Supervalu - Pittsburgh Div. Perishable Warehouse - Executive Summary
The Supervalu - Pittsburgh Division business is food products warehousing and distribution to client grocery stores and distribution centers. This building complex includes a Dairy Warehouse and a Perishable Warehouse. Both of these buildings are expansive, and both contain ammonia refrigeration systems. Only the Perishable Warehouse's system contains over 10,000 pounds of ammonia, and there are no likely events which might cause simulataneous catastrophic releases from both facilities simultaneously. The closed ammonia refrigeration system at the Perishable Warehouse contains a maximum intended inventory of 33,000 pounds. The facility is located in a rural setting, approximately 1.5 miles southwest of the intersection of Interstate 70 and 74 in western Pennsylvania. |
The facility has an active Process Safety Management Program. Access to the ammonia equipment is restricted to only a select few trained, authorized operating/maintenance personnel. The majority of the distribution
piping and air cooling evaporator units which contain ammonia are located within the refrigerated spaces, and therefore are suseptable to damage from accidental, inadvertant contact by lift trucks and lifted loads. However, all equipment and associated piping within those spaces is located as high as possible within the spaces, to minimize accidents. The most recent expansions to the refrigeration system were installed such that new piping is located above the roof, and equipment is located in penthouse-type enclosures. The facility has commenced an improvement program which will result in the relocation of nearly all distribution piping and key shutoff valves to the roof: this project is anticipated to be completed by 2002. The significant investment associated with this undertaking is an example of the commitment of management to identifying critical safety control points and improving the process accordingly.
In a worst-case scenario, the entire contents of the ammonia refriger
ation system would be expelled in 10 minutes: the release rate would be 3300 pounds per minute, or less. This might result from the rupture of a 11/2" high pressure (180 psig) liquid ammonia pipe, which is an unlikely but nevertheless plausible scenario. In such a case, the distance to toxic endpoint (200 ppm) under worst-case ambient conditions (still air) is anticipated to be 3.3 miles. Ammonia is an extremely hazardous and toxic chemical, but the toxicity level is substantial: the offensive, choking odor of ammonia is readily distinguished and familiar to most humans, who generally are intolerant of even low (<20 ppm) dosages. The toxicity concentration is 2400 ppm or above. The more-likely release scenario selected and evaluated, and having the greatest offsite risk, is the accidental rupture of a 1/2" high pressure liquid pipe on the roof: in that case, the release rate was found to be 540 pounds per minute, and the vulnerability zone (distance to toxic endpoint) is reduce
d to 0.4 miles from the facility. It is possible (but unlikely) that such a release could be on-going for a period of up to one hour before (a) the entire contents of the system are dispelled, or (b) intervening action can be taken by trained personnel. The location of the facility in the community, together with the topography and consideration for prevailiing wind direction, help to minimize the overall risk to human populations.
An OSHA-prescribed Process Safety Management Program has been in place at the Perishable Warehouse for many years. Under that Program, the major components of the process are inspected frequently. Operating conditions are constantly monitored by a computerized system with integral alarms that notify process operators of an upset. The readily-distinguished odor of ammonia alerts persons in the constantly-inhabited areas where ammonia-containing piping and equipment is located that even the slightest release may have occurred. As stated above, the compa
ny has commenced a process-improvement program which will result in the relocation of piping and all key shutoff valves to the roof area for easier access in emergency conditions. Shutoff valves which allow operators to isolate sections of piping/equipment from areas of safety, such as the maintenance and compressor room areas, were installed many years ago. The compressor room area is well vented with high volume fans, and is readily accessible in case of a release in that area.
As a testimony to the overall safety of the ammonia refrigerations at this facility, and the diligence of the process operators, no accidents have occurred within the past five years which have necessitated an off-site evacuation or have had any offsite consequences.
The Westmoreland County LEPC has included the Supervalu facility in the community emergency plan for many, many years. Every year, the LEPC contacts facility representatives for an update of plan elements. The adjoining Hempfield Township Fire
Department maintains a successful HAZMAT squad that is constantly available to provide resources in the event of an accidental release. In 1999, Supervalu - Pittsburgh Division endorsed the INTEGRATED CONTINGENCY PLAN format preferred by EPA and OSHA for preparing and implementing its onsite Emergency Action and Response Plan. This new plan will become fully implemented by the end of 1999: under this plan, emergency training and practice drills will be frequent and will cover a multitude of potential scenarios. Four key managers will become involved immediately upon the recognition and characterization of all non-incidental ammonia releases, and their duties will be as follows: (a) coordination of and direction to onsite and external emergency responders; (b) notification of agencies and on-site safety and security; (c) protection and continuation of business operations and employee welfare; and (d) communication with the public as necessary.
Supervalu - Pittsburgh Division conti
nues to investigate and implement changes to the ammonia process in order to improve safety and minimize risks associated with it. In addition to relocating piping and valves, future plans include the increase of automatic ammonia leak detection systems, improved access to safety shutoffs, reduction of the amount of ammonia contained within the system but necessary for system operation, and systems which will rapidly reduce the pressure within any major part of the piping/equipment system in case of emergency shutdown.