Adams Field Wastewater Treatment Plant - Executive Summary |
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Policy Statement It is the Little Rock Wastewater Utility's (LRWWU) policy to operate the Adams Field wastewater Treatment Plant (WWTP) safely, reducing to the greatest extent possible any hazards associated with the chlorine system and reducing any subsequent risk to the surrounding community, personnel, and environment. Safe operation depends on proper storage of chlorine, proper handling of the chlorination system, and inherent safety features in the design of the chlorination system. Safety in storage and handling is achieved through the use of safe handling procedures and training of personnel. The policy includes working with the surrounding community and local emergency response agencies to promote a spirit of cooperation and teamwork, to orchestrate an effective contingency plan in the unlikely event of a process incident occurring at the Adams Field WWTP. The emergency response plan includes procedures for notifying the Little Rock Fire Department. Stationary Sources an d Regulated Substance Handled Primary Activity: Wastewater treatment. Use of Regulated Substances: Chlorine is used primarily as a disinfectant. Other possible uses of chlorine are for odor control and to assist in the settling of biosolids in the clarification process. Quantities Handled or Stored: Total amount of chlorine stored is 18 one-ton containers, equivalent to 41,400 pounds. Chlorine Worst-case Release Scenario Failure of one liquid chlorine container resulting in a release of 2,300 pounds of chlorine gas in 10 minutes. Passive mitigation is not considered because the containers are stored in the open. The release rate of 1.74 kg/s is modeled using DEGADIS 2.1. Distance to Endpoint: Under the-worst case weather conditions prescribed by the RMP Rule, the distance to a toxic endpoint of 0.0078 mg/L (or 3 ppm) is 2.53 miles, beyond which there will be enough dispersion that a hazard to the public will no longer exist. Population Exposed: It is estimated, based on the av eraged USCB population densities for the City of Little Rock and the City of North Little Rock, that 33,500 persons would be affected within the WRS toxic endpoint circle. Environmental Receptors: There are no environmental receptors within the WRS toxic endpoint circle. Chlorine Alternative Release Scenario Release of chlorine from a <-inch-diameter pipe connecting the chlorine container to the feed manifold. For a release duration of 20 minutes, the calculated release rate is 0.018 kg/s. The release rate calculation is based on the chlorine density of 2.899 kilograms per cubic meter (kg/m3) at 298 0Kelvin (K), container pressure of 7.93 atm, the ratio of chlorine heat capacities of 1.355, and a passive mitigation of 45 percent because of the enclosed scale room. The release rate of 0.018 kg/s is modeled using DEGADIS 2.1. Distance to Endpoint: Under realistic weather conditions of 3.0 m/s wind speed and a wind stability class of "D," chlorine would travel 0.26 mile or 0.42 kilo meter (km) before dispersing enough to no longer pose a hazard to the public. The toxic endpoint of 3 ppm was used for the ARS. Population Exposed: It is estimated, based on the USCB population density for the City of Little Rock, that 360 persons would be affected within the ARS toxic endpoint circle. Environmental Receptors: There are no environmental receptors within the ARS toxic endpoint circle. Accidental Release Prevention Program and Chemical-specific Prevention Steps The LRWWU's Adams Field WWTP is in compliance with the RMP Rule, 40 CFR 68. The facility has conducted a comprehensive review of all systems and of administrative, technical, and operating and maintenance procedures, in addition to the other required program elements of the Risk Management Program (RMP) Rule. A hazard review was conducted at this facility using a "What If" analysis. Five-year Accident History The LRWWU's Adams Field WWTP has never had a release of chlorine resulting in offsite injury or dis persion, or in onsite injury. Emergency Response Program The LRWWU's Adams Field WWTP has an Emergency Procedures Plan, which coordinates response efforts with the Little Rock Fire Department's HAZMAT team, the police department, and the hospital. Response activities also have been discussed with the Arkansas Office of Emergency Services. Planned Changes to Improve Safety It was observed during the hazard review that the LRWWU's Adams Field WWTP has the necessary equipment and the operating and training procedures required for the safe operation of the chlorination system. The following recommendations for improving the safety of the chlorination process were made: 1. Change the set point for chlorine detection and alarm system to 3 ppm. 2. Provide a copy of the updated emergency response procedures for chlorine to the Little Rock Fire Department. |