Pecan Creek Water Reclamation Plant - Executive Summary |
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Risk Management Plan Executive Summary Pecan Creek Water Reclamation Plant Processes for Chlorine and Sulfur Dioxide The Pecan Creek Water Reclamation Plant is located at 1100 Mayhill Road on the East side of Denton, Texas. This facility treats wastewater used by residents of Denton, Argyle and Corinth Texas. The effluent is treated with chlorine as a disinfectant and sulfur dioxide to remove the chlorine residual before it (the effluent) is released into Pecan Creek, which flows to Lake Lewisville. The plant maintains 16,000 lbs of chlorine and 12,000 lbs of sulfur dioxide on a continuous basis, which is above the threshold limit for both chemicals. The concentrated form of chlorine and sulfur dioxide is liquefied and stored in one ton containers before it is mixed with the effluent. Chlorine or sulfur dioxide can be extremely hazardous if released to the air in significant quantities. The Accidental Release Prevention and Emergency Response Policies at the Pecan Creek Wa ter Reclamation Plant The Pecan Creek Water Reclamation Plant is committed to protecting its employees, the public, and the environment from any accidental releases of hazardous materials used at its facilities. We have implemented safety, environmental protection, and risk management programs to prevent hazardous materials releases. If there is an accidental release, we will immediately call for emergency response to minimize the effect of the release and notify the public of any actions necessary to ensure public protection, through emergency management agencies. As part of a progressive approach to the RMProgram the Utilities Department hired a consultant to do a Hazard Needs Assessment for the reclamation plant. The results were incorporated into the Hazard review documentation of the RMP. Management staff is preparing the bulk of the risk plan with comments from the consultant as sections are completed. The plant management and operators are working diligently to upgrade th e plant facilities to comply with the needs assessment. The worst-case release scenario(s) and the alternative release scenario(s). Worst-Case Release Scenario The Pecan Creek Water Reclamation Plant has conducted an offsite consequence analysis including a worst-case release scenario. As required by the EPA/RMP regulations, the worst-case scenario is defined as the release of an entire one ton container as a gas in ten-minutes. The regulations require assuming worst-case wind speed and atmospheric conditions that result in the greatest projected impact distance. The likelihood of a worst case scenario occurring is extremely remote due to these conditions. For the offsite consequence analyses, the "endpoint" concentration is defined by the Emergency Response Planning Guideline (ERPG-2) values developed by the American Industrial Hygiene Association (AIHA). AIHA defines the ERPG-2 value as, "the maximum airborne concentration below which it is believed that nearly all individual s could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair an individual's ability to take protective action." The endpoint (ERPG-2 value) established for chlorine is 0.0087 mg/L (3 ppm). For the rural setting of the Pecan Creek Water Reclamation Plant the potential distance to the endpoint concentration for the worst-case release is 3.04 miles, which extends offsite into residential population, public and environmental receptors. This distance was obtained from the American Water Works Association Research Foundation (AWAARF), "Compliance Guidance and Model Risk Management Program for Water Treatment Plants". "There are approximately 27,000 residents within the 3.0-mile radius for the worst-case scenario. However, if the worst-case release occurred, only a small fraction of these residents that are located downwind of the plant would be in the affected area. Public facilities within this rad ius include 7 schools, a hospital, 2 prisons, 7 public recreation areas and 3 major commercial/industrial areas. There are no officially designated wildlife sanctuaries, preserves, refuges, or federal wilderness areas within the worst-case radius." A major release of the magnitude represented by this worst-case scenario is extremely unlikely because of the robust design of one-ton chlorine containers (they are designed to withstand transportation mishaps) and the rigorous maintenance and prevention programs in place at the Pecan Creek Water Reclamation Plant. In fact, release reporting databases and water industry experience suggest that the worst-case release scenario as defined in the RMP regulations is so unlikely that it should not be used as the basis for emergency planning. A more reasonable potential release scenario for emergency planning is presented in "The alternative release scenario(s)" section below. Alternative Release Scenario A "credible worst-case" scenario was selected as the Pecan Creek Water Reclamation Plant alternative release scenario. "This alternate-release scenario assumes that the flexible tube connecting the 1-ton cylinder to the manifold is completely severed resulting in the release of gas. Bernoulli's equation for release of liquid through a hole was used to determine the end point distance of 0.69 miles for the rural condition. It should be noted that the alternate scenario selected is the worst case condition. The more likely scenario is the possibility of a hole puncture in the flexible line rather than complete severance of the pipe. However, for emergency planning purposes the more conservative "credible worst case" for the alternate case scenario was selected". The results of the process hazard analysis (PHA) and the facility's operating history suggest that even this credible worst-case is extremely unlikely to occur, but it can serve as the basis for emergency planning. The potential distance to the endpoint concent ration for this alternate release scenario is 0.56 miles, which extends offsite into no public receptors, public recreational areas, prisons or major commercial areas. Approximately 100 residents would be affected by this scenario. The total population within a 0.56 mile radius is approximately 100 residents, however, only a small fraction of these residents are located downwind of the Water Reclamation Plant. As with the worst-case scenario, actual distances and directions vary with terrain and weather conditions. Accidental Release Prevention Steps The Pecan Creek Water Reclamation Plant is committed to personnel safety, public safety, continued reliable operation and regulatory compliance. Based on this commitment, the Water Reclamation Plant has assumed overall responsibility for the development and implementation of the Risk Management Program. The Plant Manager has clearly defined accountability and responsibility for each of the prevention program elements to meet both E PA and OSHA Process Safety Management requirements. To ensure a worst-case or alternative release scenario does not occur, the Pecan Creek Water Reclamation Plant maintains a release prevention program with the primary focus of protecting plant employees and the public from the hazards associated with an accident or release involving chlorine. The multifaceted program includes the use of: ( chlorine detectors and alarms to rapidly alert operators to any problems; ( process safety information to document the safety of the process design; ( process hazards analyses to evaluate the site-specific chemical and process hazards; ( operating procedures for plant personnel to ensure that the system is operated safely; ( maintenance, inspection and testing procedures to ensure that the system is maintained according to applicable standards and manufacturer's recommendations; ( training, hot work permits, contractor safety and employee participation programs to ensure that all employees and co ntractors working on and around the processes are aware of the hazards; can perform their job duties safely; and know the actions to be taken in an emergency; ( management of change and pre-startup safety reviews to ensure that changes are documented, analyzed and kept within the design basis; ( incident investigation procedure to investigate each incident and "near misses" to determine root causes and make needed safety improvements; ( and periodic compliance audits to ensure that our programs are working as they should to protect both employees and the public. Five-Year Accident History Within the past five years, the Pecan Creek Water Reclamation Plant had no accidental releases. The plant has maintained an excellent safety record throughout its operating history and has never had a major chlorine release that had adverse effects on the public.Risk Management Plan Executive Summary Pecan Creek Water Reclamation Plant Processes for Chlorine and Sulfur Dioxide The Pecan Creek Water Reclamation Plant is located at 1100 Mayhill Road on the East side of Denton, Texas. This facility treats wastewater used by residents of Denton, Argyle and Corinth Texas. The effluent is treated with chlorine as a disinfectant and sulfur dioxide to remove the chlorine residual before it (the effluent) is released into Pecan Creek, which flows to Lake Lewisville. The plant maintains 16,000 lbs of chlorine and 12,000 lbs of sulfur dioxide on a continuous basis, which is above the threshold limit for both chemicals. The concentrated form of chlorine and sulfur dioxide is liquefied and stored in one ton containers before it is mixed with the effluent. Chlorine or sulfur dioxide can be extremely hazardous if released to the air in significant quantities. The Accidental Release Prevention and Emergency Response Policies at the Pecan Creek Water Reclamation Plant The Pecan Creek Water Reclamation Plant is committed to protecting its employees, the public, and the environment from an y accidental releases of hazardous materials used at its facilities. We have implemented safety, environmental protection, and risk management programs to prevent hazardous materials releases. If there is an accidental release, we will immediately call for emergency response to minimize the effect of the release and notify the public of any actions necessary to ensure public protection, through emergency management agencies. As part of a progressive approach to the RMProgram the Utilities Department hired a consultant to do a Hazard Needs Assessment for the reclamation plant. The results were incorporated into the Hazard review documentation of the RMP. Management staff is preparing the bulk of the risk plan with comments from the consultant as sections are completed. The plant management and operators are working diligently to upgrade the plant facilities to comply with the needs assessment. The worst-case release scenario(s) and the alternative release scenario(s). Worst-Case R elease Scenario The Pecan Creek Water Reclamation Plant has conducted an offsite consequence analysis including a worst-case release scenario. As required by the EPA/RMP regulations, the worst-case scenario is defined as the release of an entire one ton container as a gas in ten-minutes. The regulations require assuming worst-case wind speed and atmospheric conditions that result in the greatest projected impact distance. The likelihood of a worst case scenario occurring is extremely remote due to these conditions. For the offsite consequence analyses, the "endpoint" concentration is defined by the Emergency Response Planning Guideline (ERPG-2) values developed by the American Industrial Hygiene Association (AIHA). AIHA defines the ERPG-2 value as, "the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms that could impai r an individual's ability to take protective action." The endpoint (ERPG-2 value) established for chlorine is 0.0087 mg/L (3 ppm). For the rural setting of the Pecan Creek Water Reclamation Plant the potential distance to the endpoint concentration for the worst-case release is 3.04 miles, which extends offsite into residential population, public and environmental receptors. This distance was obtained from the American Water Works Association Research Foundation (AWAARF), "Compliance Guidance and Model Risk Management Program for Water Treatment Plants". "There are approximately 27,000 residents within the 3.0-mile radius for the worst-case scenario. However, if the worst-case release occurred, only a small fraction of these residents that are located downwind of the plant would be in the affected area. Public facilities within this radius include 7 schools, a hospital, 2 prisons, 7 public recreation areas and 3 major commercial/industrial areas. There are no officially designate d wildlife sanctuaries, preserves, refuges, or federal wilderness areas within the worst-case radius." A major release of the magnitude represented by this worst-case scenario is extremely unlikely because of the robust design of one-ton chlorine containers (they are designed to withstand transportation mishaps) and the rigorous maintenance and prevention programs in place at the Pecan Creek Water Reclamation Plant. In fact, release reporting databases and water industry experience suggest that the worst-case release scenario as defined in the RMP regulations is so unlikely that it should not be used as the basis for emergency planning. A more reasonable potential release scenario for emergency planning is presented in "The alternative release scenario(s)" section below. Alternative Release Scenario A "credible worst-case" scenario was selected as the Pecan Creek Water Reclamation Plant alternative release scenario. "This alternate-release scenario assumes that the flexible tube connecting the 1-ton cylinder to the manifold is completely severed resulting in the release of gas. Bernoulli's equation for release of liquid through a hole was used to determine the end point distance of 0.69 miles for the rural condition. It should be noted that the alternate scenario selected is the worst case condition. The more likely scenario is the possibility of a hole puncture in the flexible line rather than complete severance of the pipe. However, for emergency planning purposes the more conservative "credible worst case" for the alternate case scenario was selected". The results of the process hazard analysis (PHA) and the facility's operating history suggest that even this credible worst-case is extremely unlikely to occur, but it can serve as the basis for emergency planning. The potential distance to the endpoint concentration for this alternate release scenario is 0.56 miles, which extends offsite into no public receptors, public recreational areas, prisons or maj or commercial areas. Approximately 100 residents would be affected by this scenario. The total population within a 0.56 mile radius is approximately 100 residents, however, only a small fraction of these residents are located downwind of the Water Reclamation Plant. As with the worst-case scenario, actual distances and directions vary with terrain and weather conditions. Accidental Release Prevention Steps The Pecan Creek Water Reclamation Plant is committed to personnel safety, public safety, continued reliable operation and regulatory compliance. Based on this commitment, the Water Reclamation Plant has assumed overall responsibility for the development and implementation of the Risk Management Program. The Plant Manager has clearly defined accountability and responsibility for each of the prevention program elements to meet both EPA and OSHA Process Safety Management requirements. To ensure a worst-case or alternative release scenario does not occur, the Pecan Creek Water Rec lamation Plant maintains a release prevention program with the primary focus of protecting plant employees and the public from the hazards associated with an accident or release involving chlorine. The multifaceted program includes the use of: * chlorine detectors and alarms to rapidly alert operators to any problems; * process safety information to document the safety of the process design; * process hazards analyses to evaluate the site-specific chemical and process hazards; * operating procedures for plant personnel to ensure that the system is operated safely; * maintenance, inspection and testing procedures to ensure that the system is maintained according to applicable standards and manufacturer's recommendations; * training, hot work permits, contractor safety and employee participation programs to ensure that all employees and contractors working on and around the processes are aware of the hazards; can perform their job duties safely; and know the actions to be taken in an e mergency; * management of change and pre-startup safety reviews to ensure that changes are documented, analyzed and kept within the design basis; * incident investigation procedure to investigate each incident and "near misses" to determine root causes and make needed safety improvements; * and periodic compliance audits to ensure that our programs are working as they should to protect both employees and the public. Five-Year Accident History Within the past five years, the Pecan Creek Water Reclamation Plant had no accidental releases. The plant has maintained an excellent safety record throughout its operating history and has never had a major chlorine release that had adverse effects on the public. Emergency Response "In the event that a chlorine release does occur, the City of Denton Fire Dept. has an emergency response program that includes trained onsite emergency responders that coordinates emergency response with the regional response organizations and Denton County LEPC. If an emergency did occur, plant personnel would activate The City of Denton Emergency Response Team and notify the regional response organizations who would assist if offsite actions were needed or to help address the chlorine release. " Maintaining A Safe Operation The Pecan Creek Water Reclamation Plant continually works to safely manage the hazards of chlorine and sulfur dioxide to protect employees and the community we serve. The Risk Management Program will be maintained to reduce the risk of accidental releases and each year we will conduct training, review procedures, maintain the equipment and follow safe work practices. Periodically, we will audit our program, review our Process Hazard Analysis and coordinate with the community emergency response organization. We will also be assessing further safety enhancements to the facility over the next few years. Pecan Creek Water Reclamation Plant Page 1 of 4 O:\John H\Reclamation RMP\Exe.Sum.doc |