Yah-ta-hey Pump StationWater Chlorination Facility - Executive Summary |
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Executive Summary In June 1996, the U.S. Environmental Protection Agency (EPA) issued Risk Management Program (RMProgram) regulations (40 CFR, Part 68). Regulated under the Clean Air Act Amendments (CAAA), Section 112(r), the RMProgram requires facilities that store large amounts of listed hazardous chemical substances to prepare and implement risk management plans to reduce the probability of accidental releases and minimize the health risks to the public and the environment. The RMProgram regulates 77 listed toxic substances and 63 listed flammable substances. The RMProgram regulations apply to an estimated 7,200 public and private drinking water and wastewater treatment facilities nationwide where chlorine and/or ammonia are used as disinfectants. When properly used, chlorine has proven to be both safe and effective. The Yah-ta-hey Pump Station/Water Chlorination Facility (Yah-ta-hey) is one of the two City of Gallup water treatment facilities. It supplies water to residenti al, commercial and industrial users. Yah-ta-hey stores and uses only one regulated chemical, anhydrous chlorine, in quantities higher than the threshold quantities. The term anhydrous chlorine and chlorine are used interchangeably and specifically refer to a chemical listed in the RMProgram regulations. The chlorine is used to disinfect drinking water and prevent the spread of waterborne diseases. The chlorine is stored within a building in two 1-ton containers. The total maximum intended inventory at Yah-ta-hey is 4,000 pounds. The chlorine is liquified under pressure in the containers. Chlorine is drawn as a gas in an alternating manner from the two 1-ton containers through a vacuum feed system. The gaseous chlorine is then metered into a solution through two chlorinators. The chlorine solution is then fed to a distribution line injection point. Minimizing Risk The major driving force in the development of the RMProgram regulations is reducing the risk to public health by m inimizing the potential of a chemical release. Yah-ta-hey has a multi-layer system in place to meet this goal. The RMProgram includes the following: (1) properly trained operators to safely handle chlorine; (2) chlorine detectors located where chlorine is stored and/or used; and (3) chemical release prevention and emergency response plans in place. Trained personnel respond to chlorine alarms to assess whether a chlorine release poses an imminent danger to employees or the public. While a significant release is unlikely, the emergency response plans have been developed for just such an occurrence. The emergency response plans include procedures to be followed by operators trained to take appropriate action including contacting the City of Gallup Fire Department and New Mexico State Police. Management System Within the management and administrative roles of Yah-ta-hey, responsibility has been defined to coordinate and implement the RMProgram. Overall development and management o f the RMProgram is the responsibility of the RMProgram Manager. The Water Systems Superintendent is the designated RMProgram Manager. The RMProgram Coordinator reports to the RMProgram Manager and is responsible for the day-to-day coordination and implementation of the RMProgram. The Water Systems Production Supervisor/Assistant Superintendent is the designated RMProgram Coordinator. The RMProgram Coordinator will delegate various operators to assist in the implementation of the RMProgram. Additional program oversight is provided by the City of Gallup's Utilities Director and Risk Management Director who act as auditors of the program's implementation and overall quality. Worst Case and Alternative Release Scenarios Two potential release events for chlorine were modeled at Yah-ta-hey. EPA guidance was followed to identify a worst case release scenario and an alternative release scenario as defined by the EPA regulations. Toxic endpoints were identified using EPA-approved method s. A worst case scenario is defined by the EPA as the result of a release from the largest container and/or pipe over a span of 10 minutes. The distance to a toxic endpoint is defined by the American Industrial Hygiene Association (AIHA) emergency response planning guidelines level 2 (ERPG-2) as a concentration a person can be exposed to for up to 1 hour without experiencing serious health effects. The distance to a toxic endpoint is used to determine the affected geographical area and population for emergency planning purposes. The ERPG-2 value for chlorine is 3 parts per million by volume (ppmv), or 0.0087 milligrams per liter (mg/l). EPA states that a "worst case scenario" is useful for encouraging "community dialogue". However, because the worst case scenario does not necessarily represent events likely to occur, it is more useful for discussion purposes than for emergency planning purposes. An "alternative release scenario" is a release scenario more likely than the worst c ase scenario and should be used for emergency response planning. Yah-ta-hey stores chlorine within its property boundary in 1-ton containers. To comply with RMProgram regulations, a worst case scenario for Yah-ta-hey was conducted assuming the release of the contents of 2,000 pounds (1-ton) of chlorine in 10 minutes. Because the 1-ton containers are located in a building, the worst case scenario was modeled considering the building as a passive mitigation factor. The resulting distance to the toxic endpoint is 2.2 miles, affecting an estimated population of 1,500. Other sensitive receptors that could potentially be affected include religious institutions and a nearby commercial area. The alternative release scenario for chlorine was evaluated for emergency response planning purposes. The alternative release scenario at Yah-ta-hey is the shearing off of a 1-ton chlorine container valve caused by the mishandling of the cylinder during unloading. This scenario results in a gaseou s release of chlorine. The alternative release scenario resulted in an endpoint distance of 0.2 miles. A population of approximately 2 people could potentially be affected if this scenario were to occur. No other sensitive receptors were identified for the alternative release scenario. The off-site consequence analyses resulted in a distance to toxic endpoint for worst case and alternative release scenarios. For planning purposes, this distance is used to define a circle of the same radius around the facility. Facilities and residences within the circle are assumed to be potentially impacted by the modeling results. In reality, in the event of a release, the area impacted is more likely to be determined by the predominant wind pattern. Typical wind patterns within the Gallup area are from the southwest to the northeast. While the distance to the toxic endpoint will likely be valid as determined under modeled conditions, not every facility or residence within the circle is like ly to be affected. Yah-ta-hey is located in a topographically depressed area making it extremely difficult for a chlorine release to migrate off-site. 5-Year Accident History Any accidental releases from covered processes that resulted in deaths, injuries, or significant property damage on-site, or known off-site deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage must be reported in the RMProgram submission to EPA. Based upon interviews with plant operations, maintenance, safety, and training staff and management, no major chemical release has occurred at Yah-ta-hey in the last five years. Chemical Release Prevention Program Yah-ta-hey has a chemical release prevention program in place for its chlorination process. Key provisions of the prevention program are as follows: * Written procedures have been prepared for the chlorination process, including directions for safe startup, normal and shutdown operations and emergency shutdown. * Emp loyees who operate the chlorination system must receive training initially and periodically on safe startup and shutdown operations and emergency shutdown. * Incidences, including minor releases are investigated to improve the safety of the chlorination process. * Once completed, incident investigations are shared with employees. * A hazard review, which identifies potential hazards and ways to improve the safety of the chlorination process, is conducted every five years, or when significant changes are made to the process. * A maintenance program is in place to prevent accidental chemical releases that may result from mechanical failure of improperly maintained equipment. Maintenance practices are consistent with guidance provided by the Chlorine Institute. * Compliance audits are conducted every three years to evaluate the RMProgram and its implementation for compliance with EPA RMProgram regulations. Emergency Response Program Yah-ta-hey has an emergency response program in place. This program consists of personnel trained to recognize releases, assess the situation, and engage the proper emergency response personnel. When external emergency response is required, facility personnel will notify the City of Gallup Fire Department and/or New Mexico State Police then establish an incident command system. Incident command is transferred to the Fire Department or the New Mexico State Police upon their arrival. Facility personnel familiar with the chlorination process remain on-site to assist the emergency response agencies if necessary. The Fire Department and New Mexico State Police have access to additional emergency response resources, including the Local Emergency Planning Committee, Highway and Transportation Department, Department of Health and the EPA. |