Mayfield Dairy Farms, Inc. - Executive Summary
EXECUTIVE SUMMARY |
Description of Facility and Regulated Substance Handled:
Mayfield Dairy Farms, Inc. processes fluid milk. The facility utilizes anhydrous ammonia as a refrigerant to maintain the proper temperature of the milk within the facility. Anhydrous ammonia is an effective refrigerant that has been used for many years by most food processing facilities. Ammonia is normally a gas at ambient temperatures but is handled as a gas liquefied under pressure. The refrigeration system consists of a high-pressure receiver, evaporators, compressors, piping, and valves.
Accidental Release Prevention and Emergency Response Policies: Mayfield Dairy Farms, Inc. is committed to promoting safety for the plant, its employees and the surrounding area. The facility is complying with OSHA's Process Safety Management Standard (PSM), Title 29 Code of Federal Regulations (CFR) 1910.119, and EPA's Risk Management Program regulations (RMP), Title 40 CFR Part 68. The purpose of these programs is to en
sure that the refrigeration system is operated safely in order to prevent releases of ammonia from the system. In addition, these programs serve to develop procedures to minimize releases in the event that they do occur and to outline appropriate emergency response steps to take in the event of a release.
Worst Case Release Scenario: EPA's "Risk Management Program Guidance for Ammonia Refrigeration" (November 1998) and the International Institute of Ammonia Refrigeration's (IIAR) Risk Management Guidelines (1998) were the primary documents used to develop the worst case release scenario. The worst case release is one that is unlikely to occur. The purpose of the worst case release analysis is to support a dialogue with the community on release prevention. It is a conservative analysis and is not to serve as a rational basis for actual emergency response planning.
The worst case release scenario (as defined by EPA) is the release of the largest quantity of ammonia from a vessel or proc
ess line failure that results in the greatest distance to a toxic endpoint. The worst case release scenario for the refrigeration process is assumed to be a case where the total quantity of ammonia in the largest vessel is released. The release scenario was performed assuming that the vessel was filled to 100% capacity. The vessel, however, is normally filled to 25% capacity. There were passive mitigation systems (dikes, berms, drains, sumps or enclosures) considered in the analysis since the vessel is located indoors.
The toxic endpoint used for this scenario must be where the ambient concentration of ammonia is 0.14 mg/L or less. This endpoint is a concentration below which nearly all individuals could be exposed to for one hour without serious health effects. Based on Exhibit 4-4 in EPA's guidance, a release from the vessel would result in a situation where public receptors would be within the distance to the toxic endpoint.
Alternative Case Release Scenario: The alternative case r
elease scenario selected is one in which premature lifting of a relief valve causes a release to the atmosphere. EPA's "Risk Management Program Guidance for Ammonia Refrigeration" (November 1998) and the International Institute of Ammonia Refrigeration's (IIAR) Risk Management Guidelines (1998) were the primary documents used to develop the alternative release scenario. The alternative release scenario is one that is more likely to occur than the worst case release scenario.
The alternative release scenario must meet two criteria:
1) Must be more likely to occur than the worst case scenario, and
2) Must reach an endpoint off site, unless no such criteria exist.
A possible release scenario is one in which a relief valve lifts prematurely. The alternate release was performed assuming that a 250 lb. relief valve for the condensors lifted at 180lbs. The ammonia release would be limited to a ten-minute time frame if this failure occurred.
In addition, Mayfield has installed a sophisti
cated system of ammonia sensors that can remotely close certain isolation valves in the event of a small release and thereby limit an accidental release of ammonia. These sensors are capable of detecting releases of ammonia at low levels, and are connected to a computer that will shut certain valves to the system if ammonia is detected. In this way, potential releases of ammonia are minimized.
The toxic endpoint used for this scenario must be where the ambient concentration of ammonia is 0.14 mg/L or less. Based on EPA's guidance, the alternative release scenario would result in a situation where public receptors would be within the distance to the toxic endpoint.
Accidental Release Prevention Program and Chemical-Specific Prevention Steps: As a part of its PSM Program, Mayfield Dairy farms, Inc. has established numerous programs that serve to prevent accidental releases of ammonia. These programs include:
? Process Safety Information
? Process Hazard Analysis
? Operating Procedures
? Mechanical Integrity
? Management of Change
? Pre-Startup Review
? Compliance Audits
? Incident Investigations
? Employee Participation
? Hot Work Permits
? Contractor Safety
Emergency Response Information: As a part of the PSM Program, the facility maintains an Emergency Response Plan that was prepared in order to improve responsiveness to an emergency incident, and to increase the reliability of actions taken during an incident. The plan includes all aspects of emergency response including adequate first aid and medical treatment, evacuations,notification of local emergency response agencies as well as the public.
In the event of an emergency involving the ammonia system, it is the policy of the facility to request assistance as necessary by calling 911, which will notify the Jackson County Emergency Services. In addition, the Jackson County Emergency Service has in
cluded Mayfield Dairy Farms, Inc. in its local emergency response planning.
Five-Year Accident History: Mayfield Dairy Farms, Inc. has had an excellent record of preventing accidental releases over the last 5 years. Due to our stringent release prevention policies, there has been no accidental release during this period.
Steps to Improve Safety: Several developments and findings have resulted from the implementation of the various elements of our accidental release prevention program. Ammonia leak detection systems will be upgraded and standard operating procedures have been updated. All SOP's were reviewed and minor changes were made to the format.