Elm Grove Gas Plant - Executive Summary |
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ACCIDENTAL RELEASE PREVENTION AND RESPONSE POLICIES The Elm Grove Gas Plant has a long-standing commitment to worker and public safety. This commitment is demonstrated by the resources invested in accident prevention, such as training personnel and considering safety in the design, installation, operation, and maintenance of the facility's processes. The Reliant Energy Field Services, Inc. (REFS) policy is to implement reasonable controls to prevent foreseeable releases of substances. DESCRIPTION OF THE STATIONARY SOURCE AND REGULATED SUBSTANCES REFS operates the Elm Grove Gas Plant located in Bossier Parish, Louisiana. The location of the facility is illustrated on Figure 1, a 7.5 minute United States Geological Survey (USGS) map. The Elm Grove Plant is a natural gas processing plant that produces liquified petroleum gas (LPG), a mixture of pentanes, hexanes, C5+ compounds, by refrigeration and pressure. The LPG and condensate is transported from the site via tanker trucks. A s evidenced in the ensuing text and based on criteria outlined in the Accidental Release Prevention Program (ARP), the Elm Grove Gas Plant is a Program 2 process. The Elm Grove Gas Plant was evaluated to determine if any regulated flammable or toxic substances were present in the process and if they exceeded the threshold quantity. All equipment and vessels are considered to be connected and/or co-located; consequently, for the purposes of the ARP Program, all equipment and vessels are part of a single process. The identification of even a single vessel exceeding threshold quantities of a regulated flammable or toxic substance would subject a process to threshold determination for offsite consequence analysis. REFS identified one tank containing a regulated flammable substances and zero regulated toxic substances along with the largest single vessel quantity stored. It was determined that the LPG storage tank exceeded threshold quantity. The identification of this exceedance in dicates that the Elm Grove Gas Plant is a covered process with regulated substances subject to threshold determination for offsite consequence analysis. OFF-SITE CONSEQUENCE ANALYSIS RESULTS Worst-Case Scenarios (WCS) The Environmental Protection Agency (EPA) has defined a worst-case release as "the release of the largest quantity of a regulated substance from a vessel or process line failure that results in the greatest distance to a specified endpoint." A WCS analysis is required for each toxic substance in a covered process while only one WCS analysis is required for regulated flammable substances as a class. WCSs are assumed to occur at ground level with meteorological conditions defined as atmospheric stability class F (stable atmosphere), wind speed of 1.0 meters per second (2.2 miles per hour), and an ambient air temperature of 25:C (770F). Topography for WCSs are distinguished between rural and urban. Flammable Substances Regulated flammable substances or mixtures c ontaining flammable substances include both gases and volatile liquids. The WCS assumes that the total quantity of a vapor cloud is released and detonates. The endpoint for a WCS involving a regulated flammable substance or mixture is an over pressure of 1 pound per square inch (psi). For a regulated flammable substance, consequence distance determination is based on its heat of combustion. For regulated flammable mixtures, the component with the highest heat of combustion can be used for consequence distance determination or, if preferred, directly calculated using equation C-1 of the Offsite Consequence Analysis Guidance Document (OCAGD). The quantity of a regulated substance/mixture used to determine distance to endpoint is the largest quantity of a regulated substance/mixture in a single vessel. The LPG is a mixture of pentanes, hexanes and C5+ contained in a pressurized liquid storage vessel having the capacity of approximately 13,535 gallons (71,026 lbs.). For the purpose of identifying the maximum release quantity for use in determining potential off-site impacts, it is assumed that the entire contents of the vessel is released to the atmosphere, forming a vapor cloud. Using the criteria outlined in the ARP rule, this mixture represents the facility's worst-case scenario for flammables. Pentane, the major component of the LPG, was identified as having the highest heat of combustion (44,697 kjoules/kg). It was determined that its use would provide a more conservative consequence distance. The distance to the endpoint of 1 psi overpressure for the worst-case release of the flammable liquid mixture was calculated and determined to be 0.33 miles. The distance to endpoint is greater than the distance to public receptors. The Elm Grove Gas Plant is, therefore, classified as a Program 2 process under the ARP Program. Toxic Liquids and Gases Toxic gases include all regulated toxic substances that are gases at ambient temperature (temperature 25: C, 770F), even if they are stored as liquids under pressure or refrigeration. For the consequence analysis, a gaseous release of the total quantity is assumed to occur in 10 minutes, regardless of storage conditions. For toxic liquids, the total quantity in a vessel is assumed to be spilled onto a flat, non-absorbing surface. For toxic liquids carried in pipelines, the quantity that might be released for the pipeline is assumed to form a pool. Passive mitigation systems may be taken into account in consequence analysis for both toxic gases and liquids. The endpoint for air dispersion modeling to estimate the consequence distance for a release of a toxic gas and liquid is presented for each regulated toxic gas and liquid in Appendix B of the OCAGD in Exhibits B-1 and B-2, respectively. The Elm Grove Gas Plant does not have any toxic substances held above the threshold quantity. Analysis of one worst-case release scenario for each regulated toxic substances is, therefore, not require d. Alternative Release Scenarios (ARS) An ARS describes an incident that is more likely to occur than those cited for a WCS. One ARS analysis is required for each listed toxic substance in a Program 2 or 3 process that exceeds threshold quantity while only one ARS analysis is required for all flammable substances as a class. For ARSs, both active and passive mitigation systems can be considered. Alternative release scenarios for flammable substances should have the potential to cause substantial damage, including on-site damage. Alternative release scenarios for toxic substances should be those that lead to concentrations above the toxic endpoint beyond the process fenceline. Those releases that have the potential to reach the public are of the greatest concern. Elm Grove Gas Plant Alternative Release Scenario for Regulated Flammables A single ARS for the flammable mixture is required under the ARP Program. A hypothetical, but likely to occur, release scenario has been iden tified for the flammable mixture as follows. Seal failure on the transfer pump at the tanker truck loading area causes a release from a one-inch opening at a pressure of 200 psig and a temperature of 1000F. The release is assumed to continue for ten minutes. The flammable mixture will vaporize and may ignite a vapor cloud explosion with an endpoint of 1 psi overpressure. It was determined that a 10-minute release would involve 1,800 pounds of the flammable mixture. Using the trinitrotoluene equivalency formula from the OCAGD, it was determined that a release of this amount of a buoyant gas in a rural area would result in an ARS endpoint distance of 0.10 miles. Elm Grove Gas Plant Alternative Release Scenario for Regulated Toxics The Elm Grove Gas Plant does not have any toxic substances held above the threshold quantity. Analysis of each regulated toxic substance is, therefore, not required. FIVE YEAR ACCIDENT HISTORY The Elm Grove Gas Plant has not had any accident al releases during the past five years that meet the criteria for an accidental release as discussed in 40 CFR 68.42. LOCAL EMERGENCY RESPONSE COORDINATION The Elm Grove Gas Plant has coordinated its emergency response activities with the local emergency planning and response agencies as required in 40 CFR 68.12(b)(3). GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM The following is a summary of the accident prevention program in place at the Elm Grove Gas Plant. The Elm Grove Gas Plant processes are subject to EPA's RMP regulations but not OSHA's PSM standards because the plant is unmanned. This summary describes the management system in place to implement the accident prevention program implemented by REFS. Process Safety Information The Elm Grove Gas Plant maintains written information intended to provide a foundation for identifying and understanding the process hazards. This information addresses chemical properties, inventories, and associated hazards, as well as key proc ess parameter limits and equipment design basis/configuration information. Chemical-specific information, including exposure hazards and emergency response/exposure treatment considerations, is provided in the material safety data sheets (MSDSs). In addition, the plant has documented safety-related limits for specific process parameters and ensures limit maintenance by using highly trained personnel, process controls, and monitoring and protective instrument systems. The company also maintains documentation that provides information about the design and construction of process equipment. Equipment information includes construction materials, design pressure, and temperature and electrical ratings. REFS utilizes standard operating manuals for pumps, controls and relief valves, API Standards for pipe, vessels, and tanks, and ANSI Standards for the ESD System. This information also provides a basis for establishing inspection and maintenance activities, as well as for evaluating pr oposed process and facility changes to ensure that safety features in the process are not compromised. Process Hazard Analysis (PHA) The Elm Grove Gas Plant has a comprehensive program to help ensure that hazards associated with the various processes are identified and controlled. Within this program, each process is systematically examined to identify hazards and ensure that adequate controls are in place to manage these hazards. The Elm Grove Gas Plant primarily uses the "what if" study to perform these evaluations. The "what if" method uses questions that postulate mistakes in operations or failures of equipment. Based on the answers to the questions, consequences and preliminary recommendations can be determined. The PHA findings are promptly and systematically addressed. The Elm Grove Gas Plant assures that the recommendations are documented and resolved in a timely manner. This documentation includes the actions to be taken and a written schedule of completion dates. Th e plant also provides proof of communication with operating, maintenance, and other employees whose work assignments are in the process and who may be affected by the recommendations. To help ensure that the process controls and/or process hazards do not eventually deviate from the original design safety features, the plant periodically updates and revalidates the hazard analysis results. These periodic reviews are conducted at least every five years by the PHA team. Operating Procedures The Elm Grove Gas Plant maintains written procedures that address various modes of process operations, such as (1) initial startup, (2) normal operations, (3) temporary operations, (4) emergency shutdown, (5) emergency operations, (6) normal shutdown, and (7) startup following a turnaround or after an emergency shutdown. These procedures can be used as a reference by experienced operators and provide a consistent training basis for new operators. Operating procedures are periodically revie wed and certified as current. When a process change occurs, operating procedures are revised as necessary through the management of change process. Training To complement the written process operation procedures, the Elm Grove Gas Plant has implemented a comprehensive training program for all employees. New employees receive job specific basic training in plant operations. Employee training includes emphasis on safety and health hazards, emergency shutdown operations, and safe work practices. Operators demonstrating adequate knowledge to safely perform duties and tasks are allowed to work independently. Incident Investigation The Elm Grove Gas Plant has a plan in place to promptly investigate all incidents that resulted in, or reasonably could have resulted in, a fire/explosion, toxic gas release, major property damage, environmental loss, or personal injury. An incident investigation is initiated as promptly as possible to thoroughly investigate and analyze the incident. This investigation is lead by an incident investigation team consisting of those with appropriate knowledge and experience in the process. The findings and recommendations made by the incident investigation team are promptly addressed and resolved in a timely manner. The final resolution of each finding or recommendation is documented, and the investigation results are reviewed with all employees (including contractors) who could be affected by the findings. Emergency Planning and Response The Elm Grove Gas Plant is an unmanned site. All emergency response actions are coordinated with the Caddo-Bossier Parish LEPC. Compliance Audits To help ensure that the accident prevention program is properly functioning, the Elm Grove Gas Plant periodically conducts an audit to determine whether the procedures and practices required by the accident prevention program are being implemented. Compliance audits are to be conducted at least every 3 years. The audit team includes those knowledgeable in the process, operations personnel, and at least one person trained in audit techniques and practices. The audit team develops findings and corrective actions are tracked until they are complete. The final resolution of each finding is documented, and the two most recent audit reports are retained. |