Shawville Station - Executive Summary |
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INTRODUCTION GPU Generation, Inc. (GPU Genco) owns and operates a coal-fired, electric power generating station near Shawville, Pennsylvania. This 947-acre facility, known as Shawville station, is located 10 miles northeast of Clearfield, PA on the west branch of the Susquehanna River near state routes 879 and 970. Shawville station employs over 95 full-time staff and a considerable number of contract employees. The secondary economic impact of the facility on its many material and services suppliers is significant. For example, the station provides employment for many coal miners and trucking firms. The facility generates 597 MW of power from two identical, 175 MW units and two other units rated at 122 and 125 MW. Each unit has a state-of-the-art pollution control system for particulate and special burners to reduce nitrogen oxide emissions. 1. ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES AT THE STATIONARY SOURCE GPU Genco's policy is to comply with all ap plicable regulatory requirements, including those for accidental release prevention and emergency response. 2. THE STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED a. PRIMARY ACTIVITIES - This facility is a coal-fired, electric power generating station. b. USE OF REGULATED SUBSTANCES - Anhydrous ammonia is used at Shawville station as a fluegas conditioner. The ammonia improves the ability of the electrostatic precipitators (ESPs) to remove particulate from the flue gas. In this process, the ammonia is converted to ammonium sulfate and removed from the flue gas as particulate. No other toxic or flammable materials are stored at the facility in quantities above the regulatory threshold. c. QUANTITIES HANDLED OR STORED - The anhydrous ammonia is transported, stored and conveyed as a liquid up to evaporators. A single 10,000-gallon tank located outdoors, adjacent to the machine shop, is used to store the anhydrous ammonia liquid. The storage tank is kept under pressure to main tain the ammonia in liquid form. Administrative controls are used to ensure that the tank is not filled above the 85% level. 3. THE WORST-CASE RELEASE SCENARIO AND THE ALTERNATIVE RELEASE SCENARIO a. THE SCENARIOS - The worst-case release scenario assumes that the ammonia storage tank catastrophically ruptures and the entire contents are released onto the pavement in 10 minutes. The quantity released in the 10-minute event is calculated as: 10,000 gallons *85% *5.66 lb/gal = 50,997 lb b. The alternative release scenario assumes that the entire contents of a 4,000-gallon ammonia tank truck are spilled into the paved unloading area over a 10-minute period (due to, for example, an unloading hose rupture). The quantity released in the 10-minute event is calculated as: 4,000 gallons * 5.66 lb/gal = 22,640 lb The alternative release scenario can include the effects of active mitigation systems, and for Shawville station this is the use of water sprays to minimize the ammonia plume. Ammonia is very soluble in water, but the sprays must be activated manually after the release. Therefore, we assume that the sprays would remove only one-half of the ammonia, changing the quantity released to 2,000 gallons or 11,320 lb. c. DISTANCES TO ENDPOINT - The offsite consequences of these accidental releases were evaluated with a screening computer dispersion model (RMP*COMP, version 1.06). Offsite consequence analysis of the worst-case scenario must include highly improbable weather conditions: a wind speed of 1.5 m/s (3.4 mph), "F" atmospheric stability class, and the highest daily maximum temperature and average humidity observed over the previous three years. The more typical meteorological parameters used in analyzing the alternative release scenario include a mean wind speed of 9.1 mph and "D" atmospheric stability. The maximum calculated distance to the endpoint using the RMP*COMP model is 2.6 miles for the worst-case scenario. This represents the maximum downwi nd distance that the catastrophic release (under worst-case weather conditions) could pose a hazard to the public. For the alternative release scenario, the maximum calculated distance to the endpoint using the RMP*COMP model is a more realistic 0.2 miles. 4. GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL-SPECIFIC PREVENTION STEPS There are many safety programs in place at the station to minimize the potential for the accidental releases of ammonia considered by this plan. For example: - A comprehensive process safety management (PSM) program has been implemented for all ammonia process equipment. This includes daily visual inspections, periodic mechanical integrity checks, and operator training. - The ammonia storage tank is a registered pressure vessel that is built to exacting standards. - Ammonia tank trucks are only unloaded during daylight hours on weekdays. - Administrative controls are used to ensure that the tank is not filled above the 85% level. - The ammonia tank is located in an area between several structures, which provides a wind block to increase plume dispersion in the event of a spill (although the dispersion models do not account for this). 5. FIVE-YEAR ACCIDENT HISTORY - No accidents as defined in 40 CFR Part 68 have occurred during the past five years at this site. 6. THE EMERGENCY RESPONSE PROGRAM - In the unlikely event that an accidental release of ammonia would occur, the station has prepared a detailed written emergency response plan. This plan has been in place for many years, and yearly "spill drills" are held to test the plan under simulated conditions. Yearly reviews of the emergency response procedures are conducted to ensure that they are up to date. 7. PLANNED CHANGES TO IMPROVE SAFETY - All station safety programs, including the emergency response program, are reviewed periodically for improvement opportunities. |