximum of 60,000 pounds of chlorine is stored on-site at the GRWTP. At the GRWWTP, approximately 675 pounds per day is used and a mximum of 28,000 lbs stored. The chlorine is stored as a gas that is liquefied under pressure in containers that contain 2,000 pounds each. Chlorine Process and Safety Equipment At the GRWTP, chlorine can be added to the raw water, filter inlet and finish water at the Glades Road WTP. Liquid chlorine is withdrawn under pressure from one-ton steel containers. It is fed to evaporators, which convert liquid chlorine to ga s chlorine. On the downstream side of the evaporators, the system changes from pressure to a vacuum system via a vacuum/pressure-regulating valve. The gas is then drawn through the chlorinators and drawn to the ejectors, with finish water as the motive fluid. The stream exiting from the ejector is under pressure as a concentrated aqueous chlorine stream and is injected at the point of application. The GRWWTP adds chlorine to various points and is typically operated in the gas phase. A mechanically operated automatic switchover valve allows for switching from one bank of two containers to another bank of two containers when the supply of chlorine gas is depleted. This allows for a continuous supply of chlorine to the evaporators and chlorinators while the two empty containers are replaced with two full ones utilizing a tram rail crane and hoist system. A vacuum monitor signal to the automatic switchover panel alerts the SCADA system when a switchover has occurred since a sudden inc rease in vacuum will be observed when the bank of containers is depleted. Pressure relief valves are included in the system to vent pressurized chlorine gas to the atmosphere. Chlorine sensors on each relief system initiate an alarm in the control room informing the operators that a pressure relief valve has opened. These sensors are mounted in the piping system downstream of the relief valve. Chlorine leaks will cause the leak sensors located in various points in the chlorine area to close off the chlorine supply via a panel controlling pneumatic valves on the container-mounted yoke assemblies. Chlorine gas flows under vacuum to a series of chlorinators that are used to manually control the chlorine dose and to indicate gas flow rate utilizing a rotameter. If a chlorine leak occurs, chlorine sensors will initiate an alarm and shut the yoke mounted pneumatic valves, stopping chlorine flow from the containers. There are three chlorine sensors in the storage/evaporator area and one sensor each in the chlorinator room and at the vent line discharge across the road. At chlorine concentrations of 1.0 ppm detected by the sensors, a red warning light will flash on the roof of the building and the SCADA system will receive a leak alarm, notifying the operations staff. Risk Management and Process Safety Management Program Overview Chlorine is subject to the Environmental Protection Agency's (EPA's) Risk Management Program (RMP) regulation which can be found in 40 CFR 68 and the Occupational Safety and Health Administration's (OSHA's) Process Safety Management Program (PSMP) regulation which can be found in 29 CFR 1910.119. The primary components of the RMP are as follows: ' A five-year accident history ' An off-site consequence analysis for a worst-case and alternative release scenario ' A comprehensive prevention program to minimize risks (i.e. minimize the potential for a release) ' An emergency response program to ensure that an accidental release is appropriatel y handled ' An overall management program to supervise the implementation of the RMP Following development of the RMP, the facility must submit a Risk Management Plan (Plan) to the EPA by June 21, 1999. The Plan is a summary of the facility's Risk Management Program. The RMP will be updated every five years, or whenever a process change or a new process is added. The OSHA PSM regulation has basically the same requirements as the prevention program element of the EPA RMP. The CBRUSD GRWTP and GRWWTP RMP meets the requirements of both regulations. The following sections briefly summarize the elements of the CBRUSD GRWTP/WWTP RMP. Five-Year Accident History The GRWTP has used chlorine to disinfect water for over twenty- five years. In the last five years, the facility has had two accidental releases, which were required to be reported under the RMP regulation. It is important to note that the facility has never had an accident that resulted in the worst case nor the alternative relea se scenarios outlined herein. The accidental releases were both estimated to be less than ten pounds in quantity. The first release, caused by debris in a gas regulator and occurring in May 1997, resulted in one maintenance worker requiring medical treatment. The second release, caused by unsuitable equipment and occurring in September 1998, resulted in property damage estimated at $1500 and no injuries. The GRWWTP has used chlorine to disinfect wastewater for over twenty- five years. In the last five years, the facility has had two accidental releases, which were required to be reported under the RMP regulation. It is important to note that the facility has never had an accident that resulted in the worst case nor the alternative release scenarios outlined herein. The accidental releases were both estimated to be less than ten pounds in quantity. The first release, caused by a faulty pressure gauge and occurring in May 1995, resulted in one plant operator requiring medical treatment . The second release, caused by unsuitable equipment and occurring in May 1996, resulted in one plant operator requiring medical treatment. Worst-Case Release Scenario The worst case release scenario for a toxic gas has been defined by the EPA to be an accidental release in which the largest on-site vessel containing chlorine releases its contents as a gas over ten minutes. Since the largest container stored at either facility holds 2,000 pounds of chlorine, the worst case release scenario is a release of 2,000 pounds of chlorine over 10 minutes. These scenarios were modeled using RMP*Comp software to estimate the distance to an endpoint of 3 ppm. It should be noted that this concentration has been found to typically cause minor eye and nose irritation. Chlorine leaks will cause the leak sensors located in various points in the chlorine area to close off the chlorine supply via a panel controlling pneumatic valves on the container-mounted yoke assemblies. Alternative Release Scenario The alternative release is a "more likely" incident than the worst-case. The RMP regulation allows the owner to define the alternative release scenario based on historical experience or operations staff knowledge of their system. The alternative release scenario for the GRWTP facility was assumed to entail the flexible tubing (pigtail) connection disconnecting from the liquid chlorine valve on the ton container and liquid chlorine releases through the liquid valve (5/16 inch diameter) and the pigtail (3/8 inch diameter). It also assumes that the automatic shutoff valves will close and limit the release duration to five minutes. The scenario for the GRWWTP made the same assumptions but the release would be from the gas chlorine valve. These scenarios were modeled using RMP*Comp software to estimate the distance to an endpoint of 3 ppm. It should be noted that this concentration has been found to typically cause minor eye and nose irritation. Chlorine leaks will cause the leak sensors located in various points in the chlorine area to close off the chlorine supply via a panel controlling pneumatic valves on the container-mounted yoke assemblies. Prevention Program There are always inherent risks associated with handling and using chlorine. These risks include the potential inhalation of chlorine gas if it is accidentally released. The prevention program is a key component to reducing the risk associated with a potential chlorine gas release. Key elements of the prevention program include: ' Employee participation ' Process safety information ' Process hazard analysis ' Incident investigation ' Standard operating procedures ' Mechanical integrity ' Management of change ' Pre-startup review ' Training ' Contracts ' Compliance audits ' Hot work permits ' Trade secrets The following briefly states the benefits of the following prevention program elements: standard operating procedures, mechanical integrity program, employee training and the process haz ard analysis. The facility staff has developed up-to-date and accurate written standard operating procedures (SOPs) to ensure that operators have clear instructions for safe operation of the chlorine system. Effective SOPs, when combined with operator training, are instrumental in ensuring safe operation of the system and in preventing accidental releases. The purpose of the mechanical integrity program is to ensure the continued integrity of the process equipment. An effective mechanical integrity program is integral to preventing accidental chlorine releases that may result from mechanical failure of improperly maintained equipment. The GRWTP/WWTP mechanical integrity program includes maintenance, inspection, and testing procedures and schedules along with maintenance personnel training. Knowledgeable well-trained personnel are essential to preventing and mitigating the effects of accidental chemical releases. The GRW/WWTP training program ensures that personnel working on or nea r the chlorine system are adequately trained in operation and maintenance procedures and the appropriate response actions to an accidental chlorine release. The process hazard analysis is a valuable risk reduction tool that outlines deficiencies in equipment and procedures, identifies potential system failure modes, and provides recommendations for system and operational improvements. Emergency Response Program A comprehensive emergency response program has been prepared which outlines the procedures and lines of communication that are necessary to effectively respond to and mitigate a potential chlorine gas release. In the event of a chlorine gas release, detectors located in the chlorine area will detect the presence of chlorine gas. The detectors will activate audible and visual alarms to give warning to plant staff. Automatic shut-off valves located on the ton container valves will activate into a closed position any time a leak detector alarms. The facility emergency response pro gram includes procedures for notifying the local hazardous materials (HAZMAT) teams of the incident and procedures for evacuating the facility. The City of Boca Raton's Fire Rescue Services Department (CBRFRSD) has a hazmat team that is part of the Palm Beach County Regional Hazardous Materials Response Team that can respond to mitigate a chlorine leak. Facility staff has coordinated with the CBRFRSD to ensure that they are fully trained and equipped to quickly respond to an incident. Planned Changes to Improve Safety The City of Boca Raton Utility Services Department is planning to eliminate gas chlorine from the GRWTP and GRWWTP by installing and operating a sodium hypochlorite system. This technology and pro-active approach will provide a safer method for disinfecting the City's water supply and wastewater discharge. |