Coral Springs Water Treatment Plant - Executive Summary |
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INTRODUCTION At the turn of this century water borne diseases were a leading cause of death in the United States. Epidemics of typhoid, cholera, dysentery and other water-borne 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. Water-borne 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 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 utilizing 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. Historica lly 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 (RMP) 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 Coral Springs Water Treatment Plant staff has always understood these risks and has maintained a well-trained staff and a safely operated and maintained facility. The City of Coral Springs has taken a comprehensive approach to be in full compliance with the RMP regulation by June 21, 1999, and a proactive approach to a public informatio n program which is above and beyond the requirements of the regulation. FACILITY BACKGROUND The City of Coral Springs owns and operates the City of Coral Springs Water Treatment Plant. The facility's mission is to protect public health by providing it's customers with safe drinking water, free of harmful pathogens. Approximately 550 pounds per day of chlorine gas is used to disinfect the water and make it safe for human consumption. A maximum of 24,000 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 City of Coral Springs Water Treatment Plant is a gas feed system. It consists of an outdoor, covered chlorine storage and handling area and an adjacent enclosed room containing seven chlorinators (chlorine vapor flow control meters). The storage and handling area is fenced off from immediate access by metal mesh fence . The chlorinators regulate the flow of chlorine vapor as it is fed under vacuum to the various chlorine injection points throughout the plant. Twelve one-ton containers are stored in the chlorine storage and handling area at any one time. Each container is secured in a separate steel cradle to prevent it from moving. Four of the containers are stored in a rack of steel cradles as back-up chlorine supply. The other eight containers are hooked up to two manifolds, four containers per manifold. One manifold is in service at any one time, simultaneously feeding chlorine vapor from four containers. The chlorine containers are hooked up to the manifold through individual 2-foot, 3/8-inch diameter flexible copper tubing. The manifolds that the chlorine feed tubes are hooked up to are constructed of schedule 80 1-inch diameter black steel pipe. The chlorine gas passes through the manifold and a line strainer, and then is fed to a vacuum regulator, which drops the pressure in the syst em to a very slight vacuum. As water flows through the injectors, the vacuum created by the pressure differential draws the chlorine vapor from the regulator through the chlorinators and into the injectors. At the injectors chlorine gas is mixed with water to form a chlorine solution. The piping in the vacuum portion of the system is composed of schedule 80 PVC pipe. Should a leak develop in the piping downstream of the vacuum regulator, chlorine would not be released. Instead, air would be drawn into the injectors. In addition, loss of vacuum alarms in the chlorinators would activate. In the event of a leak, facility personnel would be warned by the chlorine leak detection system. The chlorine building has two chlorine gas detectors located in the chlorinator room and one located in the storage and handling area. There are audible and visual alarms located outside the chlorine room and throughout the plant that are hooked up to these detectors. In the event chlorine gas is d etected, the alarm sounds and indicator lights are lit in: the water plant lab and control room, by the electrical building adjacent to the vacuum filter building, and by the one-ton chlorine containers. In addition, chlorine leaks in the piping downstream of the chlorine container are controlled by the automatic shut-off valves that are located on each container. These valves are designed to fail close upon loss of air pressure to the valve. In the event of a loss of vacuum to the injectors, or a chlorine alarm, these valves will shut and stop flow from the containers. RISK MANAGEMENT AND PROCESS SAFETY MANAGEMENT PROGRAM OVERVIEW Chlorine is subject to the Environmental Protection Agency's Risk Management Program 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 PSM regulation has basically the same requirements as the prevention program element of the EPA RMP. The City of Coral Springs Water Treatment Plant's RMP meets the requirements of both regulations. The following sections briefly summarize the elements of the City of Coral Springs Water Treatment Plant's RMP. FIVE- YEAR ACCIDENT HISTORY The City of Coral Springs Water Treatment Plant has used chlorine to disinfect water for 30 years. Since the plant's inception, the facility has had one accidental release, which was required to be reported under the RMP regulation. This accident occurred on September 17, 1994. The accident occurred when a steel valve, located on the steel pressure manifold piping system, was found to be leaking chlorine. To preclude an interruption of chlorine to the water supply, the defective valve was replaced with a section of 450 psig rated schedule 40 PVC pipe (a replacement valve was on order with the supplier). Normal system pressure is 110-120 psig. The system operated without incident for approximately 14 hours. However, at approximately 11:30 p.m. on 9/17/94, the PVC pipe failed resulting in an uncontrolled release of chlorine gas from four one-ton chlorine containers. The release continued for approximately two hours until the chlorine container valves where t urned off by the responding HAZMAT Team. This incident resulted in the release of approximately 500 pounds of chlorine; injuries to two water plant operators; and the evacuation of approximately 800 nearby residences. Based on the recommendations of the investigation team, the City revised operation, maintenance, and emergency response procedures; conducted training on the use of self contained breathing apparatus; and installed an automatic shutdown system that activates "fail closed" valves when the chlorine leak detectors detect chlorine. 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 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. This scenario was modeled using RMP*C omp 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. 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 facility was to assume a pigtail disconnects from a container automatic shut-off valve, resulting in a release of chlorine gas. In addition, it was assumed that the leak detector would activate the automatic shut-off valves after a two-minute release. This scenario was 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. PREVENTION PROGRAM There are always inherent risks assoc iated 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 * Contractors * 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 hazard 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 ope ration 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 facility's 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 facility's 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 haza rd 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, a detector located in the storage area, will detect the presence of chlorine gas. The detector will activate audible and visual alarms throughout the facility to give warning to plant staff. In addition, the leak detector will cause the automatic shut-off valves on each chlorine container to close. The facility emergency response program includes procedures for notifying the local hazardous materials (hazmat) teams of the incident and procedures for evacuating the facility. There are four local ha zmat teams in Broward County that can respond to mitigate a chlorine leak. Facility staff have coordinated with the local fire department to ensure that they are fully trained and equipped to quickly respond to an incident. PLANNED CHANGES TO IMPROVE SAFETY The City of Coral Springs has undertaken a study to review the costs and qualitative issues of changing to an alternative (i.e., safer) disinfection system. The alternatives being evaluated include switching to on-site generation of sodium hypochlorite (at 0.8% concentration) and purchasing bulk hypochlorite (at 12% concentration). In addition, these alternatives will be compared to staying with chlorine gas and enclosing the existing facilities (to contain a chlorine leak) and adding an emergency chlorine scrubber. The results of this report will be used to assist in planning for future safety improvements. The results of this study were not available at the time this report was prepared. |