Doswell Combined Cycle Facility - Executive Summary |
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Accidental Release Prevention and Emergency Response All Doswell Team Members are instilled with the shared values of an injury free workplace and environmental responsibility. Before a job is started, it is reviewed for both safety and environmental impact. If a job can not be done safely, it is not done. If a job is safe but has environmental concerns, it is not done. Standard operating procedures and a preventive maintenance program partnered with the shared values are the backbone of Doswell's prevention program. All production technicians are required to complete a series of Personnel Qualifications Cards (PQC). Each system of the Facility is covered by a PQC. The PQC program defines the knowledge and skill an individual must possess to operate or maintain any given system. In addition to basic system knowledge, an individual must possess knowledge related to safety, emergency, security, integrated plant operations, and environmental impact as applies to that system. Do swell utilizes a computer based maintenance system. Preventive maintenance (PM) work orders are issued on a periodic basis established by equipment manufacturers and equipment history. PM's are used to maintain plant equipment in a good working order and prevent accidental releases due to normal equipment aging. The system also issues and tracks corrective work orders. Premature failures abnormal operating conditions, releases, safety incidents, and re-occurring corrective work orders are tracked using a computer based database, Event Response. Event Response system drives Team members to analyze each event for root cause and implement countermeasures to prevent repeating events. Event Response is used to prevent small repeating problems from growing into to future failures. While Doswell strives to have no emergencies, it is recognized that they are impossible to prevent completely. Therefore, Doswell has procedures and equipment for responding to emergencies in an orderly an d safe manner. An integrated contingency plan (One Plan) is utilized to provide a single source for emergency procedures and compliance reporting. As a part of protecting employee health and safety, Doswell designates itself as a "non-responding" facility. Facility self-designation as non-responding is recognized by the U.S. Environmental Protection Agency (EPA) and the U.S. Occupational Safety and Health Administration (OSHA). Non-responder status was established as a risk ceiling for employee response. Under no circumstances shall personnel jeopardize their health and safety or that of others in responding to an emergency. In responding, employees shall not exceed significantly the level of risk to which they normally are exposed and acclimated in their workplace. Facility and Regulated Substance Handled Doswell Combined Cycle Facility is an independent electric power production facility. The Facility consists of two identical power units. Each unit consists of two combustion turbines, two heat recovery steam generators (HRSGs), one steam turbine, one air-cooled condenser, and their plant support equipment. The primary fuel is natural gas with light distillate fuel oil as a backup fuel. The Facility has a water treatment plant to process makeup water for the combustion turbine steam injection, evaporative coolers, and boiler water losses. Wastewater produced onsite from the water treatment operation, process blowdown, and miscellaneous drains is treated in a zero discharge system. Doswell uses anhydrous ammonia to control nitrous oxide emissions from the burning of fuel oil and gas for electric power production. The ammonia is stored as a liquid under pressure, which is vaporized and mixed with air before being injected into the Selective Catalytic Reduction unit on each HRSG. The ammonia is stored in two, 10,000-gallon tanks, which have a total capacity of 103,200 pounds of anhydrous ammonia. Worst Case Release Scenario EPA requires that the "worst ca se" release scenario and its emissions rate assume release of the entire contents of a tank over a ten-minute period. EPA has also established 0.14 milligrams per liter (mg/L) as the toxic endpoint for ammonia. The guidance prepared for the ammonia refrigeration industry, Risk Management Program Guidance for Ammonia Refrigeration (Ammonia Guidance, EPA, 1998), was used for Doswell's calculations because it stores ammonia in the same manner as in this industry. The hypothetical, worst-case release scenario for Doswell is failure of primary containment at one of the Facility's 10,000-gallon tanks. In accordance with the standard operating procedures of Doswell's ammonia supplier, the Facility's tanks may not be filled beyond 87 percent capacity. Therefore, a worst case failure of one of the ammonia tanks would release up to 44,892 lb. of ammonia or 4,489 lb/min over a ten-minute period. In such a scenario, the ammonia tank's secondary containment captures the entire liquid released. Th e distance to the toxic endpoint in a rural area was estimated using the following equation from the Ammonia Guidance: D=0.607(QR)0.4923 Where: D is the distance to the toxic endpoint (miles), and QR is the release rate of the ammonia (4,489 lb/min). Based on the equation, the distance to toxic endpoint for Doswell's worst case scenario is 3.8 miles. This is the distance over which airborne ammonia concentrations decrease to 0.14 mg/L assuming a worst case release rate of 4,489 lb/min and a stable atmosphere with a light (1.5 meter/second) but directionally persistent wind. This distance extends offsite and includes public receptors. Alternative case release scenario The Risk Management Program Guidance for Ammonia Refrigeration recommends estimating emissions resulting from a hole with a < to =-inch effective diameter for an alternative release scenario. Emissions expected from this size hole are similar to a pump seal leak or gasket rupture. The modeling for the alternative rel ease scenario uses more typical weather conditions, which are neutral atmospheric stability and moderate wind speed (3 meters/second). To be conservative, a hole with a =-inch effective diameter is assumed for Doswell' alternative case. As with the worst case scenario, the Ammonia Guidance shows predictable distances to toxic endpoint for a range of emissions in both graphical and tabular form. Additionally, a table of estimated release rates and corresponding distances to the toxic endpoint is presented for ammonia stored under various pressures. Based on the table from the Ammonia Guidance, the release rate and distance to toxic endpoint for Doswell's alternative scenario are 400 lb/min and 0.4 mile. The alternative release distance of 0.4 mile would not extend offsite. Prevention Program and Chemical-Specific Prevention Steps Doswell is a Program 3 facility under the classification system in 40 CFR 69, and it has a prevention program that meets the regulatory requirements. 7 P rocess Safety Information is summarized in Doswell's One Plan. The summary discusses ammonia recognition, safety profile, normal handling, emergency handling, first aid, fire fighting, and regulatory information. 7 The initial Process Hazard Analysis was completed to comply with 29 CFR 1910.119(e). The Hazard and Operability Study method was used by Doswell Team members to review and analyze the ammonia system. 7 The Facility's Operating Procedures include the Ammonia System Normal Startup, Operations, and Shutdown Operating Procedure, the Ammonia Receiving and Unloading Procedure, and the Ammonia Storage and Supply System Description. Procedures are reviewed and revised regularly or as a result of the Event Response process. 7 Training is defined in the Ammonia Safety and Training Program. All personnel who may be involved with the handling or maintenance of anhydrous ammonia product or equipment shall receive safety training. This training will be conducted and documented before an employee is allowed to work around the anhydrous ammonia product or equipment. It will be done on an annual basis and if the procedure is changed for some reason. 7 The ammonia system and equipment was designed and constructed according to American Society of Mechanical Engineers (ASME) standards. Maintaining the Mechanical Integrity of the ammonia system is accomplished through Facility procedures and the computer based maintenance system. Preventive maintenance (PM) work orders are issued on a periodic basis established by equipment manufacturers and equipment history. 7 Management of change is addressed in the Plant Design Change (PDC) Process. All plant design changes are reviewed for safety and environmental impact. The PDC process also defines the documentation required for each change. The Ammonia Safety and Training Program requires training on procedural and operational changes 7 A Pre-startup Review will be required as part of the PDC process. 7 Compliance Audits wi ll be conducted and scheduled as required or as the result of a release or system change. 7 Incident Investigation of an incident which resulted in, or could reasonably result in a catastrophic release of ammonia will be conducted by a Significant Event Analysis Team (SEAT). The SEAT will be assembled and investigate the incident in a timely manner. The SEAT will issue a report of their findings along with recommended countermeasures before the event is closed. The Facility's Event Response system is used for tracking and reporting minor releases and safety incidents. 7 Employee Participation is developed through Doswell System Owner program. Each Doswell Team member is assigned a system or process. System owners are involved with all aspects of their system, from Operating Procedures to reviewing proposed PDC's. 7 Doswell has a Hot Work Permit Procedure in compliance with 29 CFR 1910.252(a). 7 Contractors performing work at the Facility are required to attend a safety orientat ion before work can begin. Contractors are required to abide by Doswell safety rules and procedures. Five-Year Accident History Doswell has had no offsite or significant release of ammonia since beginning its storage and use at the Facility. Emergency Response Program Doswell's One Plan instructs employees on emergency actions for employee protection and first aid, including for ammonia-related incidents. Doswell employees shall not respond to an occurrence that results or is likely to result in an uncontrolled release of a hazardous substance. In the event of such an occurrence, Doswell shall (1) take measures to protect its employees and (2) call the Hanover County Communications Center for emergency personnel and equipment to respond to the release. The Doswell non-response policy does not apply to incidental releases of hazardous substances where the substance can be absorbed, neutralized, or otherwise controlled at the time of release by employees in the immediate release a rea. It also does not apply to responses to releases of hazardous substances where there is no potential safety or health hazard, i.e., no fire, explosion, or chemical exposure. Doswell expects employees to take actions to end a leak (e.g., by shutting a valve) or clean up a spill that do not pose an immediate health or safety hazard. Those measures shall be considered incidental emergency responses and employees are allowed such activities. The One Plan has instructions for notifying and coordinating with the local agency for response activities, Hanover County, in the event of a significant ammonia release at the Facility. Hanover County will be immediately notified of any ammonia release that carries over the security fence. Doswell has reviewed the One Plan and discussed emergency response with Hanover County officials. Planned Safety Improvements Doswell strives for perfect execution of all processes and recognizes the need for training and drills. An ammonia release sc enario is to be added to Doswell's list of annual drills. The intent of the drill will be to practice responding to small releases similar to the Alternative release Scenario described earlier. Periodically, Doswell will plan a drill with off-site consequences that will allow an opportunity for Doswell team members to work with Hanover County and other emergency responders. The ammonia system is scheduled for review as part of Reliability Center Maintenance (RCM) program being implemented at the Facility. As part of RCM, a system is reviewed down to a component level and modes of failure. This information is then used to refine system maintenance and improve overall reliability. |