Nottingham Water Treatment Plant - Executive Summary |
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The Facility & the Regulated Substances Handled The Cleveland Division of Water (CWD) is a municipal water utility that provides 1.5 million people throughout the greater Cleveland area with high-quality, safe drinking water. One of four CWD water treatment plants, the Nottingham Water Treatment Plant produces approximately 26 billion gallons of drinking water each year. Chlorine is used at the plant as the primary disinfectant. Chlorine has been used to disinfect drinking water for nearly 100 years, reducing or eliminating the risk of such waterborne diseases as cholera, typhoid, and dysentery. Approximately 2,000 pounds of chlorine is used each day at the plant as a part of the treatment process. Chlorine is supplied to the water plant as a liquid under pressure in 90-ton rail cars and one-ton steel containers. Although the facility has the capacity to store two 90-ton rail cars, administrative controls only allow for a maximum of one 90-ton rail car and 27 one-ton containers (i.e., 117 tons) on-site at any one time. Summary of Major Hazards Chlorine is considered a highly hazardous chemical by both the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) as exposure to chlorine can result in serious health effects. The primary health concern from exposure to chlorine is its toxic effect when inhaled. At the Nottingham facility, the chlorination system is a closed system that converts liquid chlorine to chlorine gas and then injects the gas into water to form chlorine solution. The chlorine solution can then be added to the water in the treatment process at three locations throughout the plant. Consequences of Failure to Control the Hazard EPA regulations require CWD to analyze a worst-case and an alternative release scenario to determine the potential off-site impact zone resulting from a failure to control the chlorination system. In accordance with EPA definitions, a worst-case release scenario at Nott ingham would be the complete failure of a 90-ton chlorine rail car which releases 180,000 pounds of liquid chlorine, (with subsequent vaporization), over a 10-minute period. The worst-case release scenario does not take into consideration active mitigation measures such as equipment, devices or technologies which require human, mechanical or other energy input to function; or passive mitigation measures which require no human, mechanical or other energy input to control the release. Therefore, assuming the worst weather conditions, the resulting chlorine vapor could potentially travel 14 miles before dispersing enough to no longer pose a hazard to the public. CWD used the EPA's off-site consequence analysis modeling program RMP*Comp to calculate the estimated distance to the chlorine toxic endpoint. The potential occurrence of the worst case scenario is mitigated by both passive and active devices and procedures in place at the Nottingham facility. The railcar is designed with bu ilt-in safety devices and constructed with an insulated, metal jacket surrounding the tank. Furthermore, each rail car is equipped with an excess-flow valve that is designed to close when the rate of chlorine flow from the rail car exceeds a pre-determined value (e.g., 15,000 pounds per hour). These valves automatically prevent a complete release of the contents of the railcar. CWD further controls the likelihood of the worst case scenario by permitting only one railcar on site at a time; by implementing Standard Operating Procedures (SOPs) for safely connecting and disconnecting rail cars; through the use automatic shut-off valves; and, by the use of Chlorine Institute Emergency C Kits to minimize releases. A more realistic release scenario for the Nottingham Water Treatment Plant is the alternative release scenario which is defined as a tubing failure, bad connection or a valve failure on a one-ton container of chlorine. In this scenario, CWD analyzed the results of a liquid and gaseous chlorine release through a 5/16-inch-diameter valve body opening on the container at a release rate of 241 pounds per minute for 10 minutes. According to EPA's RMP*Comp the estimated distance to the chlorine toxic endpoint is 0.2 miles. The alternative release scenario incorporates both passive and active mitigation measures to minimize the off-site effects of a release. For example, CWD stores all of the one-ton containers in an enclosed building to minimize releases to the environment and migration off-site. We also employ the use of Chlorine Institute Emergency B Kits should a release occur further mitigating the possibility of a release migrating off site. Emergency Response Program This facility has a chlorine-specific Emergency Response Plan which identifies procedures for recognizing emergencies, securing incident areas, and responding to releases and leaks; emergency evacuation procedures, routes, and safe assembly points; procedures for accounting for all person nel following an evacuation; emergency first aid procedures for exposure to chlorine, procedures for notifying local emergency response agencies and the public; and a list of facility personnel currently assigned as members of the emergency response team and their responsibilities. All of the water treatment plant operators are properly trained to respond to and mitigate chlorine incidents that might potentially occur at the plant. The operators are also trained in the use of Chlorine Institute Emergency B-Kits for one-ton containers and C-Kits for chlorine rail cars. Nottingham is staffed with operators 24 hours a day. In addition, CWD is coordinating it's Emergency Response Plan with the Cleveland Hazardous Materials (HAZMAT) Team and the Cuyahoga County Local Emergency Planning Commission (LEPC). In conjunction with the establishment of an RMP Program, CWD established a program to conduct annual chlorine drills with Cleveland HAZMAT for preparation for response to an accidental release. Accidental Release Prevention Program CWD has long understood the hazards of handling chlorine which, if not handled properly, can pose a risk to employees, the environment, and the surrounding community. With the inception of OSHA Process Safety requirements, CWD has worked hard at building what we call a "Layers of Protection" approach to safety. CWD has developed and implemented detailed SOPs for the safe operation of the Chlorination System, a comprehensive maintenance program for inspecting, testing, repairing, and replacing chlorine equipment including detection systems, alarms, and emergency equipment; personnel protection equipment (PPE) policies; employee training; incident reporting and investigation procedures; safe work practices such as hot work permits and lockout/tagout procedures; and a Visitor Policy to control access to the plant especially to areas where chlorine is stored and/or used. These programs are in place to reduce the likelihood of an accidental chlorine release. In addition to CWD's well-maintained chlorine equipment and well-trained employees, CWD's management is committed to minimizing the potential for accidental chlorine releases and minimizing the effects of a release if one were to occur. CWD routinely re-evaluates and updates it's policies, programs, and procedures to ensure that we are providing the safest environment possible for our employees, the community, and the environment. Five-year Accident History The Nottingham Water Treatment Plant has used chlorine to disinfect drinking water for more than 40 years. In the last five years, the facility has had only two incidents which were considered serious enough to report under the RMP. One incident occurred on June 10, 1997, in which some chlorine gas that was trapped inside a defective pressure gauge escaped while an employee was carrying the gauge after it had been removed from the system. The employee was taken to the hospital, treated and released. Mainte nance procedures were revised after this incident. The second incident occurred on June 11, 1997, when two employees, who were wearing the proper protective equipment, took a defective rail car transfer whip out of service. Although the line had been purged, a small amount of liquid and gaseous chlorine was released as the whip was disconnected. No one was injured as a result of this incident, however, the area of grass surrounding the rail car was killed. CWD began purchasing better quality transfer whips and increased the frequency in which they were replaced after this incident. Planned Changes to Improve Safety CWD is always researching ways to improve safety and reduce risk. During a recent chlorine Process Hazard Analysis (PHA) at the Nottingham Water Treatment Plant, several recommendations were made to improve safety at the plant. The recommendations ranged from adding procedures to the SOPs, purchasing hand-held chlorine meters for use in inspecting containers prior to acceptance, tagging valves to coincide with SOPs, upgrading old equipment, to investigating the use and operability of motorized emergency shut-off valves for the one-ton containers. In addition, within the next year, the Nottingham plant will terminate its use of 90-ton rail cars and will begin always receiving chlorine in one-ton containers. Furthermore, over the next several years the Nottingham Water Treatment Plant is scheduled to undergo major renovations as part of CWD's Plant Enhancement Program, including the conversion from chlorine to sodium hypochlorite for disinfection of drinking water. |