Stonewall Plant - Executive Summary |
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a. The Merck Stonewall accidental release prevention policy is a unified approach, integrating technology, procedures, and management practices. The Merck Stonewall emergency response policy involves the preparation of response plans that are tailored to each covered chemical at the facility and to the emergency response services available in the community and is in compliance with the EPA Emergency Response Program requirements. b. Merck & Co., Inc. is a worldwide research-intensive health products company that discovers, develops, manufactures and markets human and animal health products. Merck's Stonewall Plant, located near Elkton, Virginia, was established in 1941. Currently, the plant employs approximately 920 people in a range of pharmaceutical manufacturing activities such as fermentation, solvent extraction, organic chemical synthesis, and finishing and packaging operations. The facility's products include broad spectrum antibiotics, anti-parasitic drugs for human and a nimal health, a cholesterol lowering drug and medicines for the treatment of Parkinson's disease and the human immunodeficiency virus (HIV). The production and emission controls of the two latter products require the use of anhydrous hydrogen chloride and propane. Anhydrous hydrogen chloride, used in the production of both products, is charged to each process from one of two railcars. Propane is used to fuel emission control devices for each process. c. The offsite consequence analysis includes consideration of two release scenarios, identified as "worst case release" and "alternative scenario". The "worst case release" is defined by EPA, which states that "the owner or operator shall assume that themaximum quantity in the largest vesselis released as a gas over 10 minutes" due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst case release scenario". Worst case release and alternate scenario modeling was performed for a tox ic gas (hydrogen chloride) and a flammable gas (propane). Atmospheric dispersion modeling was performed utilizing EPA published RMP*COMP, Version 1.06, to determine the distance traveled by the chemical released before its concentration decreases to the "toxic endpoint" selected by EPA as the Emergency Response Planning Guideline Level 2 (ERPG-2). This is defined by the American Industrial Hygiene Association (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effect or symptoms which could impair an individual's ability to take protective action." The residential population within a circle with a radius corresponding to the toxic endpoint distance was defined, "to estimate the population potentially affected". One worst case scenario for toxic materials was developed for the Merck Stonewall facility. The worst case release sc enario for anhydrous hydrogen chloride involves the failure of one full railcar. The offsite consequence analysis for this scenario was performed based on the EPA pre-defined conditions, namely release of the entire amount of material in 10 minutes, use of the one-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circle with radius corresponding to the toxic endpoint distance. EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 meters per second, and air temperature of 77 degrees F (25 degrees C) were used. One alternative release scenario for toxic gas was developed. The scenario involves leak or complete failure of liquid anhydrous hydrogen chloride transfer hose during unloading operations causing a release from the railcar and from the liquid residual material in the transfer piping. The excess flow valve (internal in the railcar) does not immediately seat. Within 5 minutes, the emergency block valv e is closed remotely. The emergency response team activates and places a water curtain on the release that effectively reduces the release by a factor of 0.2. EPA suggested meteorological conditions were utilized, namely Stability D, wind speed of 3 meters per second, and air temperature of 77 degrees F (25 degrees C). One worst case release scenario for flammable gas was developed involving the failure of the largest propane storage vessel on site. The offsite consequence analysis for this scenario was performed based on the EPA pre-defined conditions, namely release of the entire amount of material in 10 minutes, use of the one psi overpressure based on a vapor cloud explosion, and consideration of the population residing within a full circle with radius corresponding to overpressure distance. EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 meters per second, and air temperature of 77 degrees F (25 degrees C) were used. The alternative release sce nario for propane involves the same release conditions as the worst case, however the meteorological conditions were changed to the suggested EPA alternate conditions, namely Stability D, wind speed of 3 meters per second, and air temperature of 77 degrees F (25 degrees C). d. The Stonewall accidental release prevention program is based on the following process safety management key elements including: 7 Aggressive and thorough Hazard Analysis (HazOp) performed on all processes 7 Process Specific and Safety Training for operators 7 Use of best industry practice for safe handling of highly toxic and hazardous materials 7 Use of accurate and effective operating procedures 7 Implementation of both a corporate and local audit program 7 Preventative and predictive maintenance program 7 Fully trained and active site emergency response team 7 Contractor Safety program Chemical specific prevention steps include the presence of hydrogen chloride detectors, awareness of the hazardous, toxic a nd flammable properties of anhydrous hydrogen chloride and propane. e. No accidental releases of anhydrous hydrogen chloride or propane meeting the definition of 40 CFR 68.42 have occurred at this facility in the past five years. f. The facility has an emergency response program, including an on site emergency response team, fire brigade and emergency medical services team. The program has been coordinated with the Rockingham County Fire and Rescue Department, which is a member of the LEPC. This program includes emergency response guidelines and procedures for each covered chemical and a notification plan. Emergency response drill evaluations are conducted annually; emergency operation and response procedures are also reviewed at that time. g. Ten changes to improve safety (recommended actions) were identified in the 1996 reassessment of risk management audit for the two covered chemicals. All recommended action have been implemented, including upgrading hydrogen chloride sens ors, increasing the capacity of a scrubber, and implementing an improved preventative maintenance program on piping. |