Blackman Water Treatment Plant - Executive Summary |
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Introduction: The Blackman Water Treatment Plant provides drinking water to the metropolitan area of Springfield, Missouri. The plant is located at 2601 South Blackman Road. Using the James River and Fellows Lake reservoir as primary sources, the Blackman Plant produces some of the highest quality drinking water in the State of Missouri. Important steps in the treatment process include carbon adsorption, coagulation, flocculation, sedimentation, filtration, chlorination, pH adjustment, and fluoridation. Some of these steps require the addition of chemicals such as powdered activated carbon, polyaluminum chloride polymer, chlorine, fluoride, and soda ash. This plan centers on the use of chlorine at the Blackman Plant. Chlorine is a yellow-green gas with a bleach-like odor. It is used extensively as a disinfectant in public drinking water, swimming pools, and cooling water systems due to its ability to react with easily oxidizable compounds. Bacteria, viruses, and other harmful organi sms are effectively deactivated by disrupting their biochemical processes. Chlorine gas is added to the raw water during the treatment process and to the finished water prior to distribution. Unlike many disinfectants, chlorine stays in the water providing residual protection as it travels through the distribution system. Chlorine workers must take special precautions to prevent the gas from escaping. In its vapor form the oxidant can attack skin, eye, and lung tissues. The resulting damage can be serious, irreversible, and even fatal at high concentrations. The potential hazard is greatest in the immediate working area near the gas cylinders; but in a large-scale release the gas could disperse and pose an exposure risk to people and property near the plant grounds. City Utilities has never experienced such an event involving any chemicals at this facility. Accident Prevention: City Utilities has an effective chlorine safety program. The key components include contingency planning, o n-site monitoring, emergency shutoff equipment, and specialized operation and maintenance procedures. A strong emphasis on staff training reinforces these elements. For many years CU has been called upon to share expertise and training techniques with local fire departments and other water utilities in the region. Planning: The Blackman hazardous materials (HazMat) emergency response plan covers all chemicals used at the facility. This plan addresses accident scenarios during both normal operating hours and nights and weekends. The plan is integrated with the Greene County Emergency Management response plan. This relationship with the countywide plan has been tested through full-scale mock emergency training. The plan is updated as needed to account for organizational changes and is completely reevaluated every three years. Monitoring: Chlorine is added to the water from a central storage and injection system located in a totally enclosed and fireproof building situated over 800 fee t from the closest property boundary. It is equipped with a gas detection and monitoring system that operates on two levels of safety. The first monitor senses chlorine gas inside the enclosure to warn workers before entering. The second monitoring stage can detect a release that escapes the building. It consists of an array of six chlorine detectors situated around the perimeter of the structure. An alarm from any of these monitors would warn plant personnel, by warning light and bell, (or the plant security officer during unstaffed hours) and the operator at Fulbright by computer interface, of the potential for an uncontrolled release. This is one of the mechanisms that would activate the plant emergency response plan. The information from these perimeter monitors would indicate the direction and extent of chlorine drift and dispersion. This information would be valuable to civil authorities in determining whether the release posed a threat to people living or working nearby. Shut off valves: Inside the chlorine containment building, each cylinder is equipped with an emergency shutoff valve. These valves may be activated remotely by the Fulbright Plant Operator to stop the flow of chlorine if the monitors detect a continuous release. This could prevent a prolonged escape of pressurized gas. The valves are designed to close automatically either on command or when there is a power loss to the building. Procedures: City Utilities' written operating and maintenance procedures manual addresses the safe handling of chlorine cylinders. The manual draws extensively on CU's safe handling experience as well as on guidance from professional organizations such as the American Water Works Association (AWWA) and the Chlorine Institute. A proper respect for the chemical, adequate knowledge of chemical properties, proper use of tools, and good communication between employees are all important to accident prevention. These and other issues are addressed in the written procedure s for the Blackman plant. Training: CU provides chlorine safety training to all employees involved in operating and maintaining the Blackman Plant. The training centers around the specific procedures outlined in the plant chlorine procedures manual, and is augmented by additional material from AWWA and other outside sources. This training occurs at the time an employee is assigned to Water Treatment and is repeated biennially. Blackman employees also receive extensive training in chemical emergency response. The training involves general mitigation techniques, such as how to deploy a valve repair kit, as well as specific aspects of the Blackman emergency response plan. City Utilities has shared our expertise for many years by providing training programs in chlorine safety and response to other water utilities and civil authorities. We also cooperate with these entities in providing training opportunities, including joint exercises, under the OSHA/EPA HazWOPER program. Five-year ch emical safety record: City Utilities has not experienced a chemical accident at either of its drinking water facilities in the past five years. In fact there has never been an accidental release of chlorine or any other water treatment chemical recorded at either facility. Overall plant safety record: Both City Utilities water treatment plants have an enviable overall safety record. The Water Treatment Department is distinguished by the fact that it has never experienced a lost time injury. This record encompasses over 41 years of public ownership. The Water Treatment employees are deservedly proud of this distinction, and intend to make a concerted effort to keep it intact well into the future. Accident Impacts: EPA's Air Risk Management Planning rule requires a hazard evaluation for a worst-case and an alternative scenario. This does not imply necessarily that either type of incident is probable, only that they are possible and should be taken into consideration in planning emer gency response actions. Worst-case scenario: The worst-case analysis required by EPA entails the near-instantaneous release of a one-ton chlorine cylinder on a relatively calm day. The conditions stipulated include wind speed of 1.5 m/s, atmospheric stability class F, and an escape rate of 200 lbs chlorine per minute. This rate would be mitigated passively by the Blackman chlorine containment building, resulting in an atmospheric release rate of 110 lbs per minute. The EPA guidance document indicates that such a release would result in off-site consequences. The radius identified by the model encompasses public receptors but no environmental receptors. Alternate scenario: In choosing a reasonable scenario to model, City Utilities considered all aspects of the chlorination system. For the most part the scenarios evaluated did not result in off-site consequences. Because chlorine is fed as a gas rather than a liquid, scenarios involving the active physical components of the feed syste m yielded relatively low release rates. The resulting impact zones were generally contained within the rather spacious plant grounds. The alternative scenario selected involves a rupture of the header connected to all four active cylinders. This 1-inch pipe represented the largest opening through which chlorine gas could escape. The escaping gas was mitigated passively by the chlorine containment building, but we assumed that the automatic shutoff valves protecting this header failed to activate. Using weather conditions of a 3 m/sec wind with Class D atmospheric stability, the scenario resulted in offsite consequences. However, the endpoint did not extend beyond the highway adjoining the plant grounds and did not encompass any residential, commercial, or other public receptors. Similarly, no environmental receptors were impacted under this scenario. Emergency Response Program: The Blackman HazMat emergency response plan can be activated either through the monitoring and alarm sys tem noted above or by human detection. In either case, the plan calls for immediate notification of the appropriate public response agencies. Response personnel: Small chlorine leaks can be repaired immediately by properly trained and equipped Blackman personnel. However, leaks judged to be large enough for potential off-site consequences are assigned to the Springfield Fire Department HazMat response team. The City developed this local response capability, with substantial input from City Utilities, to ensure a fully staffed and equipped response team around the clock. During a Fire Department response, some Blackman employees would be deployed to help monitor offsite vapor dispersion and contain any chlorine-laden runoff. Local evacuation: The response plan calls for all plant employees not involved in response activities to evacuate the facility using their own vehicles and reassemble at a designated point in the neighborhood community. The specific assembly point would depend on the wind direction at the time of the event. General area evacuation: In an event with potential offsite impacts, the neighboring community would either be evacuated or instructed to implement in-place sheltering at the discretion of the Fire Department. Evacuation or sheltering operations would be directed through the Springfield Police Department and by the Greene County Sheriff's office. These agencies are authorized to issue evacuation orders under federal regulations. Major evacuation routes include Highway 65, Sunshine Street, Battlefield Road, and Highway D. All routes are capable of conducting high volumes of traffic. Conclusion: City Utilities places a high priority on the need to safely handle all chemicals at all locations, including the Blackman Water Treatment Plant. This responsibility has heightened as we have watched urban and suburban development move toward the originally rural plant site over the past twenty years. CU is proud of the plant safety record, with respect both to chemical usage and general work practices. We are confident in the monitoring systems, shutoff mechanisms, and response plans that make up the tiered protection plan for our employees and our neighbors. We will continue to work with local response agencies and government regulators to ensure that all parties maintain this high level of vigilance for the safety of our community. |