Crown Water Treatment Plant - Executive Summary
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 Crown Water Treatment Plant produces approximately 16 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 55-ton rail cars and one-ton steel containers. The facility can store a maximum of one 55-ton rail car and 26 one-ton containers (i.e., 81 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 Crown facility, the chlorination system is a closed system that converts the liquid chlorine to chlorine gas and then injects the gas into water to form chlorine solution. The chlorine solution can 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. According to EPA definitions, the worst-case release scenario at Crown would be the complete failure of a 55-ton chlorine rail car which results in a release of 110,000 pou
nds 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; however, it does incorporate passive mitigation. The 55-ton rail car is completely enclosed within a building. Therefore, assuming the worst weather conditions, the resulting chlorine vapor could potentially travel 7.6 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 Crown facility. First, the rail car is entirely enclosed in a building and a scrubber has been installed to mitigate any release. The rail car is
designed with built-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 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 Crown 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 5/1
6-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 0.1 miles, which does not extend beyond CWD property boundaries.
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 and the rail car in an enclosed building. In addition, the plant is equipped with a scrubber system which has the capacity to neutralize approximately one ton of chlorine in the event of a release, and Chlorine Institute Emergency B Kits are employed 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 evac
uation procedures, routes, and safe assembly points; procedures for accounting for all personnel 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. Crown is staffed with operators 24 hours a day. In addition, CWD is coordinating it's Emergency Response Plan with the Westshore Hazardous Materials (HAZMAT) Team and the Cuyahoga County Local Emergency Planning Commission (LEPC). In conjunction with the establishment of an RMP Program, CWD has established a program to conduc
t annual chlorine drills with Westshore 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 Standard Operating Procedures (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 espe
cially 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 Crown Water Treatment Plant has used chlorine to disinfect drinking water for more than 40 years. In the last five years, the facility has not had any reportable chlorine incidents or releases.
Planned Changes to Improve Safety
CWD is always researching ways to improve safety and reduce risk. The Crown Water Treatment Plant recently underwent major renovation activities to double
the capacity of the facility. During the renovation activities the chlorination system was upgraded including installing a new chlorine scrubber, electronic scales, evaporators, chlorinators, and automatic switch-over valves. Furthermore, when a chlorine alarm is triggered, all of the motorized valves automatically shut-down to minimize amount of chlorine that could potentially be released.
In addition to the recent renovation of the chlorination system, some additional recommendations were made during a recent chlorine Process Hazard Analysis (PHA) at the Crown Water Treatment 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, tying the evaporator pressure relief system into the scrubber system, expanding the new crane to eliminate having to transfer the one-ton containers between two crane systems, to investigating the use and operabi
lity of motorized emergency shut-off valves for the one-ton containers. In addition, within the next year, the Crown plant will terminate its use of 55-ton rail cars and will begin always receiving chlorine in one-ton containers. Finally, as part of CWD's Plant Enhancement Program, which is currently underway, Crown Water Treatment Plant will convert from chlorine to sodium hypochlorite for disinfection of drinking water.