Desert Mountain Ice Packaging Facility - Executive Summary |
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Desert Mountain Ice Co. has instituted a Risk Management Program for their ice manufacturing facility, as required by Federal Accidental Release Prevention (ARP) Program regulations at 40 CFR Part 68. The Risk Management Program identifies the equipment, procedures, maintenance, inspection, and training associated with Regulated Substances (RS's) handled at this facility in excess of Federal threshold quantities; describes the structured assessment of hazards which was conducted to assess possible effects on employees and offsite public and environmental receptors; provides the results of an offsite consequences analysis; defines a prevention program, emergency response program, and mitigation measures to reduce the probability and magnitude of accidental releases of RS's; and establishes a schedule and responsibilities for implementation of mitigation measures and auditing of program elements. This Risk Management Plan (RMP) is being filed as required by ARP regulations in order to report the elements of the current Risk Management Program and to describe further measures planned to mitigate or prevent accidental releases of RS's. STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED Desert Mountain Ice Co. is in the process of constructing an ice manufacturing plant located in an industrial park just east of Tolleson, Maricopa County, AZ, and will use anhydrous ammonia, an RS, to charge the refrigeration system in quantities greater than the Federal threshold quantity for this RS. Operation is scheduled to commence by May 1, 2001. There will be 15 full-time employees at this site. The plant is normally manned on the day shift Monday through Friday, and a telephone dialer system alerts operators to alarm conditions when the plant is not manned. Bulk anhydrous ammonia is received by truck and charged into the high pressure receiver under pressure. The ammonia refrigeration system serves the ice makers, a water chiller, and evaporators for room air cooling. The system is totally self-contained, and the only losses of ammonia are minor in nature, from periodic oil draining operations, minor valve packing leaks, and the like. Every few years, additional ammonia is added to the system to replace losses. The refrigeration process operates generally as follows. Compressors raise the pressure and temperature of ammonia vapor to hot gas condition, approximately 165 psig and 120 deg. F. The vapor is condensed to liquid in evaporative condensers located outside the building, transferring heat to circulating water which evaporates. Fans operate as necessary to increase the rate of water evaporation. The condensed liquid ammonia drains into the high pressure receiver, and the pressurized liquid enters the suction accumulator vessel also serving as a liquid subcooler. In the suction accumulator, the high pressure liquid is reduced in temperature from approximately 90 deg. F to approximately 38 deg. F, and reduced in pressure from 165 psig to approximately 57 psig. The subcooled liquid enters two recirculation accumulator vessels where its temperature and pressure are further reduced. Liquid ammonia pumps force the cold liquid ammonia through the ice maker heat exchanger plates and the evaporator coils, and as the ammonia picks up heat it partially boils and two-phase flow returns to the respective recirculation accumulators. Suction piping carries ammonia vapor from each of the two recirculation accumulators and the suction accumulator to the compressors where the refrigeration cycle begins again. Defrosting is carried out by directing a side stream of hot gas from the compressors to the ice makers and evaporators. The partially condensed gas is drawn into the suction accumulator. ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES It is the policy of Desert Mountain Ice Co. that the receipt and handling of anhydrous ammonia at its facility be done in a manner which meets regulatory requirements and minimi zes the probability and severity of accidental releases to the atmosphere, in order to protect the health and safety of its workers, the public, and the environment. In order to accomplish this goal, Desert Mountain Ice Co. has gathered safety information on anhydrous ammonia and on the process, equipment and procedures involving anhydrous ammonia; performed a structured assessment of hazards of the process and external events which might affect the process; performed an offsite consequences analysis of defined release scenarios; established a written program for prevention and mitigation of accidental releases; and established a written emergency response program coordinated with emergency response agencies. WORST CASE RELEASE SCENARIO A single "worst case" release scenario is required to be considered for each stationary source, resulting in the maximum distance to an endpoint for all toxic RS's contained on site above the threshold quantity. The worst case release scenario for to xic chemicals is defined in the ARP regulations as the release of the contents of the largest single container of RS (in this case anhydrous ammonia) over a period of 10 minutes. The scenario considered the release of the entire charge of anhydrous ammonia in the system as a liquid under pressure, in this case 17,000 lb. This release scenario is not physically possible, due to the characteristics of anhydrous ammonia. The air dispersion modeling resulted in a toxic endpoint located beyond the plant's property line. ALTERNATIVE CASE RELEASE SCENARIO An "alternative case" release scenario is required to be considered for each toxic RS handled in quantities greater than the threshold quantity at the site. The "alternative case" scenario is described in the ARP regulations as a likely release resulting in offsite effects, considering administrative controls and mitigation measures in place, and is to be determined by the facility operators as part of the Process Hazard Analysis requir ed to be performed during RMP development. The "alternative case" considered for this facility is the release of anhydrous ammonia from a failed relief valve on the high pressure receiver, with the release secured by emergency responders by closing the three-way relief isolation valve after 60 minutes. The air dispersion modeling resulted in a toxic endpoint located beyond the plant's property line. ADMINISTRATIVE CONTROLS Administrative controls in effect at Desert Mountain Ice Co. which were considered to mitigate the severity of the Worst Case and Alternative Case release scenarios include Desert Mountain Ice Co.'s written policies and procedures for training of operators and maintenance personnel, written procedures for control of the inventory of anhydrous ammonia at the facility, and policies regarding quality level of replacement materials and components for the system. MITIGATION MEASURES No mitigation measures were considered to limit the severity of the Worst Case scena rio. No passive mitigation measures were considered to limit the severity of the Alternative Case scenario. Active mitigation was considered for the Alternative Case, in the form of the timely response of properly trained and equipped personnel following established emergency response procedures. GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAMS General accidental release prevention programs instituted by Desert Mountain Ice Co. are categorized as administrative (management) programs; procedures, training, and engineering controls; and emergency response programs. Desert Mountain Ice Co. has instituted a Process Safety Management (PSM) Program meeting OSHA requirements at 29 CFR 1910.119 covering the ammonia refrigeration process. This constitutes the general accidental release prevention program for operations at this facility. The program and document management procedures included in the PSM Program will be used as the management system for the Risk Management Program. CHEMICAL- SPECIFIC RELEASE PREVENTION STEPS Release prevention steps specific to anhydrous ammonia have been identified and will be implemented during construction. These include tagging certain critical liquid ammonia valves with warning labels. FIVE YEAR ACCIDENT HISTORY This is a new facility under construction. There have been no accidents involving anhydrous ammonia at this facility within the past five years resulting in injuries or offsite consequences. EMERGENCY RESPONSE PROGRAM Desert Mountain IceCo.'s Emergency Response Program applicable to anhydrous ammonia has been coordinated with the City of Tolleson Fire Department and the Maricopa County LEPC. PLANNED CHANGES TO IMPROVE SAFETY All of the improvements and mitigation measures identified in the process hazard analysis which Desert Mountain Ice Co. committed to accomplish have been completed or are in progress. Any other measures identified by employees during workplace hazard surveys, or as a result of audit activities, w ill be thoroughly reviewed and considered for implementation. It is planned to install a wind sock, tag liquid ammonia valves where closing the wrong valves could create a hazard, and create numerous facility-specific written procedures. |