Hermiston Generating Plant - Executive Summary |
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Hermiston Generating Plant is a natural gas-fired combined cycle electric generation facility. The facility utilizes selective catalytic reduction (SCR) to control emissions of Oxides of Nitrogen (NOx). SCR uses a metal catalyst and ammonia injection to reduce NOx emissions to meet Oregon Department of Environmental Quality permit limits. The facility uses aqueous ammonia. Aqueous ammonia is a liquid that contains 28 percent ammonia in water. The worst-case release scenario assumes that the entire contents of the ammonia storage tank is released in a ten minute period. The tank is surrounded by a dike that would contain some of the spill. The offsite release impact distance for a worst-case release is 0.2 miles. This distance was determined using RMPComp. A worst-case release of the entire tank contents is very unlikely because the facility is staffed 24 hours/day and a leak would be identified and repaired in a timely manner. The facility was placed in commercial operation i n July, 1996 and it is very unlikely that the tank would fail. Also, the dike around the tank makes the possibility of an accident that would puncture the tank very unlikely. The alternative release scenario is based on the failure of a fill line to the tank. It is estimated that the maximum amount of ammonia that would be released in this scenario would be 7,000 gallons (54,000 pounds). This release would result in an offsite impact area of 0.1 miles. This distance was determined using RMPComp. For either the worst-case or alternative release scenarios there are no schools, residences, hospitals, prisons/corrections facilities, or recreation areas inside of the offsite consequence area. There are no environmental receptors inside of the offsite consequence area. There are two industrial businesses that are within the worst-case consequence area. The parking lot of one of these businesses is inside the offsite consequence area for the alternative release scenario. There hav e been no accidents involving ammonia at this facility. The facility complies with all Federal and State emergency response planning rules and guidelines. Employees are trained to identify spills and take immediate action to stop the leak and/or call for emergency assistance. Ammonia spill prevention steps includes written operating procedures for tank filling and ammonia handling operations. The ammonia tank has gages and alarms to monitor tank pressure and level. The ammonia tank is diked and bermed to contain any leak that might occur. The existing ammonia storage system was put into commercial operation in July, 1996. It was designed with consideration for industry standards and regulatory requirements. The facility will review safety and operating procedures on an annual basis to identify potential improvements. |