LaGrou Hammond Warehouse - Executive Summary |
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LaGrou Cold Storage, Inc., at its Hammond Warehouse, is a commercial warehouse offering frozen/ refrigerated storage facilities to the public. Stored materials are typically food products requiring refrigerated or frozen storage which may not be available at the primary manufacturer's location. This service requires a large refrigeration capacity. To supply the demand for this refrigeration capacity, LaGrou Cold Storage operates an in-house refrigeration system utilizing anhydrous ammonia as the refrigerant, and consisting of a number of compressors, condensers, common receivers, and associated pipes which carry the refrigerant to the appropriate storage areas. LaGrou Cold Storage, Inc., has long been committed to employee safety and to being a good community neighbor. To this end, LaGrou maintains an active safety management program to prevent releases of ammonia. LaGrou's overall approach to safety is to emphasize safe work practices and prevent accidents. A planned sched ule of inspection and maintenance activities, augmented by worker training, is intended to prevent accidents and releases. In addition to the program of personal inspections, a system of automatic detection and alarm devices is employed to give early warning of releases. The detection system is integrated with private off-site response providers. Senior management remains committed to a program of safety and safe procedures. Chemical safety is a serious responsibility at all levels of the Company. The subject facility is located in an industrial area, in proximity to a residential area. Materials are brought to the facility by truck for storage, and are removed via truck. The refrigeration system is sized adequately for the amount of cooling needed, and is capable of holding 12,000 pounds of anhydrous ammonia. The system includes compressors, condensers, receivers, transfer vessels, and associated lines and chillers. All ammonia at the site is stored in the system. The w orst case scenario is considered to be the rupture of the high-pressure receiver, which contains a good deal of the ammonia at any given time. It is considered that this rupture would cause loss of all the ammonia in the system over a period of 10 minutes at a constant rate. The toxic endpoint is taken to be an ERPG-2 of 200 ppm for an exposure time of one hour, and was estimated at 1.52 miles from the source. The consequences are modeled in atmospheric stability category F weather conditions with a windspeed of 1.5 m/s. These assumptions are taken from the "Model Risk Management Program and Plan for Ammonia Refrigeration", prepared by Science Applications International Corporation, Reston, VA. These assumptions were adopted because of the significant cost of doing modeling studies that are site specific, and because the final conclusions were not likely to change significantly even though site-specific information were used. This scenario has off-site receptors. There are no a ctive mitigation systems in use. Building enclosure was considered and dismissed as a passive mitigation system, as the enclosure is unreinforced cinder block construction, and not expected to withstand a 1 psi overpressure that is likely to occur on rupture of the high pressure receiver. The alternative scenario, one more likely to happen, is a gasket rupture or pump seal leak equivalent to a small orifice of diameter 1/4 to 1/2 inch. A typical rate of release would be 250 pounds/minute. Atmospheric Stability Category D with a moderate windspeed (e.g., 3 m/s) was chosen as close to average for many sites. The toxic endpoint of 1,760 feet was chosen to correspond with the smallest release rate which will have offsite receptors. This alternate scenario has off-site receptors. Passive mitigation to a release of 250 pounds/minute is considered to be the building in which the high pressure receiver and process piping is housed, because such a release would not be expected to infl ict structural damage on the building housing the receiver. Such a release could be contained until automatic and manual shutoff systems could be activated. Responders could further mitigate the release by absorption in water from a fire hose, employing the fireman's dump, and/or neutralizing the resulting aqueous mixture with acids, or releasing the solution to the sewer. The facility is subject to OSHA's PSM rule, and this plan is augmented by employee training program, and a program of regular inspection and maintenance. There have been no accidents in the last five years. LaGrou personnel are trained to respond to minor releases and situations which are minor repair/maintenance problems. However, for major releases, the facility is integrated into the response plan of the local unit of the Chicago Fire Department. Facility personnel are trained in response actions which consist of minimizing damage to the facility while assisting the orderly evacuation of all personnel. Chicago Fire Department personnel make regular inspections of the facility, and are familiar with the elements of its operation. LaGrou's program of regular review and update of relevant plans, employee training, routine inspections and regular maintenance has produced an accident-free history. The facility regularly evaluates and implements any appropriate measures to improve safety further. |