Northwest Alloys, Inc. - Executive Summary |
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Northwest Alloys, Inc. produces magnesium metal from metal containing rocks and minerals (Dolomite and Magnesite) at the Addy, Washington facility. The raw materials are fed in a uniform stream over a 12 to 15 hour time period to a furnace where the magnesium metal is liberated as vapor and subsequently condensed as a solid in a crucible. The magnesium solid in the crucible is further processed to form ingots and flux bars which are sold as product. A variety of containerized and bulk materials are used at the facility, either directly in the production of magnesium or in the supporting processes such as equipment maintenance and water treatment. These materials include solvents, fuels, water treatment chemicals, sulfuric acid, and oxygen. All of these materials are stored in tanks and containers designed and constructed to prevent spills and releases. Only one of the 140 chemicals on EPA's regulated substance list is stored at Northwest Alloys above the threshold levels. This is a flammable material (propane), which is compressed gas stored in three, 30,000-gallon tanks. The maximum amount of propane contained in one of these tanks at any given time would be 110,000 lbs. The tanks are located in Area 382, which is in the north central part of the facility. The threshold quantity for propane is 10,000 lbs. Northwest Alloys performed a detailed analysis of the processes and risks and found the worst case release scenario to be a vapor cloud explosion of the entire 110,000 lbs. contained in one of the propane tanks. This explosion would affect all areas surrounding the tank out to a distance of 0.4 miles. The nearest resident is 0.54 miles ESE of the plant in the City of Addy. Northwest Alloys has a good operating record and has not had a single incident in the past 5 years involving propane which has affected an off-site resident. |