Contra Costa Power Plant - Executive Summary |
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Please see attached RMP Executive Summary. EXECUTIVE SUMMARY FOR THE CONTRA COSTA POWER PLANT RISK MANAGEMENT PLAN FOR THE UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Prepared for United States Environmental Protection Agency Prepared by Mirant Delta, LLC 1350 Treat Boulevard, Suite 500 Walnut Creek, CA 94596 With technical assistance by URS Corporation 1615 Murray Canyon Road, Suite 1000 San Diego, CA 92108-4314 619-294-9400 Fax: 619-293-7920 March 13, 2001 Figures Figure 1-1 Location of Aqueous Ammonia Storage Facility on the Contra Costa Power Plant Figure 1-2 Aqueous Ammonia Storage Area Design Features Figure 1-3 Aqueous Ammonia Flow Diagram Figure 1-4 Predicted Ammonia Concentrations for the Worst-Case Release Scenario Section 1 EXECUTIVE SUMMARY 1.1 Background Mirant Delta, LLC (Mirant) owns and operates Contra Costa Power Plant (CCPP), an electric power generating facility located east of Antioch, California in Contra Costa County. There are seven existing units at CCPP: Units 1-3 which have been retired, Units 4 and 5 which continue to operate as synchronous condensers for support of the regional transmission system, and Units 6 and 7 which continue to operate for electric power generation. Mirant also proposes to construct and operate a new combined cycle power generation unit (Unit 8) at the CCPP site. Mirant will retrofit the existing Units 6 and 7 at CCPP with Selective Catalytic Reduction (SCR) systems in order to reduce emissions of nitrogen oxides (NOx), as required to comply with Bay Area Air Quality Management District (BAAQMD) Regulation 9, Rule 11, "Nitrogen Oxides and Carbon Monoxide from Electric Power Generating Steam Boilers". The new Unit 8 will also utilize SCR systems to reduce its NOx emissions and comply with its permitted NOx emission limits. Mirant will retrofit Unit 7 with an SCR system in Spring, 2001 and will retrofit Unit 6 with an SCR system in Spring, 2003. The ne w Unit 8 is scheduled to become operational in June, 2003. The SCR system utilizes aqueous ammonia to reduce NOx emissions from the generating units. The concentration of ammonia in the aqueous solution will be 29.4 % by weight. This substance is listed as a hazardous material under both California and federal regulations. In order to prevent accidental releases of hazardous materials and to reduce their potential impact on the public and the environment, a federal program was established in 1990 as described in Section 112(r) of the Clean Air Act. The California Office of Emergency Services established the California Accidental Release Prevention (CalARP) Program to prevent accidental releases of regulated substances and to mitigate the severity of releases that do occur. The CalARP Program specifies the regulated substances, oversees the federal requirements, and determines the requirements for the preparation of a Risk Management Plan (RMP) and offsite accidental release c onsequence analysis. In Contra Costa County, the Administering Agency overseeing the CalARP program is the Contra Costa County Health Services Department (CCCHSD), to whom this RMP will be submitted along with submission to the United States Environmental Protection Agency (US EPA). After the expansion, the quantity of aqueous ammonia to be stored and used at the Contra Costa Power Plant (CCPP) will be greater than both the Federal and State Threshold Quantities; therefore a RMP is required. As shown in this RMP, even a highly improbable worst-case release from the CCPP aqueous ammonia system will not cause the toxic endpoint concentration for ammonia (200 ppmv) to occur offsite. In addition, the more stringent 30-minute Short-Term Public Emergency Limit (STPEL) proposed by the National Research Council will not be exceeded offsite as a result of the hypothetical worst-case release. Also, CCPP has not experienced any accidental release during the last five years that caused an offsite impact. Accordingly, this process qualifies for a Program 1 RMP under both the CalARP and federal regulations. In order to fulfill the Program 1 requirements, the following actions were completed: - Analyze the worst-case release scenario. - Document that the nearest public receptor is beyond the distance to a toxic endpoint. - Document that no hazardous material accidents occurred in the past 5 years. - Ensure that response actions have been coordinated with local emergency planning and response agencies. - Certify in the RMP that "no additional measures are necessary to prevent offsite impacts from accidental releases." The remainder of this RMP documents these actions. The organization of the RMP follows that provided in the Contra Costa County CalARP Program Guidance Document and the US EPA RMP Submit User's Manual. 1.2 Accidental Release Prevention and Emergency Response Policies Mirant is committed to being a responsible member of the community in which it operates by giving top priority to operating in a safe and environmentally sound manner. It is the policy of Mirant to conduct business in a manner that protects the environment and the health and safety of the public and its employees by: - Meeting or surpassing all environmental laws, regulations and permit requirements, and verifying this commitment through environmental auditing. - Seeking to ensure that environmental laws, regulations and permit requirements are based on sound science and cost-effective technology. - Pursuing opportunities to enhance the quality of the environment. - Promoting public and employee understanding of environmental issues and the company's environmental activities. - Establishing company and organizational environmental goals and implementation plans. - Ensuring that employees are aware of their individual roles and responsibilities in implementation of this environmental policy. Mirant California, is committed to responsible business practices around the world. Mirant's paramount environmental objective is to be a good steward of the environment and to conduct business in a manner contributing to sustainable development in the communities that Mirant serves, ensuring that Mirant meets the needs of the present generation without compromising the quality of life of future generations. In an effort to continue to improve the environmental, health and safety performance at CCPP, the following lists many of the environmental, health and safety programs that are implemented: - Facility Emergency Plan - Oil Spill Prevention Control and Countermeasures Plan - Hazardous Materials Business Plan - Emergency Oil Spill Response Plan - Injury & Illness Prevention Program - Hazard Communication Program - Fuel Oil Tank Farm Operating Procedures - Contra Costa Power Plant Operating Procedures - Source Reduction Evaluation and Review Plan - Respiratory Protection Program - Hearing Conservation Program - Permit Required Confined Space - Evacuation Policy - Asbestos Policy - Bloodborne Pathogens Policy - Lead Control Policy - Fire Safety Program Policy - Contractor and New Employee Safety Orientation Policy - Lockout/Tagout Policy On-going personnel training at CCPP includes, but is not limited to the following: - Asbestos Awareness - First Responder Awareness - Hazard Communication - Injury & Illness Prevention Program - Personal Protective Equipment Awareness - Hearing Conservation - Respiratory Protection Awareness - Hazardous Materials Awareness - Hazardous Waste Management - Bloodborne Pathogens - First Responder Operations - Oil Spill Prevention Control and Countermeasures Plan - Hazardous Waste Operations and Emergency Response (HAZWOPER) - Confined Space - Ergonomics - Cardiopulmonary Resuscitation (CPR)/First Aid - Lockout/Tagout - Lead Awareness - Incipient Fire Response - Fall Protection - Oil Spill Table Top Drill In a continued effort to improve and ensu re proper implementation of the environmental, health and safety policies, the following measures are regularly employed: - Mirant Compliance Audit Program - Facility Working Safety Team Program - Facility Management Compliance Walkdown Audits - On-going Refresher Training - Master Tailboard Safety Meetings The release prevention programs to be implemented in conjunction with this RMP will strengthen the existing safety and environmental programs at CCPP. 1.3 Storage And Handling of Regulated Substance The only federal and CalARP regulated substance to be stored and handled onsite will be aqueous ammonia, which will be used in the SCR system to reduce NOx emissions from Units 6, 7 and 8. In the proposed SCR system, aqueous ammonia is pumped from the storage tanks, to a vaporizer, which produces a uniform distribution of gaseous ammonia that is mixed with the flue gas from the Units and passed over a catalyst to reduce the NOx emissions from the stack exhaust. The aqueo us ammonia facility will be located near the northern portion of the developed property of the Contra Costa Power Plant, south of Units 6 and 7 and adjacent to Unit 8, as shown on Figure 1-1. The proposed location of the aqueous ammonia unloading and storage facility has been selected largely on the basis of safety considerations. This location will maximize the distance from the property fence line, reducing any potential offsite impacts due to a spill, while minimizing the piping distance to the Units. In addition, the location was chosen because of the facility area's low occupancy, its easy access for delivery trucks, and to distance the aqueous ammonia storage system from combustible equipment and minimize potential impacts to plant personnel. The aqueous ammonia unloading and storage facility will consist of a truck unloading station and three aqueous ammonia storage tanks, as shown in Figure 1-2. The storage facility will be designed and constructed to receive and store a queous ammonia for the retrofitted Units 6 and 7 and the new combined-cycle generating Unit 8. The storage facility to service the SCRs on existing Units 6, 7 and new Unit 8 will include three 20,000-gallon carbon steel storage tanks, approximately 12 feet in diameter by 26 feet long. The tanks will be constructed in compliance with Uniform Building Code Seismic Zone 4, Uniform Fire Code Article 80, and American Society of Mechanical Engineers Pressure Vessel Code Section VIII, Division 1, Rules for Construction of Pressure Vessels. The tanks will have maximum design pressure and temperature of about 50 pounds per square inch gauge (psig) and 120?F, respectively. The aqueous ammonia tanks will be supported horizontally on concrete foundations within a walled containment basin approximately 68 feet long by 44 feet wide, that will slope to a centrally located, covered sump beneath the tanks and running the length of the containment area. This sump will be 6 feet wide and 12 feet deep to provide a volume sufficient to hold 100 percent of the contents of one ammonia storage tank, plus the maximum rainfall recorded in 24 hours in the past 43 years (3.03 inches, WRCC 1955-1998). Pumps for forwarding the aqueous ammonia to the power plant Units and for unloading will also be located within the containment basin. Aqueous ammonia will be delivered to the Contra Costa Power Plant via tanker truck. Individual tanker trucks can transport up to 6,500 gallons of aqueous ammonia. The concrete slab under the truck unloading station is designed to contain the contents of one full truck and will be sloped to quickly drain any accidental releases of aqueous ammonia into the central covered containment sump. Each storage tank will have an unloading station consisting of an ammonia fill line, where aqueous ammonia is fed from the delivery truck to the tank, and a vapor return line where vapor pressure between the tank and the truck is equalized. The aqueous ammonia delivery and injection facilities for each SCR will include aqueous ammonia feed pumps, ammonia vaporization equipment, and ammonia injection grid. In the SCR system, aqueous ammonia is piped from the storage tanks to spray nozzles in the ammonia vaporizer unit on the injection skids near the SCR reactor. The spray droplets are then mixed with a hot air diluent stream in the vaporizer to evaporate the ammonia. The vaporizer produces a uniform distribution of gaseous ammonia in the diluent stream. The diluent stream is then transported to the injection grid. Figure 1-3 presents a simple ammonia flow diagram for the SCR system. The injection grid is located upstream of the SCR reactor. This allows more thorough mixing of the ammonia-laden diluent stream with the turbulent flue gas from the Units. Although the oxidation-reduction reaction is initiated by the injection of ammonia at the injection grid, all of the reaction is completed in the SCR reactor by passing the mixture ov er a catalyst composed primarily of titanium and vanadium oxides. The treated flue gas, containing a small amount of residual NOX and excess ammonia, is discharged out of the stack. The SCR process is controlled with feed-forward and feedback control loops. An upstream NOX analyzer will measure the NOX concentration at the SCR reactor inlet. A downstream analyzer will measure the total NOx concentration downstream of the SCR reactor outlet. The ammonia demand signal, which regulates the rate at which aqueous ammonia is pumped to the vaporizer, is determined from both NOx analyzers. The aqueous ammonia solution proposed for the SCR systems at CCPP will be 29.4 percent ammonia by weight with the balance of the weight being water. Aqueous ammonia is a corrosive material although the degree of danger associated with the substance is considered to be minor. Ammonia is not a known carcinogen, but it poses acute and chronic non-carcinogenic health hazards to the respiratory system and chronic non-carcinogenic health hazards as skin irritations or other effects. Acute health hazards are those that occur from short exposures to airborne ammonia vapor, whereas chronic health effects are those that occur as a result of long-term exposures. Though there is some insoluble ammonia present in the ammonia solution, the solution has a very low vapor pressure compared to anhydrous ammonia, a more hazardous compound also used for SCR. The ammonia present will not readily vaporize if the solution is released to the atmosphere. If the ammonia evaporates from the solution, the ammonia vapor is irritating at levels above a few parts per million volume (ppmv) and acutely toxic in high concentrations. A one-hour average ammonia vapor concentration above 200 ppmv could cause respiratory irritation to exposed individuals. According to the National Research Council, exposure at the 75 ppmv STPEL level "should not result in serious effects, but would result in strong odor, l acrimation, and irritation of the upper respiratory tract (nose and throat), but no incapacitation or prevention of self-rescue." Ammonia vapor is flammable in air at concentrations of 16 percent to 25 percent, but requires a very high temperature source for ignition. Ammonia concentrations directly above an aqueous ammonia spill never approach these concentrations; therefore aqueous ammonia has no explosive flammability potential. 1.4 Worst-Case Release Scenario Mirant performed an offsite consequence analysis to examine the significance of an accidental release of aqueous ammonia. The hypothetical worst-case release scenario examined the effects of releasing an entire 20,000 gallon storage tank. Due to the designed passive mitigation systems, any spill of aqueous ammonia will drain rapidly into a covered sump through drains in the contained storage and unloading areas, leaving only the drain hole areas exposed to the atmosphere where vaporization of ammonia can occur. Th e EPA approved air quality dispersion model SCREEN3 was used to predict the spread of aqueous ammonia for the worst-case release scenario. The distance to the toxic endpoint concentration (200 ppmv) in the worst-case release scenario was calculated to be 338 feet from the center of the aqueous ammonia storage tank area (see Figure 1-4). The nearest potential public receptor to the aqueous ammonia storage facility is at least 600 feet away within the PG&E switchyard south of the ammonia storage equipment, and well beyond the distance of the toxic endpoint. Since CCPP has not had a release of a regulated substance in the past five years and there are no public receptors within 338 feet of the ammonia storage facility, CCPP qualifies for a Program 1 RMP under both the CalARP and federal regulations. 1.5 Accidental Release Prevention Program Safety was the foremost consideration when designing the aqueous ammonia unloading and storage facility. The location of the ammonia fa cility was selected to be in a low occupancy area of the plant at a maximum distance from the property fence line, to reduce potential offsite impacts due to a spill. The aqueous ammonia storage tanks will be enclosed within a walled containment basin that will slope to a centrally located, covered sump beneath the tanks that will run the length of the containment area. There will also be a walled containment pad under the tanker truck unloading facility that will drain rapidly into the covered sump under the tanks. Many accident prevention safeguards will be implemented with the aqueous ammonia storage area. For example in the event of a power outage, standby power needed for all required electrical systems, such as monitors and alarms, will be provided by the Uninterruptible Power Supply system. Also hot work permits will be required for specific activities that present the potential for fire, and personnel involved in such operations will receive appropriate training. Other safety features of the aqueous ammonia storage and unloading facility include: - Ammonia area monitoring system with audible and visible alarms, - Eyewash and shower station, - Piping and connections for washdown of containment basin with clean water, - Permanent lighting, - Lightning protection, - Truck barrier posts to protect ammonia tanks and delivery lines, - Liquid level indication and high-level alarm for each tank, easily visible from the unloading position, - Tank level and pressure indicators and pressure relief valves and alarms in the plant control room, - Shut-off valves located on the tank fill lines, which will close automatically if the emergency high-level alarm is triggered, - Local manual controls for all pumps, - Vacuum breaker valves on each tank, and - Safety equipment (for two personnel) including: two full face respiratory devices, two sets of escape respirators, two pairs of ammonia-resistant gloves, two pairs of ammonia-resistant boots, two pairs of ammonia-resistant pants and jacket/slicker, one first aid kit, and one fire extinguisher. Area sensors will be installed in the ammonia unloading and storage facility and injection skid to monitor for ambient ammonia concentrations. Alarms are designed to annunciate in the control room with local audible alarms for ammonia releases at the facilities. To minimize impacts from accidental releases, workers will be trained in the safe handling of hazardous materials, use of response equipment, procedures for mitigation of a release, and coordination with local emergency response organizations. To avoid or minimize impacts from the accidental releases of hazardous materials, nonhazardous or less hazardous materials will be used, where possible, and engineering controls will be implemented. For example, aqueous ammonia was selected for the SCR system over anhydrous ammonia, because it is less hazardous. 1.6 Five-Year Accident History Large quantities of aqueous ammoni a have not been present at CCPP in the past. During the past 5 years at the facility there have been no accidents involving regulated substances or other extremely hazardous substances that have resulted in deaths, injuries or significant property damage onsite, or known offsite deaths, injuries, evacuations, sheltering in place, property damage or environmental damage. Accidents at CCPP have been avoided by adhering to the safety and environmental programs listed in Section 1.1, continually improving the personnel safety training program and adhering to a strict maintenance program for all equipment involved with the storage and handling of hazardous substances. 1.7 Emergency Response Program CCPP has coordinated emergency response programs with the CCCHSD and the Contra Costa Fire Department. Periodically the fire department inspects the facilities that store and handle flammable hazardous materials at CCPP to ensure that the applicable Uniform Fire Code requirements are being met. 1.8 Safety Improvement Plans To continue operating a safe accident-free facility, the safety features described in this document and specifically in Section 1.4, Accidental Release Prevention Program, will be implemented upon construction of the aqueous ammonia storage and handling facilities. Regular equipment inspections, maintenance and safety reviews will ensure continued safe operations at CCPP. |