Sargent Canyon Cogeneration Company - Executive Summary |
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EXECUTIVE SUMMARY Accidental Release Prevention and Emergency Response Policies Sargent Canyon Cogeneration Company stores and utilizes anhydrous ammonia in a selective catalytic reduction (SCR) process and in a thermal energy storage (TES) system at their facility in the San Ardo oil fields near Paso Robles, California. It is Sargent Canyon Cogeneration Company's policy to comply with all applicable governmental regulations. Further, it is Sargent Canyon Cogeneration Company's objective to be a responsible citizen of the community in all of its business activities. Sargent Canyon Cogeneration Company emphasizes safe and environmentally sound operating practices and procedures through their employee training programs. In addition to job specific training, operators and maintenance personnel receive training in fire prevention, fire control, accident prevention, safety, and first aid. Additionally, an emergency action plan has been prepared for Sargent Canyon Cogenera tion Company and a chain of command to respond to emergencies has been established. Sargent Canyon Cogeneration Company has developed a detailed Compliance Audit Checklist which is used to evaluate compliance with the Process Safety Management (PSM) standard and 40 CFR Part 68 (RMP regulations). At least every three years, Sargent Canyon Cogeneration Company audits these programs and any findings of noncompliance are documented and responded to and the deficiencies are corrected. Description of the Stationary Source and Regulated Substances Texaco San Ardo Energy Company, a wholly-owned subsidiary of Texaco Producing Inc., formed a general partnership with the Anacapa Energy Company, a wholly-owned subsidiary of Edison Mission Energy Company, for the development of the cogeneration plant. The partnership, named Sargent Canyon Cogeneration Company, owns and operates the facility. The plant began commercial operation in October, 1991. The Sargent Canyon Cogeneration Company facility is located in Section 13, T32S/R10E, MDB&M in the sparsely populated San Ardo oil fields. Cogeneration, in the case of the Sargent Canyon project, is the simultaneous production of thermal energy and electrical energy from the combustion of a single fuel source. Combustion of the fuel takes place in a gas turbine that is physically coupled to an electric generator. Waste heat from the gas turbine's exhaust flows into a heat recovery steam generator (HRSG). The HRSG extracts the heat from the exhaust gases and produces steam for thermally enhanced oil recovery. Electricity is produced at the same time via the electric generator coupled to the combustion turbine. Anhydrous ammonia is used at the Sargent Canyon Cogeneration Company facility to create a reducing atmosphere in the SCR process. This reducing atmosphere in the flue gas helps convert nitrogen oxides to nitrogen and water as it passes through the catalytic reactor. The operation of the SCR system substantially lowers the emissions of nitrogen oxides from the gas turbine. Liquid ammonia is stored in a 15,000 gallon (water capacity) storage tank. The maximum intended inventory of the anhydrous ammonia storage tank is based on the American National Standard Institute's K61.1 safety requirements and the Occupational Safety and Health Administration (OSHA) regulations published in Section 1910.111 of 29 CFR (and Section 509 of Title 8, CCR). These standards and regulations limit the maximum ammonia storage capacity of the tank to approximately 69,960 pounds. Anhydrous ammonia is also utilized as a refrigerant in the TES system to cool the inlet air for the gas turbine during warm weather. The TES system includes an ammonia refrigeration system that generates ice during off-peak hours. The ice is stockpiled in an ice storage tank. During on-peak hours, chilled water is circulated from the ice storage tank to the inlet to the gas turbine. At the inlet of th e gas turbine, the chilled water flows through a heat exchanger which cools the inlet air of the gas turbine. Cooling the inlet combustion air of the gas turbine improves the turbine's power output during warm on-peak hours. The ammonia refrigeration system consists of a low pressure receiver, a high pressure pilot receiver, an evaporator, a compressor, two condensers, and an oil separator reservoir. The largest vessel in the system is the low pressure receiver which contains approximately 3200 pounds of anhydrous ammonia. For purposes of the offsite consequence analyses, the RMP regulations define the toxic endpoint for anhydrous ammonia as 0.14 mg/l (200 ppm). This concentration has been established by the American Industrial Hygiene Association as the Emergency Response Planning Guideline Level 2 (ERPG-2). ERPG-2 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or d eveloping irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action. Worst-Case Release Scenario and Alternative Release Scenario Offsite consequence analyses are used as tools to assist in emergency response planning. The RMP regulations require the owner or operator of a stationary source to analyze the offsite impacts due to an accidental release of a regulated substance. The offsite consequence analysis for a Program 3 process must analyze the worst-case release scenario and an alternative release scenario. Since Sargent Canyon Cogeneration Company's SCR system and the TES system are considered Program 3 processes, both release scenarios were evaluated in the offsite consequence analysis. The offsite consequence analysis must include an estimate of the residential population within an area potentially affected by the accidental release scenarios. This area is defined as a circle with a radius equi valent to the distance the release would travel with concentrations at or above the endpoint. This circle also defines the area in which potential environmental receptors must be identified. The worst case release is defined by the U.S. EPA as the total release of the contents of the single largest vessel or pipe within 10 minutes. For liquefied gases stored under pressure, the entire contents of the vessel or pipe are assumed to be released as a vapor. A total vapor release is highly unlikely. However, this standardized worst case scenario was developed for emergency response agencies to use for planning purposes. An alternative release scenario is a release that is more likely to occur than the worst-case release scenario. For Sargent Canyon Cogeneration Company, the alternative release scenario was selected based on the results of the Hazard and Operability Studies for the ammonia-based SCR and TES systems. The worst credible release event with the highest discha rge rate would potentially have the greatest offsite impact. A failure of the ammonia delivery hose was identified in the Hazard and Operability Studies as the worst credible release event having the highest release rate, and therefore, was chosen as the alternative release scenario. Sargent Canyon Cogeneration Company has analyzed the offsite consequences of the worst-case and alternative release. For the worst-case release scenario, the release of 69,960 lbs. of ammonia within 10 minutes, the plume would travel 3.1 miles at concentrations at or above the endpoint. Using 1990 Census data, the population potentially affected within the worst-case release scenario circle is 120. There were no sensitive or environmental receptors within the worst case release scenario circle. Sargent Canyon Cogeneration Company has installed passive and active mitigation systems to aid in the control of ammonia, if a release were to occur. A concrete containment wall surrounds the ammonia storage and vaporizer system. A release of liquid ammonia could be contained within this area. The containment would limit the ammonia surface area in contact with the ambient air, thereby decreasing the rate of volatilization. The ammonia storage system is also equipped with a water deluge system that will spray water onto and around the storage tank. In the event of a fire, this deluge system can be used to cool the tank and help mitigate a temperature induced overpressure release Although mitigation systems are installed, a specific mitigation factor cannot be assigned to the systems. Therefore, no mitigation factors were included in the modeling. As such, the modeling results should be substantially overstated. In the alternative release scenario, a failure of the delivery hose was modeled as a release of liquefied ammonia stored under pressure. For a release of 554 lb/min of anhydrous ammonia, the plume would travel 0.2 mile at concentrations at or ab ove the endpoint. No residences are located within the 0.2 mile area around the Sargent Canyon Cogeneration Company facility. As such, there would be no population impacts from the alternative release scenario. There were also no sensitive or environmental receptors within the alternative release scenario circle. The modeling performed as part of this offsite consequence analysis does not take into account the use of the remote operated shutoff valves that were installed at the ammonia tank. These isolation valves take approximately 10 to 15 seconds to fully close and could greatly reduce the impact of a hose failure release. General Accidental Release Prevention Program and Chemical-Specific Prevention Steps A PSM program, which meets the requirements of the general accidental release prevention program, has been developed at Sargent Canyon Cogeneration Company to address the anhydrous ammonia system. The PSM program includes the following chemical-specific preve ntion steps: Written process safety information, including information pertaining to the hazards of ammonia, the technology of the process, and the equipment in the process has been compiled. An initial Process Hazard Analysis (PHA) was performed and has been updated and revalidated at least every five years. Written operating procedures have been developed and implemented, and are reviewed at least annually. Safe work practices, such as lockout/tagout, confined space entry, opening process equipment or piping, and control over entrance into the facility have been developed and implemented. Each employee involved in operating the ammonia system has received initial training and refresher training at least every three years. Written mechanical integrity procedures have been established and implemented. A Management of Change (MOC) program has been developed and implemented to address all proposed changes to the ammonia system. Pre-startup safety reviews are performed when a modification is made to the ammonia system that is significant enough to require a change in the process safety information. Audits are conducted at least every three years to evaluate compliance with the RMP regulations. Incident investigation procedures have been established. A written plan of action regarding the implementation of employee participation has been developed and implemented. Hot work permits are issued for all hot work operations conducted on or near the ammonia system. A Contractor Safety Policy has been developed and implemented. To ensure that the general accidental release prevention program and the chemical-specific prevention steps are implemented, Sargent Canyon Cogeneration Company has assigned overall responsibility for the RMP elements to the Executive Director. The Executive Director has the overall responsibility for the development, implementation, and integration of the RMP elements. Five-Year Accident His tory Sargent Canyon Cogeneration Company has not had any accidental releases from the ammonia-based SCR and TES systems that have resulted in deaths, injuries, or significant property damage on site, or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage in the last five years. Emergency Response Program Sargent Canyon Cogeneration Company has established an emergency action plan and a chain of command to respond to emergencies and to notify emergency responders when there is a need for a response. However, an emergency response program does not need to be developed for the facility since Sargent Canyon Cogeneration Company employees will not respond to accidental releases of ammonia, the facility is included in the community emergency response plan, and appropriate mechanisms are in place to notify emergency responders. Planned Changes To Improve Safety The PHAs were most recently revalidated in March, 1996. Seve ral changes to inspection and offloading procedures were recommended based on the PHA revalidation. These changes were implemented by November, 1996. Through the accidental release prevention program, Sargent Canyon Cogeneration Company regularly evaluates the need for any changes to improve safety. Currently Sargent Canyon Cogeneration Company does not have any additional changes planned to improve safety. |