A. B. Jewell Water Treatment Plant - Executive Summary |
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Executive Summary The City of Tulsa stores liquid chlorine in two 25-ton aboveground storage tanks at the AB Jewell Water Treatment Plant (WTP). Chlorine is provided for primary disinfection, preoxidation, and filter cleansing. It is the City of Tulsa's policy to adhere to all applicable federal, state, and local laws. If an emergency were to occur and the City of Tulsa was not able to contain the release, the City will notify the Tulsa Fire Department HAZMAT Team and Advance Chemical to request assistance in responding to the emergency. Chlorine is a toxic gas stored as a liquid under pressure. Chlorine vapors are irritating and corrosive to eyes, skin, and the respiratory tract and react violently with easily oxidized materials. Chlorine gas is heavier the air and will tend to travel along the ground and collect in low areas and fill below ground areas such as pits and sumps. The chlorine storage tanks are located inside the chemical feed building on the east side of the AB Jewell WTP. The bulk storage tanks were designed, constructed, tested, and marked in accordance with the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, Rules for Construction of Pressure Vessels. Chlorine is fed to the process using evaporators and vacuum chlorinators. In addition, the storage room is equipped with an air collection system and packed tower scrubber to minimize the impact of a potential release. The chlorine scrubber system is designed to withdraw air containing chlorine from the building. The contaminated air passes through a weak caustic solution to neutralize the chlorine prior to discharge of the air to the atmosphere. The scrubber system was designed in accordance with the Uniform Fire Code and is large enough to treat the contents of one 25-ton storage tank. The storage tanks, relief valves, piping, and appurtenances were designed in accordance with Chlorine Institute Standards. The worst-case release scenario for the AB Jewell WTP is defin ed as the release of the entire contents of one 25-ton liquid chlorine storage tank as defined by the regulations. The tank is assumed to be 80 percent full. The release occurs inside the chemical feed building. Credit was taken for passive mitigation. The chlorine scrubber is considered active mitigation and according to the rule, no credit is taken for this system. The AWWARF Compliance Guidance and Model Risk Management Program for Water Treatment Plants guidance document, scenario CLW-3 was used to estimate the distance to the toxic endpoint. The estimated distance to the endpoint is greater than 6.2 miles. Based on 1990 Census data, approximately 110,000 people in Tulsa, Rogers, and Wagoner counties live within the 6.2-mile radius. The chlorine system is equipped with a chlorine scrubber system that is designed to minimize the impact of any chlorine release from the AB Jewell WTP. Two alternative scenarios were evaluated. Scenario 1 evaluates the scrubber system design le ak. The scrubber is designed to treat the entire content of one 25-ton bulk storage tank. The leak is assumed to occur downstream of the excess flow valve. Chlorine is assumed to leak at a rate of 7,000 lbs/hr over a period of 7 hours. When a leak is detected, normal ventilation is shutdown and contaminated air is drawn through the scrubber system. The system is designed to treat the design leak and reduce the chlorine concentration to less than 15 ppm prior to discharging the air. The endpoint for Scenario 1 was estimated using RMP CompT. The distance to the endpoint is 0.15 miles. Scenario 2 evaluates a potential release scenario that would not be contained by the chlorine scrubber. This scenario assumed that gaseous chlorine is released to the atmosphere as a result of overpressurization of the transfer line located between the bulk storage tank and the chlorine evaporator. This scenario assumes that 165 lbs. of chlorine is released over a duration of 10 minutes. The d istance to the endpoint is estimated to be 0.43 miles. The AB Jewell WTP complies with EPA's accident prevention rule and all applicable state and local regulations. The chlorine bulk storage tanks, scrubber system, piping, evaporators, and associated equipment are design, manufactured, installed, and maintained in accordance with applicable ASTM, Chlorine Institute, and Uniform Fire Code Standards. The City of Tulsa has completed a hazard review of the chlorine system and documented the findings. Operations and maintenance procedures have been developed and implemented. All employees responsible for the operation of the chlorine system have been trained and a training certification is provided in the Risk Management Plan. The AB Jewell WTP experienced a chlorine release on August 18, 1997. The release resulted from a leak in a liquid valve on the north bulk tank. The leak apparently resulted from a failure to properly remove a dust cover during installation. The chlorine m onitoring system detected the leak and activated the chlorine scrubber system automatically. The scrubber then began collecting and neutralizing the chlorine. Plant staff responded to the emergency and installed a emergency repair kit. However, the repair kit was unable to contain the liquid chlorine leak due to excessive expansion. Advance Chemical was contacted and responded to the emergency. Advance installed a second emergency bonnet and then made arrangements to empty the bulk tank to tank truck. The transfer of the chlorine was completed on August 19, 1997 and clean-up and repair were completed on August 20, 1997. The chlorine scrubber system operated as designed during the release. The volume of chlorine released to the atmosphere was estimated to the less than 10 pounds. Two City of Tulsa employees sustained minor injuries that were treated by the City physician. Three contractors working in the immediate area also sought medical check-ups but no injuries were reports . No offsite impacts were reported and no evacuations or sheltering in place were required. The City of Tulsa has prepared and implemented an Emergency Response Plan (ERP) for chlorine releases. The purpose of the ERP is to protect employees and the public in the event of the accident release of chlorine from the facility. City of Tulsa personnel will initiate the emergency response plan and will provide the initial response to a chlorine emergency. Responsible personnel have been trained in accordance with the City Health and Safety procedures and the RMP in the use of personnel protective equipment and required emergency response equipment. If AB Jewell personnel are unable to contain a chlorine release with an emergency repair kit, outside assistance will be requested. Outside assistance may be provided by the City of Tulsa Fire Department, HAZMAT Team, Police Department, and Advance Chemical (the chlorine supplier). The responsibilities of each outside agency are provided in the RMP. |