City of Fargo Water Treatment Plant - Executive Summary |
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Release prevention and emergency response policies The City of Fargo (City) takes an active role in preventing accidental releases at it's water treatment facility by ensuring that its employees are properly trained in the safe operation and maintenance of processes subject to the Part 68 rule. This training includes the safe handling of regulated substances under the rule. The City has also developed and maintained a risk management policy that contains general safety rules. Though these rules do not specifically address the covered processes and their regulated substances, compliance with the general rules significantly reduces the potential for accidental releases of the regulated substances. This facility complies with industry-standard practices for water treatment plants that use anhydrous ammonia and chlorine in bulk. As for emergency response, the City has established and maintains procedures for emergency notification and response. These are reviewed with employees on a p eriodic basis and revised to accommodate changes in staffing when they occur. In general, the City would deal only with releases of a small amount of a regulated substance. If the release is determined to be large or if the chemical is stored outside or has migrated outside from a release indoors, the City would immediately notify the City of Fargo Fire Department. For releases that are judged to require the expertise and resources of an established hazardous materials (HAZMAT) team, the facility would call on the services of the jointly operated team comprised of personnel from the cities of Fargo, North Dakota and Moorhead, Minnesota. City management understands its duty to provide a safe working environment at this facility and to take measures to prevent accidents that may have an effect on the surrounding community. This understanding is reflected in procedures described and referenced in this document. Facility and regulated substance The City of Fargo WTP treats surface water from the Red and Sheyenne rivers to provide drinking water to the community. It does this through a series of physical and chemical treatment operations that include pretreatment neutralization, flocculation and sedimentation, primary and secondary softening, ozone disinfection, and final filtration. The treated water, now ready for use by the public, is transferred to a large reservoir and pumped into the distribution system. The design capacity of the treatment plant is 30 million gallons per day. The regulated substances stored, handled, and used at this facility are anhydrous ammonia and chlorine. The ammonia is stored in one 2,000-gallon tank that is located outside. The chlorine is stored in one-ton containers with a maximum intended inventory of 25 containers on site. All of the chlorine containers are stored inside of a building. Worst-case and alternative release scenarios The worst-case release scenario for anhydrous ammonia involves the only anhydrous ammonia-con taining vessel in the process, a 2,000-gallon bulk tank. It can contain up to 9,100 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 diked area. But because of the rapid gasification of anhydrous ammonia at atmospheric pressure, the dike was not assumed to be passive mitigation. No other mitigative measures were considered. The worst-case release scenario for chlorine involves one of the one-ton containers used in the process. Each can contain 2,000 pounds of chlorine. The rule for worst-case release analysis assumes all of the contents are released in 10 minutes. The scenario assumed a release of all the contents of the container outside of any enclosure, though the containers are normally stored inside of a building. No mitigative measures were considered. The alternative release scenario for anhydrous ammonia was based on a review of accident history, hazar d review, experience at other similar facilities, and industry experience. The choice for alternative release was a pump seal leak on the delivery truck during the filling of the ammonia tank. It was assumed that the release was upstream of the emergency shutoff valve, so the release duration is thirty minutes before corrective action can be completed. Liquid anhydrous ammonia is released to the air and assumed to gasify immediately. A total of 1,080 pounds of anhydrous ammonia is released at the rate of 36 pounds per minute. The alternative release scenario for chlorine was also based on a review of accident history, hazard review, experience at other similar facilities, and industry experience. The choice for alternative release was a severed header in the storage and feed room, allowing the contents of two connected and full containers to release into the room. The scrubber works as intended and neutralizes 2,000 pounds of chlorine, but the remaining 2,000 pounds remain in the room untreated and are slowly released to the outside air over a one-hour period. The enclosure factor of 0.55 is used, so the total release to the atmosphere is 1,100 pounds at 18 pounds per minute. 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 EPA's 40 CFR part 68 rule for program 2 processes. To 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 operating the covered processes. The technological safeguards include controls, sensors, alarms, and industry-standard systems. All of these serve to prevent unintended releases of anhydrous ammonia and chlorine. Should the prevention program fail to prevent a release, the WTP is equipped with engineering controls designed to minimize the effect of the release on the surrounding community. For chlorine, the storage containers are kept inside of a building to mitigate the effects of a release. The plant also has a scrubber capable of neutralizing one ton of chlorine, the amount stored in the largest single container onsite. The scrubber is maintained on a regular basis to ensure proper operation if needed during a chlorine release. The ammonia tank is surrounded by a concrete secondary containment so that a spill of ammonia will not flow away from the storage tank. During the filling of the ammonia tank, which occurs only four to five times per year but is the most likely time for a spill or leak, the City Fire Department stands by during the loading operation. As with chlorine, the equipment in the ammonia process is operated and maintained by personnel properly trained in the hazards of the chemical and the process. Five-year accident history Within the last five years, this facility has not had an accident involving anhydrous ammonia or chlorine that caused deaths, injuries, property or environmental damage, evacuations, or sheltering in place. Emergency response program This facility has established and maintains an emergency action plan that is coordinated with local response agencies, such as the City Fire Department and the local HAZMAT team, which is shared with the City of Moorhead, Minnesota. The goals of the plan are to protect onsite employees from the hazardous effects of the releases and to minimize the effects of releases on the general public. The program is routinely reviewed and updated to reflect personnel and regulatory changes. It is also submitted to the Fire Department for review and comment. City employees handle incidental releases of anhydrous ammonia and chlorine and are trained and equipped to do so. Planned changes to improve safety Ideas for changes to improve safety are actively sought from employees. Employee meetings that focus on safety issues are held regularly at this facility. Employees are encouraged and trained to recognize hazards and present ideas to eliminate them or to minimize the potential consequences of those hazards. During the development of the risk management plan, hazard reviews were conducted with key employees to meet the prevention program requirements. During these sessions, recommendations were made for the purpose of improving safety and preventing accidental chemical releases. Each recommendation has been or is being considered and evaluated for implementation. This evaluation process will provide all affected employees with a heightened awareness of safety issues related to the covered processes. |