College Hill Water Treatment Plant - Executive Summary |
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Introduction At the turn of this century waterborne diseases were a leading cause of death in the United States. Epidemics of typhoid, cholera, dysentery and other waterborne diseases occurred. After chlorine's introduction into public water supplies, deaths from typhoid in the U.S. dropped dramatically from 25,000 in 1900 to less than 20 in 1960. Waterborne disease is even 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 that of the U.S. In the U.S., however, waterborne disease has been virtually eliminated due to an effective public health strategy utilizing chlorine for drinking water disinfection. Effective 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. As an added layer of protection, the United States Environmental Protection Agency (EPA) 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 College Hill Water Treatment Plant has always understood these risks and has maintained a well-trained staff and a safely operated and maintained facility. The track record of the City of Lynchburg is exemplary with respect to handling hazardous chemicals. Furthermore, the City of Lynchburg has taken a comprehensive approach to be in full compliance with the RMP regulation by June 21, 1999. Facility Background The City of Lynchburg owns and operates the College Hill Water Treatment Plant (WTP). The facility's mission is to protect public health by providing the City with safe drinking water, free of harmful pathogens. Approximately 250 to 350 pounds per day of chlorine gas is used to disinfect the water and make it safe for human consumption. A maximum of 20,000 pounds of chlorine are stored on-site. 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 The chlorine system at the College Hill WTP is a liquid system from the ton-containers to the evaporator on the first floor, and a positive pressure gas system from the evaporator to the vacuum regulators at the chlorinators on the fourth floor. The chlorine supply to the system consists of ton-containers. Chlorine from the ton-containers is withdrawn as a liquid and conveyed under press ure to the evaporator. From the evaporator, the chlorine gas is conveyed under pressure to the Chlorinator Room. Four vacuum regulators, four chlorinators and four injectors are located in the Chlorinator Room. As the pressurized gas from the evaporator passes through the vacuum regulators, it is reduced to a vacuum. The vacuum created by the venturi effect at the injectors conveys the chlorine gas from the vacuum regulators to the injectors. At the injectors, the chlorine gas is mixed with water and the resulting chlorine solution is then distributed to the raw and finished water application points. Safety equipment for the chlorine system includes exhaust fans and louvers for room ventilation, chlorine detectors with local and remote (chlorine storage room only) visual and audible alarms, emergency showers and eyewashes, an emergency "B" kit, ten-minute air packs, and a windsock. Risk Management and Process Safety Management Program Overview Chlorine is subject to the Environ mental 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 appropriately 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 changes or a new process is added. The OSHA P SM regulation has basically the same requirements as the prevention program element of the EPA RMP. The College Hill WTP RMP meets the requirements of both regulations. The following sections briefly summarize the elements of the College Hill WTP RMP. Five-Year Accident History The College Hill WTP has used chlorine to disinfect water for over forty years. In the last five years, the facility has had no accidental releases which are required to be reported under the RMP regulation. Off-Site Consequence Analysis An off-site consequence analysis was conducted for worst case and alternative case release scenarios. The worst case release scenario for chlorine has been defined by the EPA to be an accidental release in which the largest on-site vessel releases its contents as a gas over ten minutes. Since the largest container stored at the facility holds 2,000 pounds of chlorine, the worst case release scenario is a release of 2,000 pounds of chlorine over 10 minutes. The alterna tive 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 facility was assumed to consist of a pigtail disconnecting from the ton container valve. These two scenarios were modeled 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. Since the chlorine ton containers are in an enclosed building, the building provides passive mitigation to reduce the rate of chlorine release to the atmosphere. The results of the analysis showed that there is a significant risk associated with chlorine exposure for the College Hill WTP because of the location of the treatment plant near residential and commercial areas of the City. Since chlorine gas is heavier than air, a chlorine release woul d tend to flow downhill toward low-lying areas. Prevention Program There are always 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 of 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 ' Contractors ' Compliance audits ' Hot work permits ' Trade secrets The following briefly describes the benefits of the following prevention program elements: standard operating procedures, mechanical integrity program, employee training and the process hazard analysis. The facility staff has developed up-to-date and accurate written standard operating procedures (SOPs) to ensure tha t 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 needed to prevent accidental chlorine releases that may result from mechanical failure of improperly maintained equipment. The College Hill WTP mechanical integrity program includes maintenance, inspection, and testing procedures and schedules. Knowledgeable well-trained personnel are essential to preventing and mitigating the effects of accidental chemical releases. The College Hill WTP training program ensures that personnel working on or near 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 in the Chlorine Storage or Chlorinator Room, a detector will detect the presence of chlorine gas. The detector will activate audible and visual alarms to give warning to plant staff. The facility emergency response program includes procedures for notifying the local hazardous materials (hazmat) teams of the incident and procedures for evacuating the facility. Currently, the Virginia Area 8 regional hazmat team in Roanoke will respond to mitigate a chlorine leak. The City of Lynchburg Fire Department has received grant funding and is currently developing a hazmat team. In the future, it is expected that hazmat response will be from the City Fire Department. Planned Changes to Improve Safety |