South Columbus Water Resource Facility - Executive Summary |
|
Executive Summary Policy Statement It is the CWWs policy to operate safe water and wastewater treatment plants, reducing to the greatest extent possible any hazards associated with the processes and reducing any subsequent risk to the surrounding community, personnel, and environment. 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 South Columbus WRF. Stationary Sources and Regulated Substance Handled Primary Activities Municipal 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 settling of biosolids in the clarification process. ? Sulfur Dioxide is used in the dechlorination process to remove residual chlorine from the treated water prior to discharge. ? Digester G as is a by-product of anaerobic digestion, which is a process used to reduce the volume of excess biosolids produced during wastewater treatment. The digester gas is flammable because it contains 65 percent by volume of methane, a flammable gas. The quantity of digester gas stored is 1,600 pounds, which is below the threshold quantity for regulation under the RMP Rule. Therefore, it is not included in the Risk Management Plan. Quantities Handled or Stored ? Chlorine: Total Amount Stored: 20 one-ton containers, equivalent to 46,000 pounds. ? Sulfur Dioxide: Total Amount Stored: 12 one-ton containers, equivalent to 27,600 pounds. ? Digester Gas: 1,600 pounds (estimation based on the Digester dimensions). Worst-case Release Scenarios Chlorine and sulfur dioxide worst-case releases were modeled using DEGADIS 2.1. The model results indicate a distance of 2.53 miles to toxic endpoint for the chlorine worst-case release and a distance of 2.78 miles to toxic endpoint for the sulfur di oxide worst-case release. Therefore, sulfur dioxide is the worst-case accidental release. Sulfur Dioxide ? WRS: Failure of one liquid sulfur dioxide container resulting in a release of 2,300 pounds of sulfur dioxide in 10 minutes. Because the 12 containers are stored on a platform in an open area, passive mitigation is not considered. 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 2.78 miles, beyond which there will be enough dispersion that a hazard to the public will no longer exist. Alternative Release Scenarios Chlorine ? ARS: Release of chlorine from a <-inch-diameter pipe connecting the chlorine container to the feed manifold. For a release duration of 20 minutes, the release rate is 0.042 kg/s. Active and passive mitigation are not considered. The release rate of 0.042 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 0.41 miles or 0.66 km before dispersing enough to no longer pose a hazard to the public. Sulfur Dioxide ? ARS: Release of sulfur dioxide from a <-inch-diameter pipe connecting the sulfur dioxide container to the supply line. For a release duration of 20 minutes, the release rate is 0.037 kg/s. No active or passive mitigation systems are in place. The release rate of 0.037 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, sulfur dioxide would travel 0.40 miles or 0.64 km before dispersing enough to no longer pose a hazard to the public. Accidental Release Prevention Program and Chemical-specific Prevention Steps The South Columbus WRF is in compliance with the RMP Rule, 40 CFR 68. The facility has conducted a comprehensive review of all systems , as well as of administrative, technical, operating and maintenance procedures, in addition to the other required program elements of the RMP Rule. A hazard review was conducted at this facility using a What-If analysis. Five-year Accident History The South Columbus WRF has never had a release of chlorine or sulfur dioxide resulting in offsite injury or dispersion, or in onsite injury. Emergency Response Program The CWW has an Emergency Response Program that applies to the South Columbus WRF, which coordinates response efforts with the local fire departments Hazardous Materials (HAZMAT) team, the police department, and the hospital. Response activities also have been discussed with the Georgia Emergency Management Office. Planned Changes to Improve Safety It was observed during the hazard review that the South Columbus WRF has the necessary equipment and the operating and training procedures required for the safe operation of the chlorination and dechlorination systems. The f ollowing recommendations for improving the safety of the chlorination and dechlorination processes were made: 1. Quarterly inspections of chlorine and sulfur dioxide leak detectors 2. Installation of new chlorine detectors 3. Installation of a wind sock to indicate wind direction during an accidental release |