Water Treatment Plant - Executive Summary |
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Release prevention and emergency response policies Personnel at this City of Wichita (City) facility take a very active approach in maintaining and improving chemical safety. This facility complies with industry-standard requirements for water treatment plants that use anhydrous ammonia and chlorine in bulk containers. The policy at this facility is to adhere to all applicable federal, state, and local laws. If an emergency were to occur, the policy is to notify the City Fire Department and request that they respond to the emergency. Facility and regulated substance This facility is a 160-million gallon per day water treatment plant located in Wichita, Kansas. The facility employs a series of physical and chemical treatment operations that include: pretreatment, aeration, softening, stabilization, filtration, and disinfection processes. The covered processes include the use of anhydrous ammonia and chlorine chemicals. Chlorine is used for disinfection and ammonia is used for chloramination. Chloramination is the process of changing free chlorine to chloramines which are more persistent in providing disinfection in the water distribution system. The anhydrous ammonia is delivered in tanker trucks and the maximum intended inventory onsite is 27,300 pounds in two bulk tanks. The chlorine is delivered in tanker trucks and the maximum intended inventory onsite is 64,000 pounds in two bulk tanks. The bulk tanks of both chemicals are stored in the tank farm area at the plant. Worst-case and alternative release scenarios The worst-case release scenario for anhydrous ammonia involves the largest anhydrous ammonia-containing vessel in the system, one of the two 3,300-gallon bulk tanks. It can contain up to 13,650 pounds of anhydrous ammonia. The rule for worst-case release analysis assumes all of the contents are released in 10 minutes. The bulk storage is located outside in a walled area. But because of the rapid gasification of anhydrous ammonia at atm ospheric pressure, no enclosure was assumed as passive mitigation. No other mitigative measures were considered. Distance to endpoint is 1.5 miles. The worst-case release scenario for chlorine involves the largest chlorine-containing vessel in the system, one of the two 3,400-gallon bulk tanks. It can contain up to 32,000 pounds of chlorine. The rule for worst-case release analysis assumes all of the contents are released in 10 minutes. The bulk storage is located outside in a walled area. But because of the rapid gasification of chlorine at atmospheric pressure, no enclosure was assumed as passive mitigation. No other mitigative measures were considered. Distance to endpoint is 5.4 miles. The alternative release scenario for anhydrous ammonia was based on a methodical analysis of accident history, process hazard analysis, experience at other similar company facilities, and industry experience. The choice for alternative release was a rupture in the fill hose during the tank -filling operation. It was assumed that the release rate was less than the setting for the excess flow valve, and so this mitigative measure did not come into play. Liquid anhydrous ammonia is released to the air and immediately gasifies. The release duration is one minute at which time the truck driver shuts off a manual valve. A total of 72 pounds of anhydrous ammonia is released. The distance to endpoint is 0.1 mile. The alternative release scenario for chlorine was based on a methodical analysis of accident history, process hazard analysis, experience at other similar company facilities, and industry experience. The choice for alternative release was a rupture in the fill hose during the tank-filling operation. It was assumed that the release rate was less than the setting for the excess flow valve, and so this mitigative measure did not come into play. Liquid chlorine is released to the air and immediately gasifies. The release duration is one minute at which time the tr uck driver shuts off a manual valve. A total of 109 pounds of chlorine is released. The distance to endpoint is 0.2 mile. For both analyses, the EPA's Risk Management Program Guidance for Wastewater Treatment Plants was used. The results were verified using RMP*Comp, which is based on the formulae in the guidance document. Accidental release prevention program The facility's prevention program for both anhydrous ammonia and chlorine complies with the corresponding sections of EPA's 40 CFR part 68 accident prevention program rule for program level 2 processes and applicable state and local codes and regulations. The anhydrous ammonia and chlorine systems are design, installed, and maintained in accordance with state and local laws. To achieve and maintain this compliance, the City has in place many procedural and technological safeguards. The procedural safeguards include an employee training program and operating and maintenance procedures for those employees involved in opera ting the covered processes. The technological safeguards include controls, sensors, alarms, relief valves, and industry standard systems. All of these serve to prevent unintended releases of anhydrous ammonia and chlorine, or at least minimize the effects of a release. Five-year accident history This facility has not had an accident involving anhydrous ammonia or chlorine that caused deaths, injuries, property or environmental damage, evacuations, or shelterings in place. Emergency response program The facility has a written emergency response and preparedness plan that is coordinated with local emergency responders. The Wichita Fire Department is the primary responder. City employees handle incidental releases of anhydrous ammonia and chlorine and are trained and equipped to do so. The emergency response and preparedness plan includes causes and effects of emergencies, reducing system vulnerability, and emergency planning activities. The plan discusses mutual aid agreements with both the police and fire departments. Planned changes to improve safety The maintenance and improvement of safety is an ongoing job at this facility. Safety training takes place throughout the year. Safety-related recommendations from employees, whether made during formal sessions like hazard reviews or upon observation of a potential hazard, are always considered carefully for implementation. This process is continuous and, even at times when no major process changes are anticipated, existing safety systems and procedures are fine-tuned as a matter of course. Currently, the recommendations made during the recent hazard reviews are under consideration. |